Ten year follow up of laser in situ keratomileusis for all levels of myopia

Abstract

Editor, In 2004, we performed a retrospective study assessing the refractive and visual outcome of patients 5 years post laser in situ keratomileusis (LASIK) surgery for all levels of myopia (O’Doherty et al. 2006). All 49 patients (94 eyes) in the original study were invited to attend for a 10-year review. Thirty patients (54 eyes) attended for examination. The original range of myopia treated was from −1.5 to −13 dioptres. The eyes were grouped into mild (<−3 D), moderate (−3 to −6 D) and high (>−6D) myopia. All surgery was performed by one experienced surgeon (MO’K) using the Bausch and Lomb Technolas 217 laser platform (Bausch & Lomb, Surrey, UK). The treatment algorithm used was the plano programme. Flaps were cut to a depth of 140 μm using the Hansatome microkeratome (Bausch and Lomb) and hinged superiorly with a flap diameter of 8.5–9.5 mm. The ablation zone ranged from 6 to 7 mm. At 10-year follow-up, uncorrected (UCVA), best corrected visual acuity (BCVA), manifest refractive spherical equivalent (MRSE), corneal topography and aberrometry were measured. Patients completed a questionnaire regarding satisfaction with LASIK. Questions asked included those relating to symptoms of dry eye and night vision problems such as glare and haloes. Regression was measured in this study as eyes that had regressed more than 0.5 dioptres. Of the 94 eyes originally included (49 patients), 54 eyes of 30 patients were examined. Nineteen women and 11 men of mean age of 42.8 years (range 30–65) were assessed 10 years post-LASIK. There were seven eyes in the mild, 29 in the moderate and 18 in the highly myopic groups. The original cohort of patients (94 eyes) had 23 mild, 49 moderate and 22 highly myopic eyes. Therefore, 30% of mild myopes, 59% of moderate myopes and 82% of high myopes returned for the follow-up study. At 10-year postoperative review, 52% were within ±0.50 D and 87 within ±1.0 D of emmetropia. Fifty-six per cent of eyes had UCVA better than or equal to 6/6 and 82% better than or equal to 6/9. Fifteen eyes (27.8%) had regressed. The overall mean regression (MRSE) was −1.6D. Mean regression in the mild, moderate and high myopic groups were −1.15, −0.93 and −1.94 D, respectively. Eleven eyes (20.4%) underwent retreatment during the 10-year follow-up period with a mean time to retreatment from the original surgery of 6.1 years. Of these, 4 (36%) were retreated prior to 5-year review and 7 (64%) between 5 and 10 years. The mean overall retreatment refractive error (MRSE) was −1.77 D. The mean retreatments performed in the low, moderate and high myopic groups were −1.15, −0.88 and −1.89 dioptres, respectively. The retreatment rate was greatest in the highly myopic group. No eye was retreated more than once (see Table 1). Four eyes of three patients regressed but no retreatment was performed. Two patients with unilateral regression had useful monovision. The third patient with bilateral regression returned to wearing glasses and declined further treatment. In the 43 eyes that were not retreated, 56% had a vision of 6/6 or better and 89% had a vision of 6/9 or better. During the 10-year follow-up period, three eyes were treated for retinal tears and one underwent retinal detachment repair. Ten patients reported glare. Seven patients reported the symptoms of dry eye. There was no topographical evidence of corneal ectasia. On questioning, all patients stated to be very happy with their original decision to undergo LASIK surgery. In our study, we found that better results were achieved in mild and moderate myopia and poorer outcomes were achieved in high myopia. These findings are similar to those of Zalentein (Zalentein et al. 2009). The trend towards regression may be explained by both corneal and non-corneal changes. Clearly changes in the corneal mechanics such as ectasia and corneal epithelial thickness could be one explanation. Non-corneal causes such as increase in axial length secondary to vitreous chamber elongation have been shown to increase myopia in adulthood (Kinge & Miledfart 1999; Jorge et al. 2007) In the twelve-year follow-up after PRK, we reported a continuous small regression (O’Connor et al. 2006). There is a reasonable inference from these studies that it is very likely that non-corneal changes over time will induce an increase in myopia. Those undergoing LASIK for high myopia and younger patients who are highly myopic should be advised of this potential and that they may indeed need retreatment in the future. This study shows LASIK to be a safe procedure associated with high patient satisfaction. Long-term stability was found in low to moderate myopia; however, a much greater tendency towards regression was seen in highly myopic patients with the need for retreatment.