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J. A. Burke, K.-M. Zhang, T. Lin, Y. Li, M. Escobar, W. Orilla, C. Ghosn, L. Wheeler; A Functional and Anatomical Evaluation of Chronic BRVO in Primates. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2696.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal vein occlusions are the second most common retinal vascular diseases after diabetic retinopathy. The branch variety (BRVO) is generally modeled in animals by thermal and /or photodynamic damage to several large veins. This study evaluated the structure and function of macula and peripheral retinal areas of monkey eyes, non-invasively, two years after permanent closure of the upper temporal arcade vein, in order to understand chronic effects of BRVO.
Six monkeys weighing 4-5 kg were used in this study. Three animals underwent treatment at several spots along the upper temporal arcade, beginning 1 disc diameter from the optic disc, using a Coherent Omni Laser set to 532 nm in the F mode. The veins were retreated the next day to ensure permanent closure. The other 3 monkeys (aged-matched) served as controls. Two years following the laser procedure, retinal structure was assessed with fundus photography, fluorescein angiography, and optical coherence tomography (OCT, Stratus, Zeiss), while retinal function was assessed with multifocal electroretinography (mfERG, VERIS 5.2, stretched 103 pattern stimulus, 50° field centered at the fovea). Retinal areas considered for analysis were the fovea, the macula, and the superior (excluding the lasered area) and inferior retinal areas. Animal were anesthetized, paralyzed and dilated for the procedures. Data are presented as mean ± sem.
The BRVO model was characterized acutely by sequelae that included flame-shaped intra-retinal hemorrhages, cotton-wool spots and macula edema and chronically by a limited number of tortuous vessels that respected the horizontal raphe, and scarring in the laser zone. Superior macula, when compared to inferior macula was significantly more thinner in BRVO eyes than naïve eyes as measured by the OCT (Naive: -4±0.6%, BRVO: -10±1.5%, p<0.05). Similarly the % difference between superior and inferior retinal function as measured by mfERG was significantly greater in BRVO eyes than in naïve control eyes (Naïve: -5 ± 3%, BRVO: -21±4%, p<0.05). Central fovea did not show significant difference between BRVO and normal eyes with either OCT or mfERG. OCT central foveal thicknesses for control and BRVO groups were 122 ± 3 um and 116 ± 7 um, respectively. Corresponding foveal values for mfERG (center 7 hexagons, N1P1 amplitude) were 25 ± 6 nV/deg and 24 ± 8 nV/deg, respectively
Regionally selective variations in retinal structure and function may be measured using sensitive techniques such as the OCT and mfERG in this monkey model of BRVO.
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