Monocular and Binocular Contrast Sensitivity Functions as Clinical Outcomes in Amblyopia

Abstract

 

Purpose

 

Despite the recognition of the importance of contrast sensitivity function (CSF) deficits in amblyopia, clinical assessment of CSF deficits has not been feasible. The purpose of this study is to: 1) characterize monocular and binocular CSF deficits in amblyopia; 2) examine the potential for predicting amblyopia with CSF metrics; 3) evaluate the feasibility of CSF metrics as clinical outcomes for amblyopia.

 

Methods

 

The quick CSF method [1], a Bayesian adaptive method that estimates the full shape of the CSF, was applied to assess contrast sensitivity in participants with amblyopia (n=11), strabismus without amblyopia (n =20), myopia (n=5) and normal vision (n = 24). For each participant, assessments of one binocular and two monocular CSFs were completed in a relatively short time (~15 min), using a portable tablet device [2]. For each cohort of patients, two contrast sensitivity metrics (i) AULCSF - area under the log CSF - and (ii) CSF acuity - the cutoff-frequency at which sensitivity=2.0 - were calculated, and compared with other clinical characteristics.

 

Results

 

Contrast sensitivity of amblyopic eyes was markedly impaired compared with fellow eyes, strabismic eyes without amblyopia, myopic eyes or normal eyes (p <0.001). The CSF acuity measure accounted for 72% to 81% of the variance in logMAR acuity data (p < 0.001). Comparing binocular and monocular CSFs revealed no binocular summation for amblyopia, relative to strabismus, myopia and normal vision. Logistic regression analyses concluded that interocular differences in AULCSF and CSF acuity were sufficient to classify patients with amblyopic vs. non-amblyopic vision (p<0.05), without logMAR acuity as a predictor.

 

Conclusions

 

The CSF provides rapid classification and prognosis assessment of amblyopic vision. Monocular and binocular CSF metrics define important characteristics of amblyopia that are not captured by acuity alone. The current study provides a valuable foundation for improving monocular and binocular CSF testing (e.g., reduce testing time) as an outcome for amblyopia treatment. (1) Lesmes, Lu, Baek, and Albright (2010), JOV,10 (3):17. (2) Dorr, Lesmes, Lu, & Bex (2013), IOVS, 54, (12), 7266-7273.

 

 

Keywords: 640 pattern vision • 417 amblyopia • 709 screening for ambylopia and strabismus