Abstract
Purpose :
Simultaneous binocular retinal polarization scanning has been successfully used to distinguish bifoveal fixation from monofixation as a means of screening for amblyopia in children. Although device performance is known to be degraded by spectacles and relies on accommodation (originally designed for screening children), we evaluated the ability of retinal polarization scanning to distinguish bifoveal fixation from monofixation in adults.
Methods :
We studied 36 adults, ages 18 to 85y, presenting to an adult strabismus referral clinic. The gold standard for bifoveality was defined as at least 60 seconds of arc (arcsec) on the Randot Preschool stereoacuity test (StereoOptical, Chicago IL) performed at 40cm. Sensory monofixation was defined as 200 arcsec or worse, and indeterminate as 100 arcsec. To minimize potential confounding from poor VA, only subjects with 20/40 or better VA in each eye were included. Retinal polarization scanning was performed using the blinqPro (Rebion, Boston, MA), yielding a binocularity score from 0% to 100%. Analogous to children, we defined bifoveality by retinal polarization as a blinqPro binocularity score of 60% or better. Testing was performed through spectacles if worn. We compared assessments of bifoveality versus monofixation using kappa statistics.
Results :
Of 36 adults, 7 (19%) were classified as bifoveal based on Randot Preschool near stereoacuity testing, 8 (22%) as indeterminate and 21 (58%) as monofixational. Only 3 (8%) of subjects were classified as bifoveal by the blinqPro. Agreement in bifoveality, between Randot Preschool and blinqPro was poor (kappa = -0.07, 95% CI -0.20 to 0.06, excluding subjects indeterminate on stereoacuity testing). No adults identified as bifoveal on Randot Preschool testing were identified as bifoveal on blinqPro testing.
Conclusions :
In contrast to application of the blinq to children, where it is very useful in screening for amblyopia, the current device does not reliably distinguish bifoveality from monofixation in adults. The blinq manufacturers had already identified limitations in detecting bifoveality in adults; inadequate accommodation, attempting to scan through spectacles where coatings and reflections interfere with the signal, and image degradation from less than clear media. Further modification of methods to identify bifoveality are needed for adults.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.