Abstract
Purpose :
Freiburg Visual Acuity Test (FrACT) is an automated and criterion-free test that can assess visual acuity for very low-vision patients. The use of FrACT has been recommended for clinical trials in individuals with low vision, including optogenetics, by the International HOVER Taskforce (Harmonization of Outcomes and Vision Endpoints in Vision Restoration Trials) of over 80 of the world's experts in vision restoration and low vision. The purpose of this study is to evaluate the intervisit variability of best corrected visual acuity (BCVA) measured by FrACT in severe visually impaired individuals.
Methods :
Methods: In a prospective observational study (NCT05820100), 25 individuals with advanced Retinitis Pigmentosa (RP) and severe vision loss (BCVA worse than 1.9 logMAR, ~20/1600 Snellen equivalent) underwent BCVA assessments by FrACT at two visits four weeks apart. Other measures include visual field perimetry (Humphrey 30-2 or Octopus 900 30-2), multi-luminance shape discrimination testing (MLSDT), and Michigan Retinal Degeneration Questionnaire (MRDQ) completion.
Results :
The test-retest variability of measured BCVA in 50 eyes (of 25 individuals with severe vision loss due to RP) was evaluated by a Bland-Altman plot. The 95% confidence interval test-retest limits of agreement were found to be ±0.2 LogMAR. BCVA measured by FrACT in individuals with severe vision loss due to RP was found to be correlated with other key visual function measures: visual field index (VFI), MLSDT, MRDQ reading and MRDQ color & contrast scores.
Conclusions :
FrACT results were found to correlate highly with functional vision measures important to individuals with low vision; the 95% CI of the test-retest agreement is two lines. Utilization of FrACT to assess the effect of a therapeutic, curative or preventive intervention targeting individuals with vision non-recordable on standard (e.g. ETDRS) eye charts is reasonably likely to detect clinically meaningful change.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.