The authors developed a Bruckner device, examined volunteers and determined the relation between the luminance of the red fundus reflex and eye rotation. Eye rotation was varied continuously both horizontally (-7 to 8 degrees) and vertically (five degree total range) using moving fixation targets. They constructed 2-D maps of pupillary luminance. The right eye of six subjects was measured. Images were recorded continuously with a frequency of about 40 frames per second. For all subjects, minimum relative pupillary luminance (darkest pupil) was found when patients fixated the centre of the camera thus confirming the Bruckner effect objectively. For horizontal movements, all subjects showed the expected darkening of the red fundus reflex as fixation changed from eccentric to coaxial with the camera. The same was found for vertical movements. Many local fluctuations were found between patients. The global minimum in pupillary luminance, termed the dark spot, tended to be circle shaped with a radius of about one degree. Pupillary luminance continued to increase beyond two degrees eccentricity. The original explanation of Bruckner effect – absorption by macular pigment – was not found plausible to explain the findings.

The mechanism underlying the Bruckner effect studied with an automated high resolution, continuously scanning Bruckner device.
De Groot MJ, van der Helm FC, Simonsz HJ.
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Fiona Rowe (Prof)

Institute of Population Health, University of Liverpool, UK.

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