ניסוי פסיכופיזיקה בנבדקים עם קרטוקונוס

Introduction: Keratoconus (KC) is a corneal disease that may leads to severe visual impairments (Rabinowitz, 1998; Gomes al., 2015) including poor quality of vision (Jinabhai et al. 2012). This study measured contrast sensitivity (CS) and crowding effect (CE) in KC subjects and suspects (KCSus) versus normal matched controls (C) with relation to the progression stages of the disease using psychophysical-computerized tasks.
Methods: KC was diagnosed based on abnormal topography (Sirius) and at least one clinical signs (Rabinowitz, 2008). KCSus had typical topography pattern with no clinical signs. KC severity was defined using Amsler-Krumeich classification (Alió&Shabayek,2006). Using psychophysical tools, CS was tested with stimuli of Gabor patches under a temporal two-alternative forced-choice method in 3 frequencies (6,9 and 12 cpd) and CE was tested under two conditions using stimuli of Black E-patterns as a central single target and as 5 × 5 E-patterns. KC, KCSus and C were compared using T test.
Results: 17 KC (range of age 18-34,12 male (M), 19 eyes (E); 14 in stage (S) 1, 3 S2, 1 S3 and 1 S4) and 2KCSus (2M, 2E) and 17C (2M, 17E) participated in the study. Significant difference for KC vs C was found for VA, Cylinder, CCT and thinnest corneal site (p>0.003) but not for SPH (p=0.16). Significant effect was found for CS for 9 and 12 cpd for KC (3.38±3.54, 1.80±1.66 100/threshold) vs C (6.98±3.15, 3.5±2.14 100/threshold; p<0.01), but not for 6 cpd (p=0.08). Surprisingly, this effect was also found in KC with similar VA to C (p<0.05). There were no effects in CE (KC vs C, p=0.11). No correlation was found between severity to CS and CE (r=-0.2, r=0.43).
Conclusion: At the early stage of the disease, KC subjects, show significant lower CS compared to C. No correlation of CS to severity stage was shown, possibly due to the similar progression stage of KC eyes.

מרכזת המחקר לתואר ראשון: ד"ר עינת שניאור