Comparison of changes in functional optical zone and corneal morphology between SMILE and FS-LASIK in myopes / 中华实验眼科杂志

Objective:To compare the changes in functional optical zone (FOZ) and corneal morphology in myopes between femtosecond small incision laser lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK).Methods:A cohort study was performed.A total of 94 patients (94 eyes) who underwent FS-LASIK or SMILE at Eye Hospital, Wenzhou Medical University from March to December 2021 were enrolled.The selected patients were divided into a SMILE group (46 cases, 46 eyes) and an FS-LASIK group (48 cases, 48 eyes) according to the surgical procedure, and the follow-up period was 6 months.The primary outcome measures were postoperative changes in corneal FOZ and Q-value, and the secondary outcome measures were changes in central corneal thickness (CCT) and mean corneal curvature (Km). Corneal Q-value, horizontal and vertical FOZ diameters, CCT, and Km were recorded before surgery and at 1 day, 1 week, 1 month, and 6 months after surgery using the Pentacam anterior segment analysis system, and the differences in each parameter and the trends of changes between the two groups were compared.This study adhered to the Declaration of Helsinki and was approved by the Ethics Committee of Eye Hospital, Wenzhou Medical University (No.2021-034-k-27). Written informed consent was obtained from each subject.Results:There were statistically significant overall differences in the postoperative horizontal and vertical FOZ diameters between the two groups (horizontal diameter: Fgroup=7.06, P<0.001; Ftime=64.18, P=0.001; vertical diameter: Fgroup=11.08, P<0.001; Ftime=77.14, P<0.001). The horizontal and vertical FOZ diameters were significantly larger in SMILE group than in FS-LASIK group at various postoperative time points, and the differences were statistically significant (all at P<0.001). In the two groups, the postoperative 1-week, 1-month and 6-month horizontal FOZ diameters and the postoperative 1-week and 1-month vertical FOZ diameters were smaller than the postoperative 1-day ones, and the differences were statistically significant (all at P<0.05). There were significant overall differences in Q-values at different postoperative time points between the two groups ( Fgrouup=53.11, P=0.019; Ftime=29.18, P<0.001). The postoperative 1-day, 1-week, and 1-month Q-values of FS-LASIK group were significantly higher than those of SMILE group (all at P<0.05). The postoperative 1-week Q-value was significantly larger than the postoperative 1-day value in SMILE group ( P<0.001). The postoperative Q-values gradually decreased with time in FS-LASIK group, with significant pairwise differences at all adjacent time points (all at P<0.001). There were significant differences in CCT at various postoperative time points between the two groups ( Ftime=21.43, P<0.01). In FS-LASIK group, the CCT was decreased at 1 week than 1 day after surgery and was increased at 6 months than 1 week after surgery, and the differences were statistically significant (all at P<0.05). In SMILE group, the postoperative 1-week, 1-month and 6-month CCT was increased in comparison with the postoperative 1-day value, and the differences were statistically significant (all at P<0.05). There was no significant overall difference in the Km between the two groups ( Fgroup=27.29, P=0.41). There were significant pairwise differences in the Km at different postoperative time points between the two groups (all at P<0.001). The postoperative 6-month Km was smaller than the postoperative 1-day value in SMILE group, and the postoperative 6-month Km was greater than the postoperative 1-day value in FS-LASIK group (both at P<0.05). Conclusions:The FOZ shows a trend of gradual reduction within a month after SMILE and FS-LASIK.The FOZ is larger after SMILE than after FS-LASIK.The morphologic stability of corneal FOZ is better after SMILE than after FS-LASIK.

Changes of corneal anterior surface morphology and higher-order aberrations after Smart / 中华实验眼科杂志

Objective:To compare the changes of corneal asphericity and higher-order aberrations after smart pulse technology-assisted transepithelial photorefractive keratectomy (Smart) for low and moderate myopia and to investigate the changes in the shape of the front corneal surface in patients with different diopters.Methods:A non-randomized controlled study design was used.Ninety-eight eyes of 54 patients with moderate or low myopia who underwent Smart surgery in Tianjin Medical University Eye Hospital from November 2018 to March 2019 were included.The 41 eyes of 23 patients with low myopia were set as the low-myopia group, and 57 eyes of 31 patients with moderate myopia were assigned as the moderate-myopia group.The Pentacam anterior segment analysis system was used to measure Q value, index of surface variance (ISV), corneal higher-order aberration (HOA), corneal vertical coma (Z 3-1), corneal horizontal coma (Z 31) and spherical aberration (Z 40) before surgery, 1 month and 3 months after surgery.The anterior surface morphology was compared between the low-myopia and moderate-myopia group.Pearson correlation analysis was used to analyze the correlations between measurement parameters.The study protocol was approved by an Ethics Committee of Tianjin Medical University Eye Hospital (No.2019KY-17). Written informed consent was obtained from each patient before surgery. Results:Corneal Q value, ISV, HOA and Z 40 were 0.445±0.191, 26.973±5.611, 0.671±0.142 and 0.384±0.188, respectively, in the low-myopia group at one month after surgery, which were significantly increased than corresponding preoperative values of -0.273±0.817, 13.784±2.376, 0.433±0.687 and 0.231±0.062 (all at P<0.05). Corneal Q value, ISV, HOA and Z 40 were 0.693±0.203, 34.038±5.773, 0.874±0.216 and 0.520±0.129, respectively, in the moderate-myopia group at one month after surgery, which were significantly increased than corresponding preoperative values of -0.309±0.104, 14.838±3.992, 0.409±0.081 and 0.228±0.089 (all at P<0.05). Corneal Q values, ISV, HOA and Z 40 in the moderate-myopia group were higher than those in the low-myopia group at different time points after surgery, showing significant differences between the two groups (all at P<0.05). There was no significant difference in postoperative 1-month and 3-month corneal Z 3-1 and Z 31 between the two groups (both at P>0.05). The results of correlation analysis showed that there were no significant differences in ΔQ value and ΔISV between the two groups, both of which were negatively correlated with spherical equivalent (ΔQ value: low-myopia group: r=-0.364, P=0.044; moderate-myopia group: r=-0.589, P<0.01; ΔISV: low-myopia group: r=-0.298, P=0.039; moderate-myopia group: r=-0.409, P=0.022). ΔQ value and ΔZ 40 were positively correlated in the moderate-myopia group ( r=0.348, P=0.009); there was no significant correlation between ΔQ value and ΔZ 40 in the low-myopia group ( r=0.180, P=0.266). Conclusions:The corneal high-order aberrations and ISV after Smart are increased in comparison with preoperative values in the low-myopia and moderate-myopia eyes, and the corneal Q values change from negative to positive.The effect of Smart on corneal asphericity is less in the low-myopia eyes.

Predictibilidad en la inducción de aberración esférica basada en la asfericidad corneal post LASIK en miopes / Predictability of spherical aberration based on corneal asphericity after myopic laser customized corneal ablation

Purpose: To determine the predictability of postoperative ocular spherical aberration (Z 4,0) based on postoperative corneal asphericity (Q value) in patients with myopic astigmatism. Design: Case series, retrospective. Methods: Wavefront-guided laser in situ keratomileusis (LASIK) was performed in 40 eyes of 23 patients using the Schwind Esiris Excimer Laser. Patients were evaluated preoperatively and 3 months postoperatively. Spherical aberration was measured with a COAS Shack-Hartmann wavefront sensor, and determined for a 6 mm analysis diameter zone. Corneal asphericity was measured with the Orbscan II topographer. Correlation and linear regression analysis was performed. A P value less than 0.05 was considered statistically significant. Results: Treated eyes had a mean manifest spherical error of ­2.98 + 1.36 Diopters (D), and a mean manifest astigmatic error of 0.52 + 0.46 D. The mean Q was -0.30 + 0.13 preoperatively and +0.03 + 0.22 postoperatively. The mean spherical aberration was 0.054 + 0.109 microns preoperatively and 0.262 + 0.135 microns postoperatively. We found a positive statistically signifi cant correlation between postoperative Q value and postoperative spherical aberration (r=0.367) (P=0.02). The postoperative Q value showed a low correlation with postoperative spherical aberration (R2=0.14). Conclusions: There was an increase in corneal asphericity and spherical aberration after surgery. Postoperative corneal asphericity is mildly associated with postoperative spherical aberration. Predictability of postoperative spherical aberration in terms of correlation with postoperative Q value was poor, suggesting that corneal asphericity is not a major predictor of spherical aberration induction.

The Relationship Between Asphericity and Visual Acuity After Wearing Reverse-Geometry Lens

PURPOSE:To report the change of corneal asphericity and the relationship between asphericity and visual acuity after wearing the reverse-geometry lens. METHODS: The authors reviewed out-patient records of 37 consecutive patients wearing reverse-geometry lenses. The patients were followed up from July 2004 to December 2007. The unaided visual acuity (VA), spherical equivalent (SE) and asphericity before and after wearing the lens were compared. The relationship of SE and final VA, initial astigmatism and final VA, and asphericity and final VA was also analyzed. In addition, the relationship between the increment of VA and asphericity was determined. RESULTS: VA and SE improved and the asphericity decreased after wearing the lens (p<0.05). There was high correlation between the spherical equivalent and final visual acuity (p<0.001), and no correlation between asphericity and final visual acuity (p=0.358) was observed. However, the lower the initial asphericity, the greater the increment of visual acuity observed (p=0.048). CONCLUSIONS: Initial corneal asphericity can be a predictor of increment of VA after wearing reverse-geometry lenses.

Sustainability of Orthokeratology as Demonstrated by Corneal Topography

PURPOSE: To determine the sustaining effects of orthokeratology. METHODS: This study enrolled 58 eyes with moderate myopia. LK-DM lenses (Lucid Korea Dream Lens(TM)) were fitted daily for at least eight hours on an overnight regimen. The effects of orthokeratology and it's sustainability throughout the day were recorded twice; immediately after removal in the morning and eight hours later. Sustainability was measured by comparing the changes from morning to afternoon for best uncorrected visual acuity, apical corneal power, keratometric values, spherical equivalent and induced astigmatism. RESULTS: UCVA demonstrated improved values at all follow up periods. Fluctuations during the day stabilized after 4 weeks of lens wear. K values averaged a mean of 42.4 mm at baseline, and reduced to 40.9 mm by week 12. Unaided logMAR visual acuity changed from 0.94+/-0.14 at baseline to -0.11+/-0.17 by week 12. The sustainability of orthokeratology, defined as the difference between morning and afternoon values of unaided logMAR visual acuity, increased from -0.82 on day 1 to -0.11 on week 12. CONCLUSIONS: UCVA and spherical refractive error did not change to a significant degree after 4 weeks. Although statistically insignificant minute fluctuations during the day were observed up to week 12, these fluctuations decreased to a statistically significant level after week 4.

Sustainability of Orthokeratology as Demonstrated by Corneal Topography

PURPOSE: To determine the sustaining effects of orthokeratology. METHODS: This study enrolled 58 eyes with moderate myopia. LK-DM lenses (Lucid Korea Dream Lens(TM)) were fitted daily for at least eight hours on an overnight regimen. The effects of orthokeratology and it's sustainability throughout the day were recorded twice; immediately after removal in the morning and eight hours later. Sustainability was measured by comparing the changes from morning to afternoon for best uncorrected visual acuity, apical corneal power, keratometric values, spherical equivalent and induced astigmatism. RESULTS: UCVA demonstrated improved values at all follow up periods. Fluctuations during the day stabilized after 4 weeks of lens wear. K values averaged a mean of 42.4 mm at baseline, and reduced to 40.9 mm by week 12. Unaided logMAR visual acuity changed from 0.94+/-0.14 at baseline to -0.11+/-0.17 by week 12. The sustainability of orthokeratology, defined as the difference between morning and afternoon values of unaided logMAR visual acuity, increased from -0.82 on day 1 to -0.11 on week 12. CONCLUSIONS: UCVA and spherical refractive error did not change to a significant degree after 4 weeks. Although statistically insignificant minute fluctuations during the day were observed up to week 12, these fluctuations decreased to a statistically significant level after week 4.