The retina in amblyopic subjects: Controversy of the scientific literature

Purpose: Amblyopia is a visual developmental disorder characterized by unilateral, or rarely bilateral, reduction of the best‐corrected visual acuity. Some controversy existed since some authors have observed greater macular and choroidal thickness in amblyopic eyes using the optical coherence tomography (OCT) and OCT angiography (OCTA). The aim of this study was gathering the scientific literature to define if structural changes are present in the retina and choroid of amblyopic patients. Methods: Articles from 2016 up to January 2021 were searched in PubMed database. The study eligibility criteria included articles of structural and anatomic changes in the human retina, the vascular network, and the choroid in anisometropic, strabismic or mixed amblyopia. Results: Thirty‐three of 72 articles were included. A significant increase of the macular thickness, the retinal nerve fibre layer (RNFL) and the choroid along with a lower vascular density were shown in some articles. However, amblyopic eyes usually present different axial length than the fellow eye and most studies do not consider it despite structural differences in the retina have been described. In fact, no differences in the thickness of the macula were observed in studies that compared amblyopic with control eyes when considering the axial length. These studies did observe a tendency to a thicker RNFL, smaller foveal avascular zone, a decrease vascular density and a lower blood flow in the macula and optic nerve. Regarding the choroid, most articles suggest amblyopic eyes present greater choroidal thickness, luminal area volume and more vessels once axial length is adjusted. Conclusions: Only 11 studies that considered the axial length suggest amblyopic eyes do not present significant differences in the macular thickness compared to control, but they suggested an increased RNFL, lower density and retinal vascular flow and an increase in choroidal thickness.