Circular, elliptical flap comparison takes shape

Take-Home

Elliptical and round femtosecond laser flaps created during myopic LASIK provide excellent early visual results and high patient satisfaction.

(Top) Elliptical LASIK flap. (Bottom) iFS oval flaps. [Probst LE. Corneal and flap dimensions of oval flaps created with the femtosecond laser. ISRS/AAO Annual Meeting, Orlando, Oct. 21, 2011.] (Images courtesy of Louis E. Probst, MD)

San Francisco-In a comparison study of elliptical and round femtosecond laser flaps created during myopic LASIK, both flap configurations provided excellent early results and patient satisfaction was very high.

The study identified small increases in higher-order aberrations (HOAs) and spherical aberration, but no increase in patient complaints, said Louis E. Probst, MD, at the annual meeting of the American Society of Cataract and Refractive Surgery.

In this randomized, prospective trial, all flaps were created with a femtosecond laser (iFS, Abbott Medical Optics). Round flaps were created in 52 eyes of 26 patients, and elliptical flaps were created in 50 eyes of 25 patients. Patients were an average of 34 years of age (range, 21 to 60 years).

The eyes of all patients had <6 D of myopia and <2 D of astigmatism preoperatively, said Dr. Probst, national medical director for TLC Laser Eye Centers, Chicago. Patients in both groups were well matched demographically, with the degree of myopia slightly higher among patients treated with elliptical incisions (–2.82 ± –1.2 versus –3.35 ± –1.4 D; p = 0.041).

Dr. Probst

The femtosecond laser parameters in both groups were almost identical (speed, 150 KHz; flap size, circular 8.5 mm and elliptical 8.6 × 8.2 mm; flap thickness, 100 μm; creation time, 12 seconds; pocket size, 0.35 mm; spot/line separation 7 × 7; and side-cut angle, 110°).

Visual acuity comparisons

Preoperative distance best-corrected visual acuity did not differ between the patients treated with circular and elliptical incisions. Uncorrected distance visual acuity (UDVA) 1 day after LASIK was 20/20 in 94.2% of patients with circular incisions and 88% of patients with elliptical incisions; 57.7% and 65%, respectively, achieved 20/16, and 11.5% and 18% achieved 20/12.5.

One month postoperatively, all patients with circular incisions had 20/20 UDVA as did 94% with elliptical incisions; 80.8% and 78% had 20/16, and; 40.4% and 28% had 20/12.5, and 3.8% and 4% had 20/10.

There were no differences between the groups in sphere, astigmatism, HOAs, or spherical aberration, Dr. Probst said.

Patient satisfaction was high with both incision types. There were no significant differences between the groups in glare and halos under any conditions, such as nighttime and daytime driving or with headlights and computer use.

The postoperative target can no longer be 20/20, Dr. Probst continued. With most patients in this study having 20/20 preoperatively, surgeons must aim higher, because patients expect more.

“We are making vision better, which is exciting,” he said.

Elliptical flap advantages

“Elliptical flaps offer some advantages, because of the precise alignment they allow,” Dr. Probst said. “An elliptical flap can only fit into place one way because of its shape. A circular flap can fit in any configuration.”

Elliptical flaps are also better suited to the anatomy of myopia. Nearly all patients with myopia, 99%, have a horizontal aspect to their myopia that is better suited to an elliptical flap, he said.

An elliptical flap also creates a more robust hinge. Dr. Probst advised using superior hinges for a deeper pocket that allows for better gas escape and greater stability.

“Both flap configurations demonstrated excellent early visual results,” he said. “There were slight increases in HOAs and spherical aberration. Any subjective visual concerns actually improved from baseline to 3 months postoperatively.

“There were no increases in patient complaints and patient satisfaction with the procedures was extremely high,” Dr. Probst concluded.

Louis E. Probst, MD

E: leprobst@gmail.com

Dr. Probst is a consultant for Abbott Medical Optics and TLC Vision.

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