Abstract
Purpose:
Amblyopia is the most common cause of monocular visual loss in children, affecting approximately 3-5% of the population. Although amblyopia is associated with a wide range of visual deficits that include reduced visual acuity, loss of contrast sensitivity, spatial distortion, and abnormal binocular interaction, outcomes for amblyopia treatment currently monitor only visual acuity. A major obstacle to broad characterization of the deficits has been inefficiency of psychophysical assessments such as long testing time. The present study aims to develop novel methods for rapidly assessing correlation among these core deficits in amblyopic vision.
Methods:
Contrast sensitivity, spatial distortion and binocular interaction were assessed in subjects with strabismic amblyopia (5-46-yr-old; mean age =14.38 yrs; n=8), strabismus without amblyopia (6-84-yr-old; mean age =34.4 yrs; n=15) and normal vision (5-32-yr-old; mean age =18.71 yrs; n=24). The contrast sensitivity function (CSF) was estimated in less than 30 trials with the quick CSF method (Lesmes et al., 2010) on a handheld device (iPad). Local and global spatial distortion was measured with a dichoptic pointing task (Mcilreavy et al., 2010) in which subjects aligned a target dot presented to their amblyopic eye with a cross-hair presented to their fellow eye. Binocular interaction was measured with a dichoptic matching task (Ding & Sperling, 2006) in which subjects matched the phase of a binocular probe to the cyclopean percept of a dichoptic pair of gratings whose ratios were systematically varied. Testing was performed in an ophthalmology clinic with a total testing time of approximately 20 minutes.
Results:
Compared to subjects with normal vision or strabismus without amblyopia, subjects with amblyopia had significantly reduced contrast sensitivity (F(2,35) = 4.7, p = 0.015), significantly larger spatial distortion (F(2,37) = 4.8, p = 0.014) and decreased interocular contrast summation.
Conclusions:
Amblyopia can be characterized by pronounced deficits in contrast sensitivity, spatial distortion, and binocular interaction suggesting a higher contrast requirement for the amblyopic compared to the fellow eye. Despite the short testing time, our novel methods are as effective as conventional laboratory assessments for quantifying the core deficits in amblyopia.
Keywords: 417 amblyopia •
722 strabismus •
434 binocular vision/stereopsis