Study on the effective optical zone after SMILE in patients with different degrees of myopia / 国际眼科杂志(Guoji Yanke Zazhi)

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, &Delta;Z40 was negatively correlated with &Delta;EOZ(<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.