Optical coherence tomography (OCT) parameters in amblyopia

Publications on optical coherence tomography (OCT) parameters in amblyopic eyes compared to fellow eyes are discordant. Our study not only compares OCT data of fellow and amblyopic eyes, but is the first study to deliver pilot results on OCT parameter changes after long-term electronic monitoring of occlusion therapy.

Thirty eyes with strabismic, anisometropic or mixed amblyopia and the corresponding fellow eyes underwent OCT of the macula and optic disc with a Topcon 3D-OCT-2000. In a subgroup of six patients, the same examinations were additionally performed at the end of long-term objectively measured occlusion therapy with Occlusion-Dose-Monitoring (ODM) of ≥2135 hours. Paired t-tests or matched pairs Wilcoxon tests were performed to compare optic disc values, macular thickness, as well as thickness of different layers of the macula of the amblyopic eye versus the fellow eye. Specifically, the Ganglion Cell Layer (GCL) with the Inner Plexiform Layer (IPL) designated as GCL+, as well as combined with the Retinal Nerve Fiber Layer (RNFL) designated as GCL++, were analyzed. For the subgroup of patients with follow-up OCT, the same tests were performed to compare the values in both eyes before and after occlusion therapy.

Average thickness (AT) and total volume (TV) of the macula of amblyopic eyes (282.0 ± 13.0 µm; 7.98 mm³ ±0.37) were increased (marginally significant p=0.0495 for both) compared to fellow eyes (278.6 µm ± 13.3; 7.88 mm³ ±0.37), all other parameters did not differ. In the group with follow-up OCT, the AT and TV of the amblyopic eyes significantly decreased after occlusion (278.8 µm before vs. 268.3 µm after and 7.89 mm³ before vs. 7.59 mm³ after; p = .031 for both). The thicknesses of inner retinal layers were not significantly different between amblyopic and fellow eyes or after therapy.

Our results suggest that the macula of amblyopic eyes may be thicker than in fellow eyes, particularly in eyes with moderate-to-severe amblyopia. Occlusion therapy may lead to a thinning of the macula in the amblyopic eye or both eyes. The layers included in GCL+ and GCL++ do not seem to be the substrate of the observed structural changes.