Evaluation of photorefractive keratectomy (prk)‎ re-treatment of under correction of laser in situ keratomileusis (lasik)‎ for myopia

الملخص EN

Aim : to evaluate the results of photorefractive keratectomy (PRK) enhancements in eyes previously treated by laser in situ keratomileusis (LASIK) for myopia showing an under correction due to refractive regression or a primary under correction, when the residual stromal thickness is not in safe limits for in the bed correction.

Patients and Methods : Fourteen (14) eyes of 8 patients previously treated by LASIK for myopia ranging between -11.25 to -3.25 that after a follow-up of 12 months or more ended up with a refraction of -3.0 to -1.25.

The flap thickness was 160 mm for all eyes.

In all cases, the residual stromal bed under the flap was considered too thin (255-285 urn) to allow an in the-bed enhancement without exceeding an assumed safety thickness limit (250 um).

Those eyes were treated by PRK at least 12 months after LASIK.

The PRK ablation parameters (diameter, attempted correction) were selected to avoid theoretical flap perforation.

The deepest ablation was 75 um.

We used a Bausch and Lomb 217 C excimer laser (Bausch and Lomb, Rochester, New York).

Objectively, refraction, uncorrected and best-corrected visual acuity (BCVA), slit-lamp evidence of corneal opacity or other visible complications, and corneal topography.

Subjectively, patient satisfaction and convenience with postoperative visual acuity.

Results : the initial postoperative period was characterized by very satisfactory refractive results.

Objectively, BCVA increase (3 to 5 lines) and subjectively as regard visual acuity, all the patients were very happy with improved vision, during follow-up, myopic regression yet again occurred as well as a moderate haze (grade 1 and 2) developed in 5 eyes that induced a further myopic regression and BCVA loss 1 to 2 lines.

No further surgical treatment was needed as the final results were improvement of 2-3 lines.

Conclusions : we considered PRK -within limits-as a possible option in hand, to correct eyes previously treated by myopic LASIK that resulted in an under-correction much better when the under correction is low.