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Melanie R Lalonde, Ange-Lynca Kantungane, Alfredo A Sadun, Stuart G Coupland, Rustum Karanjia; Photopic Negative Response in Carriers and Affected Patients with Leber’s Hereditary Optic Neuropathy. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4242.
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© ARVO (1962-2015); The Authors (2016-present)
This study was to investigate whether functional photopic negative response (PhNR) correlates with subjective measures of retinal sensitivity and structural metrics in both LHON affected and carriers.
Full field PhNRs were recorded using red (640 nm) flashes at different stimulus intensities including 7 cd●s/m2, on blue (470 nm) rod saturating background. The amplitude of PhNR was compared to mean deviation (MD) values from 30-2 visual fields and to average and quadrant values from optical coherence tomography scans of both the retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC).
PhNR amplitudes were significantly reduced in LHON affected (-13.0 ± 2.9 µV; n=21) and in carriers (-23.3 ± 4.5 µV; n=27) compared to controls (-40.2 ± 3.4 µV; n=28). T-tests indicated that PhNR was statistically different across all groups: between control and carriers (p<0.001), control and affected (p<0.001), and carriers and affected (p=0.046). In affected subjects, PhNR amplitude was correlated with MD (r=-0.641, p<0.003; n=19). This correlation was not seen in carriers (r=0.086, p=0.669; n=27). Average RNFL thickness was also significantly thinner (p<0.001) in affected (67.8 ± 4.6 µm; n=19) compared to carriers (94.0 ± 2.1 µm; n= 29). PhNR and average RNFL thickness were correlated in affected (r =-0.512, p<0.03; n=18). Of interest, PhNR was statistically correlated with RNFL thickness in the inferior (r=-0.535, p<0.03) and the nasal quadrant (r=-0.618, p<0.01). No correlations were seen between PhNR and RNFL metrics in carriers. Average macular GCC thickness was significantly reduced (p<0.001) in affected (53.3 ± 1.1 µm; n=20) compared to carriers (77.9 ± 2.6 µm; n=29); however, no correlations were seen between PhNR and GCC metrics in both affected and carriers.
The PhNR amplitude correlated with both MD and RNFL thickness in LHON affected patients. The correlation was strongest in the nasal quadrants of the RNFL; the last area of loss in LHON affected patients (Sadun et al., IOVS 2012 Nov 9;53(12):7608-17). Our results suggest that PhNR is a functional parameter that can discriminate different levels of RGC dysfunction between LHON affected patients and carriers. Overall, PhNR is a promising objective measure of RGC health in LHON at different stages of the disease and could prove to be an objective quantifiable functional biomarker in this patient population.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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