1. Laser subepithelial keratomileusis (LASEK) retreatment surgery Colm McAlinden, 1,2 Jonathan Moore, 2,3 1 School of Biomedical Sciences, University of Ulster, UK; 2 Cathedral Eye Clinic, York Street, Belfast, UK; 3 Mater Hospital, Belfast Health and Social Care Trust, UK. Funding from the Department for Employment and Learning (DEL), Belfast, UK. No author has a financial or proprietary interest in any material or method mentioned.

2. Background Laser enhancement may be required when: Laser enhancement may be required when: Suboptimal visual outcome 1-3 Suboptimal visual outcome 1-3 Overcorrection Overcorrection Undercorrection Undercorrection Regression Regression Due to a variety of factors 4-6 Due to a variety of factors 4-6 Magnitude of refractive error Magnitude of refractive error Variable corneal wound healing Variable corneal wound healing Compensatory epithelial hyperplasia Compensatory epithelial hyperplasia Ablation algorithm Ablation algorithm Nonaccurate nomograms Nonaccurate nomograms Age Age

3. Background LASEK enhancements are often performed with mitomycin C in order to reduce the risk of corneal haze LASEK enhancements are often performed with mitomycin C in order to reduce the risk of corneal haze

4. Aims The aim of this study is to investigate the outcomes of LASEK retreatment surgery without the use of MMC in terms of predictability, safety, efficacy and stability. The aim of this study is to investigate the outcomes of LASEK retreatment surgery without the use of MMC in terms of predictability, safety, efficacy and stability.

5. Methods Twenty two eyes of 15 patients (mean age 32 years; age range 21 to 56 years) underwent LASEK retreatment surgery following initial LASEK. The LASEK retreatment procedure was identical in technique to the original LASEK surgery; 20% C2H5OH was instilled for 40 seconds, without the use of mitomycin C. The mean pre-operative spherical and cylindrical refraction was -3.01 dioptres (range: +5.25 to -6.00) and -1.18 dioptres (range: +0.00 to -5.00) respectively. The mean pre-retreatment spherical and cylindrical refraction was -0.47 dioptres (range: +1.50 to -1.75) and -0.47 dioptres (range: +0.00 to -1.25) respectively. All treatments were wavefront guided using the VISX S4 Star excimer laser. All procedures were wavefront-guided using the VISX S4 Star excimer laser (CustomVue)

6. Results Six months post-retreatment, the mean spherical and cylindrical refraction was +0.03 dioptres (range: -0.25 to +0.50 dioptres) and -0.02 dioptres (range: +0.00 to -0.75 dioptres) respectively. Six months post-retreatment, the mean spherical and cylindrical refraction was +0.03 dioptres (range: -0.25 to +0.50 dioptres) and -0.02 dioptres (range: +0.00 to -0.75 dioptres) respectively. The mean UCVA and BCVA was 1.19±0.11 and 1.22±0.13 respectively. The mean UCVA and BCVA was 1.19±0.11 and 1.22±0.13 respectively. No intraoperative complications were encountered. No intraoperative complications were encountered. Grade 1 haze occurred in four eyes which subsided in all cases by eight weeks with continued topical steroid treatment. Grade 1 haze occurred in four eyes which subsided in all cases by eight weeks with continued topical steroid treatment.

7. Conclusion LASEK retreatments without the use of mitomycin C provided good visual and refractive outcomes. LASEK retreatments without the use of mitomycin C provided good visual and refractive outcomes. With the known and unknown potential side-effects of mitomycin C, LASEK retreatments may be safe and effective without the use of mitomycin C. With the known and unknown potential side-effects of mitomycin C, LASEK retreatments may be safe and effective without the use of mitomycin C. Long term studies on the use of mitomycin C with retreatment surgery over a large refractive range is necessary. Long term studies on the use of mitomycin C with retreatment surgery over a large refractive range is necessary.

8. References 1. Huang D, Stulting RD, Carr JD, et al. Multiple regression and vector analyses of laser in situ keratomileusis for myopia and astigmatism. J Refract Surg. 1999; 15: 538-549. 2. Ditzen K, Handzel A, Pieger S. Laser in situ keratomileusis nomogram development. J Refract Surg. 1999; 15(suppl): S197- S201. 3. Roberts C. The cornea is not a piece of plastic. J Refract Surg. 2000; 16: 407-413. 4. Mohan RR, Hutcheon AE, Choi R et al. Apoptosis, necrosis, proliferation, and myofibroblast generation in the stroma following LASIK and PRK. Exp Eye Res. 2003; 76: 71-87. 5. Helena MC, Baerveldt F, Kim WJ et al. Keratocyte apoptosis after corneal surgery. Invest Ophthalmol Vis Sci. 1998; 39: 276– 283. 6. Ibrahim O. Laser in situ keratomileusis for hyperopia and hyperopic astigmatism. J Refract Surg. 1998; 14(suppl): S179- S182.