KAMRA Vision Implants

I have had a few people just this week enquiring about the new KAMRA Vision insert operation to restore near vision. This procedure is available now, exclusively at the Wellington Eye Clinic, and allows people to see far away and read without the need for reading spectacles!

The first part of the operation is to have LASIK eye surgery- even if your far vision is perfect, it will be necessary to induce a target prescription of -0.75D of Myopia (short sight). The KAMRA inlay is then placed and centred under the flap before it is put down. The inlay is essentially a pinhole, a very small diameter hole with a black surround, which makes it less visible against the black pupil. Pinholes work by narrowing the light entering the eye, which reduces the diameter of blur circles, and leads to clearer vision and an increased depth of focus, which should enable the treated eye to read without reading spectacles. The plan would be to leave the dominant eye good for distance and only treat the non dominant eye. The KAMRA inlay is readily removed by the surgeon, should the person have any issues.

Issues can arise because of the very small pupil in the reading eye- in dull conditions, when the pupil normally dilates, the treated eye will still have effectively a much smaller pupil, which means that more light will be getting into the untreated eye. This appears to induce a degree of the Pulfrich effect in most people.

The Pulfrich Effect causes a slight delay in transmission of the nerve impulses from the darker eye, this can cause objects moving in the Apparent Fronto Parallel Plane (AFPP)- an imaginary line on which side to side moving targets should always appear equally far away to appear to move closer and further.

This Pulfrich effect may be  induced in patients who have a KAMRA inlay*, and although the insert is easily removed, you will also require further LASIK surgery, should you wish to have your distance restored to clear without correction.

A very effective demonstration of the Pulfrich effect can be seen on this video. What you need to do is place a dark (sunglass) lens in front of one eye, and a 2D video can instantly look like a 3D movie. All because of the delay in conducting the impulses from one eye.

It is not a definite fact that someone who has an induced Pulfrich Effect following KAMRA implant surgery would have a problem in day to day life- there may be people who have this phenomenon, but just manage to live with it- if they don’t complain, they will not be diagnosed (even if they do complain, with such strange symptoms, they still might not be diagnosed) but it is something to be aware of, before making your decision to have this surgery.

Plainis S, et al. Reduced-aperture monovision for presbyopia and the Pulfrich effect. J Optom(2012)

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