The effects of blur and eccentric viewing on adult acuity for pediatric tests: implications for amblyopia detection.
OBJECTIVE
The detection of amblyopia in children relies on an accurate assessment of visual acuity. Visual deficits in anisometropic and strabismic amblyopia are different, but the influence of chart design, in particular position, and type of crowding features on visual acuity in the two types of amblyopia, is not clear. Certain aspects of amblyopic spatial vision are mimicked in healthy individuals by imposing increasing levels of blur and retinal eccentricity. We measured the effects of these conditions on visual acuity in healthy adults, with crowded and uncrowded vision tests.


METHODS
Visual acuity was measured under conditions of blur (0-4 D) and eccentric viewing (0-5 degrees) using high-contrast optotypes derived from common children's acuity charts. Optotypes were presented in isolation, in commercially available crowded configurations, and in configurations with closer target-flanker separations than those currently available.


RESULTS
Dioptric blur had similar degradative effects on crowded and isolated visual acuity (P > 0.05), whereas eccentric viewing resulted in a larger deterioration of visual acuity for crowded tests (E2 of 0.86-1.06) than for isolated optotypes (E2 of 1.57-1.72) (P < 0.05). Maximum crowding effects occurred for closer target-flanker separations than those currently used commercially.


CONCLUSIONS
In so far as blur and eccentric viewing mimic spatial acuity deficits in amblyopia, the results suggest that crowded tests might be of limited value in the detection of anisometropic amblyopia, but should be valuable in the detection of strabismic amblyopia. Crowding effects would be greater if flanking features were placed closer to the target than they currently are in commercially available charts.
Anglia Vision Research, Department of Vision and Hearing Sciences, Anglia Ruskin University, Cambridge, United Kingdom.
Monika A
MA
Formankiewicz
Sarah J
SJ
Waugh
D000328:Adult; D000550:Amblyopia / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation / Q000379:methods; D012030:Refractive Errors / Q000503:physiopathology*; D012684:Sensory Thresholds / Q000502:physiology; D014787:Vision Tests / Q000379:methods*; D014792:Visual Acuity / Q000502:physiology*; D055815:Young Adult
amblyopia; children's visual acuity charts; crowding; dioptric blur; eccentric viewing