Abstract
Purpose :
Retinitis pigmentosa (RP) is a rare inherited disease with few treatment options. Photoreceptor degeneration leads to impaired visual function with poor fixation and eventual blindness. Full-field stimulus threshold testing (FST) assesses retinal sensitivity by determining the lowest luminance stimuli that a patient can see. This analysis evaluated test–retest reliability of visual acuity (VA) and FST in an ongoing Phase 1/2a study (NCT02556736) of RST-001, an investigational optogenetic gene therapy, in patients with advanced RP.
Methods :
Data from adult patients with very poor vision, ranging from ‘light perception’ to ‘count fingers’, at screening and baseline visits (test–retest; separated by 33–85 days) were analyzed. VA assessments (converted to LogMAR) and FST were conducted (Espion ColorDomeTM LED full-field stimulator; Diagnosys LLC, Lowell, MA). Analyses were performed in SAS version 9.4.
Results :
The Phase 1/2a study is ongoing. Among 13 patients, VA in both eyes was repeatable (coefficient of repeatability [CR]: 0.3 LogMAR) and correlated (Spearman’s rank correlation coefficient: 0.78) across test–retest visits. Up to 28 eyes from 14 patients were analyzable for one or more assessments via FST. For red, white, and blue light, mean sensitivity thresholds at test (and retest) were −4.9 dB (−1.5 dB), −9.7 dB (−7.7 dB), and −15.6 dB (−16.0 dB), respectively. FST assessments were repeatable (CR: 2.7 dB, 5.3 dB, and 6.2 dB) and highly correlated (Spearman’s rank correlation coefficients: 0.97, 0.95, and 0.99) between test–retest measures. Mean sensitivity thresholds between test and retest visits were equivalent; on Bland–Altman plots, mean threshold sensitivity differences were approximately 0 dB for red and white, and −1.5 dB for blue light.
Conclusions :
VA assessments were reliable across test–retest visits but, given the qualitative aspect of vision in this low range, they lacked discrimination. FST represents a reliable and consistent test that can be effectively used in patients with advanced RP and low vision. Changes greater than ~6 dB (maximum CR in FST) could be considered clinically meaningful.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.