Study evaluates biological integrity of corneal epithelial sheet made by epikeratome in altered procedure

February 1, 2008

The use of chilled water and 0.1% hyaluronic acid during epi-LASIK improved the survival rate of corneal epithelial basal cells, according to one study.

Key Points

Kyoto, Japan-The use of chilled water and 0.1% hyaluronic acid during epi-LASIK improved the survival rate of corneal epithelial basal cells, said Shigeru Kinoshita, MD, PhD. This approach resulted in less patient pain and more rapid visual recovery.

"The epithelial sheet made by the epi-LASIK procedure is even with the basement membrane," said Dr. Kinoshita, professor of ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan. "The blade of the epikeratome runs just beneath the epithelial basement membrane. Previous published studies have demonstrated the epithelial cell sheet histologically. When the sheet is stained, almost all of the epithelial basal cells are dead by the time of the surgery, but not the intermediate or superficial cells."

In light of this finding, Dr. Kinoshita and colleagues conducted a study in which they evaluated the biological integrity of the corneal epithelial sheet made by the epi-keratome after incorporation of several technical improvements into the procedure. All procedures were performed using a proprietary epikeratome (Amadeus II, Advanced Medical Optics). The exposed side of the basal epithelial cells was moistened with chilled water and 0.1% hyaluronic acid eye drops intraoperatively to prevent epithelial cell death. Dr. Kinoshita described these steps as improvements in the procedure. In addition, no irrigation was used below the epithelial cell sheet. Samples of the epithelial sheet were processed for confocal microscopy with calcein-AM/propidium iodide staining. The ablation was performed using an excimer laser, Dr. Kinoshita explained.

In addition to using chilled water and hyaluronic acid, hyaluronic acid also was used to moisten the surface of the stromal bed just before placement of the flap to avoid damage to the basal cells. Dr. Kinoshita said that gentle handling is an important factor in this procedure, as demonstrated by the fact that no irrigation was used under the flap.

"Eight of the 26 cases had a substantial number of epithelial basal cells that survived," Dr. Kinoshita said. "Using this technique, the basal cells survived in about one-third of the cases."

He demonstrated a case in which the basal cells survived in the right eye and died in the left eye, as evidenced by staining.

"At 1 and 3 days after treatment, when we stained the ocular surface with fluorescein, we found a remarkable difference between the right and left eyes," Dr. Kinoshita said. "The left eye had a loose epithelial attachment to the underlying corneal stroma, but this was not seen in the right eye. One week postoperatively, the right eye had a nice appearance of the ocular surface."

At 1 month postoperatively, the right eye had no haze compared with the left eye, which had some haze, he said.

"The use of chilled balanced saline solution and 0.1% hyaluronic acid during the epi-LASIK procedure improved the survival rate of corneal epithelial basal cells," Dr. Kinoshita concluded. "When the cells survive, the patient has less pain, and vision recovers quickly."