Observation Of LASIK With Q-guided Aspheric And Standard Ablation For Diff-level Myopia Groups

With the widespread application of LASIK, the surgery is accepted by both doctors and patients for its safety, reliability and indolence. However, there are up to 10%～15% of patients experience vision quality problems after LASIK such as glare, halo and decreased contrasts sensitivity despite excellent uncorrected visual acuity. Conventional ablation profiles of excimer laser for myopic refractive correction change the corneal profiles. They can only correct low-order aberrations such as myopia, hyperopia and astigmatism, but induce additional imaging high-order aberrations into the optical system. This is a major cause of the observed deterioration of visual quality after such corrections. Nowadays, more and more attention was paid to how to maintain the corneal profiles and achieve better visual quality. The concept of customized ablation in excimer corneal refractive surgery was introduced recently. With the development of corneal aspherical theory, some scholars presumed that the spherical tendency of cornea after traditional LASIK surgery is the main factor leading to visual quality reduces. LASIK with Q-factor customized aspheric profile ablation was designed to reduce the spherical tendency of cornea in order to obtain better visual quality. Here we report a prospective study result of the Q-guided aspheric profile ablation compared with standard ablation LASIK to correct diff-level myopia. ObjectiveTo analyze visual acuity, diopter, conceal profile, corneal high-order aberration, entire optical system high-order wavefront aberration and contrast sensitivity in patients treated with Q-guided aspheric profile ablation of LASIK compared with patients having standard ablation to correct myopia, and to evaluate postoperative clinical effects.MethodsAccording to spherical equivalent (SE), subjects were divided into low myopic group (89 eyes of 47 patients), moderate myopic group (135 eyes of 71 patients) and high myopic group (75 eyes of 38 patients). Each group was divided into aspheric profile subgroup (F) and standard subgroup (C) randomly. Preoperative, 1mo and 3mo postoperative visual acuity, diopter,asphericity (Q), corneal high-order aberration, optical high-order aberration and contrast sensitivity were compared between F subgroup and C subgroup.Results(1) The postoperative uncorrected visual acuity (UCVA) of all eyes was satisfying after 3 months' follow-up. There was no significant difference in term of postoperative refractions between two subgroups (t-test, P>0.05).(2) The corneal profile transformed oblate corneal asphericities after surgery (P<0.01). In F subgroup of low and moderate myopic group, the increased extent of Q-value were significantly less than that in C subgroup (P<0.05). However, there was no statistical difference between two subgroups in high myopic group (P>0.05). And there was no statistical change of Q-value during 3 months' follow-up visit.(3) All patients'postoperative corneal and optical high-order aberration increased (P<0.01). In F subgroup of low and moderate myopic group, the increased extent of Z40, C12 and RMSh were significantly less than that of C subgroup (P<0.05), but there was no statistical difference between two subgroups in high myopic group (P>0.05).There were no significant difference of coma aberrations between two subgroups in all groups (P>0.05). And there was no obviously change of these indexes during 3 months' follow-up visit.(4) All patients'contrast sensitivity decreased in every space frequency at early postoperation. At 1mo postoperation, CS in 0.5, 1, 4, 8cpd space frequency were higher than preoperative level in F group (P<0.05), however, CS in 2, 16cpd space frenquency were still lower than preoperative level, there was significant difference in 16cpd space frequency (P>0.05). In C group, CS in 0.5, 1cpd space frequency recovered (P>0.05), and CS in rest space frequency were lower than preoperative level (P<0.05). At 3 mo postoperation, CS in all space frequency except 16 cpd space frequency recovered in F group and C group. In F group, CS in every space frequency were higher than CS in C group at postoperation, there were significant difference (P<0.05).ConclusionsQ-guided aspheric profile and conventional LASIK were safe and efficient for the correction of myopia. Moreover, Q-guided aspheric profile LASIK better maintained the physiology of the corneal surface, and induced a smaller increment of corneal, the entire optical system high-order wavefront aberration and a smaller decrecement of CS in every space frequency than conventional treatment. So Q-guided aspheric profile LASIK is a more effective procedure to improve visual quality compared to conventional LASIK.