Pulfrich's phenomenon in unilateral cataract

Abstract

Aims-To determine whether unilateral cataract causes a pathological Pulfrich's phenomenon. Methods-29 subjects with unilateral cataract and contralateral pseudophakia were assessed on their ability to perceive the Pulfrich phenomenon. Using a computer generated pendulum image, and graded neutral density filters, a series of forced choice trials were performed in which the subject was required to describe the direction of any apparent pendulum rotation. A pathological Pulfrich eVect was said to occur when apparent rotation was perceived in the presence of a zero strength neutral density filter. The size of any pathological Pulfrich eVect which was present was quantified by neutralising the perceived pendulum rotation with neutral density filters of varying strength placed before the better seeing eye. Results-20 out of 29 subjects were able to perceive apparent pendulum rotation when uniocular filtering was performed. In the group (n=12) which was tested both before and after cataract extraction with intraocular lens implantation, a statistically significant pathological Pulfrich effect was demonstrated preoperatively, compared with a group of normal control subjects. This eVect was abolished after cataract extraction (p=0.009). The median size of the eVect was equivalent to a 0.25 log unit neutral density filter over the non-cataractous eye. The subjects who were unable to perceive the Pulfrich phenomenon at all had a significantly greater diVerence in the visual acuity of each eye (p=0.045) and significantly worse stereoacuity than those who were able to perceive the eVect (p=0.002). Conclusions-Unilateral cataract can cause a pathological Pulfrich phenomenon. This finding may explain why some patients with unilateral cataract complain of visual symptoms that are not easily accounted for in terms of visual acuity, contrast sensitivity, or stereoacuity.

Decision-making in second-eye cataract surgery: can presence of Pulfrich phenomenon help?

“…Thus, as reported by Scotcher et al, 3 our findings confirm that unilateral cataract can cause PP. We found that presence of PP was correlated with level of VA in the cataractous eyes, but found no correlation between magnitude of PP and VA in this group.…”

“…[3][4][5] The PP is a three-dimensional visual stereoillusion that was first identified by Carl Pulfrich in 1922: An object moving in front of the subject's eyes in the horizontal plane seems to follow an elliptical pathway when one eye is covered with a lightattenuating filter. 6 This phenomenon is believed to be caused by a disturbance of the observer's perception due to a disparity between the latencies of the visual pathways of the two eyes.…”

The symptomatic Pulfrich phenomenon can be successfully managed with a coloured lens in front of the good eye—a long-term follow-up study

“…A unilateral dilated pupil, 5 asymmetric cataract, and unilateral lens capsule thickening after cataract surgery may cause the problem owing to interocular differences in retinal luminance. 6,7 (Readers can experience the phenomenon by viewing a pendulum moving as shown in Figure 1, with a sunglass lens in front of one eye.) Table 1 summarises the symptoms caused by the Pulfrich phenomenon.…”

Influence of the Pulfrich phenomenon on driving performance

“…Since then, several authors reported that patients harbouring a spontaneous Pulfrich phenomenon report having difficulties while driving [7,14,29,30,33]. Despite that, no study has ever examined the risk of driving for patients harbouring a Pulfrich phenomenon.…”