Refractive changes after excimer laser phototherapeutic keratectomy

Purpose: To study the visual and refractive changes in patients with superf icial corneal opacities after excimer laser phototherapeutic keratectomy (P TK), Setting: Eye Clinic, Kobe Kaisei Hospital, Kobe, Japan. Methods: One hundred twelve eyes of 80 patients with superficial corneal op acities had PTK with the Nidek EC-5000 excimer laser system. All patients h ad routine ophthalmic examinations including uncorrected and Landolt best c orrected visual acuity (BCVA) measurements, subjective and objective refrac tions, keratometry, EyeSys (Premier Laser Systems, Inc.) corneal topography performed before and I week and 1, 3, 6, and 12 months after PTK, and pach ymetry performed before and 12 months after PTK, The change in refractive s tatus within 12 months of PTK and the relationship between factors such as ablation depth, transition zone (TZ) setting, and use of masking agents and the amount of hyperopic shift were also assessed. Results: The BCVA increased by more than 2 lines in 65.1% of eyes and by 1 line in 24.1%, The BCVA did not change in 12 eyes (10.8%) because of catara ct or underlying retinal disease. A mean hyperopic shift of 3.42 +/- 1.15 d iopters (D) (range 1.00 to 5.25 D) was seen in all eyes at 12 months. The h yperopic shift peaked 1 month after PTK and tended to decline after that; i t stabilized at 12 months. Conclusion: Although PTK is a safe and efficient method for the treatment o f superficial corneal opacities, induced hyperopia after the procedure rema ins a major problem. A shallow ablation depth (less than 100 mum), presence of a TZ setting, and use of a masking agent decrease the hyperopic shift s ignificantly.