Changes Of Accommodation And Convergence In Myopias After Laser In Situ Keratomileusis

Objective To investigate the changes of accommodation, convergence and asthenopia after laser in situ keratomileusis (LASIK) in myopia. And analyze the effects of accommodative and convergence parameters on asthenopia.Methods A total of 73 myopia patients (146 eyes) accepted LASIK, and they were divided into groups of low myopia (20 patients 40 eyes), medium myopia(26 patients 52 eyes) and high myopia(27 patients 54 eyes) by their preoperative spherical equivalent refraction. At the same time,19 emmetropes(38 eyes) were collected as a control group. Then we measured accommodative amplitude(AMP),Negative relative accommodation/Positive relative accommodation (NRA/PRA),accommodative facility(AF),near point of convergence(NPC),range of fusion(RF),accommodative convergence per unit of accommodation ratio (AC/A) and asthenopia of two groups. The myopia patients were measured at the time before surgery and 1 week, 1 month and 3 months after surgery. Questionnaire was used to evaluate the symptoms of asthenopia.Results 1.The AMP in myopic group descended at 1 week after LASIK(P<0.05) , while recovered to the preoperative level at 1 month(P>0.05), and then surpassed the preoperative level at 3 months after LASIK(P<0.05) ,close to the normal level(P>0.05). 2.There was no significant difference of PRA in myopia group at 1 week,1 month after operation in comparison with that of preoperative. While, PRA at 3 months postoperative in myopia group was higher than that of preoperative(P<0.05), close to the normal level(P>0.05).3.There was no significant difference of NRA before and after operation(P>0.05). Compared the NRA in myopic group with that in stigmatism group, there was no difference neither(P>0.05).4.There was no significant difference of AF before and after operation(P>0.05). Compared the AF in myopic group with that in stigmatism group, there was no difference neither(P>0.05).5.The NPC in myopia group leaved far away from the eye at 1 week after LASIK (P<0.05), and then closed to the eye gradually. At the third month after operation, there was no difference of NPC between myopic group and stigmatism group(P>0.05).6,There was no significant difference of RF before and after operation(P>0.05). Compared the RF in myopic group with that in stigmatism group, there was no difference neither(P>0.05).7.The AC/A ratios in myopic group descended at 1 week after LASIK(P<0.05), while at 3 months after LASIK, the AC/A ratios recovered to the preoperative level (P>0.05), closed to the normal level(P>0.05).8.The symptoms of asthenopia aggravated significantly at 1 week after operation(P<0.05), and recovered to the preoperative level at 1 month after operation(P>0.05), and at 3 months after operation, the symptoms were relieved significantly than the preoperative symptoms(P<0.05), closed to the normal level(P>0.05). 9.The parameters of asthenopia, accommodation and the convergence had no difference in the three different myopic groups(P>0.05).10.We concluded from spearman correlation that postoperative symptoms of asthenopia were negatively related with AMP, AF and the AC/A radio before operation, and positively related with age and PRA, NPC before operation(P<0.05); The aggravation of asthenopia symptoms were related with the decrease of AMP, the decrease of AC/A ratio, and the increase of NPC(P<0.05); And the recovery of asthenopia were related with the increase of AMP and PRA(P<0.05).Conclusion LASIK improved the accommodative and convergence function and released the symptoms of asthenopia.