Purchase this article with an account.
Sowmya Ravikumar, Martin S Banks; The Pulfrich Effect with monocularly implanted small aperture Corneal Inlay. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4023.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
KAMRA is an annular aperture inlaid in the cornea of one eye. It increases the eye’s depth of field and is potentially useful for presbyopes. It also reduces the amount of light entering the eye, so the inter-ocular difference in retinal illuminance could alter perceived depth via the Pulfrich effect. Our aim was to determine if inlay patients have adapted to the illuminance difference. We measured the Pulfrich effect in inlay patients and in subjects with a short-term simulated inlay.
We measured the magnitude of the Pulfrich effect psychophysically in the two subject groups. The simulated-inlay subjects wore a custom contact lens that closely mimicked the KAMRA inlay. A finely adjustable neutral-density (ND) filter was placed in front of the non-treated eye. The stimulus was a disk that moved left and right. On each trial, subjects reported whether the disk appeared nearer when moving leftward or rightward. The filter was adjusted trial by trial to find the nulling threshold: the ND value that on average yielded no perceived depth variation.
The Pulfrich effect is present if the nulling ND value is greater than zero and is not present if the value is zero. The mean nulling value was larger in the simulated than in the KAMRA group (0.275 +/- 0.059 vs 0.155 +/- 0.132). The difference was marginally significant (p=0.063). We also examined for each subject, if the nulling value was greater than zero. The value was not statistically greater than zero in any of the six KAMRA subjects indicating no consistent Pulfrich effect. In contrast, the nulling value was statistically greater than zero in nearly all of the simulated-inlay subjects. We performed a Fisher’s exact test to evaluate the hypothesis that there was no association between subject group and the Pulfrich effect against the hypothesis that simulated-inlay subjects were more likely to observe the effect. The simulated-inlay group was indeed significantly more likely to experience the Pulfrich effect than the KAMRA group.
There was some evidence that the KAMRA group experienced a small Pulfrich effect, but the simulated-inlay group experienced a larger and more consistent effect. Thus, KAMRA subjects appear to have adapted to the reduced illuminance in the treated eye.
This PDF is available to Subscribers Only