Perceived brightness with small apertures.

PURPOSE: To quantify the relative perceived brightness when viewing through a small aperture as that used by presbyopic patients with small-aperture corneal inlays or intraocular lenses with an embedded aperture.

SETTING

Laboratorio de Óptica, Universidad de Murcia, Murcia, Spain.

DESIGN

Prospective case series.

METHODS

The relative perceived brightness when 2 apertures (3.0 mm and 1.6 mm diameters) were presented monocularly to the participant was determined. With equal transmittances in both apertures, a flickering effect caused by the different retinal illuminance for each condition is perceived. The participant's task was to modify the transmittance of the 3.0 mm pupil until the flickering was minimized. This transmittance value indicates the relative perceived brightness reduction. The measurements were performed under 3 average luminance levels.

RESULTS

The perceived relative luminance measured ranged between 38.5% and 46.9%. This represents an increase in brightness perception with a small aperture of 1.24 and 1.51, respectively, compared with what would be expected. This trend was consistent for all the participants in the study.

CONCLUSIONS

The perceived brightness with a small aperture was less pronounced than what would be predicted by the reduction in retinal illuminance. Under real visual conditions, this effect could be even more significant because binocular effects and temporal adaptation might further increase the perceived brightness with the small aperture.