Flicker fusion and translucent irides

In the normal visual system, the critical flicker fusion frequency (CFF) has a higher value when tested with a large stimulus field than with a small stimulus field. When the iris is translucent, a significant part of the stimulus light also stimulates peripheral parts of the visual field. We tested two subjects with albinism (translucent iris) and 14 subjects with a normal iris using 8- and 34-degree fields. The CFF for the small fields was increased for eyes with translucency of the iris. This may explain why albinos complain about working with computer monitors. The small-field response normalizes when contact lenses with an artificial occluding iris are worn. We conclude that this phenomenon is determined by the scattering of light by the translucent iris.