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J. Tang, R. Ursea, R.R. Buggage, S. Kurup, R.C. Caruso; Multifocal Electroretinogram Findings and Correlation with Visual Field Testing in Patients with Birdshot Retinochoroidopathy . Invest. Ophthalmol. Vis. Sci. 2004;45(13):535.
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Purpose:The aims of this study were to characterize the pattern of visual loss in patients with birdshot retinochoroidopathy (BRC) using multifocal electroretinography (mfERG), to compare these findings with those of perimetry and to correlate these measurements with the funduscopic observations. Methods:This was a retrospective case series of 4 patients who presented to the National Eye Institute diagnosed with BRC. All patients in this series were evaluated with best corrected ETDRS vision, visual fields (Humphrey 30–2), biomicroscopy and mfERG. The first kernel of the mfERG elicited by 61 stimulus areas was analyzed. Responses from the macular area, the nasal and the temporal periphery were grouped. A nasal/temporal amplitude ratio was then calculated. Results:To date, 7 eyes of 4 patients with the diagnosis of BRC who underwent electrophysiologic studies were identified. One eye was excluded from the analysis secondary to an inability to fixate from a macular scar. All patients were Caucasians of northern European ancestry and all had the HLA–A29 antigen. Our 4 patients consisted of 3 females and 1 male. The mean age was 55 years (range 43 to 70 years). All patients in our series complained of progressive worsening of night vision, abnormalities in color vision and an increase in the number of floaters seen. Funduscopically, all patients had deep yellowish choroidal lesions with a greater predominance in the nasal retina. Visual acuity ranged from 20/32 to 20/63 (ETDRS chart). An association was found between foveal mfERG amplitudes and foveal perimetric thresholds and between this last variable and visual acuity. In 7 out 7, eyes there was a mfERG nasal to temporal amplitude ratio greater than 1 (mean ± std. dev. = 1.37 ± 0.27). This implied a significant difference in the degree of function between the nasal and temporal central retina. The nasal to temporal asymmetry in the visual fields was far less marked (mean ± std. dev. = 1.05 ± 0.11). Conclusions:The mfERG is a useful method to assess the retinal contribution to the visual compromise in patients with BRC and may be useful to follow the course of the disease. The known nasal to temporal asymmetry seen in fundus findings is more clearly seen using mfERG as opposed to standard perimetry. This may be due to the fact that the first kernel of the mfERG has a major contribution from photoreceptors and bipolar cells directly underlying the choroidal lesions.
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