Abstract
Purpose :
Full-field stimulus threshold (FST) measures the minimum light stimulus required to evoke a visual response from a fully dark-adapted receptoral mechanism. We describe the distribution of luminance thresholds in subjects with severe retinitis pigmentosa (RP), aiming to establish a deep phenotyping protocol.
Methods :
RP cases with ultra-low vision (ULV) showing severe visual acuity decline (counting fingers or worse) were enrolled. Comprehensive ophthalmological examinations were performed, including full-field electroretinograms (ffERGs) recorded according to the ISCEV standard. Full-field color stimuli were generated by the Diagnosys Profile ganzfeld ColorDome (Diagnosys, LLC, MA) which utilizes narrow-band LEDs of 448 nm (blue), 530nm (green), and 627 nm (red). FST was performed according to the previously published method (Klein, Birch 2009). The dark-adapted color FST was performed after 40 minutes dark adaptation in the following order: (i) blue; (ii) red; and (iii) white stimulus.
Results :
The median age of onset/examination of 40 eyes from 23 RP cases was 9.0 (range, 0 to 40)/59.0 (11 to 82). The median visual acuity of 40 eyes was 2.28 (range, 1.40 to 3.00) LogMAR unit. The full-field ERGs were undetectable both in dark-adapted and light-adapted conditions in all 23 cases. The median value for blue/red/white FST was -1.71（range, -5.42 to 0.18）/-0.96（-2.84 to 1.04）/-1.18（-4.61 to 0.96） log10 cd.s.m-2 in 40 ultra-low vision (ULV) RP eyes. The median value of thresholds for blue/red/white FST was -7.70(-8.33 to -6.93)/-5.32(-6.24 to -4.82)/-7.11(-7.62 to -6.51) log10 cd.s.m-2 in the 40 healthy eyes. FST revealed a significantly different range of thresholds for each colour stimulus between 40 ULV RP and 40 healthy eyes.
Conclusions :
Quantitative assessment of the sensitivity of the visual field was available with FST for patients with ULV RP demonstrating undetectable ERGs, in keeping with previous reports (Roman AJ et al. Prog Retin Eye Res. 2021; Klein et al. Doc Ophthalmol. 2019). The broader distribution of luminance thresholds was illustrated in ULV RP patients, which was significantly higher than that of healthy subjects. These data would help monitor and counsel patients, as well as in the assessment of visual function in therapeutic trials.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.