Abstract
Purpose :
Amblyopia is a neurodevelopmental disorder characterised by deficits in visual acuity (VA). Amblyopes with strabismus are more sensitive to visual crowding so it is important to use crowded VA tests to enhance interocular differences (IOD). Recent research suggests that current “crowded” visual acuity tests are not optimal (Formankiewicz & Waugh, 2013; Song et al, 2014). Surrounding features should be similar to, and placed closer to, the target optotype (Fig 1). Until now, such a test has not been tested in children with amblyopia.
Methods :
Monocular VA thresholds were examined in groups of children: a control group (n=24) and amblyopic groups (n=44; n=22 anisometropic amblyopes, n=22 strabismic/mixed amblyopes), aged 3-11 years. VA thresholds for both “crowded” and isolated optotypes were obtained from self-paced, interleaved, two-down, one-up staircases combined with a four-alternative, forced-choice (4AFC) paradigm. Crowding magnitudes were calculated as: “crowded” VA - isolated VA (logMAR). VA was also obtained with the Sonksen logMAR test (SLT), a clinical flip-chart acuity test.
Results :
When compared to the SLT the following results were found. Significantly increased crowding magnitudes were seen with the optimised arrangement for all groups (p<.001), particularly for strabismic/mixed amblyopes (p<.001). In addition, IODs in crowded VA were significantly larger for strabismic/mixed amblyopes (p<.005) and significantly smaller for anisometropic amblyopes (p<.05). IODs in crowding magnitude were significantly increased in strabismic/mixed amblyopes (+0.064±0.020, p=.002) and significantly decreased for anisometropic amblyopes (-0.056±0.020, p=.007) (Fig 2).
Conclusions :
The optimised optotype arrangement increased both magnitudes of crowding and IODs (in crowded VA and crowding magnitude) for strabismic/mixed amblyopes and decreased IODs (in crowded VA and crowding magnitude) for anisometropia amblyopes, highlighting their different underlying neurological deficits and supporting the proposal that optimised crowding enhances detection of amblyopia.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.