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A.M. Mackay, M.C. Brown, R.P. Hagan, A.C. Fisher, S.P. Harding; Changes in the Pattern Electroretinogram During a Course of Photodynamic Therapy for Neovascular Age–Related Macular Degeneration . Invest. Ophthalmol. Vis. Sci. 2005;46(13):336.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Subfoveal choroidal neovascularisation (CNV) is a major cause of visual loss in age–related macular degeneration (AMD). Photodynamic therapy (PDT) is a drug and laser treatment that can slow down progression of CNV under certain conditions. This study investigates the effect of PDT on the Pattern Electroretinogram (PERG), a known measure of macular function, over a 12–month course of PDT. Methods: New patients attending a regional medical retina service with active subfoveal predominantly classic CNV secondary to AMD were recruited and the affected eye studied before receiving PDT treatment. If possible, testing was repeated three, six and 12 months later when the patient attended for follow–up assessment and treatment. PERGS in response to 4 Hz, 50’ checks were recorded between 1 and 100Hz using DTL thread electrodes. Responses were then digitally filtered between 1 and 50Hz and described by their N35:P50 amplitude, P50:N95 amplitude, and P50 latency. Each parameter was quantified within groups using the median and 95% confidence intervals (CIs). 95% CIs were also used to describe the differences in these parameters between visits. Results: 35 patients were recruited before treatment. A discernable PERG was recorded in 71% (25/35) of patients initially and this response rate did not change significantly over the 12 month study period. Deficits were shown in N35:P50 amplitude, P50:N95 amplitude and P50 latency compared to established normal ranges. Both N35:P50 amplitude and P50:N95 amplitude tended to be smaller 3 months after treatment compared to pre–treatment measurements (95%CI of difference for N35:P50=–0.66 to 3.94 and for P50:N95=–0.96 to 4.28). However, no differences were observed when 6 and 12 months measurements were compared to pre–treatment measurements (95% CI of difference for N35:P50=–1.5 to 0.85 and for P50:N95=–1.33 to 0.65). No changes in P50 latency were shown over the 12 –month course of treatment. Conclusions: Previous multifocal electroretinogram (mfERG) studies have shown deficits in the central 5° field three months after PDT. An mfERG study of the Liverpool patient group goes on to say that amplitude density returns to pre–treatment values, and may increase, six months after initial PDT. Eccentric fixation learning in the latter stages of treatment may have affected mfERGs. However, it is assumed that PERGs are unaffected and our results reflect an funtional change between three and six months.
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