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R. V. North, A. L. Jones, K. E. Mortlock, L. Phillips, J. E. Morgan, N. Drasdo; Ganglion Cell Survival Estimated from Perimetric Data in Glaucoma According to a Linear Algorithm: Correlation With PERG Amplitude. Invest. Ophthalmol. Vis. Sci. 2008;49(13):727. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Recently published data on ganglion cell receptive field density (GCRFD) across the visual field provided an opportunity to investigate the proposal that there is an approximately linear relationship between perimetric differential light sensitivity (DLS) and ganglion cell survival in glaucoma by correlating the sum of estimates from selected perimetric stimuli with the amplitude of the pattern electroretinogram (PERG).
A total of 107 subjects were examined with HFA Program 24-2 and SITA standard algorithm. The subject group comprised 28 normal controls, 30 primary open angle glaucoma, 26 normotension glaucoma and 23 ocular hypertensives. Threshold (T dB) and Total Deviation (TD dB) values from the central 8 points were recorded. DLS (S=10(T/10)) and Linearised Total Deviation scores were used to estimate GC survival, and summated values were correlated with P50-N95 PERG amplitudes. PERGs were recorded using a 19’ black and white checkerboard pattern stimulus at 95% contrast generated on a monitor subtending 24x16 degrees at a viewing distance 80cm.
Taking the combined data for all groups, the correlation and statistical significance of DLS : PERG, and estimated GCRFD: PERG (R= 0.268 and 0.264, P<0.01) were marginally better and more significant than those of MD:PERG (R=0.229, P<0.05).
It was noted that a high correlation cannot be expected due the large normative variation in GC counts, perimetric and electrophysiological data. The correlations were lower than in an earlier study perhaps due to a different range of neural damage since MD was more than double that in the current study which was designed to investigate changes in earlier stages of glaucoma. The results were therefore considered to be consistent with an approximately linear relationship, but further investigations using a wider range of defects and other criteria of neural damage are being pursued.
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