Familial exudative vitreoretinopathy (FEVR) is an inherited disorder characterized by the incomplete development of the retinal vasculature. Its clinical appearance varies considerably, even within families, with severely affected patients often registered as blind during infancy, whereas mildly affected patients with few or no visual problems may have such a small area of avascularity in their peripheral retina that it is visible only by fluorescein angiography. It is believed that this peripheral avascularity is the primary anomaly in FEVR and results from defective retinal angiogenesis. The sight-threatening features of the FEVR phenotype are considered secondary to retinal avascularity and develop because of the resulting retinal ischemia; they include the development of hyperpermeable blood vessels, neovascularization, vitreoretinal traction, retinal folds, and retinal detachments (summary by Poulter et al., 2010). For a discussion of genetic heterogeneity of FEVR, see EVR1 (133780).

Familial exudative vitreoretinopathy (FEVR) is an inherited disorder characterized by the incomplete development of the retinal vasculature. Its clinical appearance varies considerably, even within families, with severely affected patients often registered as blind during infancy, whereas mildly affected patients with few or no visual problems may have such a small area of avascularity in their peripheral retina that it is visible only by fluorescein angiography. It is believed that this peripheral avascularity is the primary anomaly in FEVR and results from defective retinal angiogenesis. The sight-threatening features of the FEVR phenotype are considered secondary to retinal avascularity and develop because of the resulting retinal ischemia; they include the development of hyperpermeable blood vessels, neovascularization, vitreoretinal traction, retinal folds, and retinal detachments (summary by Poulter et al., 2010). In 31 Chinese pedigrees clinically diagnosed with FEVR, Rao et al. (2017) analyzed 6 FEVR-associated genes and identified mutations in 12 of the probands, including 5 (16.1%) in LRP5, 3 (9.7%) in NDP, 2 (6.5%) in FZD4, and 1 (3.2%) in TSPAN12. In addition, a mutation in the KIF11 gene (148760) was identified in a patient who also exhibited microcephaly (MCLMR; 152950). The authors noted that their detection rate did not exceed 50%, suggesting that other FEVR-associated genes remained to be discovered. Genetic Heterogeneity of Familial Exudative Vitreoretinopathy Also see EVR2 (305390), caused by mutation in the NDP gene (300658) on chromosome Xp11; EVR3 (605750), mapped to 11p13-p12; EVR4 (601813), caused by mutations in the LRP5 gene (603506) on 11q13.4; EVR5 (613310), caused by mutation in the TSPAN12 gene (613138) on 7q31; EVR6 (616468), caused by mutation in the ZNF408 gene (616454) on 11p11; and EVR7 (617572), caused by mutation in the CTNNB1 gene (116806) on chromosome 3p22.

Familial exudative vitreoretinopathy (FEVR) is an inherited disorder characterized by the incomplete development of the retinal vasculature. Its clinical appearance varies considerably, even within families, with severely affected patients often registered as blind during infancy, whereas mildly affected patients with few or no visual problems may have such a small area of avascularity in their peripheral retina that it is visible only by fluorescein angiography. It is believed that this peripheral avascularity is the primary anomaly in FEVR and results from defective retinal angiogenesis. The sight-threatening features of the FEVR phenotype are considered secondary to retinal avascularity and develop because of the resulting retinal ischemia; they include the development of hyperpermeable blood vessels, neovascularization, vitreoretinal traction, retinal folds, and retinal detachments (summary by Poulter et al., 2010). For a discussion of genetic heterogeneity of familial exudative vitreoretinopathy, see EVR1 (133780).

Stickler syndrome is a connective tissue disorder that can include ocular findings of myopia, cataract, and retinal detachment; hearing loss that is both conductive and sensorineural; midfacial underdevelopment and cleft palate (either alone or as part of the Robin sequence); and mild spondyloepiphyseal dysplasia and/or precocious arthritis. Variable phenotypic expression of Stickler syndrome occurs both within and among families; interfamilial variability is in part explained by locus and allelic heterogeneity.

Myopia, or nearsightedness, is a refractive error of the eye. Light rays from a distant object are focused in front of the retina and those from a near object are focused in the retina; therefore distant objects are blurry and near objects are clear (summary by Kaiser et al., 2004). For a discussion of genetic heterogeneity of susceptibility to myopia, see 160700.