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[An analysis of regression after laser in situ keratomileusis for treatment of myopia].

OBJECTIVE
To evaluate the regression relevant reasons of laser in situ kertomileusis (LASIK) for treatment of myopia.


METHODS
Four hundred and eight eyes of 250 patients with myopia who received LASIK were studied. They were divided into 2 groups according to preoperative diopters (-6.25- -10.00 D in 194 eyes; -10.25 -15.00 D in 214 eyes). The mean follow-up was 12 months, and the results of the postoperative visual acuity, refractive diopter, corneal thickness and the diameter of the ablation zone were statistically analyzed.


RESULTS
(1) A group: There were 173 normal operative eyes (89.2%, post-operative diopter < -1.00 D), the mean pre-operative corneal thickness was (549.5 +/- 31.5) microm, the mean intra-operative laser ablation diameter was (4.96 +/- 0.35) mm, and the post-operative refractive diopter was +0.50- -0.75 D. The regressive operative eyes: There were 21 eyes (10.8%, post- operative diopter >/= -1.00D), the mean preoperative corneal thickness was (547.7 +/- 37.0) microm (P > 0.05 in comparison with that of the normal operative eyes), the mean intra-operative laser ablation diameter was (4.64 +/- 0.41 ) mm (P < 0.01 in comparison with that of the normal operative eyes), and the mean post-operative diopter was (-1.33 +/- 0.58)D. (2) B group: There were 136 normal operative eyes (63.5%), the mean pre-operative corneal thickness was (560.9 +/- 30.9) microm, the mean intra-operative laser ablation diameter was (4.51 +/- 0.28) mm, and the post-operative diopter was +0.50- -0.75 D. The regressive operative eyes: There were 78 eyes (36.5%), the mean pre-operative corneal thickness was (538.0 +/- 31.0) microm (P < 0.01 in comparison with that of the normal operative eyes), the mean intra-operative laser ablation diameter was (4.22 +/- 0.34) mm (P < 0.01 in comparison with that of the normal operative eyes), and the mean post-operative diopter was (-1.99 +/- 1.01) D.


CONCLUSIONS
In cases with small laser ablation diameter and the thin pre-operative corneal thickness of high myopia, after the surgery refractive regression is easy to occur. Some modification of the surgical algorithms and laser nomogram will help to improve predictability and reduce regression.