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A. Neri, M. Camparini, S. A. Tedesco, A. Lamedica, E. Delfini, C. Macaluso; A High-Resolution OCT Evaluation of the Foveal Region in Human Albinism. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2141.
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© ARVO (1962-2015); The Authors (2016-present)
To describe the fine retinal structure of the foveal area in patients affected by oculocutaneous albinism (OCA) by means of high-resolution, spectral-domain OCT (HD-OCT).
6 patients (3 females and 3 males, age 8-47) and 6 healthy subjects (age 20-45) participated in the study. Skin and hair pigmentation was graded basing on a scale first used by Schmitz et al. (2003). Pictures of iris and retina were taken and the grade of iris transillumination and macular pigmentation was established according to Summers et al. (1988). Clinical evaluation included ocular motility, visual acuity (ETDRS chart) and refraction. A high resolution, high-speed, spectral-domain OCT (Cirrus, Zeiss Meditec®), was used to obtain both high definition cross-sectional images and raster scans ("macular cube") of the central retina. Multiple thickness parameters were calculated by the OCT software and by manual measurements (in one patient the automated macular thickness analysis was discarded for the bad quality of the scan due to severe nystagmus).
The foveal region of all albino patients was abnormal, with reduction to absence of the foveal pit. Mean foveal thickness was 295.1 µm (min 273 - max 321 µm) in the patient group and 267.2 µm in controls (range 240 -290 µm, p<0.01). The foveal pit was clearly identified in three subjects, although shallower than in controls, being 21 µm deep (range 13-28 µm) versus 126 µm (113-140 µm). In the remaining patients the central retina profile showed foveal aplasia, but a rudimental central retina specialization was consistently observed in the form of a domed profile. Patients without foveal depression carried a more severe phenotype, with poorer visual acuity, evident nystagmus, minimal to absent pigmentation.
In albino patients various degrees of foveal hypoplasia have been described, ranging from a reduction of normal excavation to its complete absence. HD-OCT allowed accurate imaging of the fovea, when identifiable, showing that it is wider and shallower than in healthy subjects. In patients without fovea, HD-OCT demonstrated a doming profile of the central macula, resembling pre-foveation stages of embryonic retina, when photoreceptors accumulate centrally, thereby thickening the cross sectional profile of the retina. This thickening also precedes in phylogenesis the development of fovea centralis and it is observable in the area centralis of several mammalian species.
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