Laser-assisted corneal sealing is safe, effective and time saving

The procedure has been successfully applied to cataract incisions and PK grafts. With ICG adjunct, laser energy is reduced to 60 to 70 mW.

NAPLES, Italy – Corneal sealing, using diode laser photocoagulation, can close wounds in both cataract surgery and penetrating keratoplasty quickly and efficiently, according to Luca Menabuoni, MD, of Florence “S.Giovanni” Hospital. He presented the work of his team, from animal experiments to clinical application, here at the meeting of the Italian Ophthalmologic Society.

“The laser sealing process is based on both the chemical and thermal reactions of extracellular matrix proteins, forming cross-links at a temperature of about 40°C,” Dr. Menabuoni explained. “We use a diode laser, which has an infrared wavelength of 805 nm and 500 mW power, transmitted by 400 µm to 600 µm optic fibers. In association with indocyanine green (ICG) dye, which is a photosensitizer of the same wavelength, the laser energy can be conveyed to the tissues at very low power levels, between 60 mW and 70 mW. Only the photosensitized area absorbs the light, and the sealing is carried out exactly where we want it, with no thermal damage to the surrounding tissues.”

Where was the incision?

The success of experimental work on animal eyes encouraged Dr. Menabuoni to proceed to clinical trials.

“We performed laser-assisted penetrating keratoplasty on 25 rabbit eyes, obtaining such good results that even the pathologist asked, ‘Where was the incision? I can’t see anything.’ Histologic and objective examinations confirmed that healing had been rapidly accomplished and the stroma was back to its normal structure,” he said.

Rabbit eye with (top) and without sutures (middle); histologic report (bottom) 15 days after surgery.

In the following stage, 25 volunteer patients, 16 female and 9 male, had diode laser sealing performed after cataract surgery.

“To be on the safe side, we started with small incision phaco surgery,” Dr. Menabuoni said. “We knew that a 3.5-mm cut would in any case seal easily and safely, independently of the success of our procedure. Then, we went on to 5.5-mm cuts. At a further stage, we dealt with extracapsular extractions (ECCE), progressing from 7-mm to 14-mm cuts, with a decreasing number of sutures. We started with 3 and ended up with only 1 suture.”

A total of 18 phaco and 7 ECCE procedures were successfully closed using diode laser sealing.

The procedure, as described by the surgeon, is very simple. The ICG is diluted in balanced salt solution or viscoelastic and applied in the incision area. To remove excess dye the cornea is rinsed and gently wiped with a sponge. Laser sealing is then performed, directing the laser beam as perpendicular as possible over the incision area. The procedure takes only about 70 seconds, with the laser set at 70 mW.

“We examined the patients at days 1 and 3 and after a month,” said the surgeon. “We were pleased to find out that postoperative astigmatism, on average, was only half a diopter higher than preoperative astigmatism. At day 3, the ICG was completely reabsorbed and the incision was firmly sealed.

There were no side effects, and astigmatic values remained stable during the follow-up”.

Laser-assisted PK

In June 2000, Dr. Menabuoni felt ready to apply the procedure in penetrating keratoplasty (PK).

“We treated our first patient, then waited 4 months to treat a second one, so that we could have a sufficiently long follow-up. In the first case, we implanted an 8 mm graft, and this necessitated changing our program as far as the number of sutures to apply. We had to add 3 more sutures to the 8 we had planned. In the second case, the graft was 0.5 mm larger, and we managed to keep to our protocol,” Dr. Menabuoni said.

The procedure he described was initially very similar to that used for cataract incisions. Once the sutures were in place, the ICG was applied and the excess dye washed out. Laser sealing was then performed with an average power of 60 mW, using a 600 mm optic fiber. The sealing was completed in 3 minutes.

“We had excellent results in both our patients. At day 3, the eye showed no inflammatory reaction, the graft was transparent and only some residuals of ICG were visible. The corneal lens was removed and the patient was discharged from hospital. At day 10 the ICG had been completely reabsorbed in the first patient, while in the second some traces remained for over two weeks, though we still don’t know why. Results have remained stable since then. In the first patient, the 3 additional sutures were removed after 2 months. The astigmatism stabilized at 2.50 D, against-the- rule, at 60°,” said the surgeon.

Positive conclusions

“The follow-up of our second case is not yet sufficient, so we can draw conclusions only on one PK patient in addition to our cataract patients. However, we feel confident in saying that laser assisted corneal sealing works well in both procedures. It is a safe, easy technique, and reduces the sometimes lengthy sealing process to a matter of a few seconds; you see it happen before your eyes, and don’t have to worry about it any more,” said Dr. Menabuoni.

In PK in particular, he pointed out, the natural healing process of the transplanted graft usually takes more than a year with traditional sutures. Moreover, laser sealing requires less skill and a much shorter learning curve than traditional suturing. Thus PK can be used by a larger number of surgeons.

“In addition to this, there are no apparent disadvantages,” he said. “The low-power energy of the laser in association with ICG is absolutely safe, there are no side effects and postoperative astigmatism is within the average range and stable in the follow-up. It seems that there are sufficient motives to convince us that the procedure is a great step forward.”

Four cataract patients at day 1 postop.
Laser-assisted PK: results of first patient.
Laser assisted PK: results of second patient.

For Your Information:

• Luca Menabuoni, MD, can be reached at Ospedale San Giovanni, Asl 10, Florence, Italy; (39) 055-7192535; e-mail: Luca.Menabuoni@tin.it. Ocular Surgery News could not confirm whether or not Dr. Menabuoni has a direct financial interest in any of the products mentioned in this article or if he is a paid consultant for any companies mentioned.