Prediction of letter contrat enitivity uing videokeratographic indice

PURPOE: To analyze the relationhip between corneal topography and letter contrat enitivity. METHOD: Experiment were conducted on 59 eye of 51 patient who had bet pectacle-corrected viual acuity of 20/20 or better and no ocular pathology except for the corneal hape. Thirty-nine eye had an abnormal topographic pattern reulting from keratoconu, and the other 20 eye howed a normal topographic pattern. Videokeratography wa performed with the TM-2 videokeratocope, and the urface regularity index, urface aymmetry index, and coefficient of variation of power were obtained for each ubject. Letter contrat enitivity wa meaured with the CV-1000LV with pectacle correction. The correlation between the number of correct letter and topographic indice wa calculated. REULT: The abnormal topography group had a ignificantly greater lo of letter contrat enitivity (median = 20 letter) than the normal control (median = 23 letter; P = .0001). There were tatitically ignificant correlation between number of correct letter and the coefficient of variation of power (r = −.77; P = .001), number of correct letter and urface regularity index (r = −.76, P = .001), and the number of correct letter and urface aymmetry index (r = −.64; P = .001). The linear regreion equation between number of correct letter and the coefficient of variation of power wa the number of correct letter = −0.05 × the coefficient of variation of power + 23.2. CONCLUION: Our reult ugget that ubtle viual deterioration, which are barely detected by contrat enitivity teting, can be predicted objectively by the corneal topographic indice