Abstract
Purpose :
Visual acuity (VA) is the FDA standard measurement to quantify vision clarity and the ETDRS is the approved gold standard. OTG-i Vision Suite (OVS), an iPad application driving a standard 4K screen that measures VA more comprehensively than the ETDRS has been developed for use in multisites regulatory clinical study. The objective of this study was to validate the application repeatability and sensitivity with the presence of defocus for non-presbyopic and presbyopic populations.
Methods :
Three charts were evaluated: OVS letters (10 ISO letter per line) (LVA) and individual Landolt C (20 rings per line, each displayed for 300ms) (TCVA) against the ETDRS chart as control. All the charts were presented under controlled luminance (≥160cd/m2) representative of daytime lighting at 90% contrast. Repeatability (mean difference & 95% CI) was established by comparing the measurements carried out a few days apart with the participants optimal vision correction. Sensitivity (mean VA change from optimal) was measured by quantifying the vision loss associated with +0.25D and +0.50D defocus. The validation was carried out on non-presbyopic (18-39 years, n=19) and presbyopic (40-60 years, n=15) populations.
Results :
Repeatability: excellent for all three charts with a 95% CI less than 0.1logMAR in all cases and a trend towards a smaller 95% CI for LVA and TCVA than ETDRS [mean (CI)] logMAR. For 18-39yrs: LVA 0.029 (0.059); TCVA 0.041 (0.064); ETDRS 0.036 (0.078). For 40-60yrs: LVA 0.047 (0.039); TCVA 0.008 (0.065); ETDRS 0.008 (0.090)]. Sensitivity: i. Overall all three tests detected a significant change in VA (p<0.05) with both defocus and had similar magnitude of mean logMAR VA loss (+0.25D: 0.052 to 0.067; +0.50D: 0.114 to 0.137); ii. For each population group, LVA and TCVA detected a significant change for both defocus (p<0.05) but the ETDRS failed to detect a difference for the 18-39yrs with +0.25D defocus (p=0.094).
Conclusions :
The results showed that all three charts evaluated achieved high repeatability and sensitivity to detect defocus with a trend for the OVS to be more sensitive to detect slight defocus in non-presbyopic population than the ETDRS. Additionally, the TCVA demonstrated similar repeatability as the ETDRS, supporting the clinical suitability of the exposure time selected.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.