CONTINUING EDUCATION AND TRAINING Gain 2 CET credits – enter online at www.otcet.co.uk or by post : Diagnosis, contact fitting and management

Waheeda Illahi PhD, M Sc, BSc(Hons), M COptom

Contact lenses w ere first used in connection w ith keratoconus over 120 CONFUSED ABOUT 1 CET REQUIREMENTS? years ago. Lens designs and materials have changed significantly over the See www.cetoptics.com/ years and are continuing to develop. The prime focus of contact lenses for cetusers/faqs/ keratoconus remains unchanged over time: to improve vision, provide a IM PORTANT INFORMATION comfortable, stable mode of visual rehabilitation and, maintain the health Under the new Vantage rules, all OT CET points awarded will be and integrity of the . Before attempting to fit and manage the uploaded to its website by us. All keratoconic patient, both appropriately and with confidence, the clinician participants must confirm these results on www.cetoptics.com should have an understanding; first of the disease condition and second, so that they can move their points of general characteristics observed in these patients. from the “ Pending Points record” into their “ Final CET points record” . Full instructions on how to do this are available on their website.

It is hoped that practitioners who are not Prevalence already involved in managing keratocopic patients would consider exploring this Numerous studies have reviewed the preva- incredibly rewarding area of work. lence of keratoconus. Estimates lie between Keratoconus is a non-inflammatory 50 and 230 per 100,000 in the general pop- corneal thinning disorder which results in a ulation, approximately one per 2000.2,7,8 conical protrusion of the cornea. Mild to When considering the prevalence of kerato- marked impairment of vision occurs, conus the differing diagnostic criteria used depending on the extent of induced irregu- in different studies need to be taken into lar , and prot rusion.2 account. A much higher prevalence may be Keratoconus is usually bilateral but asym- found as corneal topography is used more, metrical between the two eyes. However up thanks to its greater sensitivity as a diagnos- Module 5 Part 2 to 15% of reported cases are unilateral. tic tool. 3,4,5 PAYL The onset of keratoconus is usually at Racial factors as well as climatic condi- puberty and the condition tends to be pro- tions may play a role. In a Midlands study, gressive until the third or fourth decade of Asian patients were noted to be younger at life. It usually arrests at this stage, but may the time of diagnosis of the condition and adopt a variable pattern of progression.2,6 had a fourfold increase in presentation com-

Signs Symptoms About the author Scissors reflex Frequently changing spectacle Rx and axis Waheeda Illahi is (swirling retinoscopy reflex) of astigmatism Deputy Head of Department, Distorted/ irregular keratometer mires with Poor repeatability of subjective refraction Birmingham & steep readings Midland Eye Centre. She has ten years’ Prominent corneal nerves Ghosting/ monocular experience in Glare at night specialised hospital Haloes around lights contact lens fitting Blurred/ distorted vision and a PhD on keratoconus. Table 1. Diagnostic criteria associated with early keratoconus

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Gain 2 CET credits – enter online at www.otcet.co.uk or by post pared to white patients.9 A relatively high Clinical Sign Description Method of examination incidence has been documented in the M editerranean and M iddle Eastern areas; a Corneal nerves More prominent than in relatively lower incidence has been reported normal eye in places such as Japan, Taiwan and Vogt’s striae17 Fine vertical lines in the Slit lamp Singapore.10,11,12 M ales may be at higher stroma and Descemet’s (Optical section) risk than females. In addition, the preva- membrane, usually parallel lence of the condition is about 7% in to the steep axis of the Down’s syndrome.7 cone, disappear temporarily Various studies have looked at personali- on digital pressure. ty traits in keratoconus. Increased rates of schizophrenia and phobias have been Fleischer’s ring18 Iron pigment ring forms the Slit lamp reported in keratoconic males compared to base of the cone. M ay be Cobalt blue filter. Diffuse partial or complete. Yellow- illumination 19 normals, whereas keratoconic females have brown in colour, this 13 shown increased rates of depression. depends on the amount of A more recent study looked at obsessional- ferritin deposited in the ity and a range of personality traits in kera- basal epithelial layer toconics and in myopes of at least -6.00 D.Sph. who wore hard contact lenses. No significant differences were found between the two groups in terms of these personali- Corneal thinning Corneal thinning and cone Slit lamp ty traits.14 displacement is visible in Optical section. High the central-inferior region Magnification. in moderate and advanced Early stages keratoconus. The diagnostic criteria in table 1 are not unique to keratoconus but should raise sus- picion, especially in the presence of myopic Munson’s sign Ectasic protrusion of the Slit lamp/ Burton lamp/ astigmatism. cornea on downgaze unaided produces a V-shaped In the early stages of the condition, conformation of the lower before the cornea starts to protrude, ker- lid. atometric readings may not necessarily show steep values. Patients may be Rizzuti’s sign20 Lateral illumination of the Slit lamp. Lateral asymptomatic. cornea produces a steeply Illumination Eyes which have good spectacle visual focused beam of light near acuity and show no signs of keratoconus on the limbus. slit lamp examination, have been described Moderate: beam central to limbus. Advanced: beam as a ‘forme fruste’ of keratoconus or a vari- displaced peripherally. ant of the normal.15 Corneal nerves are vis- ible in the normal cornea; however in keratoconus the nerve fibres may be more visible because nerve fibre thickening has Table 2. Clinical signs, description and method of examination been noted to occur in association with changes in Bowman’s layer and the kerato- patients compared to normals.19 microscopy.24 Further studies, looking at cytes.16 This nerve fibre thickening has the packing of fibrils in the stroma in order been found to occur in the sub-basal plexus Early keratoconus to explain stromal thinning, have found no layer. difference in the interfibrillar spacing in the In moderate to advanced keratoconus, As the cone develops, the epithelium can be keratoconic cornea.25 slit lamp findings may show clinical seen to be thinned, and enlarged superficial Changes such as ruptures or folds in changes. epithelial cells may be observed on specular Descemet’s membrane have been noted as When fitting keratoconic patients with microscopy. 21,22 Extracellelular and inter- a common feature in keratoconus.26 No real contact lenses, it is very important to carry cellular ferritin accumulate in the epithelium explanation has been found for these rup- out a thorough slit lamp examination and at the periphery of the cone, producing a tures following studies of the extracellular record all the clinical features, such as areas Fleischer’s ring.23 matrix. 27,28 of staining, as this record will enable further In terms of the changes in the stromal Eventually some form of corneal scarring changes to be documented. layer, a reduction in the number of lamellae is seen in patients with keratoconus. T h e It is also important to note that the has been noted but no changes in the actu- scars may be small focal opacities, which intraocular pressure measured by applana- al thickness of the collagen lamellae on may be sub-Bowman’s or pre-Descemet’s tion tonometry is lower in keratoconus examination of tissue by electron membrane. The small stromal scars maybe a

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ditions will influence the success of contact lens wear in the keratoconic patient.

Pathogenesis The cause of keratoconus is not yet known. More than one factor is believed to be involved. The epidemiology and biochem- istry of keratoconus has been discussed in various review articles.2,7,42 A working hypothesis for the cause of keratoconus has been suggested,43 iden- tifying various factors as involved in the process: a build-up of destructive aldehydes within the keratoconic as well as Figure 1. Moderate Keratoconus showing Figure 2. showing resid- abnormal processing of free radicals and Vogt’s striae (Courtesy BMEC) ual scarring (courtesy BMEC) peroxides; the process of apoptosis occurring in irreversibly damaged cells, result of repair of idiopathic breaks in wound healing or repair occurring in cells Bowman’s layer. that are damaged reversibly; focal areas of This type of corneal scarring is not corneal thinning and fibrosis occurring in thought to be related to contact lens wear. areas of wound healing. However, factors such as corneal staining, A genetic component in keratoconus is contact lens wear, Fleischer’s ring, steeper recognised44, 45 and its occurrence in corneas and increasing age have been asso- monozygotic twins. There are reports of ciated with corneal scarring. 29 positive family history in 6-15% of cases. 46 In the absence of clinical signs, videokerato- Hydrops graphic techniques can be used on affected Figure 3. (Orbscan Map) family members.47 An autosomal dominant In more advanced cases of keratoconus mode of inheritance has been suggested which have been studied, acute hydrops will ease process and final visual acuity. Serious with variable expression.2,48 The possibility develop (Figure 2). In hydrops, marked stro- complications can arise, so that close obser- of recessive inheritance has also been sug- mal oedema occurs as a result of the vation is essential.30 gested.49 endothelium and Descemet’s membrane Three cases were presented in 2003 in On chromosome21, close to the cen- rupturing, allowing aqueous humour to which spontaneous hydrops led to perfora- tromere, a gene for an autosomal dominant enter the stroma. The oedema usually tion or imminent perforation which required form of keratoconus has been resolves over a period of time and eventual- penetrating keratoplasty to be carried out mapped.50,51 This provides an interesting ly results in scarring. If this scarring is in the on an urgent basis. Two cases were associ- link between keratoconus and trisomy.21 area of the visual axis then the visual acuity ated with pellucid marginal degeneration The incidence of keratoconus in Down’s can decrease. and one with keratoconus. The keratoconic syndrome varies from 0.5-15% (that is, it is If, however, the scar is outside the area of patient had no presenting history of trauma, 10-300 times more common than in the the visual axis, the visual acuity may improve eye-rubbing, or ocular allergy. The patient general population).2 Various studies have as the cone flattens after resolution of the was treated with tissue adhesives and later reported on the familial rate of hydrops. had penetrating keratoplasty.35 keratoconus. A positive family history in In keratoconus, very rare cases have been 19% , 13.5% and 20% of cases has been reported where spontaneous rupture of the Associated conditions reported.52,53 cornea has occurred.30,31 Hydrops is Keratoconus has been associated with believed to occur either spontaneously or as atopy, asthma36 and eye rubbing.37 Posterior keratoconus a result of ocular trauma, for example Other conditions in which keratoconus A rarer form of the condition, posterior ker- where there is very vigorous eye rubbing, in has been noted include ocular rosacea, atoconus, has been noted in the literature in 2-3% of patients with keratoconus.32 cone-rod dystrophy, and corneal granular the form of case reports.54 In one case Various risk factors have been recognised dystrophy as well as a case of early onset of study, anterior keratoconus was noted in which can result in corneal ectasias, includ- ectasia following laser in situ keratomileusus one eye and posterior keratoconus in the ing allergy and eye rubbing, and in those of (LASIK). 38,39,40,41 other eye.55 A classification system was a younger age and poor visual acuity at the Keratoconus has also been linked with suggested on the basis of retrospective time of diagnosis.30,32,33,34 The area of the systemic conditions such as Leber’s congen- analysis of topographic maps which showed cornea affected by hydrops can vary from ital amaurosis, Down’s syndrome, and mitral significant corneal surface changes. 7% to 100% of the corneal surface and is valve prolapse. 7 Uniform corneal steepening was noted in thought to affect the duration of the dis- It is important to note that all atopic con- generalised posterior keratoconus and

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Grade Corneal radius of Equivalent dioptres curvature (mm)

8.00.-7.00 42-48

Moderate 6.90-6.50 49-52

Moderate/Advanced 6.40-6.00 53-56

Advanced <6.00 <56

Table 4. Classification of keratoconus in terms of the radius of curvature of the anterior Figure 4. Three-point-touch (ideal fit) cornea. corneal steepening was seen in localised side and can be altered. Note the elevated centres where many moderate/ advanced central and paracentral posterior kerato- heights, surface steepening and thinning keratoconic patients are managed. conus, whereas corneal flattening was seen that occurs at the apex of the keratonconic Numerous different classification systems in cases of localised peripheral posterior ker- cone. have been suggested. Table 4 outlines a atoconus.56 simple system based on the radius of curva- Pachymetry ture of the central cornea. Keratoconus Corneal topography Corneal thickness measurement provides cones can also be classified by shape and Corneal topography is a very useful aid in additional information when diagnosing position.34 This may be helpful when select- the diagnosis of keratoconus, especially in and assessing keratoconus. There are vari- ing the design of contact lens to fit the the absence of clinical signs. ous different methods for assessing corneal cornea. The suggested classes are: Caution, must, however, still be exercised thickness, including ultrasound.58 as dry-eyed patients with aqueous tear defi- Ultrasonic pachymetry (US) is currently • Nipple - small diameter (5mm); ciency and chronic drying of the ocular sur- accepted as the ‘gold standard’ when cone lies in the lower nasal quadrant with- face can exhibit changes similar to those assessing the thickness of the cornea.59 But in a few millimetres of the visual axis seen in keratoconus; that is, inferior corneal it has the disadvantage of involving the use • Oval - larger (>5mm); lies more steepening and high astigmatism. of a local anaesthetic and contact with the commonly in the infero-temporal quadrant. In the basic Orbscan height maps, a mean cornea. It can also be difficult to locate the • Globus - largest diameter radius of curvature of the corneal surface exact point on the cornea accurately when (>6mm); 75% of the cornea is effected. (best fitting sphere, BFS) is calculated and a serial examinations are required.60 Optical relative height above or below this ideal pachymetry obviates direct contact, but this Spectacles best-fitting spherical surface is shown. method has been shown to be less accu- Mild keratoconus can be corrected with Hence, the curvature of the cornea at any rate, with a 10-100µm non-linear error.61 spectacles. Retinoscopy is difficult; a normal point is not shown. Warm colours show Table 3 summarises ultrasonic and subjective refraction is required. Monocular areas which are higher than the BFS and Orbscan measurements of corneal thickness keratoconus is usually best dealt with using cooler colours which are lower than the in normals and keratoconic patients from a spectacle correction. In this group of BFS. The most appropriate colour-coded study carried out at the Birmingham and patients, motivation for contact lens wear scale for anterior and posterior maps of the Midland Eye Centre. tends to be poor. Orbscan system was proposed to be the 10µm and 20µm interval scale.57 It has been Management of keratoconus Contact lens options for suggested that an Orbscan map be classi- Management of keratoconus varies keratoconus fied as abnormal if three or more colours are considerably, depending on the contact lens When a keratoconic patient is no longer found within the central 3mm area. service available to deal with moderate to able to obtain good visual acuity as a result Figure 3 shows an Orbscan map of a ker- advanced cases. In terms of the techniques of increasing levels of irregular astigmatism atoconic eye. The maps shown are (top left) used for fitting keratoconic patients, no and higher-order aberrations, rigid contact departures of anterior surface from best single method or philosophy is best for all lenses will be required, effectively to provide sphere (top right) departure of posterior sur- patients. There are no fixed rules for fitting a new anterior surface to the eye.63 face from best fit sphere (bottom left) ker- keratoconus. A variation also exists in the Contact lenses are considered when atometry map (bottom right) pachymetry design and types of lenses preferred by the vision is not correctible to 6/9 by spectacles map. The scale is located in the left hand major Hospital Eye Service (HES) referral and patients become symptomatic.

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Rigid gas permeable lens designs

There are numerous different designs avail- able. A list follows of some of the designs commonly used by the author and col- leagues.

Different types of RGP lens designs

Early keratoconus Aspherics or multicurve lenses Kera I and II (No.7) Acuity K Rose K (David Thomas) Figure 5. Steep fitting: this method may work for very small cones but is unsuitable Moderate keratoconus for large, oval, sagging cones Figure 6. Flat fitting lens Kera II Quasar KNO7 There are many lens designs for periphery is quite acceptable. Adequate Rose K (David Thomas) keratoconus and it is difficult to predict edge clearance is required to ensure tear Woodward KC3 which design will be suitable for any exchange. particular patient. Three-point-touch actually refers to the Moderate/Advanced keratoconus Rigid gas permeable lenses area of apical central contact and two other Kera II/III Rigid gas permeable (RGP) corneal lenses areas of bearing or contact at the Rose K (David Thomas) are the lenses of first choice for correcting mid-periphery in the horizontal direction. Profile K (J Allen) the irregular astigmatism which occurs as This type of fitting philosophy works very the cornea changes shape. The aim is to well for small central cones. Advanced keratoconus provide the best vision possible with the Large diameter lenses maximum comfort so that the lenses can be 2) Apical clearance S-Lim (J Allen) worn for a long period of time. A mid to In this type of fitting technique, the lens Dyna-intra limbal (No.7) high Dk/t material is preferred by the author vaults the cone and clears the central as it provides the stability required for these cornea, resting on the paracentral cornea. Scleral lenses high powered lenses. A balance is required This type of lens was suggested as it was PMMA between a material which is deposit resist- argued that apical clearance would min- Gas permeable (Innovative Sclerals) ant especially in patients who maybe atopic, imise trauma to the central cornea. These and providing sufficient oxygen flux. lenses tend to be small in diameter and Aspheric lenses Keratoconic patients tend to have long have small optic zones; the small BOZD can Aspheric lenses flatten in curvature from wearing times and usually become long- result in glare problems. The potential the centre to the periphery. The term lens wearers. In some cases it may advantages of reducing central corneal eccentricity or ‘e value’ is independent of become necessary for the contact lens prac- scarring are outweighed by the disadvan- the base curve and determines the rate of titioner to try several different materials for tages of poor tear film, corneal oedema, flattening. Spherical lenses, on the other a patient who has poor wettability. and poor visual acuity as a result of bubbles hand, have a constant radius of curvature in becoming trapped under the lens. the optic zone and different curvatures cut Fitting into the lens in the peripheral areas. methods/philosophies 3) Flat fitting The average cornea has an ‘e value’ of 1) Three-point-touch design The flat fitting method places almost the 0.65. Decreasing the lens ‘e value’ decreas- The three-point-touch design is the most entire weight of the lens on the cone. The es the rate of flattening; increasing the ‘e popular and the most widely fitted design lens tends to be held in position by the top value’ increases the rate of flattening. The for keratoconic patients. The aim is to dis- lid. Good visual acuity is obtained as a aim of aspheric lens fit should be good tribute the weight of the contact lens as result of apical touch. Wide edge stand-off centration, central alignment or slight evenly as possible between the cone and cannot usually be eliminated. Alignment central bearing, good movement (1mm), the peripheral cornea. The ideal fit should can be obtained in early keratoconus; how- and peripheral clearance (0.5mm). Useful show an apical contact area of 2-3mm with ever, flat fitting lenses can lead to progres- for oval type cones are aspheric lenses, for mid-peripheral contact annulus. The area sion/ acceleration of apical changes example the Quasar K (No.7 Contact Lens and shape of the contact zones may be and corneal abrasions. This type of fitting Laboratory) or the Persecon Elliptical K more variable as a result of cone philosophy is useful where the apex of the (Ciba Vision) older design. asymmetry; a crescent shaped mid- cone is displaced.

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M ulticurve designs limited role in correcting corneal irregularity, difficult long-term. Ideally, try to have the All lens parameters are available from the as they tend to drape over the surface of the patient use the same care regime for the manufacturers which make these lenses cornea and result in poor visual acuity. two lenses as this will make cleaning easier, easy to fit. The Woodward C3K is a special- However, soft lenses designed specifically or alternatively consider a disposable soft ist design which can be used for moderate for keratoconus (eg Kerasoft) have a useful lens. The cornea should be observed care- to advanced keratoconus. role in early keratoconus or where a patient fully for dryness and neovascularisation. may be intolerant of RGP. Soft lenses tend to M aguire lens system be more comfortable compared with RGPs. Hybrid lens system This lens system is based on the Soper lens For example, Kerasoft Lenses (Ultravision) The Softperm lens (Ciba Vision) is a hybrid system, which is no longer used in the UK. (58% water content terpolymer), which are lens with a RGP centre surrounded by a soft The McGuire system was first introduced in available in four series, A,B,C and D, and hydrophilic skirt. These lenses tend to be 1978 and consists of three diagnostic lens Acuity K Mark I and II (Acuity Contact used in cases of RGP lens intolerance. There sets, nipple, oval or globus (see cone classi- Lenses). are many advantages to the Softperm lens fication). The optic zone sizes vary from Advantages as it provides better comfort than the RGP 6mm for the nipple cone to 6.5mm for the lenses, better centration and reasonable oval cone, and 7mm for the Globus. The 1) They afford higher levels of comfort visual acuity. In the HES, these lenses tend McGuire system has four peripheral curves; and longer wearing times, especially in to be used only in exceptional cases because the secondary curve of the system is 0.5mm patients intolerant of RGP corneal lenses or of the risk of induced corneal oedema and flatter than the central base curve. The third in monocular keratoconus. neovascularisation. curve is 1mm flatter than the secondary 2) They are useful where the cone apex The main disadvantages of Softperm lens- curve. The fourth and final peripheral may be displaced, especially if it is very low. es are frequent breakage of the lens, giant curve is 2mm flatter than the third curve. 3) They are useful for certain groups of papillary and peripheral patients, for example airline pilots. corneal neovascularisation. Rose K 4) They are relatively simple to fit. It should be noted that the Softperm lens The Rose K is a unique keratoconus lens Disadvantages was not designed for keratoconus, but for a design with complex computer-generated normal cornea. As it provides the comfort of peripheral curves based on data collected 1) Visual acuity may be variable in cases of a soft lens and visual acuity of a rigid lens it by Dr Paul Rose of Hamilton, New Zealand. very high minus lenses. has been adopted by keratoconic patients The system (26 lens set) incorporates a 2) Low-powered diagnostic lenses may who inevitably over-wear these lenses and triple peripheral curve system - standard, not provide an accurate guide to the fit of end up with complications. flat, steep - in order to order to achieve the the final lens, which may be extremely high ideal edge lift of 0.8mm. powered. Scleral lenses The design starts with a standard 8.7mm 3) There may be reduced oxygen Scleral lenses play a very significant role in diameter and works by decreasing the optic transmissibility and the risk of cases of advanced keratoconus where zone diameter as the base curve gets steep- neovascularisation if the lenses are over- corneal lenses do not work and corneal er. It is available in base curves of 4.75- worn. is contra-indicated. Scleral lenses 8.mm and diameters of 7.9-10.2mm. Toric 4) If the condition has progressed, it may completely neutralise any corneal curves are available on the front and back be difficult to change to RGP’s at a later irregularity and can help patients maintain a surfaces as well as in the periphery. The stage. normal quality of life. A PMMA lens can be practitioner has a choice of peripheral used in cases of scleral toricity. curves. Piggyback lenses PMMA scleral lenses are made by the Standard lift lenses should work 70% of Piggyback lenses are used for difficult cases, impression method. This practice is confined the time. Peripheral curves can be for instance in cases of RGP lens to the HES. An impression is taken of the configured to a toric design. Rose K lenses intolerance, proud nebulae in keratoconus, cornea, generally with alginate material are very widely used. or apical dimpling or where there are areas (orthoprint) and a clear shell is made from of recurrent epithelial erosion. The system poly-methyl methacrylate material. Optic Dyna IntraLimbal (DIL), No.7 Contact consists of a rigid lens fitted on top of a soft curves are ground on to the shell. This can Lens Laboratory lens. The aim is to maintain the same level be done in-house or the shell can be sent to These lenses are useful when stability is of visual acuity as with a single lens. Cantor & Nissel. The shell is fenestrated, required, especially in inferiorly displaced The RGP lens should be fitted first. Good adjusted, and ground until a desirable fit is cones or in cases of pellucid marginal centration is important and a slightly larger obtained. Once an acceptable fit is obtained degeneration as well as post graft. A range area of apical touch is usually acceptable as the lens can be sent for working to the of diameters is available (10.8mm to the RGP lens will be cushioned by a soft required power. 12.5mm). High Dk materials are lens. A silicone hydrogel soft lens should be Advantages recommended. used where possible, with good movement Easy to insert and remove and coverage/ centration as in a normal soft Any type of corneal irregularity is corrected Soft lenses lens fitting. Easy to store (dry) These (hydrogels, silicone hydrogels) have a Caring for the two types of lenses can be Long life

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Disadvantages Normal lens (Figure 7) fit versus kerato- Much chair time is needed conic fit. (Figures 8) A very specialised fitting technique Normal fit RGP sclerals Ken Pullum (Innovative Sclerals) confirms Good centration that these lenses are fitted from a Alignment/ slight pool on alignment preformed design and lathe cut. These 0.75 mm movement lenses are filled with saline and inserted. The aim is to obtain overall central clear- Keratoconic fit ance. These lenses have many applications. A whole range of acceptable fits. It may not Lens costs/prices be ossible to obtain the ideal fit Prices of lenses vary significantly depending Figure 7. Normal fit Ensure the cornea is observed carefully on the design and material. Lens manufac- turers who offer exchange and three month Cleaning regime warranty terms tend to charge a slightly higher price per lens. Practitioners would be Soft and corneal lenses for keratonic well advised to invest time in making a patients do not require specialised regimes. “ price list” before undertaking case work. Patients who suffer from GPC associated with keratoconus may need to use unpre- Preliminary examination served solutions. Other eyedrops may be Many patients with keratoconus will be in necessary. their late teens or early twenties. They will RGP sclerals require a special cleaning need information and reassurance. They protocol, which will be covered in a future may present with concerns about the speed series. with which their vision has deteriorated. Quite often teenagers may be accompanied Figure 8. Keratoconic fit Conclusions by their parents. • Patients with keratoconus are a chal- • It is important to explain the rea- 4) Choose the correct base curve; start lenge son why the spectacle prescription has been with the base curve equivalent to the steep- • Keratoconic patients require ongoing changing rapidly over the past 12-24 er of the two keratometer readings. Many care months. variations on this philosophy exist. • A wide range of contact lens designs • The nature of the corneal thinning 5) Allow the lens to settle for about 20 and materials is available disorder and the reasons for corneal minutes before evaluating the fluorescein • Excellent technical support is usually distortion should be explained. The advan- pattern. available tages of contact lenses over spectacles 6) Examine the central area, the mid • Keratoconics can live a normal life with should be emphasised. peripheral area and the periphery. the help of a good contact lens practitioner • The progression of the condition 7) Evaluate the lens in the central and the prognosis should be discussed. position. Once you have judged the fit, alter Acknow ledgments and disclaimer • An information leaflet explaining the fit as necessary (for example flatten, if The author does not have any personal the condition, and information about the pooling) until you obtain gentle apical touch interest in any of the products mentioned. local keratoconus support group, should be and the three-point-touch. Use the Guillon I would like to express very sincere thanks provided. grading scale for assessing the fluorescein to Dr Sudi Patel for interesting discussions in • Any cost implications should be picture. relation to this article. Also many sincere discussed. There should be minimal bearing (touch) thanks to Professor Neil Charman for at the apex of the cone, as well as an area supervising me through the fascinating Fitting protocol of bearing between the periphery of the journey of studying keratoconus. 1) After taking full history and symptoms, lens and the intermediate zone of the The author would like to acknowledge all the preliminary examination should include cornea (Figure 4). her colleagues at the Birmingham & age, occupation, and motivation. The lens should be ordered in mid-high Midland Eye Centre, and all the contact lens Any history of previous contact lens Dk material after an over-refraction has manufacturers/suppliers who agreed to intolerance or allergies should be noted. been undertaken. allow discussion of their lenses, especially 2) Full slit lamp biomicroscopy is vital. A collection appointment should be the information provided by technical 3) Examine the keratometer readings. The arranged. An aftercare appointment should advisors. mires may be very distorted, however they follow four weeks after the collection provide useful information at the initial appointment, when slight modifications References stage. may be necessary. Visit www.optometry.co.uk/references

33 | August 18 | 2006 OT CONTINUING EDUCATION AND TRAINING Gain 2 CET credits – enter online at www.otcet.co.uk or by post

M odule quest ions Course code: c-4088 Please note, there is only one correct answer. Enter online or by form provided. 1. Which of the following statements is true? c. The three-point touch method should show an apical contact area of a. The incidence of keratoconus has been documented to be higher in 2-3mm the Asian subcontinent. d. All of the above b. The incidence of keratoconus has been documented to be higher in the Mediterranean and Middle Eastern countries. 8. Which of the following statements is true? c. The incidence of keratoconus has been documented to be lowest in a. Apical clearance is a fitting method in which the lens rests on the European countries. paracentral cornea d. The incidence of keratoconus has been documented to be higher in b. Apical clearance is a fitting method in which there is a central contact Japan, Taiwan and Singapore. area of 2-3mm c. Apical clearance fitting method is suitable for large, oval sagging 2. Which of the following statements is true? cones a. Vogt’s striae are fine vertical lines which occur in the stroma and d. The advantages of the apical clearance method outweigh the Descemet’s layer and do not disappear transiently on digital disadvantages pressure? b. Vogt’s striae are fine vertical lines, which occur in the endothelial 9. Which of the following statements is false? layer and disappear transiently on digital pressure? a. Flat fitting lenses can lead to progression of apical changes c. Vogt’s striae are fine vertical lines which occur in the stroma and b. Multicurve lens designs such as the Woodward design are suitable for Descemet’s layer and disappear transiently on digital pressure? moderate to advanced keratoconus. d. Vogt’s striae are fine vertical lines, which occur in the endothelial c. DIL lenses are only useful for pellucid marginal degeneration and post layer and disappear transiently on digital pressure? graft eyes. d. The McGuire lens is a modification of the Soper lens system. 3. Which of the following statements is true? a. Corneal hydrops is believed to occur either spontaneously or as a 10. Which of the statements is false? result of contact lens over-wear in 2-3% of keratoconic patients a. Softperm lenses were specially designed for keratoconus. b. Corneal hydrops usually resolves to leave a clear cornea b. Neovascularisation is a common complication of Softperm hybrid lens- c. Corneal hydrops is believed to occur either spontaneously or as a es result of ocular trauma e.g. eye rubbing in 2-3% of patients? c. The Rose K lens design incorporates three peripheral systems, d. Corneal hydrops is a sign of early keratoconus? standard, flat and steep d. Kerasoft and Acuity M ark II are specially designed soft lenses for kera- 4. Which of the following statements is correct? toconus a. Corneal topography in keratoconus tends to produce central corneal steepening only 11. Which of the following statements is true? b. Nasal corneal steepening only? a. PMMA scleral lenses allow any kind of corneal irregularity to be c. Inferior corneal steepening and high astigmatism? corrected d. None of the above? b. PMMA scleral lenses are difficult to insert and remove c. RGP scleral lenses are only useful for keratoconus 5. Which of the following statements is true? d. Softperm lenses have a long life span a. RGP corneal lenses are the lenses of first choice for fitting Keratoconus 12. Which of the following statements is true? b. Keratoconic patients should be corrected with spectacles in the early a. Apical staining can result from a flat fitting lens stages b. To reduce a tight mid-periphery, decrease the optic zone diameter, c. Up to 15% of keratoconics have been reported to be monocular flatten the secondary or peripheral curves d. All of the above c. Dimple veiling is a result of multiple tiny bubbles creeping under the lens 6. Which of the following statements is true? d. All of the above a. The nipple cones usually affects 75% of the cornea b. Posterior keratoconus is a common form of keratoconus c. Keratometry readings are usually more than 6.5mm in advanced keratoconus? d. The oval cone lies more commonly in the inferotemporal quadrant? An answer return form is included in this issue. 7. Which of the following statements is true? It should be completed and returned to: a. The three- point touch fitting method aims to distribute the weight CET initiatives (c-4087), OT, McMillan Scott, 9 Savoy Street, London, WC2E 7HR of the lens evenly between the cone and the peripheral cornea GU51 4DA by September 20 2006. Under no circumstances will forms received b. The three-point touch philosophy works very well for small central after this date be marked – the answers to the module will have been published cones in our September 22 2006 issue.

CET answ ers Course code: c-4087 These are the correct answers to Module 5 Part 1, which appeared in our July 14, 2006 issue. 1. Correct answer is B The promotion of 4. Correct answer is D 9. Correct answer is A The first choice pervaporation through a hydrogel lens is not A lens which causes pervaporation has not been therapeutic lens for superior limbic is a thought to contribute towards the therapeutic proposed in selecting a lens for an eye with a 20.0 mmhydrogel lens. action of a lens. corneal laceration and flat anterior chamber. 10. Correct answer is A 2. Correct answer is D The ideal therapeutic 5. Correct answer is C A scleral lens is not used The first choice contact lens for pain relief in lens for recurrent erosion syndrome has high to prevent symblepharon from ocular pemphigoid. filimentary keratitis is currently Hydrogel lens. oxygen permeabilityLow modulus of elasticity, 6. Correct answer is C A silicone hydrogel with a 11. Correct answer is A A Hydrogel lens is least low coefficient of resistance. low modulus of elasticity is the lens of first choice likely to be selected in trichiasis from the four 3. Correct answer is A It is true that when to help reform a collapsed anterior chamber lenses shown. selecting a therapeutic lens for a persistent following radial keratotomy. 12. Correct answer is B A lens with the diame- epithelial defect that silicone hydrogel lenses 7. Correct answer is D A Scleral lens is most like ter of 12mm to 14mm is not typically selected should be the first choice. ly to offer protection from severe entropian. for cases with a leaking trabeculectomy. 8. Correct answer is D The first choice for correcting a is a Scleral lens.

34| August 18 | 2006 OT