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Aldo A. Oregon-Miranda, Joel Gonzalez-Baron, Francisco Gomez-Aguayo; Would A Hazy Media Affect The Photopic Negative Response Electroretinogram?. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3518.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the photopic negative response electroretinogram (PhNR) recorded through simulated opaque media and assess if it is suitable for patients with cataract and/or corneal diseases.
10 subjects/20 eyes with out ophthalmic diseases and normal color vision previously evaluated with desaturated FD15 test, were submitted to a ERG Ganzfeld red flash 2.5 Cd.m2.s(627 nm) on a blue background 10cd m2 470 nm with DTL electrodes and their pupils were dilated to 9 mm before tested. Basal normal values were obtained and 3 different neutral density (ND) filters(-0.3, -0.6, -1.0 log units) were placed on a lens trial frame, the regular PhNR protocol was used creating the simulated diffuser effect of a cataract or corneal opacity with the ganzfeld and the decreased luminance with a ND filter.
A N.D filter of 0.3 log units would decrease test luminance by half, however, the PhNR /B Wave ratio increased as well as the PhNR amplitude, when increasing the density of the filter to 0.6 log the contribution of the scotopic system increased along with the b wave amplitude and the PhNR, on the contrary the PhNR/B wave ratio decreased. The 1.0 log unit filter changed waveform characteristics increasing the b wave so the response is no longer similar to the original PhNR.
The PhNR remained a robust test under severe opaque media such as a N.D filter of 0.6 log units equivalent to block 80% of the transmitted light , maintaining its values and amplitude through the experiment. Waveform characteristics should be evaluated carefully on patients with very severe media opacities thus equivalent to -1 log unit. The PhNR/B wave ratio was not constant in our trial.
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