Analysis of Keratometric Readings and Astigmatism in Patients with Different Grades of Pterygium Attending Adult Eye Clinic at Muhimbili National Hospital

Abstract

Background: Pterygium is a worldwide disease affecting people of all races especially in tropical and sub-tropical areas. It has a direct effect on corneal curvature leading to visual impairment in the form of astigmatism especially in advanced grades. Surgical removal is the treatment of choice for a progressive pterygium. However, recurrence of pterygium after surgical removal discourages surgical intervention during early stages of the disease. Reports from literature show that encroachment of the cornea by a progressive pterygium causes astigmatism with resultant visual loss even before a pterygium obscures the visual axis. Furthermore, the grade of pterygium is related to keratometric readings and the amount of astigmatism. Knowing the grades of pterygium that are associated with changes in corneal dioptric power and astigmatism can emphasize the fact that astigmatism is an indication for surgical removal of a pterygium before visual impairment occurs. Objective: To determine and analyze the keratometric readings and astigmatism in different grades of pterygium Methodology: A hospital based cross-sectional descriptive study was conducted in adult eye clinic at Muhimbili National Hospital between June and December 2019. Consecutive sampling of 64 patients with pterygium was done. Recruited patients was underwent a short history and ophthalmological examination for assessment of the size of pterygium by using slit lamp bio microscopy. Auto refractometry and keratometry were performed. Ethical approval to conduct this study was obtained from the Research and Publication Committees of Muhimbili University of Health and Allied Sciences and the executive director of Muhimbili National Hospital. Data was analyzed with the help of the statistical package for social science software version 21. Results: 95 out of 1346 (7.06%) patients were diagnosed to have pterygium during the study period. 64 (124 eyes) patients were recruited. 34 (53%) were females. 48% were aged between 41 to 50 years with a mean age of 45.14+/- 9.93(SD) years. 34(27.4%) eyes had grade one, 41(33%) had grade two, 28(22.6%) eyes grade 3 and 21(17%) eyes with grade four pterygia. The mean keratometric reading for the vertical (K1) and horizontal meridian (K2) were 43.05D and 44.16D respectively. 79.5% eyes with grade 3 and 4 pterygia presented with astigmatism of more than 1D. The overall mean magnitude of astigmatism was 1.429DC +/- 0.6225SD. The keratometric readings and magnitude of astigmatism increased with increasing size of pterygium with a positive correlation of r=0.922 r=0.786 respectively. Conclusions and Recommendations Eyes with high grades of Pterygium and astigmatism of 1DC has a significant initial effect. It is highly recommended to do Keratometry and refraction for all patients with pterygium. Those patients found to have with the rule astigmatism of more than one diopter need be counseled for pterygium excision.