Abstract
Purpose :
Refractions identified through optimization of image quality metrics (IQM) may bypass some of the challenges of current refracting techniques for patients with Down syndrome (DS). The purpose of this study is to determine which optimized IQM identified sphero-cylindrical refractions that provided best predicted visual acuity (VA).
Methods :
Autorefraction, habitual refraction (spectacles: n=23, unaided: n=7), and dilated wavefront error (WFE) were obtained for 30 subjects with DS. For each eye, the resultant metric value for 16 IQM was calculated after >25000 sphero-cylindrical combinations of refraction were added to the measured WFE to generate residual WFE in the presence of each refraction. The single refraction corresponding to each of 16 optimized IQM value per eye was selected and used to generate acuity charts. Charts were also created for autorefraction, habitual refraction, and a theoretical zeroing of all lower-order aberrations. The resultant charts were grouped in 10 sets with a clear chart randomly inserted in each set. 5 dilated controls (≤20/20 acuity) viewed each set on a high contrast monitor through a unit magnification telescope with a 3mm pupil aperture. Observers read each chart until 5 letters were missed (logMAR scoring). Letters lost was calculated as the difference in acuity from the clear chart. Average letters lost for the 5 observers for each chart was used to rank the IQMs for each DS eye.
Results :
Average acuity for the best performing refraction for all DS eyes was within 5 letters (0.11±0.05 logMAR) of the clear chart acuity. Optimized IQM refractions had ~3.5 lines mean improvement from the habitual refraction (0.37±0.22 logMAR, p<0.001). 6 metrics (VSMTF, VSX, SRX, LIB, AreaMTF and STD) identified refractions that were ranked first, or within 0.06 logMAR of first, in >90% of eyes. Habitual refraction and autorefraction were ranked among the 3 worst performing refractions in 90% and 82% of the eyes, respectively.
Conclusions :
6 IQMs, when optimized, most consistently provided refractions with resultant acuity closest to a perfect chart, while habitual corrections and autorefraction performed among the worst, indicating that the utilization of spectacle prescriptions identified from IQM optimization techniques may be a useful tool to improve VA in this population.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.