Diagnosis is based on clinical presentation, ocular examination, and molecular genetic testing. In asymptomatic or only mildly affected patients, the electroretinogram, electro-oculogram, color vision testing and visual fields may be normal or only mildly abnormal.

Diagnosis is often made when families of patients with suspected or known FEVR are screened. In most infants, FEVR is diagnosed when they are evaluated for failure to fix and follow objects or lights, for pendular nystagmus or heterotropia, or when children and adults notice decreased vision.

Fluorescein angiography has the main diagnostic role. Molecular genetic testing for FZD4 and LRP5 is clinically available. Prenatal diagnosis for pregnancies at increased risk is feasible (analysis of DNA extracted from fetal cells obtained by amniocentesis usually performed at about 15-18 weeks' gestation or chorionic villus sampling at approximately ten to 12 weeks' gestation).

Differential diagnosis

The differential diagnosis of FEVR essentially depends on the stage of the disease. FEVR must be differentiated from ROP, Coats' disease, incontinentia pigmenti, persistent hyperplastic primary vitreous (PHPV), and Norrie disease. Important additional differential diagnoses include high myopia, Eales' disease, juvenile retinoschisis, vitreousand toxocariasis.