Foveola-Aplasie bei Tyrosinase-positivem oculocutanen Albinismus

Abstract

The eye of a 47 year old man with tyrosinase-positive oculocutaneous albinism, photophobia, nystagmus and visual acuity 0, 4-0, 5 was histologically examined after orbital exenteration for neoplasia. Histologic serial sections of the centre of the retina showed a continuous 6-8 cell-layer of ganglion cells, without any suggestion of a foveolar pit. The outer layers of the macular retina were altered secondarily by tumor-impression-folds; they were unremarkable at the periphery as were the acid mucopolysaccharides in the receptor region. Electron microscopy of the uvea and the retinal pigment epithelium showed a normal number of pigment granules but a deficiency of melanin, as well as structural anomalies. The absence of the foveolar pit and the decrease of visual acuity in tyrosinase-positive albinism is caused by definite morphologic alteration in the arrangement of ganglion cells in the macular region in the sense of a foveolar aplasia. The etiology is discussed. An identic anomaly has been described in aniridia, similar ones in other congenital ocular diseases.

The recognition and management of albinism

“…Foveal hypoplasia ~ An absence of normal foveal differentiation represents one of the principal features of albinism. Histological studies (Naumann, Lerche and Schroeder, 1976;O'Donnell et al, 1976;Fulton, Albert and Craft, 1978) have confirmed this, reporting that the ganglion cell layer seems to be present throughout the retina and that no rod-free area is identifiable. The following four features characterize the albino central retina, although the last is not a consistent finding (Abadi and Dickinson, 1983); (a) Absence of a foveal pit, and hence no foveal reflex.…”

Aberrant visual pathway development in albinism: From retina to cortex

“…In normal foveal development, anti‐angiogenic molecules form a molecular barrier to form a ‘foveal avascular zone’ (FAZ) (Provis, Sandercoe, & Hendrickson, ; Provis, ; Provis & Hendrickson, ). In albinism, this fails to happen, leading to encroachment of the inner retinal layers into the fovea, a deficiency in the formation of the foveal pit and a lack of photoreceptor specialisation (Elschnig, ; Naumann, Lerche, & Schroeder, ; Akeo et al, ; Chong et al, ). Using spectral domain optical coherence tomography (OCT), our group has previously shown that the degree of incursion of the inner retinal layers at the fovea and foveal photoreceptor specialisation are inversely related and together define the degree of foveal development.…”

Familiäre Foveahypoplasie - Klinische Einordnung

“…Im klinischen Sprachgebrauch werden sowohl die isolierten und erblich auftretenden als auch die von der Aniridie und dem okulokutanen Albinismus her bekannten Formen dieser Makulaanomalie als Foveahypoplasie/foveal hypoplasia bezeichnet. Es ist den Autoren des vorliegenden Beitrages aber klar, dass die Bezeichnung ¹Foveaaplasieª ebenso begründet ist [9,10], wenn die Fovea fehlt: Serienschnitte zeigen die Netzhautmitte anstatt durch eine Grube durch eine mehrschichtige Anordnung der Ganglienzellen markiert, während sie in der Umgebung einschichtig liegen. Diese relative Dichte der Ganglienzellen dürfte ihre Erklärung in der 1 : 1-Verschaltung zwischen Rezeptoren und Ganglienzellen haben.…”