Abstract
Purpose :
To determine if control observers can be used as a surrogate to predict actual or relative acuity of patients with Down syndrome (DS) wearing different refraction types.
Methods :
30 adults with DS (age 29±10 yrs) were enrolled in a clinical trial where clinical refractions and dilated wavefront error were obtained. Objective refractions were then determined from the wavefront measures by optimizing two vision quality metrics: PFSt (pupil fraction tessellated) and VSX (visual strehl). Monocular distance visual acuity was obtained at a 2nd study visit with a Bailey-Lovie-style chart for each refraction, plus the presenting correction (habitual). Then, 5 young adults without DS viewed acuity charts simulating the retinal image produced by the four refractions for each DS eye. Controls viewed the 240 charts monocularly through a unit magnification 3mm aperture telescope and performed the same acuity task as the patients with DS. For comparison of acuities, the group median acuity (DS vs control) for each refraction type (clinical, VSX, PFSt, habitual) was determined. To determine the ability to predict relative performance, refraction type was objectively ranked within each group and eye, such that rank 1 was assigned to the refraction with the lowest/best distance acuity. Group median ranking for each refraction type was compared using a Wilcoxon Signed Rank test.
Results :
Median visual acuity for patients with DS ranged from 0.46 logMAR (IQR: 0.32 to 0.54) with habitual correction to a best of 0.36 logMAR (IQR 0.28 to 0.54) with VSX, whereas controls ranged from 0.37 logMAR (IQR: 0.29 to 0.42) with habitual correction to 0.01 logMAR (IQR: -0.02 to 0.05) with VSX. When comparing relative performance of the refraction types, there was no significant difference in the median rank of PFSt between groups (OD: p=0.27; OS: p=0.21), indicating good agreement. All other correction types resulted in a significant difference in rank (p<0.001) with DS subjects having relative higher rank with habitual and clinical compared to controls, and lower relative rank with the VSX.
Conclusions :
Actual visual acuity did not match between the patients with DS and controls; however, relative performance was in agreement for PFSt. Visual acuity in patients with DS did not show the same level of vision improvement with VSX as in controls, indicating that another factor besides optical quality must be limiting the acuity of those with DS.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.