Functional and Structural Changes of Retina in Amblyopic Eyes

Abstract

Purpose: : To explore the functional and structural changes in the retinas of amblyopic eyes.

Methods: : Seventeen unilateral amblyopic patients were included. Pattern visual evoked potentials (PVEP), full-field electroretinogram (ERG), and multifocal electroretinogram (mfERG) tests were performed on both amblyopic and nonamblyopic eyes of the patients with Roland Consult-RetiScan^TM system. Retinal sensitivity of retina was assessed by using mean deviation (MD) of Humphrey visual field test. The retinal nerve fiber layer thickness (RNFL) and central macular thickness (CMT) were measured by optical coherence tomography (OCT, Stratus^TM).

Results: : The mean ages of patients was 22±2,4. In PERG, P₅₀ and N₉₅ amplitudes were significantly reduced in amblyopic eyes (p<0.001, for both). There was no significant difference in P₅₀ and N₉₅ latencies between amblyopic and nonamblyopic eyes (p>0.05, for both). In PVEP, P₁₀₀ amplitudes were significantly reduced (p=0.005); but, P₁₀₀ latency values did not differ between amblyopic and nonamblyopic eyes (p=0.554). Mean RNFL thickness, nasal quadrant RNFL thickness and CMT were significantly increased in amblyopic eyes (p=0.006, p=0,005 and p<0.001, respectively). The retinal sensitivity was significantly higher in amblyopic eyes (p=0.002). This was more evident in the foveolar thresholds (p<0.001). P1 amplitudes in central 2.3 degree of mfERG were significantly lower in amblyopic eyes (p=0.017).

Conclusions: : Functional and structural changes of retina may occur in amblyopic eyes beside classically seen central supression in PVEP. The retinal structural changes in the amblyopic eyes may be a compensatory mechanism due to the decreased macular visual stimulation.

Keywords: amblyopia • electrophysiology: clinical • nerve fiber layer