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T.C. Prager, R. Seaman, P. Wollan, Y. Zou, S.C. Allison; Determining the Effect of Refraction/Eye Length on Electroretinogram B–Wave Amplitudes . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5692.
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In a review of 286 patients ranging in age from 18to 85 years, there was a decrease in ERG amplitude with ageand scotopically females show larger amplitudes than males byabout 10% (e.g. females regression= 594 µv + 1.87 * ageversus males = 547 µv + 1.44 * age). To test that thedifference in B–wave amplitude is due to eye refraction/axiallength a cohort of 39 subjects were evaluated.
Using ISCEV standards for electroretinography, 27 femalesand 12 males, ages 19 to 59 with varying refractive error (range–8.75 D to +0.75 D females, –10.75 to +1.75 D males)were tested at scotopic bright white and photopic 30 hertz testconditions. A commercial instrument, Nicolet Spirit, and Jetcorneal electrodes were used to record data. An I3A–scanwith an immersion shell provided axial length information. Datawas converted to logarithms prior to linear stepwise regression(backward) statistics using SPSS software.
Obtaining normative values for B–wave amplituderequires both patient age and refraction/axial length. Between20 and 50 years there was an average per decade decrease inscotopic amplitude of 5.5%, photopic 8%. Eye length may explainthe reported difference between female and male B–waveamplitudes. Both axial length and refraction correlated significantlywith change in scotopic B–wave amplitude, although thiswas not the case for photopic amplitudes. The scotopic correctionfactor for axial length is 674.39 + –6.41 * axial length(6.41 µv/mm or 1.23% per mm) and for refraction, 506.48+ 2.91 * refraction (2.91 µv/D or 0.5% per D).
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