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J.C. Chen, B. Brown, K.L. Schmid; Delayed Multifocal Electroretinogram Responses in Myopia . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5601.
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Purpose: It is known that the first order kernel multifocal electroretinogram (mfERG) responses are reduced in amplitude and increased in latency in individuals with myopia. These changes have been suggested to be primarily due to the increased axial length that accompanies myopia. We sought to investigate whether the characteristics of mfERG responses were different between emmetropes and myopes and determine the contribution of axial length to the mfERG data. Methods: Thirty subjects, with a mean age of 24.2±4.0 years, underwent mfERG testing using VERIS I. Subjects were divided into emmetropic (n=10) and myopic groups (n=20) based on their refractive error. The mfERG stimulus array consisted of 61–scaled hexagons and flickered according to a pseudorandom binary m–sequence. The amplitude and latency of the first positive peak of the first order kernel were analysed. Results: Mean refractive error of emmetropes and myopes was 0.04±0.35 D and –3.60±2.21 D respectively (p < 0.0005), with corresponding axial lengths of 23.42±0.73 mm and 24.86±0.99 mm (p = 0.001). The mfERG response latency of myopes was significantly greater (by 1.6 to 3.1 ms, F1, 28 = 4.185, p = 0.05) than that of emmetropes. This difference was significant even when axial length was taken into account as a covariate (F1, 28 = 10.819, p = 0.003). There were no differences in response amplitudes between the groups (F1, 28 = 0.114, p = 0.738). Conclusions: Delayed mfERG responses are observed in myopes and this is not simply due to their greater axial length compared to emmetropes. This suggests that there are underlying differences in retinal processing that result from being myopic.
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