The Relation Between The Corneal Ablated Zone Diameter And The Pupil Diameter After Dark Adaptation

Objective:According to the clinic data, the preoperative and postoeratinve visual quality of patients who undertook LASIK, gathered and analysed by us, we study the relation between the corneal ablated zone diameter and the pupil diameter after dark adaptation and get relevant conclusions to discuss the size of the corneal ablated zone of individual LASIK in clinical work for improving the postoperative patients'visual quality.Method:The 242 eyes of 450 patients (122 males,232 eyes; 120 females,220 eyes; age:from 18 to 24 years, mean age:21.6±1.4。the pupil diameter after dark adaptation:5.0—8.0 mm; corneal curvature:40.0—45.0 D; the thickness of corneal optical region:(540.67±29.56)μm; DC:(0～2.00D), DS:(-0.50～-9.00D) who underwent aspheric LASIK in Kunming General Hospital of Chinese PLA and insist on follow-up visit between May 2010 and December 2010 were divided into three myopia levels including primarymyopia (-0.50～-3.00D) moderate myopia (-3.25～-6.00D) and high myopia(-6.25～-9.00D). This three myopia levels'patients were averagely distributed into five groups stochastically. According to the relation between the corneal ablated zone diameter and the pupil diameter after dark adaptation, this three myopia levels'patients were averagely distributed into five groups stochastically. Group A:the corneal ablated zone diameter(0.1mm—0.5mm) is longer than the pupil diameter after dark adaptation., Group B:the corneal ablated zone diameter is equal to the pupil diameter after dark adaptation and the corneal ablated zone diameter which is shorter than the pupil diameter after dark adaptation is divided into Group C:0.1mm—1.0mm, Group D:1.1mm—2.0 mm and Group E:2.1 mm—3.0mm. Based on the patients'naked vision data in preoperatively three days,postoperatively at day 1,1 month,3 months and 6 months and the patients' visual contrast sensitivity condition postoperatively at 1 month,3 months and 6 months, analysis relatively and synthetically to get conclusions. The visual quality mentioned in the issue is measured by Mesotest-Ⅱcontrast sensitivity instrument(the visual contrast sensitivity of mesopic vision and glare). Mesopic vision is an apparatus to examine the ability of cone and Rod cells.Results:In 242 eyes of 450 patients underwent LASIK,68.44 percent of the total's naked visual acuity reached preoperative corrected visual acuity postoperatively at 1 day,85.78 percent of the total's naked visual acuity reached preoperative corrected visual acuity postoperatively at 1 month,90.67 percent of the total's naked visual acuity reached preoperative corrected visual acuity postoperatively at 3 month, and 91.78 percent of the total's naked visual acuity reached preoperative corrected visual acuity postoperatively at 6 month.The postoperative visual quality in five groups:The patients'postoperative visual contrast sensitivity of mesopic vision and glare is developed and visual quality is improved obviously from Group A (the corneal ablated zone diameter of 0.1mm—0.5mm is longer than the pupil diameter after dark adaptation and Group B (the corneal ablated zone diameter is equal to the pupil diameter after dark adaptation), and there is significant difference (P<0.05). The patients'postoperative visual contrast sensitivity of mesopic vision and glare is developed and visual quality is improved obviously from Group C (the corneal ablated zone diameter of 0.1mm—1.0mm is shorter than the pupil diameter after dark adaptation and Group D (the corneal ablated zone diameter of 1.1mm—2.0mm is also shorter than the pupil diameter after dark adaptation), and there is significant difference (P<0.05). The patients in Group E (the corneal ablated zone diameter is from 2.1mm to 3.0mm) postoperative visual contrast sensitivity of mesopic vision and glare is developed and visual quality is improved obviously, but compare to the patients in Group C and Group D, the postoperative visual contrast sensitivity of mesopic vision and glare is decreased and visual quality is declined obviously. Accordingly there is significant difference (P<0.05).In every group, the patients'postoperative 3-month visual contrast sensitivity of mesopic vision, glare and visual quality are better than the patients postoperatively 6 months, and there is no significant difference (P>0.05).90 percent of the total patients'naked visual acuity reach the preoperative corrected visual acuity at postoperatively 1 day,1 month,3 months and 6 months.There is no obvious difference between preoperative and postoperative visual contrast sensitivity of mesopic vision and glare in 18 eyes of 9 patients.Conclusion:The patients', whose corneal ablated zone diameter from 0.1mm to 0.5 is shorter than the pupil diameter after dark adaptation, postoperative visual contrast sensitivity of mesopic vision and glare is developed and visual quality is improved obviously. The patients', whose corneal ablated zone diameters from 0.1mm to 1.0mm and from 1.1mm to 2.0 mm are shorter than the pupil diameter after dark adaptation, postoperative visual contrast sensitivity of mesopic vision and glare is developed and visual quality is improved obviously. The patients', whose corneal ablated zone diameter from 2.1mm to 3.0 mm is shorter than the pupil diameter after dark adaptation, visual quality is declined obviously, so their corneal ablated zones are not good for improving postoperative visual quality.Based on no obvious difference between preoperative and postoperative visual contrast sensitivity of mesopic vision and glare in 18 eyes of 9 patients, the postoperative visual quality has significant relation with the ability of patients'cone and Rod cells.