By Roibeard O'hEineachain

CANNES--A new computerised pupillometer can enable refractive surgeons to determine more accurately the optimal ablation zone in their LASIK patients with large pupils, thereby avoiding the optical aberrations that can often occur in such individuals, according to Emanuel Rosen, MD, FRCS, Manchester, UK, who will be presenting his findings here at the Winter Refractive Meeting of the ESCRS.

The Procyon P2000 SA, a 'static averaging pupillometer,' provides an easy and accurate way of determining pupil size to within 0.05 mm under a variety of lighting conditions. The pupillometer and its associated laptop computer can be used on a desk in a doctor's office. The device is already in use in various fields of medical research for measuring autonomic system responses and for testing mydriatic agents, Dr. Rosen told EuroTimes in an interview, adding:

"One of the major issues that we deal with in refractive surgery is the pupil. If the pupil is large, particularly in relation to LASIK or phakic intraocular lenses, then the patients can get multiple images. It is an area that people have paid little attention to and up until now there has been no satisfactory clinical method of measurement other than using a ruler of one form or other." Now Standard Procedure Dr. Rosen and his associates are currently using the pupillometer as part of their standard pre-operative assessment in patients undergoing refractive procedures. To test pupil size, patients place their eyes on the instrument's eyepieces while a camera in the device camera takes a series of pictures of their pupils under internal illumination, which can simulate a broad range of lighting conditions. The computer then averages the size of the pupil and tabulates it in graphic and text format which can then be used in other software applications such as spreadsheets or statistical analysis packages.

The pupillometer's software (Procyon PupilFitTM) enables physicians to check the validity of the measurements by means of a powerful circle-fitting algorithm which automatically analyses the image and then super-imposes circles corresponding to the best fit to the pupil back onto the original images.

"We've been using the machine for just a few weeks and it has already changed our mode of practice. In fact, I now make sure to test even those patients I had booked for LASIK before I obtained the device. We have a flying-spot laser which enables us to make an ablation of any dimensions we like. So, for example, if we had a very large 7mm pupil we can ablate 8 mm.

"The pupillometer is also helpful in determining what to do in patients with problems after undergoing LASIK elsewhere. We are now often better able to demonstrate the nature of their problems and look for a solution. In addition, using the pupillometer we have been able to show that, as regards phakic IOLs, the 6mm design is quite big enough to cover the pupil," Dr. Rosen continued, adding:

"I first came across this instrument by chance, having heard of its use in pharmacological fields but I think refractive surgery generally would gain through adopting this technology. In the short time we have been using it we have found that it provides excellent data very quickly and is a real guide to selection of patients and avoidance of post-operative problems."

Dr. Rosen has no financial interest in Procyon.