Pulfrich's phenomenon in unilateral cataract

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 effect 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 effect 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 effect was abolished after cataract extraction (p=0.009). The median size of the effect 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 difference in the visual acuity of each eye (p=0.045) and significantly worse stereoacuity than those who were able to perceive the effect (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.


Real world outcomes of ocriplasmin use by members of the British and Eire Association of Vitreoretinal Surgeons

Purpose: To describe a survey of the use of ocriplasmin by members of the British and Eire Association of VitreoRetinal Surgeons (BEAVRS) for VitreoMacular Traction (VMT) and Full Thickness Macular Hole (FTMH) and compare it to published MIVI TRUST trial data. Methods: All 173 BEAVRS members were contacted by email in October 2014 requesting data on all cases treated with ocriplasmin up to that date. The total number of cases, FTMH closure rate, VMT release rate and the frequency of adverse events were recorded. Results were compared with trial data. Results: 48 members responded reporting results from 241 eyes. The respective BEAVRS and MIVI TRUST trial closure rates for small FTMHs were 42.1 and 58.3% (P=0.09) and for medium FTMH 12.7 and 36.7% (P=0.01). The respective VMT release rates were 34.1 and 37.4% (P=NS). Retinal detachment was observed in 3.3% of the BEAVRS cohort compared with 0.4% in MIVI TRUST. Reduction in visual acuity to <6/60 was observed in 5.8% of the BEAVRS cohort and 0.6% in MIVI TRUST. Other complications not reported in the MIVI TRUST trial included an increase in FTMH basal diameter following unsuccessful ocriplasmin use in 46.9% of BEAVRS cases and zonular instability at the time of subsequent phacoemulsification in 2.4%. Conclusion: Macular hole closure rates were lower in the BEAVRS survey than published in the MIVI TRUST trial data. The incidence of adverse events was greater than previously reported. The reasons for these disparities are unknown but could include positive reporting bias inherent to retrospective surveys, treatment and population differences