SIMULTANEOUS OR SEQUENTIAL SURGERY in EYES with PTERYGIUM? the Sequence Depends on the Size and Location of the Growth

Home , Pterygium (conjunctiva)

COVER FOCUS Decisions, Decisions: SIMULTANEOUS OR SEQUENTIAL SURGERY IN EYES WITH PTERYGIUM? The sequence depends on the size and location of the growth.

BY SUDEEP DAS, MBBS, DO, DNB; AND NIKHIL NEGALUR, MBBS, MS

Pterygium is a triangular vas- which affects the outcome following cataract surgery.6 Hence, cularized fibroelastic growth pterygia that interfere with keratometry (K) readings should be arising from the limbic con- removed before proceeding with cataract surgery. junctiva that extends over the In eyes with pterygia, corneal topography is more valuable cornea, replacing the epithe- than keratometry because it provides a more detailed picture lium and Bowman membrane. of the refractive status of the cornea, detecting curvature A systematic review and meta- changes that induce astigmatism. Large, fleshy pterygia that are analysis of population-based vascularized and inflamed change the shape of the cornea. studies estimated the prevalence of pterygium to be around By contrast, small pterygia that have not changed the corneal 10.2% (range 6.3%–16.1%).1 The incidence increases with age curvature (Figure 1) are best left alone. In these eyes, cataract sur- and geographic latitude. Similarly, cataract is a common age- gery can be done first, with pterygium excision planned later for related condition; it is estimated that more than 100 million eyes refractive correction or cosmesis. Generally, only pterygia that are have a visual acuity of less than 6/60 due to cataract and that more than 3 mm in size cause topographical distortion (Figure 2). perhaps three to four times that number of eyes have a visual Postoperative refractive surprises are prevented by ensuring acuity of less than 6/18 due to cataract.2 accurate and stable keratometry. The K values used for IOL Pterygium has a causal relationship with exposure to UV-B power calculation will not remain the same following excision radiation,3,4 and there is a high incidence of cataract in tropical of visually significant pterygia. Thus, when pterygium excision countries such as India.5 With the incidence of both conditions is combined with cataract surgery or performed after cataract so high in tropical countries, it is no wonder that many patients surgery, the altered K values cause a refractive surprise. develop cataract and pterygium concomitantly. The question The corneal astigmatism induced by pterygium is often arises as to whether surgery for these concomitant conditions reversible on excision, unless it has caused corneal scarring, as is should be performed simultaneously or sequentially. seen in atrophic ones of long standing. Large pterygia covering (Continued on page 59) SURGICAL SEQUENCE The case for simultaneous surgery. The susceptible population in tropical areas consists largely of daily wage earners AT A GLANCE without access to insurance, and loss of days of work on account of surgery amounts to loss of income. The propo- • For small pterygia, simultaneous surgery may not make nents of simultaneous surgery argue that a single procedure a difference in the outcome; for larger, visually significant results in reduced hospitalization, costs, morbidity, and loss of ones, however, sequential surgery can add significant workdays compared with two procedures. For small pterygia, morbidity and recovery time. simultaneous surgery may not make a difference in the out- • Pterygia that interfere with K readings and those that come; for larger, visually significant ones, however, sequential cover the visual axis should be removed before proceeding surgery can add significant morbidity and recovery time. with cataract surgery. Further, as a rule, any pterygium of The case for sequential surgery. (See Three Cases for 3 mm or greater should be excised before cataract surgery. Sequential Surgery.) Large pterygia induce refractive astigmatism,

MARCH 2015 | CATARACT & REFRACTIVE SURGERY TODAY EUROPE 57 THREE CASES OF SEQUENTIAL SURGERY A B COVER FOCUS COVER

Figure 1. Case No. 1: Slit-lamp photo of regressing pterygium (A). Topography on Pentacam (Oculus Optikgeräte) shows regular astigmatism not induced by the pterygium, which is causing only peripheral changes in the topography (B). This patient can undergo cataract surgery without any prior surgical intervention for the pterygium. A B

Figure 2. Case No. 2: Slit-lamp photo of a large, fleshy pterygium (A). Although it is difficult to detect the extension of the pterygium into the central cornea on the slit-lamp photo, the Pentacam shows irregular astigmatism of the central cornea induced by the pterygium (B). This patient would benefit from pterygium excision before cataract surgery. A B C

Figure 3. Case No. 3: Slit-lamp photos of an extensive pterygium covering the visual axis (A, B). Topography shows irregular mires and is not reliable (C). Topography is not required in this patient at this time, as pterygium excision is mandatory before cataract surgery.

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A B C D Figure 4. Online toric IOL calculators from Alcon (A), Abbott Medical Optics (B), and Carl Zeiss Meditec (C); Hoya Toric Calculator on the iTrace aberrometer (D).

(Continued from page 57) pterygia, the quadrant opposite the pterygium should be the site the visual axis (Figure 3) must be removed before the cataract of the phaco tunnel. Thus, a temporal approach is preferable in a surgery. It is impossible obtain a good corneal topography nasal pterygium, as this would place the wound the furthest away image before excision of these pterygia. from the site of the pterygium. In patients with corneal thinning Present-day pterygium surgery involves excision of the pte- and obvious flattening of the horizontal meridian, phacoemulsi- rygium followed by gluing of a conjunctival autograft over the fication can be performed through a superior tunnel to induce bare sclera. Mitomycin C 0.02% is reserved almost exclusively some flattening of the vertical meridian, negating to some extent for use with recurrent pterygia. Use of mitomycin C and glued the with-the-rule astigmatism. In patients who have previously conjunctival autografts may affect outcomes when cataract undergone removal of a two-headed pterygium, the only surgery is combined with pterygium excision. Thus, it may be approach for phacoemulsification would be superior or oblique. better to perform sequential surgery and allow corneal healing Visibility through a scarred cornea during cataract surgery is to complete before scheduling cataract surgery. poor. Staining the capsule with trypan blue dye can aid in visual- As a rule of thumb, any pterygium of 3 mm or greater izing the rhexis margin during surgery (eyetube.net/?v=ninif). should be excised before cataract surgery. Patients with irregular mires on keratometry or irregular central curvature or high IOL CHOICE corneal astigmatism on topography are candidates for primary The choice of IOL depends primarily on the presence or excision of the pterygium. Patients with small pterygia at the absence of corneal astigmatism. Keratometry or topography limbus with regular mires on keratometry, regular central cur- should be repeated 6 weeks after pterygium excision and vature on topography, and low or absent astigmatism can have preferably repeated 2 weeks later to determine whether the cataract surgery before pterygium excision. (Continued on page 66) Following pterygium excision, one should wait 6 to 8 weeks for corneal curvature to stabilize before assessing the patient for cataract surgery. Keratometry or topography should then be repeated 2 weeks later to ensure the stability of the cornea WATCH IT NOW before these measurements are used for biometry. Staining the capsule with trypan blue dye can aid in visualizing the capsulorrhexis margin during surgery. TECHNIQUE AFTER PTERYGIUM EXCISION Limbal stem cell deficiency has been implicated as a major cause of pterygium.7,8 Pterygium surgery itself may induce a further loss of stem cells.9 Hence, it is advisable to use a clear corneal cataract incision and opt for the smallest possible wound size, as with microcoaxial phacoemulsification. Any surgery that involves extensive dissection of the conjunctiva, such as extracapsular cataract extraction or manual small-incision cataract surgery, is best avoided in these patients. In patients with scarred conjunctiva following excision of large

MARCH 2015 | CATARACT & REFRACTIVE SURGERY TODAY EUROPE 59 (Continued from page 59) astigmatism is still changing. PTK can benefit patients with central superficial corneal opacities,10 and topography-guided PRK can help to regularize an irregular cornea.11 In patients without significant corneal astigmatism or demon- strable higher-order aberrations (HOAs), any IOL of one’s prefer- ence can be used. Patients who had large, scarred pterygia may be left with significant irregular astigmatism; toric IOLs are not of much use in these patients, but contact lenses may help to regularize the front refracting surface of the eye. Toric IOLs can be used for regular corneal astigmatism of more than 1.00 D. Online toric IOL calculators (Figures 4A through 4C)

COVER FOCUS COVER or offline calculators using the built-in software in aberrometers such as the iTrace (Tracey Technologies; Figure 4D) can aid in choosing the appropriate toric IOL and the correct axis of place- ment. Unlike online calculators, software solutions allow a greater degree of manipulation of toric IOL models and can be used to check the effect on residual astigmatism. Multifocal IOLs are not a good option in patients with irregular astigmatism or high levels of HOAs or in any patient with high degrees of corneal aberration.

CONCLUSION Simultaneous pterygium and cataract surgery is necessary only in patients who cannot easily access eye care facilities. In all other cases, sequential surgery may be preferred. Pterygium surgery should be sequenced before cataract surgery when the pterygium is large enough to induce corneal curvature changes. This order will significantly reduce the incidence of refractive surprise after cataract surgery. Small pterygia near the limbus, especially those that are atrophic, can be left alone, and one can proceed with cataract surgery only. Topography may detect subclinical extensions of the pterygium into the center of the cornea. n

1. Liu L, Wu J, Geng J, Yuan Z, Huang D. Geographical prevalence and risk factors for pterygium: a systematic review and meta- analysis. BMJ Open. 2013;3(11):e003787. 2. Foster A. Vision 2020: The Cataract Challenge. Community Eye Health. 2000; 13(34):17-19. 3. Saw SM, Tan D. Pterygium: prevalence, demography and risk factors. Ophthalmic Epidemiol. 1999;6(3):219-228. 4. Threlfall TJ, English DR. Sun exposure and pterygium of the eye: a dose-response curve. Am J Ophthalmol. 1999;128(3):280-287. 5. Chatterjee A, Milton RC, Tyles S. Aetiology of senile cataract. Br J Ophthal. 1982;66:35. 6. Maheshwari S. Effect of pterygium excision on pterygium induced astigmatism. Indian J Ophthalmol. 2003;51:187-188. 7. Kwok LS, Coroneo MT. A model for pterygium formation. Cornea. 1994;13(3):219-224. 8. Dushku N, Reid TW. Immunohistochemical evidence that human pterygia originate from an invasion of vimentin-expressing altered limbal epithelial basal cells. Curr Eye Res. 1994;13(7):473-481. 9. Sridhar MS, Vemuganti GK, Bansal AK, Rao GN. Impression cytology-proven corneal stem cell deficiency in patients after surgeries involving the limbus. Cornea. 2001;20(2):145-148. 10. Sher NA, Bowers RA, Zabel RW, et al. Clinical use of the 193-nm excimer laser in the treatment of corneal scars. Arch Ophthalmol. 1991;109(4):491-498.

Sudeep Das, MBBS, DO, DNB n Senior Consultant, Cataract and Refractive Surgery, Narayana Nethralaya, Rajajinagar, Bangalore, India n [email protected] n Financial disclosure: None

Nikhil Negalur, MBBS, MS n Fellow, Cataract and Refractive Surgery, Narayana Nethralaya, Rajajinagar, Bangalore, India n Financial disclosure: None

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