Bruckner test sensitivity to detect foveal dimming

الملخص EN

Objectives : to assess the sensitivity of the Brückner test in detecting a change in the brightness of the fundus reflex (Brückner reflex) when the fixation point changes between the ophthalmoscope light and a visual target beside the ophthalmoscope.

Methods : in a prospective, single blinded, randomized study, 3 experienced examiners conducted the Brückner test on 10 subjects with central fixation, normal visual acuity (≥ 1.0), and absence of any organic eye disorder.

The test was performed at a distance of 1 m with and without pupillary dilatation, allocating 4 different degrees of ocular deviation (2.5 deg, 5 deg, 7.5 deg, 10 deg) on either side of the ophthalmoscope.

The lateral fixation targets were marked by bold crosses.

The subjects were asked to close one eye and to change fixation between the light of the ophthalmoscope and one of the 8 crosses starting either at the light or at one of the eccentric targets.

The sequence of targets was unpredictable for the examiner and followed a previously prepared chart on which the targets were called A or B in a pseudo-random order.

In each trial, the examiner had to state in which position, either A or B, the Brückner reflex appeared brighter, this when the subject was fixating the light or the eccentric target (or vice versa).

Subjects were divided into 2 groups, 5 emmetropes aged 17-24 years (mean 21 years), and 5 myopes (0.25-2.50 diopters) aged 21-25 years (mean 23.6 years).

Results : with non-dilated pupils, in 97.2 % of 160 trials on emmetropes (OD, 96.2 % ; OS, 98.1 %) and 97.5 % of 160 trials on myopes (OD, 96.9 % ; OS, 98.1 %), the red reflex appeared brighter when the subject fixated the eccentric target.

With dilated pupils, corresponding rates were 97.2 % (OD, 95.1 % ; OS, 99.3 %) in 144 trials on emmetropes and 99.7 % (OD, 99.4 % ; OS, 100 %) in 160 trials on myopes, regardless of horizontal direction and degree of eccentricity.

Conclusion : in eyes without organic pathology, the Brückner test allows for sensitive discrimination between alternate central fixation of the ophthalmoscope light and fixation of a target beside the light.