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Magella M. Neveu, John J. Sloper, Anthony T. Moore, Glen Jeffery, Graham E. Holder; Asymmetric Hypopigmentation in Albinism. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6086.
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To present nine patients with uniocular intra-cranial misrouting of the type that is usually associated with albinism.
Nine patients suspected of ocular (n=3)/oculocutaneous (n=6) albinism with asymmetrical inter-ocular fundal pigmentation were ascertained (age range 5 - 52 yrs, 5 female, 4 male). VEPs to pattern appearance (PappVEP) and flash (FVEP) stimulation were recorded using 5 active electrodes across the occiput. VEPs were analysed in terms of amplitude and peak time. ERGs and when possible, fundus photography and OCTs were also performed. Fundal pigmentation was assessed using fundus photography and foveal morphology using OCT.
Four of nine patients had foveal hypoplasia in the less/minimally pigmented eye and a normal fovea in the fellow eye; 2 of 9 patients had bilateral foveal hypoplasia. Five patients had bilateral iris transillumination and 5 patients had nystagmus. All ERGs were normal from both eyes. Five of 9 patients had fundus photography. All showed asymmetrical pigmentation and pigment distribution differed between eyes. Retinal blood vessel patterns differed between eyes with the less/minimally pigmented eye having abnormal vasculature. In all patients, FVEP and/or PappVEPs from the less/minimally pigmented eye showed clear contralateral predominance. FVEP and/or PappVEPs from the more pigmented eye were normal.
All patients have the features of ocular/oculocutaneous albinism but the characteristic intra-cranial misrouting of the visual pathways is confined to only one eye, and appears to be related to the degree of pigment deposition in the retinal pigment epithelium demonstrated on fundus photography. This reveals that the influence of melanin deposition on chiasmal decussation during development is independent between eyes, and thus may result in uniocular misrouting. Further, this shows that chiasm formation in man does not depend on stereo-typic midline interactions between the two optic nerves as both ‘normal’ and ‘abnormal’ chiasmatic pathways from separate eyes can develop in the same individual.
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