The Brückner transillumination test: limited detection of small-angle esotropia

Abstract

Objective: To evaluate the sensitivity of the Brückner test in detecting esotropia of 2° to 10° by interocular asymmetry of the red fundus reflex.

Design: Single-blinded evaluation of the diagnostic test.

Participants: Five blinded observers and 20 isometropic orthotropes.

Testing: Set-up 1 included monocular evaluation of the Brückner reflex test for each eye of 10 subjects. The subjects alternated fixation between an ophthalmoscope light and an eccentric target (2.5°, 5°, 7.5°, and 10°). Set-up 2 comprised simulation of esotropia of 2° to 5°, 7.5°, and 10° by base-in prisms placed in front of both eyes of 20 subjects. The subjects fixated with either their right or left eye. As a control experiment, 0.5° base-in prisms were used.

Main outcome measures: Set-up 1 tested the sensitivity in detecting a change in reflex between central and eccentric retinal illumination. Set-up 2 tested the sensitivity and specificity in detecting asymmetry of the Brückner reflex between the 2 eyes as a dimming of the reflex of the fixating eye in a 2° to 10° simulated esotropia.

Results: In set-up 1, fixation of the ophthalmoscope light owing to foveal dimming was discriminated from fixation of the eccentric target in 98.2% of the trials, regardless of target eccentricity. In set-up 2, esotropia of 2° to 5° was detected in 62% of 100 trials by red reflex asymmetry. Dimming of the reflex in the fixating eye was found in 48% of 100 trials. Esotropia of 7.5° and 10° was detected in 85% and 97% of the trials, respectively. Dimming in the fixating eye was present in 75% and 86% of the trials, respectively. Thirty-six percent of the 300 control tests were false-positives.

Conclusions: When the eccentric fundus reflex was compared with the central reflex in the same eye, dimming owing to central fixation of the ophthalmoscope was reliably detected. However, comparison of the eccentric red reflex in the strabismic eye with the central reflex in the fixating eye showed that the Brückner red reflex test was not suitable for detecting small angles of squint.

Financial disclosure(s): The authors have no proprietary or commercial interest in any of the materials discussed in this article.