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Objective:To investigate the influence of long-term wear of soft contact lenses on corneal transparency.Methods:A cross-sectional study was conducted.The corneal optical density of female myopic patients who planned to undergo corneal refractive surgery in Jinan Mingshui Eye Hospital from January 2018 to December 2020 was examined.The patients were divided into ≥2-<5 years group, ≥5-<10 years group, and ≥10 years group according to the duration of wearing contact lenses.Age- and sex-matched patients without wearing soft contact lenses were enrolled as a control group.There were 50 eyes from 50 cases in each group.The cornea was divided into 0-2, 2-6, 6-10, and 10-12 mm corneal vertex-centered annuli.The cornea over each annulus was divided into a superficial layer (≤120 μm from the outer surface of the cornea), a deep layer (≤60 μm from the inner surface of the cornea) and a central layer (between the superficial and deep layers). Measurements of the right eye were taken for analysis.The corneal optical density of different layers over different corneal ring regions was compared.This study adhered to the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of Jinan Mingshui Eye Hospital (No.2018-005). Written informed consent was obtained from each subject before any medical examination.Results:The corneal optical density tended to decrease as the wearing duration of corneal contact lens extended.The corneal optical density values of control group, ≥2-<5 years group, ≥5-<10 years group, and ≥10 years group were 18.51±1.79, 18.25±2.10, 18.16±1.89 and 17.83±1.65, respectively, showing no significant difference ( F=1.152, P=0.329). There was no significant difference in the corneal optical density of the superficial layer over 0-2, 2-6, and 6-10 mm annuli among the four groups ( F=2.077, 2.080, 2.229; all at P>0.05). There was a significant difference in the corneal optical density of the superficial layer over 10-12 mm annulus among the four groups ( F=5.016, P=0.002), and the corneal optical density of the superficial layer was greater in ≥5-<10 years group than in ≥2-<5 years, and greater in ≥10 years group than in control group, showing statistically significant differences (both at P<0.05). There were significant differences in the corneal optical density of the central layer over 0-2 and 6-10 mm annuli ( F=3.808, 2.813; both at P<0.05), and the corneal optical density of the central layer was lower in ≥10 years group than in control group, showing a statistically significant difference ( P<0.05). There were significant differences in the corneal optical density of the deep layer over 0-2, 2-6, 6-10 and 10-12 mm annuli ( F=5.485, 5.625, 3.398, 2.775; all at P<0.05). The optical density of the deep layer was lower in ≥5-<10 years than in control and ≥2-<5 years groups over 0-2, 2-6, and 10-12 mm annuli, lower in ≥5-<10 years group than in control group over the 6-10 annulus, and lower in ≥10 years group than in control group over 0-2, 2-6, and 6-10 mm annuli, and the differences were statistically significant (all at P<0.05). Conclusions:For women, the long-term wear of soft contact lenses for 5 years does not affect corneal transparency, and long-term wear for more than 5 years can cause a decrease in the transparency of the superficial peripheral cornea.
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Objective:To measure the effective optical zone (EOZ) after small incision lenticule extraction (SMILE) by using corneal topographic map and modulation transfer function (MTF), and to analyze the related factors affecting the EOZ.Methods:A retrospective observational case series study was performed.Sixty-two myopic patients (62 eyes) who underwent SMILE between December 2015 and July 2017 in Jinan Mingshui Eye Hospital were enrolled.The EOZ was measured by using tangential corneal curvature topographic map and MTF pre- and 6-month post-operatively.The repeatability of data was determined by intraclass correlation coefficient (ICC) and Cronbach Alpha coefficients; the agreement of data was identified by using Bland-Altman plot; the correlations between EOZ and surgical parameters were analyzed by utilizing Pearson correlation coefficient.This study protocol was approved by the Ethics Committee of Jinan Mingshui Eye Hospital(No.2015[013]). Written informed consent was obtained from each patient before surgery.Results:The ICC and Cronbach Alpha coefficients of EOZ measured by corneal topographic map were greater than 0.9, which showed high intraobserver repeatability.The Bland-Altman plots displayed relatively good agreement between the two methods.The 95% limits of agreement was -0.49 to 0.89 μm.Six months after SMILE, the EOZ measured by tangential corneal curvature gradient topographic map was (5.32±0.25)mm, which was (1.18±0.25)mm smaller than predicted optical zone, and the EOZ measured by MTF method was (5.07±0.32)mm, which was (0.20±0.35)mm smaller than corneal tomographic EOZ, and the difference was significant ( t=-4.487, P<0.01). A negative correlation was found between the EOZ and attempted refractive correction ( r=-0.364, P=0.004). The positive correlations were found between the EOZ and ΔKm or ΔQ 6 months after SMILE ( r=0.367, 0.514; both at P<0.01). Conclusions:The EOZ measured by tangential corneal curvature topographic map after SMILE is of high repeatability and is consistent with the result calculated by MTF method.The EOZ is significantly reduced after SMILE.
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Background Corneal epithelial remodeling will happen after laser refractive surgery,But there have been few studies to evaluate the changes of the corneal epithelial thickness after integrated transepithelial photorefractive keratectomy (TranspRK).Objective This study was to evaluate the changes in epithelial thickness profile within the optical zone and its related factors following TransPRK for myopia.Methods In this retrospective non-randomized controlled study,forty-three patients (43 eyes) who underwent TransPRK with the spherical equivalent refraction-1.25 to-6.25 D from August 2014 to May 2015 in Jinan Mingshui Eye Hospital were included under the informed consent.Epithelial thickness was measured using spectral-domain optical coherence tomography in different corneal zones (central,2 mm;paracentral,2-5 mm,and mid-peripheral,5-6 mm) preoperatively at 1 week and 1,3,and 6 months postoperatively.Correlations between epithelial thickness changes and the amount of correction,optical zone,and Q-value changes (△Q) were analyzed 6 months postoperatively.Results The mean epithelial thickness in the central zone were (53.97±4.33),(51.03 ±4.11),(55.14±5.46) and (56.68 ± 5.09) μm at 1 week,1 month,3 months and 6 months after surgery,respectively.The epithelium were thicker at 3 months and 6 months after surgery compared to preoperative measurements ([52.37±3.42] μm),with significant differences between them (both at P＜0.05).Compared to preoperative values,the epithelial thickness at 6 months after surgery was (3.69 ±4.23),(5.19 ±3.88) and (6.23 ±3.91) μm thicker in the center,paracenter,and midperiphery zone,respectively,with significant differences between them (all at P ＜ 0.01).Epithelial thickness was positively correlated with programmed spherial equivalent correction and △Q (all at P＜0.05).A significant positive relationship was observed between epithelial thickening and ablation depth paracentrally and mid-peripherally (r=0.380,0.383;both at P＜0.05).Significantly negative relationships were observed between epithelial thickening and optical zone at the center,paracenter,and mid-periphery,respectively (r =0.405,0.485,0.384;all at P＜0.05).No correlation betwcen epithelial thickness change and ablation depth at the central zone was detected (P＞0.05).Conclusions The epithelial thickness shows a lenticular change with more thickening mid-Peripherally after TransPRK,which results in increased oblateness postoperatively.Epithelial remodeling may modify the profile after surface ablation.
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Background Integrated transepithelial photorefractive keratectomy (TransPRK) is a new kind of surface ablation and has a fast reepithelialization and uncorrective visual acuity (UCVA) recovery as well as slighter postoperative pain,and epipolis laser in situ keratomileusis (Epi-LASIK) has been recognized to be an effective method for myopia.But there have been few studies to evaluate the dynamic change of the corneal biomechanical properties and posterior corneal elevation after TransPRK.Objective This study was to assess and compare the effectiveness and safety between TransPRK and Epi-LASIK for myopia with thin cornea.MethodsThis study was approved by Ethic Committee of Jinan Mingshui Eye Hospital,and written informed consent was obtained from each patient.In this prospective non-randomized controlled study,93 right eyes of 93 myopic patients with the central corneal thickness 460 to 500 μm were included in Jinan Mingshui Eye Hospital from June to December 2013 under the informed consent.The eyes were divided into TransPRK group for 46 eyes and Epi-LASIK group for 47 eyes.UCVA,manifest refraction,haze,corneal biomechanical properties,posterior corneal elevation,Qvalue and corneal high order wavefront aberration were analyzed before and 1 week,1 month,3 months and 6 months after operation,respectively,and the examination results were compared between the two groups.Results There was no statistically significant difference in the eyes of postoperative UCVA and manifest refraction between the TransPRK group and the Epi-LASIK group at various time points (all at P＞0.05).Six months after surgery,the percentage of eyes with UCVA of 1.0 or better was 93.9％,and 90.9％ eyes exhibited the targeted refraction in ± 1.00 D in the TransPRK group.Corneal haze was most obvious 1 month after surgery in both groups,with the incidence of 32.6％ (15/46) in the TransPRK group and 17.4％ (8/47) in the Epi-LASIK group,but no significant difference was found in the eye numbers with haze between the two groups (x2 =2.841,P =0.092).No significant differences were seen in the corneal hysteresis(CH) values and corneal resistance factor(CRF) values between the two groups (CH:Fgroup =0.000,P =0.999;CRF:Fgroup =0.110,P =0.741),however,the postoperative CH values and CRF values were significantly declined in comparison with preoperative ones,with significant differences among various time points (CH:Ftime =103.658,P =0.000;CRF:Ftime =132.008,P =0.000),while there were no remarkable differences between any two time points in postoperation (all at P＞0.05).Posterior corneal surface height shifted rearward 1 week,1 month,3 months and 6 months after surgery,showing remarkable differences in comparison with before surgery in both groups (Ftime =12.868,P =0.001),but no significant differences between the two groups (Fgroup =1.923,P=0.169).No significant differences were found in Q-value between the two groups (Fgroup =0.191,P=0.663).Root mean square (RMS) and spherical aberration values elevated in postoperation compared with preoperation,with significant differences between them(all at P＜0.01),but the comparison between intergroup was insignificant (RMS:Fgroup =0.299,P =0.586;Spherical aberration:Fgroup =1.290,P =0.259).Conclusions TransPRK for myopia with thin cornea is safe and stably effective like Epi-LASIK.TransPRK affects corneal biomecbanical properties early after surgery but the effect gradually lessens over time.The posterior corneal elevation shows a tiny backward displacement,while posterior corneal asphericity has no change.
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Objective To evaluate the predictability of ablated depth in photorefractive procedures by Zeiss MEL80 and VISX Star S4 excimer laser.Design Prospective,comparative case series.Participants 168 eyes of 84 people with myopia and cylinder.Main Outcome Measures Corneal thickness and ablated depth.Methods The thickness of cornea by Zeiss MEL80 and VISX Star S4 were measured by anterior segment OCT.The actuality ablated depth and calculated depth were compared.Results There were no significant differences between actuality ablated depth and calculated depth in Zeiss MEL80.And in VISX Star S4,the actuality ablated depth was more than calculated depth.Linear regression of changes in ablated depth on myopia and cylinder yielded the following formulaus:△ablated depth(VISX Star S4)= 2.324 *|myopia|+ 5.270 *|cylinder|-6.772.Conclusions Different excimer laser has different changes between actuality ablated depth and calculated depth.To guarantee the safety of LASIK,Ophthalmologists should know the characteristics of the excimer laser.