Yugui Zhou

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.

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.].

Genetic polymorphisms of the sortase A gene and early childhood caries in two-year-old children

OBJECTIVE To explore and compare the genetic polymorphisms of the sortase A (srtA) gene found in Streptococcus mutans (S. mutans) infecting two-year-old children suffering early childhood caries to those found in caries-free children through molecular identification methods. METHODS Clinical S. mutans strains were isolated from the dental plaques of two-year-old children. Fifteen strains of S. mutans from the caries-active group and 15 strains of S. mutans from the caries-free group were collected. Genomic DNA was extracted from the S. mutans isolates. DNA fragments, including the srtA gene, were amplified by PCR. The PCR products were purified, sequenced and analyzed. A chi-square test and BioEdit software were used to analyze the sequencing results. RESULTS All 30 clinically isolated S. mutans strains had a 741 base pair (bp) srtA gene. There were no nucleotide sequence insertions or deletions observed in the srtA genes. Twenty mutations were identified in the srtA genes that taken from the 30 clinical strains. There were 10 silent point mutations at the 78, 99, 150, 165, 186, 222, 249, 261, 312, and 636bp positions. The other 10 mutations were point mutations resulting in a missense mutation at the 23, 34, 36, 47, 112, 114, 168, 176, 470, and 671bp positions. None of the positions were enzyme-activity sites of srt A. The missense mutation rates of the two groups did not exhibit statistically significant differences. CONCLUSION There were no genetic polymorphisms of the sortase A gene associated with early childhood caries in two-year-old children.

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.].

Effects of missense mutations in sortase A gene on enzyme activity in Streptococcus mutans

BackgroundStreptococcus mutans (S. mutans) is the major aetiological agent of dental caries, and the transpeptidase Sortase A (SrtA) plays a major role in cariogenicity. The T168G and G470A missense mutations in the srtA gene may be linked to caries susceptibility, as demonstrated in our previous studies. This study aimed to investigate the effects of these missense mutations of the srtA gene on SrtA enzyme activity in S. mutans.MethodsThe point mutated recombinant S.mutans T168G and G470A sortases were expressed in expression plasmid pET32a. S. mutans UA159 sortase coding gene srtA was used as the template for point mutation. Enzymatic activity was assessed by quantifying increases in the fluorescence intensity generated when a substrate Dabcyl-QALPNTGEE-Edans was cleaved by SrtA. The kinetic constants were calculated based on the curve fit for the Michaelis-Menten equation.ResultsSrtA△N40(UA159) and the mutant enzymes, SrtA△N40(D56E) and SrtA△N40(R157H), were expressed and purified. A kinetic analysis showed that the affinity of SrtA△N40(D56E) and SrtA△N40(R157H) remained approximately equal to the affinity of SrtA△N40(UA159), as determined by the Michaelis constant (Km). However, the catalytic rate constant (kcat) and catalytic efficiency (kcat/Km) of SrtA△N40(D56E) were reduced compared with those of SrtA△N40(R157H) and SrtA△N40(UA159), whereas the kcat and kcat/Km values of SrtA△N40(R157H) were slightly lower than those of SrtA△N40(UA159).ConclusionsThe findings of this study indicate that the T168G missense mutation of the srtA gene results in a significant reduction in enzymatic activity compared with S. mutans UA159, suggesting that the T168G missense mutation of the srtA gene may be related to low cariogenicity.

Evaluation of Human Corneal Lenticule Quality After SMILE With Different Cap Thicknesses Using Scanning Electron Microscopy

Purpose: To evaluate the surface characteristics of lenticules created by small-incision lenticule extraction (SMILE) with different cap thicknesses. Methods: This prospective study included 20 consecutive patients who underwent bilateral SMILE. Surface regularity of the extracted corneal lenticule was analyzed using scanning electron microscopy (SEM) combined with 2 methods: qualitative and quantitative regularity. Qualitative regularity of SEM images was graded by masked observers using an established scoring system. Quantitative regularity of SEM images was assessed by counting the total number and areas of tissue bridges using Image-Pro Plus software. Four different cap thickness of 120, 130, 140, and 150 &mgr;m were compared. Refractive outcomes of patients were measured at baseline and 1 month after surgery. Results: As 10 specimens were not analyzable, only 30 eyes were included. Postoperatively, all eyes had postoperative uncorrected distance visual acuity of 20/20 or better; 43% had an unchanged corrected distance visual acuity; 43% gained 1 line; 10% lost 1 line. Ultrastructurally, surface irregularity was primarily caused by tissue bridges. The average surface regularity score obtained was 10.87 ± 2.40 for 120 &mgr;m, 10.78 ± 2.60 for 130 &mgr;m, 8.76 ± 2.16 for 140 &mgr;m, and 8.70 ± 2.66 for 150 &mgr;m (P < 0.001). The total number and areas of tissue bridges of 120 to 130 &mgr;m were significantly less than 140 to 150 &mgr;m (P < 0.05). Surface regularity decreased as cap thickness increased (P < 0.05). Conclusions: There is smoother appearance of the lenticular surface as seen through SEM when a thin cap is created compared with a thick cap qualitatively and quantitatively.

Reversible Femtosecond Laser-Assisted Endokeratophakia Using Cryopreserved Allogeneic Corneal Lenticule.

PURPOSE To evaluate outcomes, reversibility, and wound healing response after the femtosecond laser-assisted endokeratophakia procedure in a rabbit model. METHODS Allogeneic rabbit corneal lenticules were cryopreserved in liquid nitrogen for 3 months. Twenty rabbits underwent the monocular endokeratophakia procedure and were divided into four groups according to the follow-up periods. The first three groups were killed at 3 days, 2 weeks, and 6 months after endokeratophakia, respectively. The rabbits in the fourth group received re-extraction of implanted lenticules at 6 months after endokeratophakia and were killed at 1 month after re-extraction. The rabbits were monitored by slit-lamp microscopy, ultrasonic pachymetry, in vivo confocal microscopy, optical coherence tomography (OCT), Corvis ST tonometry (Oculus Optikgeräte, Wetzlar, Germany), and Ocular Response Analyzer (Reichert Ophthalmic Instruments, Depew, NY). The tissue responses were analyzed by immunohistochemistry and transmission electron microscopy. RESULTS After endokeratophakia, corneal clarity improved continually with time. The changes in the refraction and corneal thickness were stable after implantation and could be reversed after re-extracting the lenticules. The interfaces were clearly visible on confocal microscopy and transmission electron microscopy images over the entire follow-up period. There were significant numbers of TUNEL-positive keratocytes in lenticules after endokeratophakia. CD11b-positive cells and deposition of fibronectin and tenascin were observed at earlier follow-up times. No alpha-smooth muscle actin-positive fibroblasts could be detected. In addition, the corneal biomechanics parameters were not significantly increased after endokeratophakia. CONCLUSIONS The endokeratophakia procedure using allogeneic cryopreserved lenticules was clinically stable and could be reversed. The wound healing response was mild, limited, and produced no scars. [J Refract Surg. 2016;32(8):569-576.].