Cover Test Reliability in Non-strabismus between Experienced and Novice Clinicians

Abstract

Purpose: : The purpose of this study was to determine the test-retest variability between experienced and novice clinicians of the prism neutralized alternating cover test (ACT) on non-strabismic subjects and to compare the values to objective results obtained by eye tracking.

Methods: : Two experienced optometrists and two second-year optometry students performed the alternating cover test at 40 cm on 50 male and female non-strabismic subjects without amblyopia who were between the ages of 20 and 40 years. The objective phoria range within the group was between 6^Δ eso and 19^Δ exo. The order of subject examination was randomized between the clinicians and the results were blind to the other clinicians. No specific instructions on test procedure were given to the clinicians. Within two hours of the clinical examination the ACT was repeated by an independent member of the research team with the subjects wearing a head mounted, video-based eye tracker. The saccade amplitude of the eye movement recordings was used to determine the phoria. The test-retest variability was determined using Bland-Altman plots and 95% limits of agreement.

Results: : The signed mean difference in values between the experienced clinicians (0.7^Δ) and between the novice clinicians (-0.1^Δ) was not statistically significantly different (p>0.05). The difference between the experienced and novice clinicians (0.8^Δ) was statistically (p<0.05) but not clinically significant. The eye tracker had statistically (p<0.05) but not clinically significant difference from both experienced (0.6^Δ) and novice (1.4^Δ) clinicians. The half widths of the 95% limits of agreement between the experienced clinicians was 3.0^Δ, the novice clinicians 4.4^Δ, the experienced and novice clinicians was 3.5^Δ, the experienced clinicians and the eye tracker was 3.5^Δ and the novice clinicians and eye tracker was 3.6^Δ.

Conclusions: : While the mean differences between experienced clinicians, novice clinicians and eye tracker values on the ACT is not clinically significant, the range of the 95% limits of agreement was quite high (±3.0-4.4^Δ). This information is useful for clinical decision making, student education and student evaluation.

Keywords: binocular vision/stereopsis • clinical (human) or epidemiologic studies: systems/equipment/techniques • vergence