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L.M. Ventura, R. De Los Santos, N. Sorokac, W. Feuer, V. Porciatti; Relationship Between Pattern Electroretinogram and Retinal Nerve Fiber Layer Thickness in Early Glaucoma . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4009.
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© ARVO (1962-2015); The Authors (2016-present)
To compare reduction of retinal ganglion cell (RGC) function and retinal nerve fiber layer (RNFL) thickness in early glaucoma.
Subjects were 84 patients with suspicion of glaucoma due to disc abnormalities (GS: mean age 56.6 ± 13.8 years, Standard Automated Perimetry (SAP) Mean Deviation –0.58 ±1.34 dB), and 34 patients with early manifest glaucoma (EMG, mean age 65.9 ± 10.7 years, SAP–MD –2.7 ± 4.5 dB). Both GS and EMG patients had normal corrected visual acuity ( 20/25), and no other systemic or retinal disease. RGC function was measured by means of Steady–State Pattern Electroretinogram (PERG) and RNFL thickness with Optical Coherence Tomography (OCT). RGC axons recruited by the PERG stimulus enter the disc in a temporal sector whose angle subtends about 60º above and 75º below the horizontal axis. RNFL thickness was measured for this sector (PERG–matched RNFL) as well as for standard optic nerve quadrants.
In the average patient population (GS+EMG), PERG amplitude tended to decrease with decreasing mean RNFL thickness (R=0.285, P=0.001) as well as with decreasing PERG–matched RNFL (R=0.235, P=0.01). The relative amount of loss (deviation from age–predicted normal values) was, on average, larger for the PERG amplitude (GS: –22.6%; EMG: –41.8%) compared to the PERG–matched RNFL (GS: –4.3%; EMG: –13.3%). Losses exceeding the lower 95% tolerance intervals of the normal population were more frequent for PERG amplitude (GS: 26%; EMG: 56%) than for PERG–matched RNFL (GS: 2%; EMG: 24%).
Reduction in RGC electrical activity exceeds the proportion expected from lost RGC axons, suggesting that a population of viable RGCs in the central retina is dysfunctional in early glaucoma. Combining PERG and OCT may provide unique information on the functional status of anatomically present RGC axons.
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