Assessing residual visual function in severe vision loss.
OBJECTIVE
Vision restoration is a fast-approaching reality for some people with profound vision loss. In order to reliably determine treatment efficacy, accurate assessment of baseline residual visual function is critical. The purpose of this study was to compare residual function as detected on Goldman visual field (GVF) and full-field ERG (ffERG), and correlate with the remaining photoreceptor layer as determined by spectral-domain optical coherence tomography (SD-OCT), in subjects with severe vision loss.


METHODS
Fifty-four subjects with advanced retinitis pigmentosa and no discernible signal on ffERG were included. Trace residual function was assessed using discrete Fourier transform (DFT) analysis of the 30-Hz flicker ffERG and the percentage of remaining GVF. The horizontal extent of the outer nuclear layer (ONL) on SD-OCT was assessed.


RESULTS
Thirty percent of the study eyes had a 30-Hz flicker response after DFT analysis of the ffERG, and 57% had a measurable GVF. Thirty-five percent had a visible ONL on SD-OCT. There was no significant correlation between the magnitude of the 30-Hz flicker response and the percentage of remaining GVF (r = 0.172, P = 0.213) or the extent of remaining central photoreceptors (r = 0.258, P = 0.06). Only 17% of the eyes had all three parameters detected.


CONCLUSIONS
Discrete Fourier transform analysis of the 30Hz-flicker ffERG response and GVF can detect trace residual function. Evidence of this residual function is not always supported by the structural correlate of a measurable ONL. Our findings highlight the importance of completing a multimodal assessment to accurately define the important parameters of retinal structure and function in people with profound vision loss.
Centre for Eye Research Australia, The University of Melbourne, Royal Victorian Eye and Ear Hospital, East Melbourne, Victoria, Australia.
Lauren N
LN
Ayton
Nicholas V
NV
Apollo
Mary
M
Varsamidis
Peter N
PN
Dimitrov
Robyn H
RH
Guymer
Chi D
CD
Luu
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004596:Electroretinography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D012160:Retina / Q000473:pathology / Q000503:physiopathology*; D012174:Retinitis Pigmentosa / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology; D012720:Severity of Illness Index; D041623:Tomography, Optical Coherence / Q000379:methods; D015354:Vision, Low / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D014792:Visual Acuity / Q000502:physiology*; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology*
electroretinography; low vision; retinitis pigmentosa; vision regeneration; visual function