Normal and abnormal foveal development

Abstract

Normal foveal development begins in utero at midgestation with centrifugal displacement of inner retinal layers (IRLs) from the location of the incipient fovea. The outer retinal changes such as increase in cone cell bodies, cone elongation and packing mainly occur after birth and continue until 13 years of age. The maturity of the fovea can be assessed invivo using optical coherence tomography, which in normal development would show a well-developed foveal pit, extrusion of IRLs, thickened outer nuclear layer and long outer segments. Developmental abnormalities of various degrees can result in foveal hypoplasia (FH). This is a characteristic feature for example in albinism, aniridia, prematurity, foveal hypoplasia with optic nerve decussation defects with or without anterior segment dysgenesis without albinism (FHONDA) and optic nerve hypoplasia. In achromatopsia, there is disruption of the outer retinal layers with atypical FH. Similarly, in retinal dystrophies, there is abnormal lamination of the IRLs sometimes with persistent IRLs. Morphology of FH provides clues to diagnoses, and grading correlates to visual acuity. The outer segment thickness is a surrogate marker for cone density and in foveal hypoplasia this correlates strongly with visual acuity. In preverbal children grading FH can help predict future visual acuity.

Feasibility and Repeatability of Handheld Optical Coherence Tomography in Children With Craniosynostosis

“…Handheld OCT has been utilized to describe the normal development of the optic nerve 14 and fovea 15 in children, with excellent feasibility. Furthermore, handheld OCT has been utilized in numerous pediatric conditions, 16 including primary congenital glaucoma, 17 nystagmus, 18 foveal hypoplasia, 19,20 optic nerve hypoplasia, 21 achromatopsia, 22 retinopathy of prematurity, 23 and craniopagus twins, 24 among others. Other OCT devices have demonstrated potential for detecting papilledema and IH in craniosynostosis, but handheld OCT has not yet been used in this patient population.…”

Blue Cone Monochromatism with Foveal Hypoplasia Caused by the Concomitant Effect of Variants in OPN1LW/OPN1MW and GPR143 Genes

“…Differently from the common morphological presentation of BCM, SD-OCT showed the presence of foveal hypoplasia (FH) associated with focal irregularities and fragmentation of the ellipsoid layer in the foveal area. Foveal hypoplasia has been divided into a typical and an atypical form [28]. Typical FH has been described in albinism, PAX6 mutations, SLC38A8 mutations, retinopathy of prematurity, optic nerve hypoplasia, and isolated cases of arrested retinal development in different disorders, and is characterized by the continuation of inner retinal layers posterior to the foveola.…”

A comparison of posterior segment optical coherence tomography findings in full-term and preterm children without retinopathy of prematurity

“…Premature patients present retention of the inner retina, especially at the expense of the ganglion cell and the inner plexiform layers, which results in an abnormally thick, hypoplastic fovea. [ 5 6 9 12 13 14 ] In addition, they exhibit altered vasculogenesis that gives rise to foveal avascular zones (FAZs) of smaller diameter with capillaries that cross the fovea, modify its elasticity, and prevent the adequate formation of the foveal depression. [ 9 12 14 ] Other macular architecture characteristics have been related as signs of foveal maldevelopment.…”

“…[ 5 6 9 12 13 14 ] In addition, they exhibit altered vasculogenesis that gives rise to foveal avascular zones (FAZs) of smaller diameter with capillaries that cross the fovea, modify its elasticity, and prevent the adequate formation of the foveal depression. [ 9 12 14 ] Other macular architecture characteristics have been related as signs of foveal maldevelopment. Mainly, a broad and shallow foveal pit, sometimes reaching absence of foveal depression, and retention of inner retinal layers at the foveola have been found in preterm patients.…”

“…Mainly, a broad and shallow foveal pit, sometimes reaching absence of foveal depression, and retention of inner retinal layers at the foveola have been found in preterm patients. [ 14 15 ] These findings, previously described as foveal aplasia or fovea plana, are now encompassed in the more suitable term “foveal hypoplasia,” for which Thomas et al . have developed a grading system as follows: grade 1: characterized by retention of inner retinal layers, but outer segment lengthening (OSL) and outer nuclear layer (ONL) widening present (1a: nearly normal foveal pit; 1b: shallow foveal indent); grade 2: as grade 1 but absence of foveal pit; grade 3: as grade 2 but absence of OSL; and grade 4: as grade 3 but absence of ONL widening.…”