Abstract
Purpose :
Vision impairments contribute to poor balance and falls. While prior research has investigated effects of eye diseases such as age-related macular degeneration and glaucoma on balance, the link between retinitis pigmentosa (RP) and postural control is not understood. The purpose of this project is to identify vision-related factors that are associated with worse balance in RP.
Methods :
Fifty (N=50) adults with RP and thirty-seven (N=37) healthy adults underwent assessments of their vision and balance evaluations under multiple sensory conditions. The focus in the present analysis is on the most challenging condition for RP participants, specifically standing on foam with eyes open. Participants were asked to stand as still as possible for 20 seconds while sway was recorded using an Opal IMU system (Opal APDM; APDM Inc., Portland, OR). Data were filtered using a zero-phase Butterworth filter (3Hz cutoff frequency). Root-mean-square (RMS) and time-normalized path length (NPL) of the anterior-posterior acceleration time-series were computed as balance metrics. RP participants were classified as having good or worse balance using an NPL threshold based on the data from the controls group (mean + 1 S.D.). Regression models were used to compare vision-related parameters between the normal and worse RP groups while controlling for age, height and weight. The vision-related parameters, evaluated in the better and worse eye, included visual acuity, contrast sensitivity, visual field tests parameters, ellipsoid zone width (EZW), retinal thickness and dark adaptrometry metrics. Statistical significance was set at 0.05.
Results :
Only EZW both in the better eye (p=0.03, F-ratio=5.09) and worse eye (p=0.03, F-ratio=5.21) were statistically significant different between the RP group with normal balance and the RP group with worse balance. More specifically, EZW was nearly doubled in the group with good balance compared to the findings in the worse balance group (e.g. 8.9o vs. 4.9 o in the better eye, and 7.7o vs. 3.8o in the worse eye).
Conclusions :
This is the first study relating postural control performance and EZW, which is often used as a biomarker of photoreceptor structure. The structural integrity of the ellipsoid zone has been previously associated with visual functional outcomes in ocular diseases. The findings of this study warrants further research into EZW as a biomarker of reduced balance control.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.