X-linked Alport syndrome is a basement membrane disease with important ocular manifestations. The lens is usually normal at birth but lens opacities eventually occur in a significant number of individuals with the most characteristic type being anterior polar in location. Involvement of the anterior lens capsule often results in bilateral anterior lenticonus (25%) and may be progressive. It is claimed that the severity of the lenticonus is a valuable marker in judging the overall disease severity. In early stages it may be difficult to detect but its presence is suggested by an 'oil droplet' reflex during retinoscopy or slit lamp examination. All males with anterior lenticonus should be evaluated for Alport syndrome.
Posterior polymorphous corneal dystrophy and posterior subcapsular opacities have also been noted. The defect in basement membranes may lead to recurrent corneal erosions, even in children, which can be incapacitating and difficult to treat. Involvement of Bruch's membrane has been considered the source of retinal pigment epithelial changes described as a flecked retina, or 'fundus albipunctatus', found in 85% of patients. More recent evidence using OCT suggests that the dot-and-fleck retinopathy results primarily from abnormalities in the internal limiting membrane and the nerve fiber layer. The yellowish and/or whitish flecks are most commonly located in the posterior pole and particularly in the macula. There is no night blindness or visual impairment from the retinal involvement. Fluorescein angiography shows patchy areas of hyperfluorescence. The amount of visual impairment depends primarily on the extent of lens involvement.
Termporal macular thinning occurs to some extent in all types of Alport syndrome based on OCT findings. In one series all patients with X-linked disease had temporal thinning suggesting that this might be a useful diagnostic sign. However, similar thinning is also seen in Leber hereditary optic neuropathy (535000), and dominant optic atrophy (165500).