New microkeratome produces more consistent flaps

Paris-The performance of the new Zyoptix XP microkeratome (Bausch & Lomb) is comparable to that of the Hansatome microkeratome (Bausch & Lomb), according to Wing Kwong Chan, MD.

Dr. Chan explained that the construction of the Zyoptix XP blade allows tighter manufacturing tolerance of blade extension, which is responsible for flap thickness, with an improvement in the standard deviation of blade extension from 22 to 8 µm. The benefits of such construction are highly consistent flap thickness, quality superior to other keratomes, as well as quality superior to generic blades.

"The instrument is ergonomically well designed and is comfortable to use," explained Dr. Chan, who is senior consultant and head of the Refractive Surgery Service, Singapore National Eye Centre. In addition, he noted, when using the instrument for lamellar keratectomy, the keratectomy edges are sharp and even.

Design improvements While the Zyoptix XP has many good features, there were a number of areas where improvement was needed and these became apparent during the phase I trial. During the clinical study of the microkeratome, surgeons identified functional issues by using the instrument. The first was the need for installation of a safety stop to prevent the microkeratome from beginning to cut a flap before it was completely engaged. This prevented the potential for microkeratome jamming.

A second problem was microkeratome loading on the suction ring. The head design of the instrument used during the phase I trial was modified to include a sweep applanation plate.

"The introduction of the sweep applanation plate means that there is less contact with the cornea during seating of the handpiece. The plate is designed to improve seating and feedback that the keratome is properly seated," he explained.

The third problem was concern about the obstructed view of the cornea by the microkeratome head. To address this, the nose of the head was shortened to improve visibility of the cornea while seating the handpiece.

A final issue was that of head labeling to reflect the actual flap thicknesses resected. Heads will be relabeled as 120, 140, and 160 µm based on clinical data.

In a multicenter, prospective, randomized controlled clinical trial carried out in Singapore, China, and the Philippines, the performance of the Zyoptix XP was compared with the Hansatome. The investigators found that there was no difference in the mean diameters of the corneal flaps created by the two microkeratomes. Both instruments cut flaps that were consistently thinner than the nominal head thickness. However, as Dr. Chan pointed out, the degree of variation in the flap thickness from the nominal value was significantly less for eyes that underwent lamellar keratectomy with the Zyoptix XP microkeratome.

Dr. Chan pointed out that he is generally happy with the performance and safety profile of the XP microkeratome.

"I am impressed by the quality of all aspects of the keratectomy-the flap, the stromal bed, and the flap edges. The XP microkeratome received higher surgeon ratings compared with the Hansatome in the phase II study," he said.