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Jessica Tang, Flora Hui, Xavier Hadoux, Bernardo Soares, Michael Jamieson, Jonathan G Crowston; An optimised protocol for the portable electroretinogram device to probe changes in glaucoma. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3028.
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© ARVO (1962-2015); The Authors (2016-present)
The photopic negative response (PhNR) of the full-field electroretinogram (ERG) can provide objective measurement of retinal ganglion cell function. To enhance its utility for clinical monitoring of glaucoma, we have developed a protocol optimised for a portable ERG system. We assessed the PhNR correlation with visual field (VF) and retinal nerve fibre layer (RNFL) thickness and evaluated its change over a year in healthy controls and patients following primary trabeculectomy.
Photopic ERGs were recorded using the RETeval™ (LKC Technologies Inc., Gaithersburg, MD, USA) in one dilated eye of glaucoma (n=41, age-range=32-85 years) and control participants (n=19, 26-73 years). Further, 9 patients scheduled for trabeculectomy were recruited. For each of the red flash intensities (-1 to 1.1 log cd.s/m2) on a blue background (10 cd/m2), 100 sweeps were recorded and averaged. PhNR (baseline-to-trough) was extracted for each intensity and fitted to a saturating hyperbolic function to obtain the maximum amplitude (Vmax). ERGs were repeated within 1-month in all controls, and at 12 months in 7. Trabeculectomy patients had ERGs recorded pre-surgery, 1-, 3- and 12-months after surgery. All glaucoma participants had VF (24-2 Humphrey Field Analyser) and RNFL thickness measurements (Cirrus HD-OCT, Carl Zeiss Meditec, Dublin, CA; RS-3000 Advance, NIDEK, Aichi, Japan). Pearson correlation coefficient and 95% coefficient of repeatability (COR%) were evaluated.
Vmax was significantly correlated with VF mean deviation (MD, R2=0.22, p=0.0018) and RNFL thickness (R2=0.37, p<0.0001). COR% for Vmax in controls was ±34% (CI: 20–49%) at 1-month and ±35% (CI: 11–60%) at 1-year. In the trabeculectomy group, Vmax changed beyond test-retest variability at 1 and 3-months in 6 patients, which was sustained at 12 months in 4. The magnitude of IOP reduction after trabeculectomy was not significantly correlated with the magnitude of Vmax change at 1 year (p=0.51).
The optimised ERG protocol for the portable device can reliably measure the PhNR longitudinally. The positive correlation with MD and RNFL thickness, along with detectable changes in Vmax after trabeculectomy, indicate its potential value for clinical monitoring.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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