LASIK allows faster recovery than PRK

However, in the long term, visual results are similar in both procedures for low refractive corrections.

ByMichela Cimberle

ACICASTELLO, Italy – A comparative study of LASIK and photorefractive keratectomy (PRK) results finds LASIK the preferable technique, with fewer complications, faster rehabilitation and a wider range of potential correction. In long-term follow-up, however, results are similar in correction of low to moderate refractive errors with the two procedures.

The study was carried out by Francesco Zagari, MD, and E.G. Canino, MD, at the Cannizzaro Eye Clinic.

A total of 100 eyes of 83 patients were treated with either LASIK or PRK using a Schwind (Kleinostheim, Germany) Keratom MultiScan excimer laser.

“An interesting feature of the Schwind laser is in its special aspherical profile rotating masks,” Dr. Zagari said. “They minimize ablation depth and give a uniform, smooth corneal surface.”

The laser is also equipped with an eye-tracker for continuous dynamic centration of the fixation point and automatic stop beyond a maximum excursion of 3 mm.

Patient selection

Patient ages were between 20 and 55 years. Myopia ranged from 3 D to 8 D. The hyperopic range was 4 D or less. Myopic or hyperopic astigmatism was within 4 D, with spherical equivalent less than 9 D. The follow-up was between 6 and 18 months.

“Patients were divided in two groups,” Dr. Zagari explained. “The 47 patients of the first group were treated with LASIK. Forty-four of them were treated in one eye (five had PRK in the other eye) and three were treated bilaterally, giving a total of 50 LASIK eyes. The second group was made up of 41 patients treated with PRK. In 9 cases we performed a bilateral treatment, whereas in 32 cases only one eye was operated (5 of them were the same patients from the first group, who had LASIK in the other eye), giving the same total of 50 eyes.” (See tables 1 and 2.)

Surgical procedure

All patients were treated under topical anesthesia. LASIK flaps were performed with a Moria (Antony, France) Carriazo-Barraquer microkeratome using the down-up procedure. PRK patients had the corneal epithelium prepared and cleaned for the ablation.

“We used a 7 mm ablation zone for myopic and astigmatic correction, and a 6 mm to 7 mm ablation zone for hyperopia,” Dr. Zagari said.

After PRK, a bandage contact lens was applied.

Patients progressively regained visual acuity after the postoperative physiological decrease, Dr. Zagari said. “The process was faster in LASIK patients. Functional recovery was achieved within 4 to 7 days, against the average 20 to 30 days for PRK patients,” he said.

“After this period, some degree of visual fluctuation still remained. It was perceived by the patient as a difficulty in focusing images in the morning, which improved during the day,” he added.

Six months after surgery, best corrected visual acuity (BCVA) was equal to or better than preoperative BCVA. Late complications occurred in four cases: three PRK patients developed moderate to severe haze, and one LASIK patient developed central islands.

High myopia and LASIK

“Patients with myopia within 3 D to 5 D had a similar response to the two procedures,” Dr. Zagari noted. “Differences in the results were not statistically significant, and emmetropia was achieved or nearly achieved in long-term follow-up. On the contrary, small but statistically significant differences were reported in higher myopic patients (6 D to 8 D). The higher the myopia, the better the LASIK results were in comparison with PRK results in the long-term follow-up.”

A variable degree of haze was observed in PRK patients and not in LASIK patients. In most cases it was only a temporary complication that disappeared with topical steroid treatment.

“Interestingly, patients who received a different treatment in the two eyes (PRK and LASIK) also had different responses to topical steroid treatment,” Dr. Zagari said. “Intraocular pressure increased only in the PRK eye.”

According to Dr. Zagari, the integrity of Bowman’s membrane could play an important role in such cases, reducing the quantity of medication that penetrates into the anterior chamber.

Hyperopic patients showed good response to both treatments. “However, it must be said that the range of hyperopic treatment is much lower than that of myopic treatment,” Dr. Zagari noted.

Astigmatic correction had the lowest rate of success. “The two procedures gave comparable results when treating astigmatism up to 2 D. With higher values, there were problems with both. In most cases, we didn’t achieve complete correction, and had to perform some additional PTK treatment with masking fluid.”

Comparison of LASIK and PRK
Two groups had similar characteristics preoperatively
Group	Eyes	BCVA>20/25	BCVA>20/40	Sphere	Cylinder
PRK	50	38	50	–8/+4	–4/+4
LASIK	50	38	50	–8/+4	–4/+4
Group	Eyes	Myopic astigmatic	Hyperopic	Myopic	Hyperopic astigmatic
PRK	50	18	10	14	8
LASIK	50	18	10	14	8
Refractive results are similar at 6 months
Group	Eyes	UCVA>20/25	UCVA>20/40	BCVA>20/25	BCVA>20/40 ±SD
PRK	50	39	47	47	49 0.29±0.73
LASIK	50	42	49	49	50 0.36±0.24

Conclusions

“In the long follow-up, there was no substantial difference in the spherical equivalent achieved by the two groups. However, it must be considered that LASIK offers the advantages of a faster recovery and a wider range of myopic correction. The surgical procedure of PRK is simpler and has fewer risk factors,” Dr. Zagari noted. “Most LASIK problems are connected with the cutting and repositioning of the flap. The interface quality is an absolute condition for the positive outcome of the technique.”

Other advantages of LASIK, according to Dr. Zagari, include maintenance of the structural integrity of the ocular surface, rarity of increased intraocular pressure, no postoperative haze and less postoperative discomfort.

Photophobia, tearing and postoperative pain are common complaints of PRK patients, in spite of the application of bandage contact lenses, he said.

For Your Information:

Francesco Zagari, MD, is head ot the Cannizzaro Eye Clinic. He can be reached at his private clinic, Centro Oftalmico Villa Zagari, Via Vampolieri 26, 95021 Acicastello (CT), Italy; telephone and fax: (39) 095-272441; e-mail: Villa.Zagari@octonline.it.