Optical coherence tomography measurements of retinal nerve fiber layer thickness in amblyopic and non–amblyopic eyes

Abstract

Abstract: : Purpose:Factors affecting outcome of amblyopia treatment are not yet well understood. There is a subset of amblyopes, who fails to improve at the end of occlusion treatment, in spite of good compliance. Some Authors (Bellizzi, 2000) observed, by means of GDx NFA measurements, a reduction of nerve fiber layer (RNFL) thickness in amblyopes, not confirmed by others (Bozkurt et al, 2003). Studies about retinal modifications in amblyopic eyes are still inconclusive and controversial. We compared RNFL thickness and macular volume of the amblyopic eye with that of the normal fellow eye in patients with unilateral amblyopia, using OCT. Methods: OCT measurements of RNFL thickness were performed on amblyopic and non–amblyopic eyes of 20 patients (mean age 14,7 ± 6 years; range 8–26 years) with anisometropic or strabismic amblyopia, who did not show any other eye disease (particularly coloboma, glaucoma and high myopia). Results:Best corrected visual acuity was significantly lower in amblyopic eyes (mean non–amblyopic eyes: 1.04 ± 0.32; mean amblyopic eyes: 0.64 ± 0.13; t = 3.49, p = 0.004). Spherical equivalent refractive errors were not statistically different (mean non–amblyopic eyes: +0.82 ± 3.2 D; mean amblyopic eyes: +1.13 ± 4.3 D; t = –0.78; p = 0.44). RNFL thickness (mean non–amblyopic eyes: 105.2 ± 16.4 µm; mean amblyopic eyes: 104.1 ± 13.9 µm; t = 0.26; p = 0.79) and macular volume (mean non–amblyopic eyes: 0,182 ± 0,02 µm³; mean amblyopic eyes: 0,179 ± 0,02 µm³; t = –0.51; p = 0.61) did not show significant differences. Conclusion:There was no statistical difference in thickness of RNFL in amblyopic and normal eyes. This study may be a further proof of the well–known theory of ocular dominance columns.

Keywords: amblyopia • nerve fiber layer • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)