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M. Gari, A. Colotto, T. Salgarello, A. Fadda, A. Di Renzo, G. Anselmi, E. Balestrazzi, B. Falsini; Photopic Negative Response From Retinal Hemifields in Glaucoma. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5302.
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© ARVO (1962-2015); The Authors (2016-present)
Recent studies have shown that the photopic negative response (PhNR) of the electroretinogram (ERG) is a sensitive tool for detection of glaucoma. The aim of this study was to evaluate the PhNR of the focal ERGs from different retinal hemifields (RHFs) in chronic open angle glaucoma (OAG).
PhNRs of the focal ERGs (Colotto et al., IOVS, 2000) were recorded from superior (S), nasal (N), temporal (T) and inferior (I) RHFs in 24 OAG patients (age range 37-76 years; Humphrey 30-2 mean deviation: -1 - -8 dB) and 12 age- matched control subjects. Stimulus was the on-off modulation of a high-resolution TV monitor uniform field (20 x 12 degrees, frequency 2.8 Hz, mean luminance 80 cd/m2, modulation depth 90%) presented on a steady adapting background to the different RHFs, by appropriately orienting subjects’fixation. Amplitude and time-to-peak of the PhNR as well as the amplitude ratio of PhNR to b-wave (PhNR/b) were measured.
Mean PhNR amplitudes and times-to-peak of PhNRs from all RHFs were reduced (by 50%, p < 0.01) and delayed (by 12 ms, p < 0.01), respectively, as compared to control values. The mean PhNR/b ratio from all RHFs was reduced (p < 0.01) compared to control values. Mean PhNR and PhNR/b losses observed in patients did not differ between S and I RHFs but were greater for the N compared to the T RHF. In individual patients, RHF PhNR losses did not always mirror qualitatively the corresponding perimetric losses.
PhNR of the focal ERG from all RHFs is significantly altered in OAG. RHF responses appear to add useful information to the standard centrally-recorded PhNR, showing N-T asymmetry, although their relationship with localized perimetric losses requires further study.
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