Familial Exudative Vitreoretinopathy

Familial exudative vitreoretinopathy (FEVR) is a bilateral, clinically and genetically heterogeneous condition that is characterized by a failure of peripheral retinal vascularisation. It has a remarkable similarity to retinopathy of prematurity but occurs in full-term infants who are otherwise healthy and have not been treated with oxygen in the neonatal period. The changes may be mild with a peripheral retinal avascular zone, detectable with certainty only by fluorescein angiography, or may slowly progress to cause peripheral neovascularisation and exudative or tractional retinal detachment and vitreous haemorrhage. Rhegmatogenous retinal detachment may also occur. Progression of fundus changes and threat to vision is rare after age 20 years. There is a high incidence of myopia, anisometropia and amblyopia, especially in asymmetric disease. Progressive disease may be treated with peripheral photocoagulation or cryotherapy. Vitreoretinal surgery may be challenging because of adherent posterior hyaloid membrane [20]. Since the original description in 1969 [7] demonstrating autosomal dominant inheritance, many more reports

Familial Exudative Vitreoretinopathy
Fig. 12.5. Characteristic foveal and peripheral features ofX-linked retinoschisis

have confirmed autosomal dominant, X-linked and even autosomal recessive forms.

The autosomal dominant form (EVRi) can be caused by mutations in the frizzled-4 gene (FZD4) on chromosome iiqi3-q23 and also by mutations in the LRP5 (low-density lipoprotein receptor-related protein-5) gene, which maps to iiqi3.4. The X-linked form (EVR2) can be caused by mutations of the Norrie disease gene (NDP), which has been mapped to Xpii.4. The gene products are proteins important in Wnt signalling pathways that regulate vascular development in the eye [4i, 46]. The gene underlying EVR3 which has been mapped to iipi2-i3 has yet to be identified. Mutations in the LRP5 gene have been suggested to cause autosomal recessive as well as autosomal dominant FEVR [2i].

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