SURVEY OF VOLUME 39. NUMBER 5 MARCH-APRIL 1995

MAJOR REVIEW

Diving and Hyperbaric Ophthalmology

CAPTAIN FRANK K. BUTLER, JR., MD

Department of Ophthalmology, U.S. Naval Hospital, Pensacola, Florida

Abstract. Exposure of the human body to ambient greater than that at sea level may result in various disorders, some of which have ocular manifestations. Additionally, some disorders and postoperative states may be adversely affected by the or other hyperbaric exposures. The prevalence of recreational, military, and , as well as the medical use of hyperbaric therapy, requires that ophthalmologists be familiar with the effects of the hyperbaric environment on the normal and diseased eye, The ophthalmology and diving medical literatures were surveyed for publications relating to the ophthalmic aspects of diving and hyperbaric exposures. Un- derwater optics, underwater refractive correction, and ophthalmic aspects of a fitness-to- dive evaluation are summarized. The evaluation and management of ocular manifestations of sickness and arterial gas embolism are reviewed and guidelines for diving after ocular surgery are proposed. (Surv Ophthalmol 39:347-366, 1995)

Key words, arterial gas embolism contact diving glaucoma hyperbaric oxygen ocular ~ ophthalmic surgery photorefractive keratectomy radial keratotomy

The normally exists in a world perienced while diving could cause acceleration where it is exposed to an ambient which of their optic nerve damage. Radial keratotomy is the result of the combined and equally distrib- patients will ask if and when it is safe to dive after uted of all of the gases in the earth's their surgery. Contact wearers will want to atmosphere. At sea level, this pressure is de- know if they can dive in their lenses and which scribed as one atmosphere absolute (ATA). Ex- lenses are best tolerated in the underwater en- posure to increased entails a vironment. new set of potential ocular disorders and raises Many of these issues are not well addressed in new issues in the management of common oph- the ophthalmic literature, and this review was thalmic medical and surgical conditions. undertaken to examine these topics. Medline The popularity of recreational searches with the key words noted above (and continues to increase and the value of hyperbaric others, as seemed appropriate) were performed as a treatment modality is being and were supplemented with an issue-by-issue recognized in a growing number of disorders. As review of the major journals in ophthalmology more and more individuals participate in such and for the last six years. Stan- activities, the likelihood that ophthalmologists dard texts in both ophthalmology and diving will encounter patients with diving-related prob- medicine were reviewed as well as research re- lems will grow. Glaucoma patients will want to ports from U.S. Navy hyperbaric laboratories. know whether or not the increased pressure ex- Essentially all references identified which dealt

347 348 Surv Ophthalmol 39 (5) March-April 1995 BUTLER

read 33 FSW, but is at an absolute pres- sure of 2 ATA. Another way of expressing this relationship is to say that tile absolute pressure ill ATAs is the gauge pressure plus one atmos- phere. When using depth in feet of sea water, this is expressed by the formula ATA = (depth + 33)/(33). The absolute pressures at various depths and altitudes are depicted in Fig. 1. The response of the body to changes ill ambi- ent pressure depends on the anatomy of the or- gan system in question. A fluid-filled space or a solid organ will not change in size as pressure changes, since fluids are not compressible. A gas- Fig. I. Ambient absolute pressures at different depths filled space with elastic walls, however, will and altitudes. (Photograph courtesy of Dr. Richard change in size according to Boyle's law. This law Vann) states that the volume of a certain quantity of gas is inversely proportional to the absolute pressure (the product of pressure and volume is a con- specifically with the ophthalmic aspects of diving stant). For example, a balloon with a volume of and hyperbaric exposures were included. Addi- one cubic foot of air on the surface ( 1 ATA) would tional references were added as necessary to help shrink to a volume of one-half cubic foot if taken answer diving-related questions on various ocu- to a depth of 33 FSW (2 ATA) and to one-fourth lar diseases and post-operative states. of a cubic foot at 99 FSW (4 ATA). The effect of increasing ambient pressure on volume is illus- I. Hyperbaric Terminology trated in Fig. 2. and Physics In most tissues within the body, however, the A review of basic diving terminology and phys- spaces within which gas is located (i.e., lungs, ics will help to acquaint ophthalmologists with middle ear) have only a limited capability to some of the pertinent aspects of hyperbaric ex- change their volume. This presents no problem posures. At sea level, the body is exposed to one as long as the quantity of gas within the space is ATA of pressure. This magnitude of pressure allowed to change to compensate for changes in may be expressed in other units. For compari- pressure. This is the basis for teaching divers to son, 760 millimeters of mercury (ram Hg), 33 clear their ears (add gas to the middle ear cavity) feet of sea water (FSW), and 14.7 pounds per on descent and to exhale on ascent. If this equal- square inch (psi) all denote a pressure equivalent ization is not accomplished, the tissues adjacent to one ATA. The normal to the gas space may be damaged by stretching or of 1 ATA is often used as a reference point from tearing, as occurs with an "ear squeeze" or pul- which other pressures are measured. When one monary alveolar rupture. Damage to tissues states that the intraocular pressure (lOP) is 15 caused by changes in pressure is called baro- mm Hg, one means that the lOP is 15 mm Hg trauma. more than the surrounding environment. In A second physical law of importance in diving point of fact, the absolute pressure inside the eye is Henry's law. This law states that the amount of is 775 (760 -+ 15) mm Hg. The lOP that we gas that will dissolve in a liquid at a given tem- measure with the tonometer is therefore a perature is directly proportional to the partial "gauge" pressure, meaning that the pressure dis- pressure of that gas. This law is central to under- played is the actual pressure minus the constant standing the pathophysiology of decompression 1 ATA of atmospheric pressure. sickness. As a diver descends in the water col- An analogy using a diver helps to illustrate the umn, the increased pressure causes more nitro- point. The of a diver on the surface gen to enter into in his tissues than was will read "0," but the ambient pressure to which present at the surface. If enough nitrogen enters the diver is exposed is 1 ATA. An ambient pres- into solution and the diver then returns to the sure of 0 mm Hg is encountered only in space surface too quickly, the excess inert gas will beyond the influence of planetary atmospheres. not have a chance to be eliminated gradually At 33 feet under the water, the depth gauge will through the lungs. The nitrogen will then come DIVING AND HYPERBARIC OPHTHALMOLOGY 349

Fig. 2. Boyles law in action: the mechanism ofbarotrauma. The can on the right was open on the bottr to allow water to enter and equalize the pressure in the gas space on descent. The can on the left was closed and pressure equalization was achieved by collapse of the can. (Photograph courtesy of Dr. Richard Vann)

out of solution and a gas phase (bubbles) will dality for a growing number of disorders, includ- form in the blood and body tissues. These bub- ing decompression sickness, arterial gas embo- bles may result in the clinical entity known as lism, carbon monoxide poisoning, clostridial decompression sickness (DCS). This disorder myonecrosis, crush injuries, diabetic leg ulcers, will be discussed further in Section VI. failing skin grafts, refractory osteomyelitis, ther- mal burns, necrotizing soft tissue , and II. Types of Hyperbaric Exposures osteoradionecrosis. :~,99 Recreational SCUBA diving is the most com- Compressed air is commonly used in under- mon type of hyperbaric exposure. This pastime water construction and tunneling projects to has undergone an explosive growth in popular- prevent the entrance of water into the working ity over the last decade. The Diver's Alert Net- space. Personnel in these hyperbaric environ- work (DAN) located in Durham, N.C., is the best ments are also at risk from decompression sick- known civilian referral facility in the United ness and the other dysbaric conditions described States for diving medical emergencies. DAN sta- in the sections to follow. tistics indicate that there are over two million III. Underwater Optics active recreational SCUBA divers in the USA. A great deal of diving is also done for military and A. LIGHT ATTENUATION commercial purposes. As light travels through water, it is attenuated Hyperbaric exposures other than diving are by both scattering and absorption. 56 With in- also encountered. Hyperbaric oxygen (HBO) creasing depth, the amount of light decreases therapy in which a patient is compressed in a dry and the water becomes progressively darker. chamber to pressures equivalent to depths of Even in the clearest ocean water, only about 20% 30-60 FSW and given 100% oxygen to breathe is of incident light reaches a depth of 33 FSW and now being used as an adjunctive treatment mo- only 1% reaches 260 FSW. 27 In clear water, suffi- 350 Surv Ophthalmol 39 (5) March-April 1995 BUTLER cient light tor unaided vision is present during D. VISUAL FIELD the day to a depth of approximately 400 FSW. 9~ The sides of the face mask cause a significant If, however, the water contains impurities, such reduction in the diver's visual field. :'7 The normal as silt, algae, or chemical pollution, the amount horizontal visual field encompasses ahnost 180 of light transmitted is greatly reduced. In very degrees. This field is reduced to approximately turbid water, visibility may be reduced to a dis- 85 degrees with a standard face mask. t~ Vertical tance of a foot or less even at very shallow depths fields are also decreased; the decrease in the infe- in bright sunlight. rior visual field is probably of the greatest func- tional significance, since this may result in divers B. COLOR PERCEPTION experiencing difficulty in seeing their equip- ment. The decrease in visual field is reduced by Perception of color changes underwater with changes in mask design which bring the face increasing depth because different wavelengths plate closer to the . The use of clear plastic of light are selectively absorbed as visible light plates in the side pieces may also help to reduce passes through water. Clear water has a maxi- the decrease in peripheral vision imposed by the mum transparency to light in the blue range of face mask. This design, however, results in an the spectrum with a wavelength of 480 nano- interruption in the continuity of the horizontal meters. ~7 Light of longer wavelengths is ab- visual field at the junction of the side plates and sorbed first, so red colors disappear quickly as center plate which may be disconcerting. The depth increases. Red colors are usually not seen visual fields produced by different types of face at depths below 30 feet and yellow colors disap- masks have been described, 57 but the presence of pear around 75 feet. At depths below 100 feet, an adequate watertight seal and a comfortable fit only blues and greens remain. 9~ Red objects are probably outweigh any other considerations in perceived as black, m0 This effect may be reversed selecting a face mask. temporarily by the introduction of artificial light, such as in underwater flash photography, which IV. Underwater Refractive Correction allows objects to be photographed in their actual color at depth. For ametropic individuals who must consider the refractive options available to them in the un- derwater environment, the two primary choices C. REFRACTIVE CHANGES are contact lenses and prescription face masks. Refractive changes underwater may be illus- trated by two situations. When a diver is without A. CONTACT LENSES a face mask and has his or her eyes open under- If contact lenses are to be used, soft contact water, the refractive power of the eye changes lenses are the preferred type for diving. 2"'2:':-'9":'4x~ dramatically. The air- interface is changed Hard (PMMA) contact lenses have been shown to to a water-cornea interface. The refractive power cause corneal edema during decompression and of this interface is determined by the formula after dives. ~7'Ss'~v-' These changes are caused by (N2-N l/r) where N 1 is the of air the formation of nitrogen bubbles in the precor- or water, N2 is the refractive index of the cornea, neal tear film which interfere with normal tear and r is the radius of curvature of the cornea in film physiology and result in epithelial edema. meters. For air, this equation becomes (1.37- Bubble formation would be expected to be more 1.00)/(0.008) or 46 diopters. In water, the equa- common during dives with significant decom- tion changes to (1.37-1.33)/(0.008) or 5 diopters. pression stress. The presence of a 0.4 mm fenes- This loss of refracting power causes an induced tration in the center of a PMMA lens has been hyperopia and blurring of underwater vision. reported to prevent bubble trapping and the re- When a facemask is worn, the resulting air sultant corneal edema. -~9'8~ Although the in- space restores the air/cornea interface to the creased gaseous properties of rigid gas front corneal surface. This eliminates the in- permeable contact lenses theoretically decreases duced hyperopia. In this case, however, light the probability of bubble formation in the tear traveling toward the eye will be refracted away film, use of these lenses while diving has also from the normal as it exits the water medium and been demonstrated to cause bubble formation in enters the air space of the face mask. This causes the tear film with secondary corneal epithelial the object of regard to be magnified by approxi- disruption. ~9 mately 30% and to appear closer than it actually Corneal edema was not observed in two stud- is f7. ]00 ies which examined the use of soft contact lenses DIVING AND HYPERBARIC OPHTHALMOLOGY 351

while diving. 2~ The most frequent complication excess gas volume generally escapes without inci- of contact lens use in diving is loss of the lens, 34':'7 dent. but the larger size and more secure fit of soft Barotrauma will also occur in patients who contact lenses reduce the frequency of this occur- dive with intraocular gas bubbles in the anterior rence. 57 The risk of lens loss can be minimized by chamber or vitreous cavity. Pressure-induced ensuring a good seal on the face mask. Should changes in the volume of this bubble may result the mask leak or become displaced during the in retinal, uveal, or vitreous hemorrhage, as well dive, narrowing of the palpebral fissure may help as partial collapse of the . One patient who to decrease the chance of a contact lens floating attempted to dive while an iatrogenic bubble was off of the surface of the eye) 4 If spherical soft still present in the eye after a gas-fluid exchange contact lenses are unsatisfactory because of sig- had been performed during vitreoretinal sur- nificant , a toric soft contact or a fe- gery noted the immediate onset of very severe nestrated rigid gas permeable lens may be re- eye pain upon descent and quickly aborted his quired to provide satisfactory acuity. dive (Personal communication, Dr. Tim Peter- son, San Diego, CA). Patients with intraocular B. CORRECTIVE FACE MASK LENSES gas should not be allowed to dive as long as any of the bubble remains in the eye. Prescription ground face mask lenses provide The need to add extra gas to the face mask air another refractive alternative. A face mask with space during descent makes it clear that swim corrective lenses bonded onto the face plate of , which cover only the eyes and not the the mask is also a possibility, but may present nose, should never be used for diving. Ocular problems with eventual erosion of or bubble for- barotrauma is inevitable with these goggles if the mation in the bonding substance used. When diver descends more than several feet under the considering the purchase of an expensive pre- surface. scription face mask, however, one needs to be mindful of the corollary of Murphy's law which VI. Decompression Sickness applies to diving: "Weight belts always fall on the face masks with prescription lenses." A. PATHOPHYSIOLOGY When the body experiences a rapid reduction V. Ocular Barotrauma in ambient pressure, inert gas dissolved in the The eye is normally filled with the non- tissues may come out of solution as bubbles. compressible aqueous and vitreous humors and These bubbles may form in the venous blood, in solid tissues and is therefore protected from the muscuioskeletal system, or in other body tis- barotrauma. Once a mask is placed over the face, sues. When these bubbles result in clinical signs however, a different circumstance exists. The or symptoms, the condition is called decompres- face mask creates an air-filled space of which the sion sickness (DCS). eyes and 9cular adnexae form part of one wall. Adherence to published decompression tables As the diver descends, if he or she does not expel reduces the risk of DCS, but does not eliminate it gas through the nose into the face mask, a rela- entirely. Many cases of DCS have been reported tive negative pressure develops in this space. As in divers who have been decompressed in strict the pressure differential increases, the eyes and compliance with published tables. The incidence ocular adnexae are drawn toward this space. of DCS for the commonly used U.S. Navy air Marked lid edema and ecchymosis as well as sub- decompression tables is approximately 1.25%. H,7 conjunctival hemorrhage may result as tissues Because the presenting symptoms and treat- and blood vessels are disrupted by this disten- ment of decompression sickness and arterial tion. The results may be disconcerting to the div- gas embolism resulting from pulmonary baro- er, but typically resolve without sequelae. In se- trauma (covered in the next section) may be very vere cases of ocular barotrauma, such as may similar, the term "" has occur when an unconscious diver sinks a signifi- been proposed to describe both disorders. 4~ cant distance in the water column, more serious Modifiers are added to this term to describe the injury including hyphema may be seen (Personal evolution of signs and symptoms, the organ sys- communication, CDR Clint Fletcher, Pensacola, tem affected, the length of time after the dive that FL). Subperiosteal orbital hemorrhage has also symptoms began, the inert gas burden, and the been reported as a sequela of barotrauma. 2 level of suspicion of pulmonary barotrauma. The Overpressurization of the face mask as a diver degree to which this new terminology will even- returns to the surface is not a problem since the tually replace the existing classification is uncer- 352 Surv Ophthalmol 39 (5) March-April 1995 BUTLER

new decompression tables and decompressi(m computer programs were reported by Thai- mann et al to have a predominance of Type 1 symptoms, with 106 cases of Type I as compared to 37 cases of Type lI DCS: '4-': In contrast, re- ports of DCS in recreational divers and diving fishermen note a higher incidence ot: more seri- ous symptoms. Kizer published a series of 50 cases with approximately half of the cases being from each of these two groups and noted 24 pa- tients with Type I and 26 patients with Type II DCS. 5~ Another study reported 58 cases of DCS in diving fishermen in Singapore.~'4 These cases involved significant delays to recompression and Fig. 3. (;as bubbles in the eye of an experimental ani- had a much higher incidence of serious cases mal exposed to decompression stress. (Photograph than the previous reports with 47 out of 58 pa- courtesy of Dr. Richard Vann) tients experiencing Type II symptoms.

C. OPHTHALMIC MANIFESTATIONS tain at present, but it is currently encountered in Ocular involvement in DCS was first noted in some diving medical texts and journal articles. 1670 by Sir when he observed gas bubbles in the anterior chamber of the eye of a B. SYSTEMIC MANIFESTATIONS viper which had been experimentally exposed to Decompression sickness is a multisystem dis- increased pressure. H Anterior chamber bubble ease. Limb pain is the most common complaint ibrmation has also been reported during altitude in DCS, 3:~'38'1~ with pain in the elbow, shoulder, exposures? ~ Fig. 3 shows a rat with this phenom- hip and knee joints being the most prevalent enon. Ocular manifestations of DCS are relative- sites. The skin may be involved, displaying a mot- ly infrequently noted in the ophthalmic litera- tled appearance known as "cutis marmorata." ture, s2 but there are additional reports in the Bubbles in the lymphatic system may result in diving medical literature. 1~'2:~:~:~'~~l:j'-''l~ Signs regional lymphedema. Cases of decompression and symptoms described include nystagmus, di- sickness limited to musculoskeletal, skin, or lym- plopia, visual field defects, scotomas, homony- phatic manifestations are often referred to as mous hemianopias, orbicularis oculi pain, corti- Type I DCS. More severe cases may involve the cal blindness, convergence insufficiency, optic brain, the spinal cord, or the cardiopulmonary neuropathy and central retinal artery occlusion. system.4~ Neurologic manifestations may include The incidence of ocular symptoms in patients sensory deficits, hemiplegia, paraplegia, par- with DCS was found to be 7% and 12% in two esthesias, loss of consciousness, cranial nerve pal- large series. ~jm These signs and symptoms are sies, and peripheral neuropathies. ~~ Possible summarized in Table 1. cardiopulmonary effects include massive pulmo- studies of divers nary gas emboli or myocardial infarction. De- have documented retinal pigment epithelial ab- compression sickness with neurologic or cardio- normalities indistinguishable from those seen in pulmonary symptoms is often referred to as eyes with choroidal ischemia. These changes Type II DCS. were attributed to decompression-induced intra- The presenting symptoms of DCS are influ- vascular gaseous microemboli. 7v The incidence enced by the depth and bottom time of the dive, of these lesions was directly related to the length the inert gas breathed, the adequacy of decom- of diving and a history of decompression sick- pression, and the delay to presentation. Lam and ness. No divers suffered a loss of Yau reported 793 cases of DCS during a com- from these abnormalities, but the paper notes pressed air tunneling project in Hong Kong har- that the long-term effects of this phenomenon bor. All cases but one in this series were Type I. remain to be studied. This report awaits con- The US Navy Diving Manual notes that the ma- firmation from additional studies with age- jority of DCS cases involve musculoskeletal matched controls. pain. ~~ Even relatively high-risk experimental Decompression sickness may also result when dive series conducted by the Navy to develop an individual without a previous hyperbaric ex- DIVING AND HYPERBARIC OPHTHALMOLOGY 353 posure is suddenly exposed to a decrease in pres- TABLE 1 sure. One study of altitude DCS found that oph- Ocular Manifestations of Decompression Sickness thalmic manifestations were the most common neurologic presentation observed. 2:~ Altitude 1. Nystagmus 2. Dipiopia DCS presenting as optic neuropathy has been 3. Visual field defects reported. ~5 The risk of DCS may be increased if 4. Scotoma an altitude exposure is undertaken after diving 5. Homonymous hemianopia without allowing an appropriate time interval to 6. Orbicularis oculi pain pass so that residual excess gas ira solution has a 7. Cortical blindness 8. Convergence insufficiency chance to equilibrate at one atmosphere. 9. Central retinal artery occlusion 10. Optic neuropathy D. TREATMENT Decompression sickness is treated with re- compression to 60 FSW or deeper and hyper- baric oxygen . In the USA, this therapy gas , but from pulmonary baro- is usually guided by a Navy Treatment "Fable. 101 trauma of ascent. This barotrauma results in These tables are very effective, especially when rupture of the alveoli with gas bubbles entering recompression therapy is begun promptly. ~:~ the pulmonary venous system where they are Ophthalmologists seldom encounter this disease carried to the heart and from there to the sys- in an acute setting because most divers know to temic circulation. seek recompression therapy for signs or symp- toms of DCS. Since treatment generally resuhs in B. SYSTEMIC SYMPTOMS resolution of all symptoms, most patients with Most symptoms in this disorder are localized visual symptoms prior to treatment are asymp- to the cerebral circulation, although cardiac ar- tomatic following recompression treatment and rest may result from embolization of the coro- are not referred to ophthalmologists. 14 Should nary vessels. The classic presentation of arterial an ophthahnologist encounter a patient with gas embolism is the sudden onset of uncon- visual disturbances compatible with DCS in an sciousness within minutes of reaching the surface acute setting following a hyperbaric exposure, after a dive; other possible presentations include the patient should be referred to the nearest hemispheric motor and/or sensory deficits, con- available recompression chamber and diving fusion, and convulsion. Peripheral neuropathies medicine specialist on an emergent basis, since and muscuioskeletal pain are not seen with AGE. DCS may increase rapidly in severity if not treat- ed. Physicians unsure of the location of the near- C. OPHTHALMIC SYMPTOMS est diving medicine specialist or recompression Retrochiasmal defects such as hemianopias or chamber should call the at cortical blindness are potential ocular manifesta- 1-919-684-8111. tions of cerebral AGE, 47 and CRAO may result Incomplete response to treatment, or a recur- from gas emboli in the ophthalmic or central rence of symptoms following treatment may retinal artery. bring the patient with ocular DCS to the ophthal- mologist on a less emergent basis. These patients D. TREATMENT should be managed in conjunction with a diving Management is similar to that for DCS, with medicine specialist. Recompression therapy and emergent recompression and hyperbaric oxygen hyperbaric oxygen should be administered even therapy indicated in all cases. when presentation is delayed, since such treat- ment may be successful despite delays of up to VIII. Other Causes of Decreased several weeks. ~:~ Vision after Diving

VII. Arterial Gas Embolism Decompression sickness and arterial gas em- bolism should be considered whenever vision is A. PATHOPHYSIOLOGY acutely decreased after diving because of the pos- Arterial gas embolism (AGE) is another disor- sible emergent need for recompression therapy. der in which dysbaric intravascular bubble for'- Other disorders, however, may also affect vision mation may occur. The pathophysiology of this after a dive. disorder is different, however, in that the bub- The possibility of corneal edema resulting bles in AGE typically originate not from inert from the formation of gas bubbles under PMMA 354 Surv Ophthalmol 39 (5) March-April 1995 BUTLER

"IABLE 2 nosis apparent. Table 2 provides a summary of Causes of Acutely Decreased Vision after Diving possible causes of an acute decrease in vision tol- lowing a dive. 1. Decompression sickness 2. Arterial gas embolism IX. Central Nervous System 3. Displaced contact lens 4. Anti-fog keratopathy Oxygen Toxicity 5. Ultraviolet keratitis A. PATHOPHYSIOLOGY 6. Corneal edema resulting from bubbles under PMMA or rigid gas permeable contact lenses Although hyperbaric oxygen therapy is of 7. Contact lens adherence syndrome great benefit in the treatment of DCS, AGE, and other disorders, its use is not without . Oxygen at high partial pressures may have a number of adverse effects. Even in normoxic conditions, oxygen produces super- and rigid gas-permeable contact lenses has been oxide anions and other potentially harmful radi- discussed previously. A soft contact lens wearer cals. These radicals are removed by superoxide who complains of blurred vision after a dive dismutase and other cellular defense mecha- should be checked to ensure that the lens has not nisms. In hyperoxic conditions, these defense been lost or displaced. mechanisms may be overwhelmed and oxygen Another possible nondysbaric cause of de- toxicity may ensue. The entity of pulmonary oxy- creased vision following a dive is an epithelial gen toxicity is well known to most physicians and keratopathy induced by chemical agents used to may result when patients receive supplemental reduce face mask fogging. Fogging of face masks oxygen therapy for extended periods of time, is a common problem during diving. The time- even at partial pressures less than one ATA. honored application of saliva to the interior sur- Manifestations of pulmonary oxygen toxicity in- face of the mask reduces but does not eliminate clude pleuritic chest pain, cough, and decrease this problem. This led to the development of in vital capacity. If oxygen administration is not commercial antifog agents designed to be ap- discontinued, a life-threatening Adult Respirato- plied to the inside surface of face masks. These ry Distress Syndrome-type picture may ensue. At preparations may contain volatile compounds partial pressures of oxygen above 1.2 ATA, the potentially toxic to the corneal epithelium such onset of central nervous system oxygen toxicity as glycols, alcohols, surface-active agents, and may precede the development of pulmonary tox- phenol derivatives. Exposure to these com- icity. The likelihood of CNS oxygen toxicity in- pounds may result in blurred vision, photopho- creases exponentially with increases in the par- bia, tearing, and blepharospasm which presents tial pressure of oxygen and limits the therapeutic shortly after the dive. 1~3 Slit-lamp examination use of oxygen to partial pressures of 2.8 ATA and typically reveals a diffuse superficial punctate below. keratopathy. Development of this condition commonly results from improper use of the anti- B. SYSTEMIC MANIFESTATIONS fog agent, specifically an overly generous appli- The use of hyperbaric oxygen therapy in the cation of the agent and a failure to rinse the mask treatment of a growing number of clinical disor- before use. ders increases the likelihood that ophthalmol- Contact with sea water can cause soft contact ogists may encounter questions about the ocular lenses to become tightly adherent to the cor- manifestations of CNS oxygen toxicity. With the nea. 54 Individuals who wear this type of lens may use of enriched oxygen gas mixtures (ni- experience recurrent mild ocular irritation and trox) for sport SCUBA diving, CNS oxygen tox- blurring of vision after dives as a result of this icity may also be encountered in this setting. phenomenon. Symptoms are usually relieved Common systemic symptoms of CNS oxygen with a few drops of isotonic artificial tears. toxicity include muscle twitching, tinnitus, dys- Ship husbandry and phoria, nausea, and generalized convulsion)-l~- commonly require the performance of welding The likelihood of an individual developing these while diving. Failure to use appropriate ultravio- symptoms is affected by a number of factors, in- let radiation protection may result in an ultravio- cluding the depth and time of the exposure, ex- let keratitis. A history of welding, eye pain, and ercise rate, immersion, and the photophobia, as well as typical findings on slit- of inspired carbon dioxide. Symptoms may have lamp examination will usually make this diag- a sudden onset and convulsions often occur with DIVING AND HYPERBARIC OPHTHALMOLOGY 355 little warning. If the patient is not post-ictal, The development of cataracts has been report- symptoms typically disappear rapidly after dis- ed in patients undergoing a prolonged course of continuation of oxygen breathing. 1~ daily HBO therapy at 2.0-2.5 ATA. 74'98 Seven of fifteen patients with clear nuclei at the start of C. OPHTHALMIC MANIFESTATIONS therapy developed cataracts during their treat- Ocular symptoms are a well recognized mani- ment course. These lens opacities were not com- festation of CNS oxygen toxicity.9-12'17'v1'98 The pletely reversible after HBO therapy was discon- most commonly described ocular symptoms of tinued] 4 CNS oxygen toxicity are twitching, Hyperbaric oxygen has been shown to be a blurred vision, and visual field constriction. Vi- powerful retinal vasoconstrictor. ~~ The re- sual hallucinations II and transient unilateral loss duced blood flow caused by the vasoconstriction of vision vl have also been reported. The patient is offset by the greatly increased oxygen-carrying who experienced the unilateral visual loss had a capacity of the blood in hyperoxic environments, previous history of retrobulbar optic neuritis in with the retinal venous oxygen saturation in- the index eye. Loss of the peripheral visual field creasing by as much as 23% while oxygen is may be severe, but is reversible upon termina- breathed at 1 ATA. 7'2 This increase in oxygen- tion of the hyperoxic exposure. In one study, 18 carrying capacity may not be protective in all subjects breathed oxygen at a partial pressure of cases, however. The presence of a cotton-wool 3.0 ATA for up to 3.5 hours. Peripheral visual spot associated with a visual field defect present- field loss began at 2.5 to 3.0 hours of exposure ing two weeks after hyperbaric oxygen breathing and progressed to an average loss of 50% of the in a healthy 44-year-old man has been report- total field .98 Central visual acuity was not affected ed) ~ No symptoms were noted during oxygen- and recovery of peripheral vision was complete breathing and subsequent fluorescein angiog- 30-45 minutes after the exposure was termi- raphy revealed no vascular abnormalities and no nated. areas of capillary non-. Another study examined changes in visual re- Oxygen exposures at 3 ATA have been shown action time as a predictor of imminent overt CNS to cause selective damage to the rod cells in the oxygen toxicity, but no predictive value was dis- . >-, A decrease in rod sensitivity associated covered. 22 with breathing hyperbaric oxygen was reported by one author, 5~ but this effect was not found to D. TREATMENT result in significant changes in dark adaptation When CNS oxygen toxicity is encountered, in a second study. :~4 oxygen breathing should be discontinued imme- Xl. Hyperbaric Oxygen Therapy for diately. In most cases, symptoms resolve within Ocular Disorders several minutes, although some episodes prog- ress to generalized convulsions despite a reduc- The success of hyperbaric oxygen therapy in tion in the oxygen partial pressure. CNS oxygen treating the ischemia produced by DCS and AGE toxicity typically is without residua, unless secon- has led to its use in other clinical disorders. dary trauma or other complications ensue from a Among these are several ocular diseases. convulsion. A. CYSTOID MACULAR EDEMA X. Other Ophthalmic Effects of Hyperbaric oxygen has been proposed as a Hyperbaric Oxygen therapeutic modality for chronic cystoid macular A myopic change in following re- edema (CME). 75 Ogura et al reported two pa- peated hyperbaric oxygen treatments may cause tients treated with HBO for CME which followed a reduction in visual acuity. 4'5'74''Js The rate of a branch retinal vein occlusion. 7:~ Visual acuities myopic change in patients receiving daily HBO were 20/70 in both eyes following the develop- treatments has been reported to be approxi- ment of CME and were not improved by argon mately 0.25 diopters per week and was progres- laser photocoagulation. Oxygen treatments were sive throughout the course of HBO therapy. 4 administered at 2 ATA for one hour and were This change is attributed to an increase in the repeated twice a day for 14 days in both cases, refracting power of the lens. 5 Reversal of the my- with one patient receiving once-a-day treatments opia after cessation of therapy usually occurs for a third week. Acuities after HBO treatment within 3-6 weeks, but may take as long as 6-12 were 20/30 and 20/20 two months and one months. 98 month after treatment, respectively. Benner and 356 Surv Ophthalmol 39 (5) March April 1995 BUTLER

Xiaopinff reported success in treating three pa- though carbon dioxide has a vasodilating effect tients with chronic aphakic CME with oxygen on the cerebral vasculature, oxygen and carbon delivered at 1 ATA into a goggle chamber. Treat- dioxide mixtures often recommended for ther- ments were for six hours per day, six days a week apy of CRAO 4~ should not be used in hyperbaric for three weeks. Visual acuities in both patients settings because of the potentiation of CNS oxy- fbr whom 10-month follow-up was obtained im- gen toxicity caused by the latter gas. proved from 20/80 to 20/30. The mechanism by which HBO improves vision in this disorder is D. RHINO-ORBITAL-CEREBRAL not well understood. 6~ MUCORMYCOSIS Fungal organisms of the family Mucoraceae B. RADIATION-INDUCED OPTIC can cause a devastating disease process in im- NEUROPATHY munocompromised individuals. The rhino-or- Guy and Schatz ~* reported the successful treat- bital-cerebral variant of this disorder is initiated ment of radiation-induced optic neuropathy when an airborne spore colonizes the nasal with HBO. Two patients treated with HBO with- mucosa. In individuals with normal immune sys- in 72 hours following the onset of visual loss had tems, the spores are usually contained by a pha- a return of visual function to baseline levels. gocytic response. In immunocompromised indi- Treatment of two other patients two and six viduals, however, germination may ensue and weeks after the onset of symptoms was not effec- hyphae then develop. 115 As the pro- tive. The authors recommend emergent HBO gresses, the hyphae invade blood vessel walls and therapy for patients with radiation optic neurop- cause tissue and necrosis. The mainstays athy if the symptoms have been present less than of therapy are intravenous amphotericin B and two weeks. A more recent report documents the surgical debridement, but permanent neurologi- complete reversal of visual field loss due to cal deficits or death may ensue despite aggressive radiation-induced optic neuropathy with HBO therapy with both modalities. therapy] Hyperbaric oxygen markedly elevates the ar- terial partial pressure of oxygen. At a pressure of C. CENTRAL RETINAL ARTERY OCCLUSION 2 ATA, breathing 100% oxygen generally results Currently accepted therapy for central retinal in an arterial oxygen pressure of 1000-1200 mm artery occlusion (CRAO) includes supplemental Hg. At 3 ATA, this increases to 1500-1800 mm oxygen.46 It has been proposed that hyperbaric Hg. 69 Elevated partial pressures of oxygen have oxygen would allow the entire retinal demand been shown to be fungistatic.~2 In addition, the for oxygen to be met by the choroidal circula- oxygen may help to reverse the tissue hypoxia tion. ~6 HBO would seem to be a logical treatment and necrosis caused by the propensity of the fun- for cases of CRAO if supplemental oxygen at 1 gal hyphae to invade blood vessels. The clinical ATA is not effective and the patient has not al- use of HBO in rhino-orbital-cerebral mucormy- ready suffered irreversible retinal damage. cosis was first reported by Price and Stevens in a The rationale for therapeutic success in treat- patient who subsequently recovered despite re- ing CRAO with HBO depends therefore on an fusing surgical therapy. TM Other authors have re- intact choroidal circulation. The brief temporal ported an apparent benefit from the use of HBO window in which this therapy must be employed in conjunction with amphotericin B and sur- also presents a problem in the use of HBO for gery. 21'37'42'43 In their review of rhino-orbital-ce- treatment of CRAO. One study in which HBO rebral mucormycosis, Yohai et al identified 28 therapy was used in 69 patients with retinal arte- patients with bilateral involvement who would be rial occlusions 1-12 days after the onset of visual expected to have a very poor prognosis. Of the loss showed no clear benefit from this treat- 18 patients who received amphotericin B ment. 67 Anderson et al reported three patients and/or surgical therapy without HBO, only four with central retinal artery occlusion treated with survived. Six patients were also treated with HBO. No benefit was noted in the two patients HBO; of this group, five survived) ~5 Despite who were treated 40 hours and six days after the the small size of this sample, the authors found onset of symptoms. A third patient treated within a statistically significant benefit from HBO hours after the onset of symptoms recovered therapy. from finger counting to 20/20 vision. 3 Anadditional concern is the oxygen-induced E. UHMS RECOMMENDED INDICATIONS retinal vasoconstriction discussed previously. A1- The Undersea and Hyperbaric Medical Soci- DIVING AND HYPERBARIC OPHTHALMOLOGY 357 ety (UHMS) in Kensington, Maryland, is an in- city water. If the hyperbaric exposure being con- ternational scientific organization founded to sidered is a chamber dive in which no face mask foster the exchange of data on the physiology is worn and immersion is not anticipated, only and medicine of diving and hyperbaric expo- item (3) above remains a consideration. sures. This organization has a standing Commit- No controlled studies specifically addressing tee on Hyperbaric Oxygen Therapy which was the requisite length of convalescence before a established in 1976 to review the scientific and return to diving were found in the literature. clinical data on the evolving applications of hy- The recommendations below are based on the perbaric oxygen and to provide recommenda- application of wound healing observations in tions on which diseases and conditions are cur- other studies and on clinical experience. rently recognized indications for HBO therapy. At approximately three-year intervals, this com- A. CORNEAL SURGERY mittee publishes a report with an updated list of The possibility of barotrauma-induced rup- the recommended indications for HBO therapy ture of a corneal wound is a theoretical possibility for use as guidelines by third party payers and after any incisional corneal surgery and suggests practitioners of . The most that a convalescent period should be allowed for recent publication by this committee was in 1992 the corneal wound to heal before returning to and included necrotizing soft tissue infections as diving. Studies on the healing rate of corneal an indication for HBO. 9~ Although the discus- wounds have been done in the case of full thick- sion of this indication focuses primarily on bacte- ness incisions. 8~ Very little healing is noted in rial infections, it also states that HBO should be the first week, followed by a rapid rise to about helpful in all necrotizing soft tissue infections, 30% of normal strength at one month. Wound which would include rhino-orbital-cerebral mu- strength then gradually increases to approxi- cormycosis. CME, radiation-induced optic neu- mately 50% of normal by 3-6 months. ~9'44 Surgi- ropathy, and CRAO were not listed as recom- cal procedures such as penetrating keratoplasty mended indications. in which full-thickness incisions are made in the cornea should be followed by a six-month conva- XII. Diving After lescent period before a return to diving. Patients Individuals who have undergone ophthalmic who have undergone radial and astigmatic kera- surgical procedures should allow an appropriate totomy, which do not entail full-thickness corne- period of time for wound healing before re- al incisions or prolonged topical steroid therapy, suming diving Diving entails a number of may be allowed to dive after three months. Since factors which increase the risk of post-operative eyes in animal models which have had microper- complications: forations at surgery have been shown to rupture 1) the water in which diving is performed of- at significantly lower pressures than those with- ten harbors pathogens which may cause infec- out such occurrences, 61 consideration should be tions when they contaminate non-epithelialized given to extending the convalescent period prior wound surfaces of the cornea, sclera, conjuncti- to diving in eyes with micro- or macroperfora- va, or lid tissues; tions at the time of RK. Photorefractive keratec- 2) these pathogens may enter the eye through tomy, in which there are no such incisions, per- non-healed corneal or scleral wounds and result mits a return to diving after re-epithelialization in vision-threatening endophthalmitis; of the cornea is complete and acute post-opera- 3) gas in the anterior chamber or vitreous cav- tive symptoms subside. ity may be affected by changes in pressure and result in vision-threatening intraocular baro- B. trauma; and The limbal wounds made in extracapsular 4) face mask barotrauma may result in sub- cataract surgery heal more rapidly than clear conjunctival hemorrhage, lid ecchymosis and corneal wounds because of the increased limbal edema, and could theoretically cause the rup- blood supply. It is common surgical practice to ture of incompletely healed corneal or scleral remove sutures from these incisions at two wounds. months, indicating that a three-month wait The risk of infection due to contact of the eye should be adequate to allow for wound healing with water is much greater with diving in poten- before diving is resumed. Scleral tunnel incisions tially contaminated ocean, river, or lake water now used in single-stitch or sutureless phacoe- than with showering or bathing in chlorinated mulsification cataract procedures are designed 358 Surv Ophthahnol 39 (5) March-April 1995 BUTLER to be self sealing as a resuh of the pressure of the ber. A one-week wait betore diving is recom- aqueous huntor on the corneal valve. The possi- mended after removal of corneoscleral sutures. bility of pathogens entering the eye through the healing scleral tunnel must also be considered, F. OTHER SURGERY however. A one-ntonth period of convalescence Most other types of ocular surgery do not pre- is recommended for patients with scleral runnel dispose to a significant risk of imraocular baro- incisions, and a two-month period is recom- trauma, corneoscleral wound rupture, or intra- mended after procedures employing corneal ocular infection. These procedures require only valve incisions made in clear cornea. a long enough period to allow reepithelialization of the wound and for acute post-operative symp- C. VITREORETINAL SURGERY toms to subside. A period of two weeks should Vitreoretinal surgery poses a different set of suffice in these cases. A summary of various oph- considerations. The small scleral incisions made thahnic surgical procedures and their recom- in pars plana vitrectomies and for drainage of mended convalescent periods prior to diving is subretinal fluid in retinal detachment repair provided in Table 3. would be expected to be well healed after two months. The presence of any intraocular gas fol- XlII. Ophthalmic Considerations in lowing a vitreoretinal procedure is an absolute Fitness-to-Dive Evaluations contraindication for diving (or flying) and the Guidelines have been published on medical patient should be warned of this fact after the standards for divers which include ocular consid- procedure. erations. 2~:3~ These standards are published by such diverse groups as the National Institute D. GLAUCOMA FILTERING SURGERY of Occupational Safety and Health, the US Navy, Patients who have undergone glaucoma filter- the British Commercial Diving Industry and var- ing surgery are at risk for two complications ious diving medicine specialists, and vary some- should they elect to dive alter their surgery. A what in their recommendations. It is important face mask squeeze could result in subconjuncti- to consider precisely what question is being an- val hemorrhage and chemosis that may compro- swered before reviewing the ophthalmic stan- mise the function of their fher. The risk of this dards for hyperbaric exposures. occurrence is small, however, because of the low Fitness-to-dive evaluations are pertbrmed in incidence of significant face mask barotrauma. two settings. The first is an evaluation done for a No reports were found which documented the patient who is a recreational diver and asks his or loss of a tunctioning filter as a result of this com- her personal physician "Is it safe for me to dive?" plication. This calls for a response based solely on medical The well-known risk of late endophthalmitis in safety considerations for the patient. patients with filtering blebs raises the question of The second type of fitness-to-dive evaluation is pathogens gaining access to the anterior cham- one done in an occupational setting where a pa- ber through the conjunctiva. This is more of a tient who is or hopes to be a military or commer- problem in the setting of bacterial conjunctivitis, cial diver is evaluated by a physician who works and has not been reported as a complication of for the employer. In this case, the interests of diving. The small magnitude of the risk to pa- both the employer and the patient must be con- tients from these two complications makes the sidered and the physical standards which are es- presence of a functioning filter a relative rather tablished may be quite different depending on than an absolute contraindication to diving. A the mission to be accomplished by the diver in minimum of two month's convalescence is rec- each setting. ommended after this procedure. Patients who Additional questions must be considered in oc- elect to continue diving with a filter should be cupational settings. Is it economically feasible to advised of the risk of these two complications and expend significant medical specialty resources to the need to avoid face mask barotrauma. determine for candidates who have borderline conditions when there is a very E. CORNEOSCLERAL SUTURE REMOVAL large pool of candidates to draw from who do not Removal ofcorneoscleral sutures after cataract require such evaluation? What is the potential surgery or glaucoma filtering surgery has the medicolegal and workman's compensation liabil- potential to create microscopic tracts into the ity to the employer who allows individuals with corneal stroma and possibly the anterior chain- borderline conditions to dive? What is the indi- DIVING AND HYPERBARIC OPHTHALMOLOGY 359 vidual's value to the employer based on the train- TABLE 3 ing and experience he or she has accumulated? Recommended Minimum Convalescent Periods Prior to These questions may be exceedingly complex Diving after Ophthalmic Surgery and must be answered differently in each oc- Recommended Conva- cupational setting and for each individual cir- Procedure lescent Period cumstance. Anterior segment surgery The fitness-to-dive recommendations found in Penetrating keratoplasty 6 months the following paragraphs will focus only on Corneal laceration repair 6 months medical safety considerations for the patient and Cataract surgery attempt to address three issues: Non-corneal valve inci- sion 3 months 1) Does the condition impair the individual in Corneal valve incisions such a way as to endanger him or her in the Clear corneal 2 months hazardous hyperbaric environment (e.g., inad- Sclerai tunnel 1 month equate visual acuity); Radial keratotomy 3 months 2) Is the condition one which may be made Astigmatic keratotomy 3 months Glaucoma filtering surgery 2 months worse by hyperbaric exposures (e.g., neurologi- (Relative contraindi- cal residua from DCS); cation) 3) Would hyperbaric exposures possibly re- Photorefractive keratec- sult in complications from a pre-existing condi- tomy 2 weeks tion (e.g., intraocular barotrauma fi'om diving Pterygium excision 2 weeks Conjunctivai surgery 2 weeks with intraocular gas). Corneal suture removal 1 week Argon laser trabeculo- , A. VISUAL ACUITY plasty or No wait necessary What level of visual acuity is required to dive Yag laser No wait necessary safely? Specific acuity limits recommended or re- Vitreoretinal surgery quired by different sources vary considerably. :r176 2 months 6~.~,103 In fact, diving is a relatively undemanding (Diving contraindi- activity from a visual standpoint when compared cated until intraoc- ular gas resorbed) to other activities, such as driving. Anyone who is Retinal detachment repair 2 months able to see well enough to operate an automobile Pneumatic retinopexy 2 months traveling at 65 mph on a freeway should be able (Diving contraindi- to dive safely from a visual acuity standpoint. In cated until intraoc- many diving environments, visibility may be sev- ular gas resorbed) Retinal cryopexy or laser eral feet or less, even for an individual with excel- photocoagulation for lent vision, so every diver should be capable of breaks 2 weeks functioning in conditions of markedly reduced Oculoplastic surgery visibility. The ability to see well enough to possess Sutured wound 2 weeks a driver's license is a convenient and reasonable Skin graft or granulating Until epithelializa- standard for visual acuity in diving. If a person wound tion is complete fails to meet this criterion, the decision on fitness Enucleation 2 weeks (Diving contraindi- to dive must be based on a careful assessment of cated with hollow the patient's ability to function with his or her orbital implants) level of vision and the particulars of diving in Strabismus surgery 2 weeks which he or she wishes to participate.

B. COLOR VISION Color vision is not required for safe function- ing in the underwater environment. 25':~~ As de- This is not a concern to the vast majority of scribed in Section III, colors may be altered or recreational divers who confine themselves to air absent at great depths or in conditions of re- diving. Poor color vision may call for increased duced visibility. The requirements concerning care in the case of the minority of recreational color vision in occupational diving standards j~ divers who dive using cylinders of specially pre- stem from the practice of color-coding SCUBA pared mixtures of nitrogen and oxygen (). bottles and supply lines containing different gas- The increased percentage of oxygen in these es or from other occupational considerations. mixtures may result in CNS oxygen toxicity if 360 Surv Ophthahnol 39 (5) March-April 1995 BUTLER used al depths where the partial pressure of to study corneal weakening after RK often in- oxygen exceeds 1.2 ATA. Careful labelling of volve surgery on postnu)rtenl eyes and do not nitrox cylinders in addition to color coding allow ii)r postoperative wound healing. should suffice to avoid confilsion between the :Mthough the absolute pressure may increase two gas mixtures. well beyond the pressures described above dur- ing diving, there is generally not a significant C. CORNEAL AND CATARACT SURGERY pressure differential across the cornea except in Questions about diving after radial keratot- the case of a face mask squeeze. As mentioned omy (RK) are often encountered. Individuals previously, this is an uncommon occurrence in whose has been corrected with this pro- diving since the diver need only be able to exhale cedure are prohibited fi'om entering diving pro- through a single nostril during descent to pre- grams in the Navy. "~:~ Applicants who have had vent its development. The author has seen only this procedure may not even be allowed to serve one clinically significant case of face mask baro- in less visually demanding military positions, m'' trauma in many years of association with Navy Two recent reviews of RK in the military have and activities. recontmended that the procedure continue to be Despite the theoretical potential for corneal disqualifying tbr Navy divers :v-' and for Army avi- rupture to occur in divers who have had RK, ators. :~ Edmonds et al "-'9 recommend that people such occurrences have not been reported. 5'a Most who have had RK not be allowed to dive unless of the reported corneal ruptures following RK they use tace masks designed to equalize the have been the result of direct blunt trauma to the pressure within the mask to that of the ambient eye. :~~':5'6~'*~Also worthy of note are the reports of pressure. Davis '-'5 states that until further data is blunt trauma severe enough to cause hyphema available, a person who has had RK should be and facial fractures in which radial keratotomy disqualified from diving. scars remained intact) :~'9~ The potential complications of RK are well Kluger recommends that RK not he consid- documented and include halos, glare, diurnal ered a contraindication to diving in his review on fluctuations in visual acuity, progressive hyper- diving after corneal surgery. 59 The author has opia, irregular astigmatism, decrease in best cor- examined three US Navy divers and one Coast rected visual acuity, recurrent corneal erosions, Guard diver who underwent bilateral RK subse- and increased susceptibility to traumatic corneal quent to completing initial , pre- rupture. :~5"~-''~~176176The additional question of sumably being unaware of the restrictions on re- possible barotrauma-induced rupture of RK in- fractive surgery for divers. These individuals had cisions in the hyperbaric environment is often continued to dive for varying lengths of time raised when evaluating these individuals for fit- after their procedures before being referred for ness to dive. ophthalmic evaluation for fitness to dive. They Alcaraz found that the pressure required to had all returned to diving shortly after having rupture at least one corneal incision in post-RK had RK performed and had, by the time of their human cadaver eyes is approximately 215 mm evaluation, been diving for periods of four to ten Hg. ~ Additional intormation is available from years without suffering corneal wound dehis- animal models. Campos et al studied 20 enu- cence or other adverse eftects. All were allowed cleated pig eyes that had undergone either RK to continue diving and have had, to the author's or PRK. ~ lntraocular pressure was then raised knowledge, no problems related to their eye using lateral compression until the eye ruptured surgery. or until a maxinmm measurable pressure of 280 There were also no reports of any corneal mm Hg was reached. Nine of the 10 control eyes wound ruptures occurring as a result of diving in ruptured at the sclera, and the other ruptured at patients who had undergone penetrating kerato- the optic nerve. All control eyes ruptured at pres- plasty. Although the potential for rupture is sures above 280 mm Hg. Similar results were greater than that in eyes which have only under- obtained with the PRK eyes, with all 10 eyes rup- gone the partial thickness incisions of radial ker- turing at scleral sites at pressures above 280 mm atotomy, this risk also remains theoretical and at Hg. In contrast, all 10 of the RK eyes ruptured at present should not be considered a contraindica- corneal incision sites at an average pressure of tion to diving after the patient has been appro- 240 mm Hg. Other studies have also shown an priately informed and the recommended six- increased susceptibility to pressure-induced rup- month convalescent period has passed. ture of the globe alter RK in animal models. 64'u3 It Photorefractive keratectomy (PRK) is a new is important to note that animal models designed refractive surgical procedure which is cmrently DMNG AND HYPERBARIC OPHTHALMOLOGY 361 in phase III of FDA testing. Unlike radial kera- posed, but rather the magnitude of the differ- totomy, it entails no corneal incisions which ence between the intraocular and extraocular would decrease the ability of the cornea to with- pressures, v~ The picture is further complicated stand blunt trauma. Published series of PRK by current thoughts about the multifactorial eti- cases have shown that the incidence of visually ology of glaucomatous optic neuropathy H~4'm~ significant post-operative complications expe- and the lack of investigational data about how rienced with this procedure is very low. 76'84'85"93 these various ihctors are altered by exposure to As noted above, this procedure was not found to an elevated absolute pressure. The only glauco- increase the susceptibility of the eye to rupture ma patients who should be definitely excluded when subjected to elevated pressures. '6 Individ- frmn diving are those with visual loss severe uals who have had this procedure may be al- enough to impair their ability to function in the lowed to dive two weeks after their surgery, underwater environment. Functioning filters assuming that they have had an uneventful are a relative contraindication to diving, as noted postoperative course with resolution of pain and previously. Glaucoma patients on medical ther- photophobia. apy to control their pressures should be evaluat- No reports were found of barotrauma-in- ed for the presence of" side effects which may duced wound rupture or other complications oc- present problems during or after a dive. These curring as a result of diving after cataract sur- are discussed in the following section. gery. Diving after this type of surgery should also not pose a problem after the recommended con- F. VITREORETINAL DISORDERS valescent period. Retinal detachment surgery or treated retinal breaks should not be a problem for diving once D. ENUCLEATION the recommended convalescent period has After the convalescent periods recommended passed. "5 Degenerative and metabolic ocular dis- in the previous section, diving should be possible orders have not been reported to be exacerbated after almost any type of eye surgery. One excep- by hyperbaric exposures. The limiting factor for tion is an individual who has undergone enuclea- such patients will be reductions in visual acuity or tion and who has a hollow implant. There are the limitations imposed by the systemic disorders reports of pressure-induced collapses of hollow themselves. silicone orbital implants at depths as shallow as 10 feet.-"-' A hollow glass implant was also tested G. VISUAL RESIDUA FROM DECOMPRESSION and did not implode at a maximum test depth of SICKNESS 115 feet, but diving with hollow glass implants Many diving medical officers feel that neuro- could not be recommended on the basis of this logical symptoms of decompression sickness one test. Individuals with hollow orbital implants which do not resolve after therapy may predis- should not dive. pose to further episodes of DCS, although this has not been addressed in a controlled study. E. GLAUCOMA These residual deficits are felt to be contraindica- The question of whether or not patients who tions to diving by some authors, 24 while others have glaucoma should dive is an intriguing one. recommend that shallow diving be allowed if the Ophthalmologists treat glaucoma by reducing residual deficits are stable over a period of the intraocular pressure. A doctor who has inter- months and not disabling38 The author recom- vened therapeutically to reduce the pressure in mends that any visually significant deficit from a the eye of a glaucoma patient from 25 to t5 mm previous episode of DCS be considered a contra- Hg may be concerned at the prospect of the pres- indication to any further recreational or occupa- sure in this eye being increased to over 2000 mm tional compressed gas diving. Hg when he or she descends to a depth of 60 FSW. Saturation divers working at a depth of H. MISCELLANEOUS 800 feet have intraocular pressures of over Patients with breaks in the corneal epithelium 19,000 mm Hg. They remain at these depths should not dive until these breaks are completely for durations exceeding 30 days without suf- re-epithelialized. In fact, most patients will prob- fering any symptoms of glaucomatous optic ably not feel much like diving until these breaks neuropathy. are healed. Individuals in the acute phase of any How is this possible? Clearly, the issue is not ocular disorder which produces significant pain, the absolute pressure to which the eye is ex- decreased visual acuity, photophobia, diplopia, 362 Surv Ophthalmol 39 (5) March-April 1995 BUTLER

rlABLE 4 asthma, o1" COPD should neither be allowed to Ophthalmic Contraindications to Diving dive nor given beta-blockers. Timolol has been reported to reduce the heart 1. Intraocular gas 2. Presence of a hollow orbital implant rate in glaucoma patients from 79 to 71 beats per 3. Any acute infectious or inflammatory ocular disor- minute without having any appreciable effect on der which produces significant pain, photophobia, blood pressure. ~~ In another study comparing diplopia, or decrease in vision the cardiovascular effects of timolol and apra- 4. Recent ophthalmic surgery prior to completion of clonidine on healthy female volunteers, timolol the recommended convalescent period 5. Inadequate vision to function safely in tile under- was found to reduce both the resting heart rate water environment and exercise-induced tachycardia. 18 Since a small 6. Visually significant deficits fi'om previous episodes percentage of divers may be at risk of loss of ofdecnmpression sickness or arterial gas embolism consciousness underwater from vagotonic bra- 7. Functioning glaucoma filter (relative contraindica- dyarrhythmias when diving in cold water, 8 timo- tion) 1ol may be considered to increase this risk. Su- praventricular tachyarrhythmias may also place the diver at hazard, however, 8 and timolol may have a protective effect against this occurrence. It should be noted that increased vagal tone and or other disabling symptoms should refrain from a resting bradycardia are common in well-condi- diving until the problem has been treated and tioned individuals, 8 and that this bradycardia is the acute symptoms have resolved. not considered a contraindication to diving. Pa- Table 4 provides a summary of ophthalmic tients who wish to dive while on timolol should contraindications to diving. Once again, most of wait several weeks after therapy is initiated and the restrictions to diving noted above do not ap- have their heart rate checked by a physician. If ply to hyperbaric oxygen therapy. Hyperbaric the heart rate is normal, diving should be per- exposures which occur in a dry chamber do not mitted. Ira significant bradycardia exists, the ad- entail immersion of the eye or the possibility of vice of a diving medicine consultant should be face mask barotrauma. Decompression sickness obtained. is a consideration only for chamber attendants not breathing 100% oxygen. Many critically ill B. PILOCARPINE patients are routinely treated in dry chambers with HBO. Only the presence of intraocular Pilocarpine causes miosis and stimulation of gas or hollow orbital implants remain as pos- the ciliary muscle. TM This may result in frontal sible ocular contraindications to diving in these headache as well as reduced peripheral and sco- patients. topic vision. Fluctuations in visual acuity may be very bothersome to younger patients on pilocar- XIV. Ocular Medications and Diving pine. Although pilocarpine is a parasympathetic The use of ocular medications may present agonist and theoretically may cause bradyar- special problems in the underwater environ- rhythmias, this is generally not clinically signifi- ment. Probably the most common agents en- cant. 1~ Patients recently started on pilocarpine countered are anti-glaucoma medications, anti- should be examined before being allowed to re- biotics, and antiinflammatory agents. turn to diving to ensure that they are not having headaches which may be confused with DCS A. TOPICAL BETA-BLOCKERS after a dive. Fluctuating visual acuity may be Timolol and other beta-adrenergic antago- treated by switching to a sustained-released nists are commonly used antiglaucoma medica- delivery system, although the effects, if any, tions with few side effects in otherwise healthy of the hyperbaric environment on the sustained- individuals. 86 Potential adverse effects of the use release delivery system are not known. Mild re- of topical beta-adrenergic antagonists include ductions in peripheral vision and night vision decreased heart rate, exacerbation of pre-exist- should not prevent an individual from diving ing congestive heart failure (CHF), broncho- safely. spasm in individuals with asthma or chronic ob- structive pulmonary disease (COPD), and C. DIPIVEFRIN fatigue. The~se agents do not typically cause CHF Dipivefrin produces the most troublesome or bronchospasm in patients without pre-exist- ocular surface symptoms of the three commonly ing disease, and patients who suffer from CHF, used topical anti-glaucoma medications, but is DIVING AND HYPERBARIC OPHTHALMOLOGY 363 relatively free of adverse systemic effects. Ther- stances of divers becoming aware of bubbles apy with this agent should not impact on fitness tbrming in the medial canthus of the eye while to dive. performing the Valsalva manuever to equalize their ears. This phenomenon may occur if the D. CARBONIC ANHYDRASE INHIBITORS valve of Hasher allows air to enter the nasolacri- Acetazolamide and methazolamide are car- mal duct during the Valsalva manuever. The air bonic anhydrase inhibitors used to lower intraoc- then travels up the duct and exits at the punctal ular pressure in glaucoma patients when topical openings. medications alone are insufficient or are not tol- erated. Side effects from these agents include renal calculi, paresthesias, electrolyte and acid- References base disturbances, depression, skin eruptions, 1. Alcaraz LG, Banez MA, Haight DH, et al: Comparative loss of appetite, and blood dyscrasias: 6 The most study of wound integrity after excimer laser photoabla- tion and radial keratotomy (abstract). Invest Ophthalmol common symptom encountered with carbonic Vis Sci 33 (Suppl):999, 1992 anhydrase inhibitors which would be problemat- 2. Andenmatten R, Piguet B, Klainguti G: Orbital hemor- ic for diving is the peripheral paresthesias which rhage induced by' barotramna (letter). Am J Ophthalmol 118:536-537, 1994 could easily be mistaken for manifestations of 3. Anderson B, Saltzman H, Heyman A: The effects of neurological DCS. Divers started on these medi- hyperbaric oxygenation on retinal arterial occlusion. cations should be checked four to six weeks after Arch Ophthalmol 73:315-319, 1965 4. Anderson B, Farmer JC: Hyperoxic myopia. Trans Am the initiation of therapy. Should significant par- Ophthabnol Soc LXX VI:116-12 4, 1978 esthesias be present, the medication should be 5. Anderson B, Shehon DL: Axial length in hyperoxic nay- discontinued and other treatment modalities, opia, in Bore AA, Bachrach AJ, Greenbaum LJ (eds): Ninth International Symposium on Underwater and Hyper- such as argon laser , undertaken. baric Physiology. Bethesda, Undersea and Hyperbaric Patients with clinically significant depression or Medical Society, 1987, pp 607-611 mood change resulting from carbonic anhydrase 6. Benner JD, Xiaoping M: Locally administered hyper- oxic therapy for aphakic cystoid macular edema (let- inhibitor therapy should be counseled not to ter). Am J Ophthalmol 113:104-105, 1992 dive unless the medication is discontinued. A 7. Borruat FX, Schatz NJ, GlaserjS, et al: Visual recovery blood count and serum electrolytes should be from radiation-induced optic neuropathy. 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t~t('ll)l'S ill rhino-orl)ilal-r lntlcorlnvcosis. ,~ltFu XI1. Diving after eve surgery Op/*lhahmd 39:3-22, 1994 A. Corneal surgery B. Cataract surgery C. Vitreoretinal surgery Outline D. (;laucoma filtering surgery E. Corneoscleral suture removal I. Hyperbaric terntinology and physics F. Other surgery II. Types of hyperbaric exposures XII1. Ophthalmic considerations in fitness to dive III. Underwater optics evaluations A. Light attenuation A. Visual acuity B. Color perception B. Color vision C. Refractive changes C. Corneal and cataract surgery D. Visual field D. Enudeation IV. Underwater refiactive correction E. Glaucoma A. Contact lenses F. Vitreoretinal disorders B. Con'ective face mask lenses G. Visual residua from decompression sick- V. Ocular barotrauma ness or gas embolism VI. Decompression sickness H. Miscellaneous A. Pathuphysiology XIV. Ocular medications and diving B. Systemic manifestations A. Topical beta-blockers C. Ophthahnic manifestations B. Pilocarpine D. Treatment C. Dipiveti'in VII. Arterial gas embolism D. Carbonic anhydrase inhibitors A. Pathophysiology E. Topical steroids B. Systemic manifestations F. Topical antibiotics and anti-viral agents C. Ophthalmic manifestations XV. Miscellaneous ocular problems D. Treatment VII1. Other causes of decreased vision after diving IX. Central nerwms system oxygen toxicity The author wishes to express his appreciation to the tol- A. Pathophysiology lowing ophthahnologists, diving medical officers, and hyper- B. Systemic manifestations baric physiologists whose council and expertise were invalu- C. Ophthalmic manifestations able in the preparation of this manuscript: Dr. Van Aldred, D. Treatment Dr. Banks Anderson, Dr. Peter Bennett, Dr. Steven Chalfin, X. Other nphthahnic etfects of hyperbaric oxygen CDR Clint Fletcher, Dr. Ed Galbavy, Dr. David Harris, CAP-I" XI. Hyperbaric oxygen therapy for ocular disor- Marie Knafelc, Dr. Tim Peterson, CAPT Hank Schwartz, and Dr. Richard Vann. ders The opinions expressed in this paper are those of the au- A. Cystoid macular edema thor and do not necessarily reflect the opinions or the policies B. Radiation-induced optic neuropathy of the Department of the Navy or the Department of Delense. C. Central retinal artery occlusion Reprint address: CAPT Frank K. Butler,Jr., M.D., Depart- D. Rhinn-orbital-cerebral mucormycosis ment of Ophthahnology, Naval Hospital, Pensacola FL E. UHMS recommended indications 32512.