Effect of pterygium on contrast sensitivity.

The purpose of this study is to evaluate the effect of pterygium on contrast sensitivity. Thirty-six eyes with pterygium and 18 eyes without pterygium were included in the study. The size of the pterygium was measured on the slit lamp both vertically at the limbus and categorized into three groups (≤3, 3.1 to ≤5, >5 mm), and horizontally on the cornea and categorized into two groups (0.5 to ≤2, >2 mm), and the area calculated by multiplying the two measurements was then categorized into three groups (≤7, 7.1 to ≤14, >14 mm(2)). Contrast sensitivity was measured using CSV-1000E charts (Vector Vision) at 3, 6, 12 and 18 cycles per degree under photopic and mesopic conditions. The mean vertical length of pterygium was 4.41 ± 1.12 mm, mean horizontal width was 2.09 ± 0.68 mm and mean area was 9.7 ± 5.01 mm(2). Significant differences in both photopic and mesopic contrast sensitivities at all frequencies were noted between normal eyes and vertical length of pterygium >3 mm, horizontal width ≥0.5 mm and area >7 mm(2). Contrast sensitivity had significant negative correlation with all three parameters. Pterygium with vertical length >3 mm, horizontal width ≥0.5 mm and area >7 mm(2) caused a significant decrease in both photopic and mesopic contrast sensitivity at all spatial frequencies. Contrast sensitivity had significant negative correlation with all three parameters.