Astigmatism Induced by Spherical Photorefractive Keratectomy Corrections

• Published in: Ophthalmology (Rochester, Minn.) Vol. 104; no. 8; pp. 1317 - 1320
• Main Authors: Shah, Sunil, Chatterjee, Anupam, Doyle, Stephen J., Bessant, David A.R.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.08.1997; Elsevier
• Subjects: Astigmatism - etiology; Astigmatism - physiopathology; Biological and medical sciences; Humans; Laser Therapy - adverse effects; Lasers, Excimer; Medical sciences; Photorefractive Keratectomy - adverse effects; Postoperative Period; Refraction, Ocular; Reoperation; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Surgery of the eye and orbit; Human; Eye disease; Surgery; Vision disorder; Excimer; Refractive error; Laser; Complication; Armature; Comparative study; Astigmatism; Photorefractive keratectomy
• ISSN: 0161-6420; 1549-4713
• DOI: 10.1016/S0161-6420(97)30141-9

Purpose: The purpose of the study is to evaluate the induced astigmatism after spherical photorefractive keratectomy on the Summit Omnimed (Summit Instruments, Waltham, MA) and the Nidek EC-5000 (Nidek Co. Ltd, Aichi, Japan) excimer lasers. Methods: A total of 4269 eyes of 3289 patients were treated with a 5-mm optical zone using the Summit Omnimed excimer laser and 1825 eyes of 1303 patients treated with the Nidek EC-5000 excimer laser. The final astigmatic refractive outcome was compared with the initial refraction by vector analysis (Alpin and Jaffe method). Results: Subjective astigmatic refraction for the Summit laser reduced from a mean of -0.39 diopter (D) ± standard deviation (SD) 0.33 D (range, 0 to -2.50 D) to -0.33 D ± SD 0.41 D (range, 0 to -3.00 D). Surgically induced astigmatism (SIA) had a mean of 0.42 ± SD 0.34 D (range, 0 to 2.89 D). Mean SIA increased with increasing preoperative astigmatism by 0.60D SIA for every 1.00 D of preoperative cylinder. For the Nidek laser, subjective astigmatic refraction changed from a mean of -0.18 D ± SD 0.21 D (range, 0 to -1.25D) to -0.30 D ± SD 0.33 D (range, 0 to -3.OOD). Surgically induced astigmatism had a mean of -0.32 D ± SD 0.29 (range, 0 to 3.05 D). Mean SIA increased with increasing preoperative astigmatism by 0.47 D SIA for every 1.00 D of preoperative cylinder. Conclusions: The authors show that spherical photorefractive keratectomy corrections can induce significant astigmatic change, particularly if a large amount of preoperative astigmatism is present.