The Impact of Pterygium Excision on Corneal Astigmatism Faisal Aziz Khan1, Shafaq Pervez Khan Niazi2 and Dilshad Alam Khan3

ORIGINAL ARTICLE

ABSTRACT Objective: To compare the corneal astigmatism before and after the excision of pterygium and also to determine the correlation of pterygium size with the postoperative corneal astigmatism. Study Design: Cross-sectional interventional study. Place and Duration of Study: Eye Department, Combined Military Hospital, Abbottabad, from May 2011 to March 2012. Methodology: Thirty patients underwent pterygium excision. Pre-operatively Snellen visual acuity, manifest refraction and slit lamp examination was done. The size of the pterygium was recorded in mm by projecting a horizontal slit lamp beam from the limbus to the apex. All the pterygium were equal to or greater than 2.5 mm. Keratometry was performed with an automated keratometer. Keratometric data was recorded pre-operatively and at 28 days postoperatively. Wilcoxon signed rank test was used for comparing the pre-operative and the postoperative corneal astigmatism. Spearman's rank order was calculated to observe correlation of pterygium size with the postoperative astigmatism. Results: The median (mean rank) pre-operative astigmatism of 2.25 (15.50) reduced to a median (mean rank) postoperative astigmatism of 1.30 (14.96). This decrease in the postoperative astigmatism was statistically significant (p < 0.001). There was a statistically non-significant correlation between the postoperative astigmatism and the pterygium

size (rs = -0.29, p = 0.12). Conclusion: Pterygium excision caused significant reduction in corneal astigmatism.

Key Words: Corneal astigmatism. Corneal topography. Pterygium. Pterygium surgery.

INTRODUCTION change in pterygium induced astigmatism following Pterygium is a fibroelastic degeneration of the conjunc- pterygium excision and also to determine the relation- tiva with encroachment onto the cornea.1 Pterygia cause ship between pterygium size and corneal astigmatism corneal distortion and induce a significant amount of after it is removed from the corneal surface. astigmatism.2,3 This astigmatism may occur either due to pooling of tears in advance of the pterygium or by METHODOLOGY traction generated by the pterygium mechanically pulling This interventional study was conducted at the Eye on and distorting the cornea, or both.4 Department of Combined Military Hospital, Abbottabad. The effect of pterygium on the corneal refractive status Thirty eyes of 30 patients were selected for the study. has been measured by refraction, keratometry and The duration of study extended from May 2009 to March corneal topography.5-9 Recently, computerized video 2010. Patients aged 25 - 65 years with nasal primary keratoscopy has been used extensively to study the pterygium and a length of 2.5 mm or more were included effect of the size of pterygium and its excision on corneal in the study. The exclusion criteria were pseudop- topography which includes the corneal spherical power, terygium, recurrent pterygium, corneal scarring from any and astigmatism during the early and late postoperative cause and any previous ocular surgery. The study was period.10,11 approved by the institutional Ethical Committee. In Pakistan, the automated keratometer is still the most A written informed consent was obtained from all the widely available tool for decision-making in pterygium patients. After obtaining ocular and systemic history, surgery. The aim of this study was to use keratometric ocular examination was done which included Snellen readings of the automated keratometer to determine the visual acuity, manifest refraction and slit lamp anterior segment examination. The size of the pterygium was 1 Department of Ophthalmology, Combined Military Hospital, measured using the Haag Streit slit lamp biomicroscope Sargodha. by projecting a horizontal slit beam from the limbus to 2 Department of Ophthalmology, Rai Medical College, the apex of the pterygium and recording the length in Sargodha. millimeters. An automated keratometry was performed 3 Department of Ophthalmology, Combined Military Hospital, with Canon Auto-Refractokeratometer. Abbottabad. All surgeries were performed by the same surgeon and Correspondence: Dr. Faisal Aziz Khan, Department of a free conjunctival autograft was sutured in all cases. Ophthalmology, Combined Military Hospital, Sargodha. The surgery was performed under topical anaesthesia E-mail: [email protected] using proparacaine and local infiltration of 0.1% Received: February 20, 2013; Accepted: February 14, 2014. lignocaine HCl with 1:100000 adrenaline into the body of

404 Journal of the College of Physicians and Surgeons Pakistan 2014, Vol. 24 (6): 404-407 Corneal astigmatism after pterygium excision the pterygium. A drop of 10% phenylephrine was instilled Table I: Comparison of keratometric astigmatism before and after for hemostasis.The pterygium head was dissected from pterygium excision (n=30). its corneal edge using no.15 Bard Parker blade till the Keratometric Before excision After excision p-value limbus.The pterygium was separated with blunt astigmatism(Diopter) (n=30) (n=30) dissection from the underlying sclera till the insertion of Median (mean rank) 2.25 (15.50) 1.30 (14.96) < 0.001 the medial rectus muscle and also separated from the overlying bulbar conjunctiva. Then the pterygium was Table II: Correlation between postoperative astigmatism and pterygium excised alongwith its accompanying tenon's fascia. The size (n=30). bare scleral defect was measured with calipers and a Pterygium size Postoperative astigmatism rs p-value free limbal conjunctival graft was harvested from the (mm) (Diopter) 3.05 ± 0.11 1.30 ± 0.22 -0.29 0.12 superotemporal conjunctiva of the same eye and sutured into the receptor bed with approx. eight conjunctival (graft)-episcleral-conjunctival 7 - 0 vicryl DISCUSSION interrupted sutures. The conjunctival graft was placed Pterygium is a worldwide disease which is particularly 2 mm from the limbus with care taken to maintain the common in tropical and sub-tropical regions such as limbal orientation of the graft towards the cornea and Pakistan.12 Through its astigmatic impact it is often the also not to turn the epithelial side down. A tobramycin / cause of several subjective visual complaints, which dexamethasone ointment was applied and the eye was include decreased visual acuity or visual aberrations padded. The eye pad was removed on the first such as glare or diplopia.13 postoperative day and tobramycin/dexamethasone eye In Pakistan, the automated keratometer is readily drops three times daily were prescribed for 04 weeks. All available to the Ophthalmologist as compared to the the patients were followed-up on day 6,15 and 28 and other instruments. Its utility in analyzing the astigmatic then monthly for 6 months. Keratometric data was effects of pterygium and then deciding whether to excise obtained on day 15 and 28 with the same automated it or not is very convenient. At the national level, keratometer used pre-operatively. Patients were although many similar studies have correlated the size followed up for 06 months postoperatively. of pterygium with the pre-operative astigmatism, but Statistical analysis was performed using Statistical none have attempted to determine the influence of Package for Social Sciences (SPSS) version 16.0 for pterygium size on postexcisional corneal astigmatism. windows. Descriptive statistics were used to describe the clinico-demographic data. Frequency and percent- The type of astigmatism that pterygium causes in the ages were calculated for qualitative variables. Median majority of cases is with the rule. This astigmatism and mean rank were used for numerical data. Wilcoxon occurs by mechanical pull which causes localized signed rank test was selected for comparing the pre- flattening of horizontal meridian of the cornea occurring 14 operative corneal astigmatism and the postoperative up to the leading apex of the pterygium. However, corneal astigmatism. Spearman's rank order was pterygium also induces against the rule and oblique 15 calculated to observe correlation of pterygium size with astigmatism. In this study, the majority of the patients the postoperative corneal astigmatism. Mean ± standard (76%) had with the rule astigmatism; 20% had oblique deviation was used for description of age statistics. astigmatism and 3.3% had against the rule astigmatism A p-value < 0.05 was considered statistically significant. which agrees with the published literature. Large pterygium is associated with a greater amount of RESULTS astigmatism. There is a statistical correlation between Average age of the patient was 43.43 ± 14.3 years and pterygium size and induced corneal astigmatism.13,16 male to female ratio was 3:1. Pterygium length ranged Among the three parameters which include length, width from 2.5 to 4.5 mm with a median of 3.05 ± 0.11 mm. and area of the pterygium, it is the length of pterygium The median (mean rank) pre-operative astigmatism was on the cornea and its total area that have the strongest 2.25 (15.50) which reduced to a median (mean rank) correlation with the induced astigmatism.15 postoperative astigmatism of 1.30 (14.96) as mentioned Various authors have reported variable amount of in Table I. This decrease in the postoperative astig- astigmatism by comparing the length of pterygium using matism was statistically significant (p < 0.001). corneal topography. Pterygium which are less than 2.5 Pre-operatively 23 (76%) patients had with the rule mm induce less astigmatism of 1.25 D compared to astigmatism, 6 (20%) had oblique astigmatism and 01 those greater than 2.5 mm which induce on average (3.3%) patient had against the rule astigmatism. 3.94 D of astigmatism.17 Hansen et al. reported that Pterygium size correlated negatively with the post- pterygium greater than 3.0 mm induced 1.97 D of 18 operative corneal astigmatism (rs = -0.29) but this was astigmatism versus 1.11 D in less than 3 mm. statistically non-significant (p = 0.12) as mentioned in Kampitak reported a 2 D or more of astigmatism with Table II. Only one patient (3.3%) out of 30 had length greater than 2.25 mm.19 Recently, Jaffar et al. recurrence of pterygium. found a strong correlation with a mean size of 2.84 ±

Journal of the College of Physicians and Surgeons Pakistan 2014, Vol. 24 (6): 404-407 405 Faisal Aziz Khan, Shafaq Pervez Khan Niazi and Dilshad Alam Khan

0.557 mm and inducing a 3.46 ± 1.441 D (p=0.01) of within the limits of surgery.19 Salih considered surgical astigmatism.13 On the contrary, Fong et al. results did intervention at 2.2 mm length.15 On the contrary, Oner not accord with other studies who found that pterygium et al. recommended that pterygia whose length exceeds had to be greater than 3.5 mm to induce 1 D of 3.0 mm or width exceeds 3.0 mm should be considered astigmatism.20 Based on the findings of the published within the limits of surgery.24 Based on the results of this literature, the authors operated upon only those pterygia study, it is suggested that if excision is to be decided whose length exceeded 2.5 mm. In this study, the only on the pterygium size than the length alone should median pterygium size was 3.05 mm which induced a not be the sole criteria. The width and total area of the median astigmatism of 2.25 D. pterygium should also be considered. 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