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Angharad Elizabeth Hobby, Byki Huntjens, Omar Abdul Rahman Mahroo, David P Crabb, Alison M Binns; Association between number of injections during long-term anti VEGF therapy and retinal electrophysiological parameters. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1446.
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Some studies report a reduction in retinal ganglion cell layer thickness during long-term antiVEGF therapy in neovascular age-related macular degeneration (nAMD). We explored whether electroretinogram (ERG) parameters, including those derived from ganglion cells, were related to number of injections.
Patients undergoing antiVEGF treatment for nAMD were recruited from medical retina clinics. Photopic ERGs were recorded following mydriasis, using conductive fibre electrodes. Ganzfeld stimuli were delivered (ColorDome, Diagnosys, Lowell, MA), including 41Hz flicker (30cd.m-2, 635nm), international standard photopic flashes (3cd.s.m-2, white) and stimuli to elicit a photopic negative response (PhNR; red stimulus, 635nm, 0.42cd.s.m-2, blue background, 465nm, 158.8cd.m-2). Associations between number of injections and ERG parameters were evaluated (Spearman correlation). In a subsequent study, patients were recruited from another medical retina clinic and underwent PhNR recordings (1.5cd.s.m-2red flashes; 10 cd.m-2 blue background) using a hand-held device (RETeval, LKC Technologies Inc., Gaithersburg, MD) and skin electrodes.
In the first study, recordings were made on 31 patients with median (interquartile range[IQR]) age 84 (74, 86) years. Median (IQR) number of prior anti-VEGF injections was 9 (3, 14). Correlation between PhNR amplitude and number of injections was statistically significant (rho=-0.50; p=0.007): amplitude decreased with increasing injections. No other parameters showed significant correlations. In the second study, 25 patients were examined but only 20 produced reliable recordings, and one more was excluded because of incomplete injection data. In this cohort (n=19, median[IQR] age 78 [69,85] years; median[IQR] 6 [2,14] prior injections), many recordings exhibited noise. No significant correlation was seen between PhNR amplitude and number of injections.
PhNR measures cone-driven ganglion cell function. Reduced amplitudes with increasing injections in this cross-sectional study are consistent with reduced ganglion cell function in long-term therapy. In the second study, no significant association was found, possibly due to different stimulus parameters or the substantially poorer signal-to-noise ratio with skin electrodes. The findings invite further exploration in a larger, longitudinal study.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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