OBJECTIVES: To investigate angle Kappa and diopter distribution in myopic patients and the changes of angle Kappa and corneal morphology after Sub-Bowman-Keratomileusis (SBK), and to analyze the effects of the surgery on corneal morphologic changes and the patients' near fixation characteristics. METHODS: The clinical data of 134 myopic patients (268 eyes) undergoing SBK from August 2015 to August 2016 were retrospectively analyzed. Angle Kappa, corneal curvature in the central corneal region of 3 mm, and post-corneal Diff value were measured by Orbscan IIz Corneal Topography System before operation, 1 month and 6 months after operation. According to the values of angle Kappa before SBK, the patients were divided into 2 groups: the large K group (angle Kappa≥5°, 71 eyes) and the small K group (angle Kappa<5°, 197 eyes). Correlation analysis of the factors influencing angle Kappa at 6 months after operation was performed. RESULTS: In the large K group, angle Kappa was (5.67±0.65)°, spherical equivalent was (-4.84±2.32) D, and angle Kappa was decreased after operation (both CONCLUSIONS The angle Kappa is decreased in low-moderate myopia patients with large angle Kappa, while is increased in high myopia patients with small angle Kappa after SBK. Myopia patients after SBK will look for the new balance of the binocular accommodation and vergence function for improving the comfort in the near-work situations.
Cornea/surgery* ; Humans ; Keratomileusis, Laser In Situ ; Myopia/surgery* ; Refraction, Ocular ; Retrospective Studies

OBJECTIVE: To compare the different intraocular lens (IOL) calculation formulas available on the American Society of Cataract and Refractive Surgery (ASCRS) IOL power calculator website among Asian eyes with previous corneal refractive surgery. METHODS: A retrospective cohort study of 84 eyes in 68 Asian patients who had phacoemulsification with previous LASIK or photorefractive keratectomy (PRK) was done. Using the post-phacoemulsification manifest refraction spherical equivalent (MRSE) as target refraction, IOL prediction error (PE) for each formula was calculated as the implanted minus the predicted IOL power. Refractive PE was determined by calculating that 1 diopter (D) of IOL PE produces 0.7 D of refractive error at the spectacle plane. RESULTS: Comparing the Shammas, Haigis-L, Barrett True-K No History, ASCRS Average IOL Power No History, Barrett True-K, and ASCRS Average IOL Power with Change in Manifest Refraction (ΔMR), the mean IOL PEs ranged from -0.23 to -0.62 D, with the Barrett True-K having the lowest PE. The median refractive PEs for all formulas were similar at 0.35 D, except for the Haigis-L at 0.53 D. The ASCRS average with ΔMR had a statistically higher percentage of eyes within 0.5 D of target refraction versus other formulas (p<0.05). The Haigis-L IOL PE and refractive PE were significantly higher than the Barrett True-K (p<0.001), and the ASCRS average with ΔMR (p<0.001) respectively. The ASCRS average with ΔMR produced a significantly smaller variance of IOL PE (p<0.05). CONCLUSION: Accounting for PEs and variance, the ASCRS average IOL power with ΔMR is recommended, followed by the ASCRS average IOL power No History if without historical data.
Keratomileusis, Laser In Situ

The decrease of corneal stiffness is the key factor leading to keratoconus, and the corneal collagen fiber stiffness and fiber dispersion are closely related to the corneal biomechanical properties. In this paper, a finite element model of human cornea based on corneal microstructure, namely collagen fiber, was established before and after laser assisted in situ keratomileusis (LASIK). By simulating the Corvis ST process and comparing with the actual clinical results, the hyperelastic constitutive parameters and corneal collagen fiber stiffness modulus of the corneal material were determined before and after refractive surgery. After LASIK, the corneal collagen fiber stiffness modulus increased significantly, and was highly correlated with central corneal thickness (CCT). The predictive relationship between the corneal collagen fiber stiffness modulus and the corresponding CCT before and after surgery was: = exp(9.14 - 0.009CCT ), = exp(8.82 - 0.008CCT ). According to the results of this study, the central corneal thickness of the patient can be used to estimate the preoperative and postoperative collagen fiber stiffness modulus, and then a personalized corneal model that is more consistent with the actual situation of the patient can be established, providing a theoretical reference for more accurately predicting the safe surgical cutting amount of the cornea.
Biomechanical Phenomena ; Cornea ; Corneal Topography ; Finite Element Analysis ; Humans ; Keratomileusis, Laser In Situ ; Myopia

Presbyopia is an age-related condition that progressively decreases the ability to focus on near objects. Minimally invasive surgical techniques have been developed to improve near vision, including laser in situ keratomileuses (LASIK) and corneal inlay. Most have similar approaches using monovision or increasing the depth of focus. Monovision laser refractive surgery is a combination of conventional LASIK, LASIK which creates a multifocal cornea (central near or peripheral near) and aspheric micro-monovision LASIK with a special ablation profile, which develops spherical aberration. Conductive keratoplasty is a method that uses radiofrequency energy to shrink the mid-peripheral corneal stromal tissue. However, it is not used because of regression. A corneal inlay is a small device that is implanted in the corneal flap or pocket made by a femtosecond laser. It is inserted into the non-dominant eye. There are various inlays such as the Flexivue Microlens (refractive), Raindrop (corneal shape-changing), and KAMRA (small-aperture) inlays. However, the safety and effectiveness of these inlays have not been proven over a long follow-up period, so care is required when performing inlay implantation. All presbyopia treatments can improve near vision but also have limitations and side effects such as reduced far vision, contrast sensitivity, or increased glare. Therefore, it is essential to select patients carefully. Mechanisms associated with presbyopia are not fully understood, and presbyopia remains challenging for ophthalmologists.
Contrast Sensitivity ; Cornea ; Corneal Transplantation ; Follow-Up Studies ; Glare ; Humans ; Inlays ; Keratomileusis, Laser In Situ ; Methods ; Presbyopia ; Refractive Surgical Procedures ; Vision, Monocular

PURPOSE: To evaluate the efficacy of 3% diquafosol tetrasodium (DQ) after laser-assisted in-situ keratomileusis (LASIK). METHODS: This prospective randomized study included 150 eyes in 75 patients who were scheduled for LASIK. The patients in the 3% diquafosol tetrasodium (DQ) group (37 patients, 74 eyes) were instructed to apply one drop of DQ, six times daily post-op, while the patients in the 0.3% sodium hyaluronate (HA) group (38 patients, 76 eyes) were instructed to apply one drop of HA, six times daily post-op. A Schirmer test, tear film break-up time (BUT), corneal and conjunctival fluorescein staining score (FLSS), and ocular surface disease index (OSDI) were evaluated pre-op and at 1, 4, and 12 weeks post-op while the tear osmolarity was evaluated pre-op and at 4 and 12 weeks post-op. RESULTS: There was no significant difference between the two groups regarding Schirmer test results or tear osmolarity and conjunctival FLSS. The BUT was significantly higher in the DQ group at 1 week and 12 weeks post-op. The corneal FLSS was significantly lower in the DQ group at 1 week, 4 weeks and 12 weeks post-op. The OSDI was significantly lower in the DQ group at 1 week post-op. CONCLUSIONS: Use of 3% diquafosol tetrasodium after surgery improved ocular dryness and increased the tear film stability.
Fluorescein ; Humans ; Hyaluronic Acid ; Keratomileusis, Laser In Situ ; Osmolar Concentration ; Prospective Studies ; Tears

PURPOSE: We compared the results of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) for the correction of hyperopia. METHODS: Patients who underwent PRK or LASIK, under +6.00 diopters (D) hyperopia and under −2.00 D astigmatism were included. In total, 21 patients (38 eyes) underwent PRK surgery and 25 patients (41 eyes) underwent LASIK surgery. We compared the visual acuity, refractive error, safety, and efficacy between the two groups. RESULTS: The manifest refractive spherical equivalent (MRSE) of the PRK and LASIK groups at 1 and 3 months after surgery was significantly different between the two groups (p < 0.05). However, the MRSE was not significantly different at postoperative 6 and 12 months between the two groups. The uncorrected visual acuity (UCVA) of the PRK and LASIK groups at 1 month after surgery was significantly different between the two groups (p < 0.05). However, the UCVA was not significantly different at postoperative 3, 6, and 12 months between the two groups. The best-corrected visual acuity was not significantly different at postoperative 1, 3, 6, and 12 months between the two groups. The safety index was not significantly different between the two groups at postoperative 1, 3, 6, and 12 months. The efficacy index of the PRK group was lower than that of the LASIK group at 1 month after surgery. However, the efficacy index was not significantly different at postoperative 3, 6, and 12 months between the two groups. There was no statistically significant difference between the predictability of the two groups at postoperative 1 year. CONCLUSIONS: After PRK treatment, temporary myopic deviation was observed after 1 month, but there was no significant difference between the two treatments after 3 months of follow-up. In the correction of hyperopia, there was no significant difference between PRK and LASIK in efficacy or safety.
Astigmatism ; Follow-Up Studies ; Humans ; Hyperopia ; Keratomileusis, Laser In Situ ; Photorefractive Keratectomy ; Refractive Errors ; Visual Acuity

PURPOSE: To evaluate laser in situ keratomileusis (LASIK) flap thickness predictability and morphology by femtosecond (FS) laser and microkeratome (MK) using anterior segment optical coherence tomography. METHODS: Fifty-two candidates for the LASIK procedure were stratified into two groups: FS laser-assisted (Allegretto FS-200) and MK flap creation (Moria 2). Flap thickness was determined at five points. The side-cut angle was measured in three directions at the margin interface. LASIK flap assessment was performed one month postoperatively by Spectralis anterior segment optical coherence tomography. RESULTS: Fifty-two patients (93 eyes) were recruited; 49 eyes were stratified to the FS group and 44 eyes to the MK group. The FS group had relatively even flap configurations, and the MK group had meniscus-shaped flaps. Mean differences between planned and actual flap thickness were 12.93 ± 8.89 and 19.91 ± 5.77 µm in the FS and MK groups, respectively. In thin flaps (100 to 110 µm), there was a significant disparity between the two groups (7.80 ± 4.71 and 19.44 ± 4.46 µm in the FS and MK groups, respectively). However, in thicker flaps (130 µm), comparable flap thickness disparity was achieved (18.54 ± 9.52 and 20.83 ± 5.99 µm in the FS and MK groups, respectively). Mean side-cut angle was 74.29 ± 5.79 degrees and 32.34 ± 4.94 degrees in the FS and MK groups, respectively. CONCLUSIONS: Comparable flap thickness predictability was achieved in thicker flaps (130 µm), while the FS laser technique yielded a more predictable result in thinner flaps (100 to 110 µm). Different flap morphology was observed in meniscus flaps in MK-LASIK and flap morphology in FS-LASIK.
Humans ; Keratomileusis, Laser In Situ ; Tomography, Optical Coherence

PURPOSE: To determine deep optic nerve head structure changes after transient intraocular pressure elevation during laser in situ keratomileusis (LASIK) for myopia. METHODS: Enhanced depth imaging-optical coherence tomography was performed in each myopic eye that underwent LASIK surgery. Enhanced depth imaging-optical coherence tomography images were created at postoperative 1 day, 1 week, 2 weeks, and 1 month. Lamina cribrosa (LC) thickness, LC depth and prelaminar thickness at the superior, middle and inferior portions of the optic nerve head were measured by two investigators. RESULTS: Forty eyes in 40 patients were included in the present study. During follow-up, there were no significant differences in prelaminar thickness or LC depth. The LC demonstrated increased thickness at postoperative 1 day at all three locations (superior, middle, and inferior) (p < 0.001, p < 0.001, p < 0.001, respectively). However, no significant changes were observed at postoperative 1 week, 2 weeks, and 1 month. CONCLUSIONS: The LC thickness could increase at 1 day after LASIK surgery. However, the thickness will gradually return to baseline morphology. Temporary intraocular pressure increase during LASIK does not appear to induce irreversible LC thickness changes.
Follow-Up Studies ; Humans ; Intraocular Pressure ; Keratomileusis, Laser In Situ* ; Myopia ; Optic Disk ; Research Personnel

PURPOSE: To report a case of irregular astigmatism caused by a free flap during laser-assisted in situ keratomileusis (LASIK) surgery that was treated with a flap rotation based on postoperative topography. CASE SUMMARY: A 21-year-old female underwent LASIK, which was complicated by a free cap on her right eye. Because the gentian violet markings were no longer present, the exact orientation of the cap was unknown. At 3 months after surgery, the astigmatism of the right eye was −3.00 diopters (D) with an uncorrected visual acuity (UCVA) of 0.4, and the astigmatism of the left eye was −0.75 D with an UCVA of 1.0. The corneal topography was analyzed in order to return to the existing position. Free cap repositioning was performed and irregular astigmatism was corrected to improve the UCVA to 1.0. CONCLUSIONS: If the preoperative markings cannot be identified on a free flap during LASIK, secondary postoperative corneal topographic analysis can be performed to restore the corneal free flap to its original position to minimize astigmatism with good visual outcomes.
Astigmatism ; Corneal Topography ; Female ; Free Tissue Flaps ; Gentian Violet ; Humans ; Keratomileusis, Laser In Situ ; Visual Acuity ; Young Adult

PURPOSE: To evaluate changes in clinical practice in the field of refractive surgery in Korea over the past 10 years. METHODS: A survey consisting of 59 multiple-choice questions regarding the preferred types of refractive surgery, excimer laser machine, and presbyopia surgery was mailed to 742 members of the Korean Society of Cataract and Refractive Surgery in January 2016, and 50 members responded to the survey. These data were compared with the 2005 or 2007 survey results.
Cataract ; Keratectomy, Subepithelial, Laser-Assisted ; Keratomileusis, Laser In Situ ; Korea ; Lasers, Excimer ; Myopia ; Phakic Intraocular Lenses ; Postal Service ; Presbyopia ; Refractive Surgical Procedures ; Surveys and Questionnaires