רגישות לניגודיות בחולי קרטוקונוס

Introduction:

Keratoconus (KC) is a corneal disease that may leads to severe visual impairments (Rabinowitz, 1998; Gomes al., 2015). Subjects with KC can have normal VA but suffer from poor quality of vision (Jinabhai, O'Donnell et al. 2012). The aim of this study was to examine how and if contrast sensitivity (CS) and crowding effect (CE) change in KC patients with relation to the progression stages of the disease using computerized tasks and compare these functions to normal healthy control.

Methods:

KC was diagnosed based on abnormal topography and at least on one clinical signs using standard clinical tests (Rabinowitz, 2008). KC severity was defined using Amsler-Krumeich classification (Alió & Shabayek, 2006). Visual functions were tested using psychophysical tests, i.e., CS (Polat, Sterkin et al., 2007) and CE (Bonneh, Sagi et al., 2004). We compared CS and CE in KC to controls using T test analysis and correlate KC severity to CS and CE using Pearson correlation.

Results:

9 KC subjects (7 eyes in stage 1, 2 eyes in stage 2, mean age of 23±3.84 years) and 9 healthy subjects (mean age of 26±0.70 years) have participated in the study. Significant difference was shown for KC compared to controls for Cyl (p=0.004), for the thinnest site of the cornea (p=0.014) and for CS (p=0.002, p=0.06, p=0.04 for 6, 9 and 12 cpd respectively). No difference was shown between KC and control eyes for CE (p=0.34). No correlation was found between KC severity and for thickness to CS and CE.

Conclusion:

KC subjects, in the early stage of the disease, show significant lower CS in all frequencies compared to healthy subjects, although no differences in CE and no correlation to severity have been found, maybe due to the similar stage of the disease in KC eyes.

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