Topography-guided customized laser-assisted subepithelial keratectomy for the treatment of postkeratoplasty astigmatism
Accepted 15 November 2005.
Purpose
To assess topography-assisted corneal wavefront excimer laser surface ablation for the correction of ametropia and irregular astigmatism after keratoplasty.
Setting
Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom.
Methods
In this pilot study, 15 patients (16 eyes) who were intolerant of spectacle and contact lens correction due to astigmatic anisometropia after keratoplasty (15 penetrating and 1 lamellar) had topography-assisted customized excimer laser treatments. Corneal topographic data using a Keratron Scout, Placido disk system allowed for preoperative analysis of wavefront anomalies of the anterior corneal surface from which a customized excimer laser correction of both lower-order aberrations (LOAs) and higher-order aberrations (HOAs) was prepared (ORK software) for treatment with a Schwind Esiris flying-spot laser. All eyes had laser-assisted subepithelial keratectomy (LASEK) using 15% alcohol with a 20-second to 30-second application. Four eyes received an application of mitomycin-C (MMC) 0.2 mg/mL for 1 minute after stromal ablation.
Results
The mean preoperative spherical equivalent (SE) was −3.50 diopters (D) ± 3.97 (SD) (range +1.625 to −9.25 D). The preoperative cylindrical error was −7.2 D (range −2.75 to −13.5 D). The programmed laser correction was −3.14 D (range +1.62 to −9 D) with a maximum attempted cylindrical correction of −7 D. Adherent LASEK epithelial flaps along suture lines and the graft–host junction were noted in 9 eyes (56%), although it was possible to obtain and replace a partial flap. A follow-up of 18 months was achieved in all eyes. At the final follow-up visit, the mean postoperative SE was −1.08 ± 1.85 D (range +3 to −4.78 D) (P<.01, F<.01). Ten eyes (62.5%) were within ±1 D of the intended correction. The mean postoperative cylindrical error was −2.72 D (range −0.5 to −6.5 D) (P<.001), with vector analysis demonstrating a mean 6.23 D correction. Analysis of HOAs using a 6.0 mm pupil size demonstrated a significant reduction of higher-order root mean square (RMS) (P<.002), trefoil (P<.005), and 4th-order spherical aberration (P<.02) at 18 months compared with preoperative values. Uncorrected visual acuity improved in all eyes (P<.0001). Best spectacle-corrected visual acuity was unchanged or improved in 13 eyes (81%) and worse in 2 eyes by 1 line; 1 eye lost 3 lines due to an increase in preexisting cataract. In eyes that did not receive MMC, corneal haze (grade II to IV) was encountered in 3 eyes (27%). One eye required phototherapeutic keratectomy with MMC application at 12 months. Of the 4 eyes treated with MMC, 1 had trace haze and 3 had no detectable haze. There were no reported cases of epithelial instability, ectasia, or graft rejection.
Conclusions
Topography-assisted customized LASEK was effective in the correction of postkeratoplasty astigmatism. A significant improvement of both LOAs and HOAs was obtained with good refractive stability for over 18 months. Iatrogenic haze typically occurred but appeared to be minimized with adjunctive use of intraoperative MMC.
From the Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom
Reprint requests to Madhavan S. Rajan, MRCOphth, FRCS, Specialist Registrar, Department of Ophthalmology, St. Thomas' Hospital, Lambeth Palace Road, London SE1 7EH, United Kingdom.
Supported by provision of a Schwind Esiris flying-spot excimer laser from Schwind Eye-Tech Solutions and by a research grant from Iris Fund for Prevention of Blindness, London, United Kingdom.
No author has a financial or proprietary interest in any material or method mentioned.
ABSTRACT