Prediction of letter contrast sensitivity using videokeratographic indices

Am J Ophthalmol. 2000 Jun;129(6):759-63. doi: 10.1016/s0002-9394(00)00380-9.

Abstract

Purpose: To analyze the relationship between corneal topography and letter contrast sensitivity.

Method: Experiments were conducted on 59 eyes of 51 patients who had best spectacle-corrected visual acuity of 20/20 or better and no ocular pathology except for the corneal shape. Thirty-nine eyes had an abnormal topographic pattern resulting from keratoconus, and the other 20 eyes showed a normal topographic pattern. Videokeratography was performed with the TMS-2 videokeratoscope, and the surface regularity index, surface asymmetry index, and coefficient of variation of power were obtained for each subject. Letter contrast sensitivity was measured with the CSV-1000LV with spectacle correction. The correlation between the number of correct letters and topographic indices was calculated.

Results: The abnormal topography group had a significantly greater loss of letter contrast sensitivity (median = 20 letters) than the normal control (median = 23 letters; P =.0001). There were statistically significant correlations between number of correct letters and the coefficient of variation of power (r = -.77; P =. 001), number of correct letters and surface regularity index (r = -. 76, P =.001), and the number of correct letters and surface asymmetry index (r = -.64; P =.001). The linear regression equation between number of correct letters and the coefficient of variation of power was the number of correct letters = -0.05 x the coefficient of variation of power + 23.2.

Conclusions: Our results suggest that subtle visual deteriorations, which are barely detected by contrast sensitivity testing, can be predicted objectively by the corneal topographic indices.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Contrast Sensitivity / physiology*
  • Cornea / physiopathology*
  • Corneal Topography*
  • Eyeglasses
  • Female
  • Humans
  • Keratoconus / physiopathology*
  • Male
  • Vision Screening / instrumentation