Microkeratome delivers 80-µm flaps for thin-flap LASIK

From Maria
Copyright Advanstar Communications, Inc. May 15, 2006
[Headnote]
Good surface, edge quality
[Headnote]
Flaps created with device are reasonably accurate and predictable with a high safety profile
Reviewed by Ernest W. Kornmehl, MD
San Francisco-Thin-flap LASIK with the K-4000 microkeratome (Becton Dickinson) is safe and delivers flaps that are significantly thinner than with other available heads. Thin-flap LASIK is the preferred choice with the K-4000 microkeratome, according to Rupal S. Shah, MD.
The microkeratome head creates 80-µm flaps and Dr. Shah has been using it for about 18 months, she reported at the annual meeting of the American Society of Cataract and Refractive Surgery. In this study she and her colleagues compared the results obtained with the 80-µm head with those obtained using the 130-µm head.
The prospective study included 20 eyes of 10 patients. One eye of each patient was randomly assigned to the 80-µm group and the other eye to the 130-µm group. The investigators evaluated the flap thickness, the postoperative visual acuity, and the safety of the procedure.
Standard ultrasound pachymetry was used to measure the flap thickness. Corneal pachymetry was performed before cutting the flap and immediately before lifting the flap, she explained, to nullify the effect of any trauma to the cornea because of flap formation, and on the stromal bed immediately after the flap was lifted.
Dr. Shah, clinical director of New Vision Laser Centers, Baroda, Gujarat, India, reported that at the beginning of the case, the average pachymetry value was 506 µm in the 80-µm group and 503 µm in the 130-µm group.
"After the flaps were cut, there was swelling in both groups, likely because of trauma to the cornea. After lifting the flap the average pachymetry value in the 80-µm group was 435 µm and 404 µm in the 130-µm group. The average thickness in the 80-µm; group was 86 um (standard deviation, 11 µm; range, 77 to 105 µm) and in the 130-µm group 119 µm (standard deviation, 14 µm; range, 110 to 135)," Dr. Shah reported.
Regarding the thin flaps, she pointed out that they were difficult to handle but worked well.
"The flap created with this microkeratome does not fall back on itself. The surface quality and the edge quality are quite good," she commented.
The visual recovery was more rapid with the 80-µm head compared with the 130-µm head. The mean visual acuity within 1 hour after the end of the surgery, according to Dr. Shah, was 0.78 in the 80-µm group and 0.66 in the 130-µm group.
On the first postoperative day, the mean visual acuity in the 80-µm group was 1.12 and in the 130-µm group it was 1.07. Three months after the surgeries, 94% of the eyes from both groups had 20/20 or better vision. Dr. Shah described the results as very encouraging.
No flap-related complications occurred with either head. In addition, there was no increased incidence of flap striae.
"An 80-µm cutting head with the BD K-4000 microkeratome creates flaps that are reasonably accurate and predictable with a high safety profile," Dr. Shah said. "Patients who have a thin stromal bed who previously were not candidates can probably be treated. The 80-µm head can probably be the head of choice in conjunction with the K-4000 microkeratome in these patients."
FYI
Rupal S. Shah, MD
E-mail: vadodara@nevwisionindia.com
Dr. Shah did not indicate a proprietary interest in any of the products or companies.