Excimer laser photorefractive keratectomy for high myopia: Four-year experience with a multiple zone technique

• Published in: Ophthalmology (Rochester, Minn.) Vol. 104; no. 10; pp. 1554 - 1565
• Main Authors: PIOVELLA, M, CAMESASCA, F. I, FATTORI, C
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier 01.10.1997
• Subjects: Adult; Biological and medical sciences; Cornea - physiopathology; Cornea - surgery; Corneal Opacity - physiopathology; Female; Humans; Lasers, Excimer; Male; Medical sciences; Middle Aged; Myopia - physiopathology; Myopia - surgery; Nitrogen - administration & dosage; Patient Satisfaction; Photorefractive Keratectomy - methods; Refraction, Ocular; Reoperation; Retrospective Studies; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Surgery of the eye and orbit; Treatment Outcome; Visual Acuity - physiology; Human; Vision disorder; Myopia; Retrospective; Photorefractive keratectomy; Eye disease; Surgery; Excimer; Refractive error; Laser; Technique; Severe; Comparative study
• ISSN: 0161-6420; 1549-4713
• DOI: 10.1016/S0161-6420(97)30096-7

The purpose of the study is to evaluate the results of the authors' 4-year experience with excimer laser photorefractive keratectomy (PRK) and multiple optical zone corneal ablation in highly myopic eyes. The authors retrospectively evaluated 56 eyes of 44 patients (mean refraction, -11.3 diopters [D]; range, -5.75 to -24.5 D) who underwent PRK with a Visx Model 20/20 laser (Visx, Santa Clara, CA). Preoperative visual acuity of 20/40 or better was present in 46 eyes. Corneal ablation was divided into concentric optical zones (4, 5, and 6 mm), allowing corrections of up to 18 D, with a refractive goal of within -1 D from emmetropia in 49 eyes. A hand-held fixation system was always used, and a nitrogen-blowing system (NBS) was used in the first 21 eyes only. Before retreatment, the range of final cycloplegic refraction from emmetropia in eyes treated with NBS versus not was within +/-1 D in 6 (28.6%) and 15 eyes (44.1%), between -1.25 and -3 D in 5 (23.8%) and 14 eyes (41.1%), and more than -3 D in 10 (47.6%) and 5 eyes (14.7%), respectively. No lines of visual acuity were lost in 37 eyes (80.4%) with 20/40 or better visual acuity before surgery. Three eyes showed vision loss due to worsening of myopic maculopathy and one due to corneal haze. Correction stabilized within 9 months, and at a mean time of 25.6 months, the correction attained was of -8.5 +/- 3.6 D, achieving 90.3% of attempted correction. Eyes with preoperative myopia less than -10 D (n = 27) showed regression less than -1 D in 8 eyes (29.6%), between -1.25 and -3.00 D in 5 eyes (18.5%), and greater than -3.00 D in 1 eye (3.7%); eyes with more than -10 D (n = 29) regressed in 3 (10.3%), 6 (20.7%), and 1 eye (3.4%), respectively. Severe haze was observed in 11 eyes (19.6%) 3 months after surgery. Two eyes showed decentration greater than 1.5 mm. At last examination, night driving problems were reported by 12 (41.4%) of 29 patients evaluated who drive. After the NBS was eliminated, the multiple-zone technique achieved a long-term, stable 83.1% reduction of preoperative myopia. Patients with severe myopia appreciated reduction of most of the refractive defect, although perception of halos was noted by 16 patients.