ABSTRACT
@#AIM: To explore the changes and influencing factors of effective optical zone(EOZ)after femtosecond laser small incision lenticule extraction(SMILE)in patients with different degrees of myopia.<p>METHODS:Retrospective study. From October 2019 to October 2020, fifty patients(92 eyes)with myopia who underwent SMILE surgery in the Affiliated Eye Hospital of Nanchang University and whose preoperative optical zone diameter was designed to be 6.5mm were selected. According to the preoperative equivalent spherical diopter, the patients were divided into three groups: low myopia group(-0.50D to -3.00D, 18 cases, 34 eyes), moderate myopia group(>-3.00D to -6.00D, 20 cases, 36 eyes)and high myopia group(>-6.00D, 12 cases, 22 eyes). The uncorrected visual acuity, best corrected visual acuity, manifest refraction spherical equivalent, optical zone diameter, corneal Q-value and high-order aberrations(HOA)were collected before and 3mo after operation.<p>RESULTS:The postoperative 3mo EOZ of patients with low, moderate and high myopia were 5.07±0.69, 5.08±0.43 and 4.50±0.58 mm, respectively, and the corneal Q-values were 0.22±0.17, 0.57±0.34 and 0.63±0.73, there were significant differences among the three groups(all <i>P</i><0.05). The diameter of effective optical zones after operation in all three groups was lower than that predicted by 6.5mm before operation(<i>P</i><0.001). There were significant differences in postoperative total HOA, spherical aberration(Z40)and vertical coma(Z3-1)among the three groups(<i>P</i><0.05). The diameter of effective optical zone after SMILE was positively correlated with preoperative manifest refraction spherical equivalent and residual corneal thickness(<i>r</i>=0.357, 0.275,all <i>P</i><0.05), and negatively correlated with central corneal ablation depth and postoperative corneal Q-value(<i>r</i>= -0.316, -0.353, all <i>P</i><0.05). After operation, ΔZ40 was negatively correlated with ΔEOZ(<i>r</i>= -0.336, <i>P</i><0.05).<p>CONCLUSION:The EOZ after SMILE was lower than that expected before operation, and the higher the myopia was, the smaller the optical area was and the more the postoperative corneal spherical aberration increased. In addition, the depth of corneal ablation, residual corneal thickness and aspheric changes of cornea can affect the size of EOZ after operation.
ABSTRACT
@#AIM: To study the postoperative optical zone decentration and visual quality by taking visual axis corneal reflect point(VACRP)and corneal vertex(CV)as the ablation center, exploring the femtosecond laser small incision lenticule extraction(SMILE).<p>METHODS: Prospective randomized controlled trial. Totally 70 myopic patients(140 eyes)who underwent SMILE surgery in our hospital from May to June 2020 were randomly divided into two groups, 68 eyes of 34 cases took the VACRP as the ablation center(VACRP group), and 72 eyes of 36 cases took the CV as the ablation center(CV group). The visual acuity, refractive diopter, offset from corneal ablation center, and high-order corneal aberrations were observed before and 3mo after surgery. <p>RESULTS: Three months after operation, there was no difference in uncorrected visual acuity, best corrected visual acuity and refractive diopter between the two groups(<i>P</i>>0.05). The ablation center deviation in CV group(0.20±0.13mm)was less than that in VACRP group(0.27±0.14mm, <i>P</i><0.01). The total corneal high-order aberration(totHOA), spherical aberration(totZ40), vertical coma(totZ3-1)and horizontal coma(totZ31)in CV group were lower than VACRP group(<i>P</i><0.05). Three months after operation, the totHOA, total high-order aberration change(ΔtotHOA), totZ40, totZ3-1 in VACRP group were correlated with ablation center deviation(<i>r</i>=0.470, 0.486, 0.254, -0.366, <i>P</i><0.001, =0.001, 0.037, 0.002), totZ31 in CV group was correlated with the ablation center deviation(<i>r</i>=-0.352, <i>P</i>=0.002).<p>CONCLUSION: SMILE surgery can obtain satisfactory uncorrected visual acuity and the same level of refractive diopter with the VACRP and the CV as the ablation center, but taking the CV as the ablation center can reduce the postoperative decentration and high-order corneal aberrations and obtain better visual quality.