Corneal topography patterns in healthy volunteers from the North-West of Pakistan

Salim Khan

Purpose:
To determine the proportion of normal and abnormal corneal topography patterns in healthy volunteers using computer-assisted videokeratography.

Methods:
We evaluated the topography patterns of 91 subjects using the SHIN-NIPPON CT-1000. Sample size was calculated using Epi info 6 (Expected frequency of abnormal patterns is 39% with precision of 1- and confidence interval 95%.). Males and females between 18 to 60 years of age were recruited. Topography maps obtained were placed into one of five specific categories based on defined criteria. The normal patterns include round, oval and symmetric bow-tie. Abnormal patterns are asymmetric bow-tie and irregular.

Results:
Asymmetric bow-tie (55.5%) was the most common topography pattern in our study. This was followed by irregular (22.5%), symmetric bow tie (13.1%), round (5.5%) and oval (3.3%) patterns. Abnormal patterns were seen in 78% of the topography maps. Eighty percent of male and 75% of female subjects showed abnormal topography patterns. In subjects under 30yrs of age, 79 of 118 eyes showed asymmetric bow-tie patterns.

Conclusions:
The provided data can help in understanding the spectrum of corneal topography present in the local population. Abnormal topography patterns were surprisingly frequent in this study. In young adults, the asymmetric bow-tie was the dominant pattern.
A normative database of corneal topography of the local population is needed. One that includes all age groups and backgrounds. It would serve as a reference for detecting early corneal disease. Planning of keratorefractive surgeries and topography-guided ablation is based on this data.