Eye and Vision (Sep 2020)
Advances in myopia research anatomical findings in highly myopic eyes
Abstract
Abstract Background The goal of this review is to summarize structural and anatomical changes associated with high myopia. Main text Axial elongation in myopic eyes is associated with retinal thinning and a reduced density of retinal pigment epithelium (RPE) cells in the equatorial region. Thickness of the retina and choriocapillaris and RPE cell density in the macula are independent of axial length. Choroidal and scleral thickness decrease with longer axial length in the posterior hemisphere of the eye, most marked at the posterior pole. In any eye region, thickness of Bruch’s membrane (BM) is independent of axial length. BM opening, as the inner layer of the optic nerve head layers, is shifted in temporal direction in moderately elongated eyes (axial length 26.5 mm), BM opening enlarges with longer axial length. It leads to a circular gamma zone. In a parallel manner, the peripapillary scleral flange and the lamina cribrosa get longer and thinner with longer axial length in highly myopic eyes. The elongated peripapillary scleral flange forms the equivalent of parapapillary delta zone, and the elongated lamina cribrosa is the equivalent of the myopic secondary macrodisc. The prevalence of BM defects in the macular region increases with longer axial length in highly myopic eyes. Scleral staphylomas are characterized by marked scleral thinning and spatially correlated BM defects, while thickness and density of the choriocapillaris, RPE and BM do not differ markedly between staphylomatous versus non-staphylomatous eyes in the respective regions. Conclusions High axial myopia is associated with a thinning of the sclera and choroid posteriorly and thinning of the retina and RPE density in the equatorial region, while BM thickness is independent of axial length. The histological changes may point towards BM having a role in the process of axial elongation.
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