Relationship between topographic patterns and corneal astigmatism in Korean adults

The anterior corneal surface is one of the most important elements determining the optical performance of the eye. Corneal topography provides quantitative data about the anterior corneal surface. We studied the corneal topography of 200 normal corneas in 110 adult subjects. All of the eyes were examined using the Corneal Analysis System (EyeSys 2000, Houston, Texas). The topographic maps were grouped into the following patterns: round, oval, symmetric bow tie, asymmetric bow tie, and irregular. The symmetric and asymmetric bow tie patterns were the most common topographic pattern (33.0%, and 32.5%, respectively) in our study population, followed by oval (14.5%), irregular (12.5%), and round (7.5%) patterns. The mean corneal astigmatism calculated from videokeratographic data was 0.32 D for round, 0.63 D for oval, 1.16 D for symmetric bow tie, 1.21 D for asymmetric bow tie, and 0.43 D for irregular patterns. There were significant differences among the corneal astigmatic values in the topographic patterns (p < 0.01, Gabriel post hoc test). The distributions of symmetric and asymmetric bow tie patterns were skewed toward greater amounts of corneal astigmatism. In conclusion, the results of this study demonstrate the relationship between topographic patterns and corneal astigmatism and should provide one possible normal standard for corneal topography in Korean adults.