רגישות לניגודיות ו - crowding effect בקרב חולי קרטוקונוס
Contrast sensitivity and crowding effect in Keratoconus patients

הסטודנטיות: ויקטוריה מישצ'נקו ויוליה וייסברג
שם המנחה: ד"ר רביד דורון

Introduction: Keratoconus (KC) is a corneal disease, characterized by stromal thinning (Galvis et al., 2015) and weakening (Rabinowitz, 1998). This study measured corneal parameters, contrast sensitivity (CS) and crowding effect (CE) in KC and KC suspects compered to healthy matched controls (C) with relation to the progression stages of the disease.
Methods: Visual acuity (ETDRS, LogMAR chart), over refraction correction, High Order Aberration (RMS), slit-lamp biomicroscopy and corneal tomography (Sirius) were tested. KC subjects were diagnosed based on abnormal topography and at least one clinical sign (Rabinowitz, 2008). KC Suspects had typical topography pattern with no clinical sign. Severity of KC was defined according to the Amsler-Krumeich classification (Alió & Shabayek, 2006). CS with various frequencies (6,9,12 cpd) and CE were tested using psychophysical measurements and were compared to healthy subjects using T-test.
Results: 18 KC (range of age 17-34 years, 5 female (F), 20 eyes (E); 14 in stage (S) 1, 4 S2, 1 S3 and 1 S4) and 3 suspects (3F, 3E) and 28C (20F, 28 E) participated in the study. Significant difference for KC vs C was found for VA, Cylinder, CCT, thinnest corneal site and RMS high order aberration (p<0.008) but not for SPH (p=0.8). KC showed significant lower CS for all frequencies (p<0.004). This effect was also found in KC with normal VA to C (20/20, p<0.05). There were no effects in CE (p=0.1). No correlation was found between severity to CS and CE (r=-0.2, r=-0.12).
Conclusion: At the early stage of the disease, CS is lower in keratoconus subjects, although similar visual acuity to controls. More subjects in different stages of the disease should be evaluated. These can provide insight into the pathophysiologic mechanism of keratoconus and may potentially become a sensitive tests for early Keratoconus diagnosis.

מרכזת המחקר לתואר ראשון: ד"ר עינת שניאור