Eye tracker for laser monitors position of undilated pupil

October 15, 2004

Vienna, VA-The 200 Hz Eye Tracker is an excellent addition to the EC-5000 excimer laser system (Nidek), according to Nancy A. Tanchel, MD.

Vienna, VA-The 200 Hz Eye Tracker is an excellent addition to the EC-5000 excimer laser system (Nidek), according to Nancy A. Tanchel, MD.

Dr. Tanchel, a private practitioner in Vienna, VA, had the eye tracker installed a few weeks after it became available.

"The laser responds much more quickly with this faster eye tracker, and the system has worked well in my hands to yield excellent all-around results," she said.

How it works The system determines the pupil center by analyzing color, hue, and saturation changes. Its active component follows the pupil center and the passive feature stops the ablation if the eye moves >0.5 mm off-center for longer than an allotted period. Treatment resumes when the eye is recentered, or if the surgeon prefers, the ablation can be finished without the tracker.

"The Nidek laser features crosshairs that the surgeon can use to assure the eye is perpendicular to the laser," Dr. Tanchel said. "Because the system shuts down automatically if the eye moves too much, surgeons can be sure they are delivering the exact amount of laser energy exactly where they want.

"In contrast, other trackers will continue to follow the eye and allow the ablation to proceed wherever the eye moves, resulting in a cosine effect and risk of astigmatism," Dr. Tanchel added.

The eye tracker has been used successfully in patients with nystagmus and works well once the flap is lifted.

Instruments moving in and out of the field do not interfere with the tracker's performance, and unlike other systems that lose their reference point and shut down when large amounts of tissue are ablated, the eye tracker continues to operate, she said.

A cyclotorsional module able to account for changes in sitting versus supine astigmatism will be available in the United States in the future.

Dr. Tanchel noted she has had the opportunity to use the 200 Hz eye tracker to treat some patients participating in the Nidek hyperopia clinical trial and found the entire system works well in correcting hyperopia.

"Ablation with the Nidek laser for the treatment of hyperopia uses a very wide zone, and we have seen some excellent results with that protocol," she said.