Comparison of Objective and Subjective Techniques of Strabismus Measurement in Adults With Normal Retinal Correspondence

Abstract

Purpose: Accurate measurement of strabismus is vital to proper diagnosis and treatment. Objective and subjective measurement techniques can be used. The authors hypothesized that subjective measurement techniques would measure larger deviations than objective ones.

Methods: Adults with strabismus, visual acuity greater than 20/50 in each eye, and normal retinal correspondence were measured in primary gaze at distance and near using the alternate prism and cover test and the red glass test.

Results: Seventy-three patients were prospectively enrolled. Objective mean deviations were 9.1 (distance horizontal), 5.1 (distance vertical), 10.0 (near horizontal), and 2.6 (near vertical) prism diopters (PD). Subjective mean deviations were 10.2 (distance horizontal), 6.8 (distance vertical), 12.2 (near horizontal), and 3.2 (near vertical) PD. Subjective measurements were larger by a statistically significant margin and were more likely to show the presence of a vertical deviation not measured objectively (19 occurrences vs 2 at near, P = .008; 15 occurrences vs 0 at distance, P = .004). The measured deviations were within 5 PD horizontally and 3 PD vertically most of the time (range: 66.7% to 83.6%).

Conclusions: The red glass test was more likely to measure a larger deviation at distance and near and to identify a vertical deviation not seen objectively at both distance and near. The mean difference between the tests was usually not large enough to affect surgical treatment, but could potentially result in different amounts of prescribed prism for patients treated optically. [J Pediatr Ophthalmol Strabismus. 2017;54(4):216-220.].