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Abigail christie, Renee A Denlar, Amy Thompson, Timothy Nguyen, Martin Klein, David G Birch, Karl G Csaky; The Association between Rod Function and Low Luminance Acuity. Invest. Ophthalmol. Vis. Sci. 2020;61(7):3990.
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Low luminance deficits (LLD) have been demonstrated to be increased in age-related macular degeneration (AMD). However, the exact mechanisms of this impairment are unclear. Rod photoceptors interact with cone photoreceptors and therefore it has been hypothesized that rod dysfunction may be a key driver of loss of luminance visual acuity (LLVA). In the present work, this hypothesis was tested by determining the degree of LLVA loss in subjects with retinitis pigmentosa (RP) and minimal rod function and by assessing the effects of dark adaptation on LLVA in subjects with intermediate AMD and non-foveal geography atrophy (GA).
BCVA, LLVA, and full field electroretinograms (ffERG) were taken from subjects with RP (n= 9). LLVA was assessed by placing a 2.0 log unit neutral density filter over best corrected vision and reading a normally illuminated ETDRS chart. Following initial BCVA and LLVA, intermediate and non-foveal GA (n= 9), and control (n= 5) subjects were then dark adapted (DA) for 30 minutes. LLVA and BCVA were then taken again. All vision scores are in ETDRS letters. Statistics were analyzed using JASP 0.11.1.
RP, AMD, and control subjects were observed to have the following BCVA (μ= 75± 6, 77± 9, 84± 3), and LLD (μ= 13± 7, 22± 13, 11± 3) letter scores, respectively. The RP subjects had reduced rod function as shown by the ffERG b-wave amplitude (μ= 4.12± 9.01μV). An independent t-test showed no difference between the LLD of the RP (μ= 13± 7 letters) and control subjects (μ= 11± 3 letters, p> 0.05), but AMD subjects had a greater LLD (μ= 22± 13 letters) than the control group (μ= 11± 3 letters, p< 0.05). No difference was found between the pre dark adaptation and post dark adaptation LLDs in either the controls (μ= 4± 4 letters, p> 0.05) or the AMD group (μ= 0± 6 letters, p> 0.05).
The absence of any correlation between rod loss in RP subjects and LLD and the absence of any improvement in LLD following dark adaptation is counter to the hypothesis that rod function plays a role in low luminance visual acuity.
This is a 2020 ARVO Annual Meeting abstract.
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