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.
- Embryology and development
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Contributors Conception and design: MT and IG. Literature review and manuscript drafting: MT, EP and HK. Critical appraisal and final approval: MT, EP, HK and IG. Overall responsibility: MT and IG.
Funding This work was supported by the Ulverscroft Foundation (05/38), Fight for Sight (grant ref: 5009/5010 and 24NN181), Academy of Medical Sciences (SGL021/1066) and the Medical Research Council (MRC), London, UK (grant number: MC_PC_17171, MR/J004189/1 and MRC/N004566/1). MGT is supported by NIHR (CL-2017-11-003).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer-reviewed.
Data availability statement There is no unpublished data in this review.
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