Fourier analysis of induced irregular astigmatism. Photorefractive keratectomy versus laser in situ keratomileusis in a bilateral cohort of hyperopic patients.
J Cataract Refract Surg
; 29(9): 1709-17, 2003 Sep.
Article
em En
| MEDLINE
| ID: mdl-14522289
ABSTRACT
PURPOSE:
To analyze corneal topographic data by Fourier analysis to determine differences in irregular astigmatism following spherical hyperopic correction by photorefractive keratectomy (PRK) or laser in situ keratomileusis (LASIK).SETTING:
Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom.METHODS:
Thirty-six eyes of 18 patients with moderate hyperopia had LASIK in 1 eye and PRK in the other eye. The flap was cut on a nasal hinge with a Moria LSK One microkeratome. The laser was a Summit SVS Apex Plus with an optical zone of 6.5 mm and a blending zone of 1.5 mm. Corneal topographic data were acquired with a TMS-1 topographer (Computed Anatomy Inc.) preoperatively and 1, 3, 6, and 12 months postoperatively. The ASCII files containing the dioptric power values were extracted and analyzed with custom-written software to extract the Fourier harmonics.RESULTS:
The irregular astigmatism increased in both groups postoperatively, peaking at 3 months and then decreasing over the next 9 months. There was no statistically significant difference between the 2 groups at any time point (P<.05). The change in the topographically derived equivalent sphere showed undercorrection in both groups at all time points. Regular astigmatism showed a marginal statistically significant increase in the LASIK group at 12 months (P =.049).CONCLUSION:
Irregular astigmatism, equivalent sphere, and regular astigmatism were not significantly different in the PRK and LASIK groups during the follow-up. Based on the corneal topography, the 2 procedures induced an equal amount of irregular astigmatism.
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Base de dados:
MEDLINE
Assunto principal:
Astigmatismo
/
Ceratectomia Fotorrefrativa
/
Ceratomileuse Assistida por Excimer Laser In Situ
/
Análise de Fourier
/
Hiperopia
Tipo de estudo:
Etiology_studies
/
Incidence_studies
/
Observational_studies
/
Prognostic_studies
/
Risk_factors_studies
Limite:
Adult
/
Female
/
Humans
/
Male
/
Middle aged
Idioma:
En
Ano de publicação:
2003
Tipo de documento:
Article