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Hongxin Song, David R. Williams, Lisa Latchney, Alfredo Dubra, Mina M. Chung; Fluorescence Adaptive Optics Scanning Laser Ophthalmoscopy Demonstrates Intraretinal Spots and Low Cone Density in Fundus Albipunctatus. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5675.
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© ARVO (1962-2015); The Authors (2016-present)
Fundus albipunctatus (FA) is a form of congenital stationary night blindness characterized by yellow-white spots which were classically described as subretinal. To date, no morphological data has been available at the cellular level. In this study, we used fluorescence adaptive optics scanning laser ophthalmoscopy (FAOSLO) and spectral-domain optical coherence tomography (SD-OCT) to study the cone photoreceptors and albipunctate spots in a patient with FA.
FAOSLO and SD-OCT (Bioptigen) were used to image the retina in a patient with FA. Near infrared reflectance FAOSLO images were obtained at the central fovea and along the superior and temporal meridians to generate 20x1.5 degree montages. Cones were counted in a 200x200 µm window at the foveal center using custom automated cone marking software followed by manual editing. The location of highest cone density was taken as the foveal center. Peripheral cones were counted in 50x50 µm windows at 100µm intervals. In the area of the albipunctate spots, through-focus reflectance FAOSLO images, autofluorescence FAOSLO images (excitation 561 nm, emission 624α40nm) and SD-OCT images were obtained.
Cone density was reduced at the fovea (67.8x103 cones/mm2, normal = 199.2±87.2 x103 cones/mm2) and at all tested eccentricities. At 1 degree and beyond, dark circular rings were present in the photoreceptor mosaic suggesting defective cones. In the area of the albipunctate spots, through-focus reflectance imaging showed the spots appeared below the nerve fiber layer and extended through the photoreceptor layer. No photoreceptors were identified in these areas. FAOSLO images showed the spots were hypo-autofluorescent. SD-OCT confirmed the spots extend from the outer nuclear layer (ONL) through the retinal pigment epithelium (RPE).
This study provides the first in vivo morphological data at the cellular level in a patient with FA. Although the predominant clinical symptom of night blindness suggests a primary rod dysfunction, cone density is also significantly reduced. Hypo-autofluorescence suggests that the albipunctate spots do not represent lipofuscin. The location of the spots is consistent with a previous report and suggests that the pathological foci occur within the photoreceptors as well as the RPE.
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