Manli Liu

Differences in the Corneal Biomechanical Changes After SMILE and LASIK

PURPOSE To compare the corneal biomechanical properties before and after small incision lenticule extraction (SMILE) and femtosecond laser-assisted LASIK in different levels of myopia with the Ocular Response Analyzer (Reichert Ophthalmic Instruments, Depew, NY). METHODS A total of 187 and 79 eyes that received SMILE or LASIK, respectively, between January and June 2013 at Zhongshan Ophthalmic Center were enrolled in this study. Patients were grouped according to surgery type (SMILE or LASIK) and -6.00 diopters (D) or less (> -6.00 D) or myopia greater than -6.00 D (>-6.00 D). Corneal hysteresis, corneal resistance factor, and 37 waveform parameters were recorded and compared preoperatively and at 1 week and 1 and 3 months postoperatively. RESULTS There was a significant decrease of corneal hysteresis, corneal resistance factor, p1area, and p2area, and an increase of path1 and path2 in both SMILE and LASIK. In myopia -6.00 D or less, the differences between SMILE and LASIK were not significant (P > .05), but in myopia greater than -6.00 D, the corneal hysteresis, corneal resistance factor, p1area, and p2area decreased significantly more in LASIK than in SMILE (P < .05). CONCLUSIONS When comparing SMILE with LASIK, myopia was greater than -6.00 D, and the corneal hysteresis, corneal resistance factor, p1area, and p2area decrease was less after SMILE.

Orthokeratology to Control Myopia Progression: A Meta-Analysis

Objective To evaluate the clinical treatment effects of orthokeratology to slow the progression of myopia. Methods Several well-designed controlled studies have investigated the effects of orthokeratology in school-aged children. We conducted this meta-analysis to better evaluate the existing evidence. Relevant studies were identified in the Medline and Embase database without language limitations. The main outcomes included axial length and vitreous chamber depth reported as the mean ± standard deviation. The results were pooled and assessed with a fixed-effects model analysis. Subgroup analyses were performed according to geographical location and study design. Results Of the seven eligible studies, all reported axial length changes after 2 years, while two studies reported vitreous chamber depth changes. The pooled estimates indicated that change in axial length in the ortho-k group was 0.27 mm (95% confidence interval [CI]: 0.22, 0.32) less than the control group. Myopic progression was reduced by approximately 45%. The combined results revealed that the difference in vitreous chamber depth between the two groups was 0.22 mm (95% confidence interval [CI]: 0.14, 0.31). None of the studies reported severe adverse events. Conclusion The overall findings suggest that ortho-k can slow myopia progression in school-aged children.

Clinical Outcomes After SMILE and Femtosecond Laser-Assisted LASIK for Myopia and Myopic Astigmatism: A Prospective Randomized Comparative Study.

Purpose: To compare the clinical outcomes of small-incision lenticule extraction (SMILE) and femtosecond laser-assisted LASIK (FS-LASIK) for the correction of myopia and myopic astigmatism. Methods: In this prospective, randomized, comparative study, SMILE surgery was performed in 113 eyes with a mean spherical equivalent (MSE) of −5.22 ± 1.70 diopters (D) and FS-LASIK was performed in 84 eyes with an MSE of −5.18 ± 1.93 D. Contrast sensitivity and uncorrected and corrected distance visual acuities were measured preoperatively and 1 day, 1 week, 1, 3, and 6 months postoperatively. Higher-order aberrations were evaluated preoperatively and 6 months postoperatively. Results: At postoperative day 1, the uncorrected distance visual acuity in the FS-LASIK group was better (P < 0.05), whereas no statistically significant difference was found at 6 months postoperatively (P = 0.9). There was no significant difference in terms of logMAR corrected distance visual acuity and MSE during the 6 months of follow-up between the SMILE and FS-LASIK groups (all P > 0.05). The contrast sensitivity in the SMILE group was lower at 1 day and 1 week postoperatively (all P < 0.05). The spherical aberration at 6 mm diameter at 6 months postoperatively was lower (P < 0.05) in the SMILE group (0.12 ± 0.22 &mgr;m) than in the FS-LASIK group (0.28 ± 0.26 &mgr;m). Conclusions: Both FS-LASIK and SMILE procedures achieved good visual outcomes in the correction of myopia and myopic astigmatism. SMILE had a lower induction rate of spherical aberration at 6 months postoperatively in the analysis of 6 mm diameter than that of FS-LASIK.

Decentration of optical zone center and its impact on visual outcomes following SMILE.

Purpose: To evaluate decentration from pupil center and corneal vertex normal following femtosecond laser small incision lenticule extraction (SMILE) for the treatment of myopia and myopic astigmatism. Methods: This study evaluated 101 eyes of 101 patients with a spherical equivalent (SE) of −5.30 ± 1.72 diopters (D). Decentration was measured in the pupil-centered group (PC group) by video capture images and in the vertex normal–centered group (VNC group) using the WaveLight Oculyzer II (Alcon). The PC and VNC groups were further divided into 4 subgroups (1 PC, 2 PC and 1 VNC, 2 VNC) based on the displacement of the lenticule center. Uncorrected and corrected distance visual acuities, manifest refraction, and wavefront errors were measured preoperatively, and at 1 day, 1 week, 1 month, and 3 and 6 months postoperatively. Results: Regarding efficacy and safety, at 6 months postoperatively, 65, 71, 83, and 53% of eyes had unchanged corrected distance visual acuity in 1 PC, 1 VNC, 2 PC and 2 VNC groups, respectively. Also, 97, 98, 100, and 97% of treated eyes had a postoperative uncorrected distance visual acuity 20/20 or better in the subgroups, respectively. In the groups mentioned above, 96, 100, 100, and 95% of eyes, respectively, were within ±0.5 D of the targeted SE. In terms of total higher-order aberrations, the 1 PC group was significantly higher than the 1 VNC group (P = 0.04), whereas the 2 VNC group was significantly higher than the 2 PC group (P = 0.02). Conclusions: Our results demonstrate that better refractive outcomes will be achieved when the lenticule center is closer to the corneal vertex normal.

Optical Defocus Rapidly Changes Choroidal Thickness in Schoolchildren

The current study aimed to examine the short-term choroidal response to optical defocus in schoolchildren. Myopic schoolchildren aged 8–16 were randomly allocated to control group (CG), myopic defocus group (MDG) and hyperopic defocus group (HDG) (n = 17 per group). Children in MDG and HDG received additional +3D and -3D lenses, respectively, to their full corrections on the right eyes. Full correction was given to their left eyes, and on both eyes in the CG. Axial length (AXL) and subfoveal choroidal thickness (SFChT) were then measured by spectral domain optical coherence tomography. Children wore their group-specific correction for 2 hours after which any existing optical defocus was removed, and subjects wore full corrections for another 2 hours. Both the AXL and SFChT were recorded hourly for 4 hours. The mean refraction of all subjects was -3.41 ± 0.37D (± SEM). SFChT thinned when exposed to hyperopic defocus for 2 hours but less thinning was observed in response to myopic defocus compared to the control group (p < 0.05, two-way ANOVA). Removal of optical defocus significantly decreased SFChT in the MDG and significantly increased SFChT in the HDG after 1 and 2 hours (mean percentage change at 2-hour; control vs. hyperopic defocus vs. myopic defocus; -0.33 ± 0.59% vs. 3.04 ± 0.60% vs. -1.34 ± 0.74%, p < 0.01). Our results showed short-term exposure to myopic defocus induced relative choroidal thickening while hyperopic defocus led to choroidal thinning in children. This rapid and reversible choroidal response may be an important clinical parameter in gauging retinal response to optical defocus in human myopia.

Comparison of 120- and 140-μm SMILE Cap Thickness Results in Eyes With Thick Corneas.

Purpose: To evaluate clinical outcomes after small incision lenticule extraction (SMILE) with different cap thicknesses in thick corneas. Methods: Forty patients with central corneal thickness of more than 560 &mgr;m were recruited in this prospective, randomized, masked, paired-eye study. Patients were randomized to receive SMILE with a 120-&mgr;m cap thickness in 1 eye and 140-&mgr;m cap thickness in the other. Uncorrected and corrected distance visual acuity (CDVA), contrast sensitivity (CS), higher-order aberrations (HOAs), and morphologic modifications of corneal architecture were measured during the 3-month follow-up period. Results: Postoperative refractive outcomes, visual outcomes, CS, and the changes in HOAs were similar between both groups. The persistence of brightly reflective particles in the corneal interface layer was 1388.6 ± 219.5/mm2 in eyes with 120-&mgr;m cap thickness and 54.7 ± 8.6/mm2 in eyes with 140-&mgr;m cap thickness (P < 0.001). The hyperreflectivity line at the interface layer almost disappeared in all eyes with 140-&mgr;m cap thickness, and it still persisted in 43% of the fellow eyes at 3 months postoperatively. The anterior surfaces of lenticules in the 140-&mgr;m cap thickness group exhibited more smoothness than in the 120-&mgr;m cap thickness group. Conclusions: There was a lower level corneal wound-healing response after SMILE with a 140-&mgr;m cap thickness than with a 120-&mgr;m cap thickness, although the thickness of cap creation did not affect visual outcomes by 3 months postoperatively.

Femtosecond Laser-assisted Endokeratophakia Using Allogeneic Corneal Lenticule in a Rabbit Model.

PURPOSE To investigate the feasibility of allogeneic corneal lenticule implantation using the femtosecond laser as a method for cornea remodeling. METHODS Small incision lenticule extraction was performed on the right eyes of 15 New Zealand white rabbits. Corneal intrastromal pockets were created with a femtosecond laser on the left eyes. Allogeneic corneal lenticule implantation was performed on the left eye immediately after the lenticule was extracted from the right eye. All animals had preoperative and postoperative slit-lamp photography, ultrasonic pachymetry, corneal endothelial cell count, anterior segment optical coherence tomography, in vivo confocal microscopy, and retinoscopy refraction during the observation period of 8 weeks. The rabbits were killed 8 weeks after surgery. Corneal wound healing response was analyzed by transmission electron microscopy, hematoxylin-eosin staining, TUNEL assay, and immunofluorescent staining. RESULTS Mild corneal edema and decreased clarity were noted the first few days after implantation, improving to normal 8 weeks after surgery. The corneal thickness and retinoscopy refraction were stable during the observation period. Viable keratocytes could be detected within the lenticule lamellae by ultrastructural analysis 8 weeks after surgery. The anterior and posterior border of the lenticule showed acellular layers with highly irregular collagen arrangement on transmission electron microscope images. Proliferating Ki-67 positive cells were present only in the epithelium layer. CONCLUSION Femtosecond laser-assisted endokeratophakia using allogeneic corneal lenticule may be feasible for reshaping cornea, providing a new possibility in refractive surgery and keratoconus treatment.

Impact of Suction Loss During Small Incision Lenticule Extraction (SMILE)

PURPOSE To evaluate the clinical results of suction loss in eyes during small incision lenticule extraction (SMILE). METHODS This prospective paired-eye case study enrolled 8,490 eyes of 4,296 patients, of which 35 eyes experienced suction loss during the SMILE procedure while being treated for myopia or myopic astigmatism. The eyes with suction loss were re-treated with SMILE, femtosecond laser-assisted LASIK (FS-LASIK), or pseudo SMILE, and the fellow eyes were treated with SMILE. Patients were examined before surgery and at 1 day, 1 week, and 1 and 3 months postoperatively. Corrected distance visual acuity (CDVA) and uncorrected distance visual acuity (UDVA), manifest refraction, higher order aberrations (HOAs), and morphologic modifications of corneal architecture were evaluated. At 3 months, patients were asked if they preferred the vision in either eye. RESULTS High-contrast CDVA was worse in the eyes that suffered loss of suction than in the fellow eyes at 1 week postoperatively (two-tailed paired t tests, P = .04), but not at 1 and 3 months. There was no statistical significance between the two treatments in the safety and efficacy indices or the 3rd and 4th order aberrations at 3 months postoperatively (two-tailed paired t tests, all P > .05). No apparent abnormalities were observed in the corneas by frequency-domain optical coherence tomography. CONCLUSIONS Re-treatment with femtosecond laser for incomplete SMILE was safe, predictable, and effective, and the patients did not perceive a difference in vision. [J Refract Surg. 2016;32(10):686-692.].

Aspheric Micro-monovision LASIK in Correction of Presbyopia and Myopic Astigmatism: Early Clinical Outcomes in a Chinese Population

PURPOSE To analyze early clinical outcomes of aspheric micro-monovision LASIK for correction of presbyopia and myopia with or without astigmatism. METHODS Prospective, non-comparative case series of 80 eyes of 40 patients with a mean age of 43.4 ± 4.9 years (range: 38 to 63 years) treated bilaterally using an aspheric micro-monovision protocol. The target refraction was plano for the distance eye and between -0.75 and -2.25 diopters (D) for the near eye. Visual acuity, ocular aberrations, contrast sensitivity, corneal topography, amplitude of accommodation, binocular sensorial function, and satisfaction score questionnaires were evaluated at 3 months after surgery. RESULTS Three months after surgery, the mean spherical equivalent (SE) refraction in the distance eye was -0.08 ± 0.27 D, whereas the attempted and achieved SE in the near eye were -1.41 ± 0.28 and -1.32 ± 0.35 D, respectively. Ninety-three percent of eyes were within ±0.50 D of target correction of SE. The uncorrected distance visual acuity (UDVA) after surgery was -0.10 ± 0.06 logMAR (20/15.5), 0.22 ± 0.12 logMAR (20/34), and -0.11 ± 0.06 logMAR (20/15), for distance eyes, near eyes, and binocularly, respectively. Ninety-five percent of patients achieved simultaneously uncorrected distance visual acuity 0.0 logMAR (20/20) or better and uncorrected near visual acuity J2 (20/25) or better. Stability was achieved from 1 week of follow-up. The overall satisfaction score for surgery was 92 ± 6. CONCLUSIONS The aspheric micro-monovision protocol provided a well-tolerated and effective means for treating myopic astigmatism and alleviating presbyopic symptoms simultaneously. [J Refract Surg. 2016;32(10):680-685.].

Correction: Orthokeratology to Control Myopia Progression: A Meta-Analysis

There is an error in affiliation 1 for authors Yuan Sun, Fan Xu, Ting Zhang, Manli Liu, Danyang Wang, Yile Chen, and Quan Liu. Affiliation 1 should be: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, Guangdong Province, China.