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Alcohol-free LASEK procedure proves effective in pilot study
No patients experienced sloughing of the parted epithelial layer using GenTeal Gel to aid in manipulation of the LASEK sheet.
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WAIKOLOA, Hawaii — An alcohol-free variation of laser epithelial keratomileusis that uses microkeratome suction and a methylcellulose gel to create the epithelial sheet was effective in a small pilot study presented here.
Marguerite B. McDonald, MD, lead surgeon involved in the study, told Ocular Surgery News GenTeal Gel (Novartis Ophthalmics) does not stiffen the epithelial cells as alcohol does. Instead, the cells are stripped with the assistance of suction and manipulated on a cloud of gel.
“Once the sheet has been stripped using suction, they will disintegrate like cotton candy,” Dr. McDonald said. “The only way to get them to do what you want is to push them around on a cloud of GenTeal Gel. Metallic instruments should never touch the epithelium because it hasn’t been stiffened with alcohol.”
LASEK, in its original form developed by Massimo Camellin, MD, of Italy, uses a 20% alcohol solution to loosen and stiffen the epithelial sheet for manipulation.
“It’s a big step forward, but has its drawbacks,” Dr. McDonald said in her presentation. “The alcohol can irritate or kill the peripheral corneal and conjunctival epithelium. Big sheets of dead cells can slough, and dead cells can impede the advance of new cells from the limbus.”
The procedure Dr. McDonald used is similar to the standard LASEK technique and uses a standard LASEK tray, familiar LASEK instruments, a microkeratome suction ring and a new curved cannula with fine holes along the side through which GenTeal Gel (hydroxypropyl methylcellulose 0.3%) can simultaneously emanate.
The curved cannula was specially made for Dr. McDonald by Mastel Precision for this LASEK technique.
GenTeal Gel is currently approved for treatment of postop dry eye and is not approved for intraoperative use. For the study, Dr. McDonald received approval from an institutional review board to use the substance intraoperatively.
“We didn’t have a lot of resources for the pilot study, it was basically just a proof of concept study,” she said. “Now that we think there actually is something to this, we are going to compare the exact number of days to re-epithelialization in a prospective, randomized study. But it appeared as if the stripped sheet of epithelium was healthy in our pilot study. Certainly, we had not one patient who sloughed any epithelium.”
She said a prospective, randomized trial in which patients agree to have one eye done the classic way using alcohol and the other eye using GenTeal Gel is about to begin. At press time, Dr. McDonald was enrolling patients for the trial and initial procedures were about to be performed.
Pilot study
Dr. McDonald’s pilot study included 42 eyes of 22 patients followed for 3 months.
Postoperatively, the patients received levofloxacin four times daily for 1 week, diclofenac four times daily as needed for the first 3 days, prednisolone acetate four times daily, GenTeal Gel every 1 to 2 hours and Mepergan Fortis (Wyeth) as needed every 4 to 6 hours for pain.
No suction was used on the initial seven patients treated. After suction use was initiated, all patients over age 40 had complete sheets successfully raised.
Average keratometric readings were 44.83 (range 42.86 to 49.89). Average keratometric cylinder was 1.15 (range 0.32 to 2.77).
Thirty-nine eyes (89%) were treated for distance and five eyes (11%) were treated for near. Dr. McDonald said one patient was removed from the database postoperatively because of marked accidental corneal trauma to the left eye, which prevented her from cooperating for full exams on either eye.
The average preoperative refraction was –5.53 D (range –1.25 D to –9.125 D).
At 1 month, 6% of patients achieved 20/12.5 visual acuity, which improved to 13% at 3 months. Dr. McDonald said that with time, the percentages shifted in the direction of improvement, and 75% of patients were 20/25 or better and 100% were 20/32 or better at 3 months.
There was one case of allergic toxic keratitis and dermatitis. Dr. McDonald said the patient was allergic to most ophthalmic drops used but is doing very well.
“We don’t think it was an allergy specifically to the GenTeal Gel. It seemed to be an allergy to everything, from eye drops to face creams to detergents. She has recovered and her vision is excellent,” she said.
The study also included psychometric testing at preop, 1 week, 2 weeks, 1 month and 3 months.
Dr. McDonald said no patients thought their main goal for having the surgery had not been achieved by 3 months of follow-up. Half said it had somewhat been achieved and half said it had been fully achieved.
“We also asked whether they thought having LASEK had been a good choice. No one said that LASEK had not been a good choice,” she said.
Procedure used
In the procedure, Dr. McDonald applies generous amounts of GenTeal Gel to the corneal surface to keep the epithelium in good condition. A rounded cataract blade is used to make a small linear aberration in the far periphery of the cornea. Ten drops of NaCl 5% are added for 10 seconds to slightly stiffen the epithelium, which is followed by placement of the suction ring.
“I use the SKBM (Summit Krumeich-Barraquer microkeratome, Alcon Surgical). While the suction is on, I slip a LASEK spatula through the 1-mm or 2-mm linear abrasion that I made. Using that hole as a fulcrum, I make a spatulating motion and I strip off the epithelium. I press down and I saw in and out of the little linear abrasion,” she said.
Dr. McDonald said she never applies suction for more than 30 seconds at a time and never applies it more than twice.
“Whatever epithelium I’ve taken off at that time, that’s it. I don’t want to keep applying suction. Then I slip under the epithelium the new curved cannula I developed, manufactured for me by Doug Mastel. The epithelium is stretchy. You start blowing out GenTeal Gel and the epithelium domes up,” she said.
Once the epithelial sheet is stretched above Bowman’s layer, the surgeon bisects the sheet with Vannas scissors, creating two halves.
Dr. McDonald said a small or medium-sized ablation zone may require only parting of the two halves of the epithelial sheet, still pushing with a cloud of gel.
After parting the two sides, the surgeon uses a wet Weck-cel sponge to remove the gel from Bowman’s layer and performs the ablation. Following ablation, the surgeon again applies GenTeal Gel, herds the epithelial sheet back into position and places a bandage contact lens.
“I use the Protek from CIBA Vision because it is the only approved bandage contact lens in the United States and is perfect for this. Once it’s on, I slap it gently a couple of times with a wet Weck-cel to burp out any excess gel trapped under the epithelium. Then I just put in the postoperative drops,” she said.
Dr. McDonald said in a large ablation zone, instead of parting the epithelial sheet in two halves, the surgeon may sometimes need to quadrisect it by cutting it again.
“Then you just reflect those four pieces backward,” she said.
For Your Information:
- Marguerite B. McDonald, MD, can be reached at Southern Vision Institute 2820 Napoleon Ave., Suite 750, New Orleans, LA 70115; (504) 896-1240; fax: (504) 896-1251; e-mail: mbm2626@aol.com. Dr. McDonald is a paid consultant for Novartis and Alcon.
- Novartis Ophthalmics, makers of GenTeal Gel, can be reached at 11695 Johns Creek Pkwy, Duluth, GA 30097; (770) 905-1000; fax: (770) 905-1883.
- Mastel Precision, makers of the curved canula used in this procedure, can be reached at 2843 Samco Rd., Suite A, Rapid City, SD 57702; (800) 657-8057; (605) 343-3631; e-mail: mastel@mastel.com.
- Alcon Surgical, makers of the Summit Krumeich-Barraquer Microkeratome, can be reached at 6201 South Freeway, Fort Worth, TX 76134; (817) 293-0450; fax: (817) 568-6142.
- Hawaii 2002, the Royal Hawaiian Eye Meeting, was sponsored by Ocular Surgery News in conjunction with the New England Eye Center.