corneal aberrations in myopic patients.METHODS: This retrospective, observational case series included 57 eyes (29 patients) that received treatment for myopia using SMILE. Visual acuity measurement, manifest refraction, slit-lamp examination, autokeratometry, corneal topography, and evaluation of corneal wavefront aberration were performed preoperatively and at 1 and 3 months after surgery. We analyzed the safety, efficacy, vector parameters, and corneal aberrations at 3 months after surgery.RESULTS: Preoperatively, mean manifest refraction spherical equivalent refraction was −4.94 ± 1.94 D (range, −8.25 to 0 diopters [D]), and the cylinder was −1.14 ± 0.82 D (range, −3 to 0 D). Mean manifest refraction spherical equivalent improved to −0.10 ± 0.23 D at 3 months postoperatively, when uncorrected distance visual acuity was 20 / 20 or better in 55 (96%) eyes. The linear regression model of target induced astigmatism vector versus surgically induced astigmatism vector exhibited slopes and coefficients (R²) of 0.9618 and 0.9748, respectively (y = 0.9618x + 0.0006, R² = 0.9748). While total corneal root mean square higher order aberrations, coma and trefoil showed statistically significant increase, spherical aberration did not show statistically significant change after SMILE.CONCLUSIONS: SMILE has proven to be effective and safe for correcting myopia and astigmatism. We showed that SMILE did not induce spherical aberrations. A small increase in postoperative corneal higher order aberration may be associated with increase in coma and trefoil.]]>
Astigmatism ; Coma ; Corneal Topography ; Corneal Wavefront Aberration ; Humans ; Linear Models ; Lotus ; Myopia ; Refractive Surgical Procedures ; Retrospective Studies ; Visual Acuity

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

In view of the problem that there is no standard diagnosis for early stage keratoconus disease,at the same time to assist the special examiner and ophthalmologist to make the early diagnosis effectively,the advantages and disadvantages of each testing instrument were analyzed.In order to construct an assistant system for early diagnosis of keratoconus,a deep learning technique was applied in corneal OCT examination.The system used improved VGG-16 to realize the recognition accuracy of about 68% keratoconus keratopathy,and the clinical results showed that the system can help doctors to give diagnosis confidence to a certain extent.At the same time,the physician's re-marking of OCT can help train the system for more accurate judgment.
Corneal Topography ; Deep Learning ; Early Diagnosis ; Humans ; Keratoconus ; diagnostic imaging ; Tomography, Optical Coherence

In the evaluation of tear film stability based on corneal topography, a pretreatment algorithm for tear film video was proposed for eye movement, eyelash reflection and background interference. First, Sobel operator was used to detect the blur image. Next, the target image with highlighted ring pattern was obtained by the morphological open operation performed on the grayscale image. Then the ring pattern frequency of the target image was extracted through the Hough circle detection and fast Fourier transform, and a band-pass filter was applied to the target image according to the ring pattern frequency. Finally, binarization and morphological closed operation were used for the localization of the ring pattern. Ten tear film videos were randomly selected from the database and processed frame by frame through the above algorithm. The experimental results showed that the proposed algorithm was effective in removing the invalid images in the video sequence and positioning the ring pattern, which laid a foundation for the subsequent evaluation of tear film stability.
Algorithms ; Cornea ; Corneal Topography ; Tears

PURPOSE: To compare corneal astigmatism, keratometry and corneal higher order aberrations between the light emitting diode corneal topography analyzer and Scheimpflug Imager. METHODS: This prospective study involved 45 patients (45 eyes) who visited Seoul St. Mary's hospital before cataract surgery from June 7, 2017, to August 2, 2017. For each eye, keratometry, astigmatism and its axis of cornea, higher-order aberrations were evaluated with a Scheimpflug Imager (Pentacam HR®, Oculus, Wetzlar, Germany) and a color-LED corneal topographer (Cassini®, i-Optics, Den Haag, The Netherlands). RESULTS: Astigmatism magnitude measured using Cassini® and Pentacam® showed no statistically differences but anterior and total astigmatic axes were significantly different, as measured by the two devices (p < 0.05). Anterior and total mean keratometry were statistically significantly different, as measured by the two devices (p < 0.05). J0 and J45 vectors of anterior and total cornea were statistically different (p < 0.05). In addition, Cassini® and Pentacam® showed discrepancies between total corneal astigmatism, total J0 and J45 vectors. Corneal anterior spherical aberration, vertical and horizontal coma, and oblique and horizontal trefoil aberrations were not statistically different between the two devices. CONCLUSIONS: Astigmatic axes obtained from the two devices based on different principles showed statistically significant differences. Astigmatism magnitude was not statistically different but showed a discrepancy between the two devices.
Astigmatism ; Cataract ; Coma ; Cornea ; Corneal Topography ; Corneal Wavefront Aberration ; Humans ; Lotus ; Prospective Studies ; Seoul

PURPOSE: To compare the efficacy and complications of scleral fixation of posterior chamber intraocular lens (IOL) and retropupillary fixation of iris claw IOL for dislocated IOL or aphakia without sufficient capsular support. METHODS: This retrospective study was comprised of 17 eyes of 16 patients undergoing scleral fixation and 14 eyes of 13 patients undergoing retropupillary fixation from August 2013 to June 2018. Uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), intraocular pressure (IOP), slit lamp examination, corneal topography, refractive indices, corneal curvatures, corneal endothelial cell density, and complications of both groups were examined preoperatively and 1 day, 1 week, 1 month, 2 months, and 6 months postoperatively. RESULTS: Six months after the operation, UCVA and BCVA improved in both groups; however, there were no significant differences between the two groups (UCVA, p = 0.162; BCVA, p = 0.418). IOP was temporarily higher in the scleral fixation group at one day postoperatively (p = 0.023). The mean absolute prediction error was smaller in the retropupillary iris fixation group at 6 months postoperatively (p = 0.034). Postoperative total astigmatism, corneal astigmatism, and corneal endothelial cell density were not significantly different between the two groups. CONCLUSIONS: The retropupillary iris fixation group did not show significant improvement in visual acuity compared with the scleral fixation group. However, the retropupillary iris fixation group provided better mean absolute prediction error and a low risk of postoperative increase in IOP compared with the scleral fixation group. Retropupillary fixation of iris claw IOL is a promising option for scleral fixation of posterior chamber IOL for dislocated IOL or aphakia without sufficient capsular support.
Animals ; Aphakia ; Astigmatism ; Corneal Topography ; Endothelial Cells ; Hoof and Claw ; Humans ; Intraocular Pressure ; Iris ; Lenses, Intraocular ; Refractometry ; Retrospective Studies ; Slit Lamp ; Visual Acuity

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 compare the differences of parameters of 9.3 mm and 8.8 mm rigid gas permeable lenses (RGP lenses) that were prescribed by trial lens fitting. METHODS: Ninety-three eyes of 49 patients were prescribed RGP contact lenses (YK spherical lens, Lucid Korea, Bonghwa, Korea) by a single ophthalmologist at the same hospital. We analyzed the differences of parameters of 9.3 mm and 8.8 mm rigid gas permeable lenses (RGP lenses) that were prescribed by trial lens fitting. Steep keratometric value (Ks), flat keratometric value (Kf), and corneal astigmatism (Kast) were measured by keratometer. Simulated steep keratometric value (Sim Ks), simulated flat keratometric value (Sim Kf), simulated corneal astigmatism (Sim Kast), white to white corneal diameter (WTW), and eccentricity were measured by corneal topography. We also analyzed the differences of back optic zone radius (BOZR) and lens power between the two groups. RESULTS: In this study, 40 eyes wearing 8.8 mm lenses and 53 eyes wearing 9.3 mm lenses were included. Keratometric value and eccentricity were significantly higher in the 8.8 mm lens group, while WTW and BOZR were significantly lower. Corneal astigmatism (Kast, Sim Kast) and lens power were not significantly different between the groups. CONCLUSIONS: RGP lenses with a smaller diameter were likely to be prescribed to patients with higher keratometric value, higher eccentricity, and shorter WTW, and the average BOZR of the prescribed RGP lenses with a smaller diameter was likely to be steeper.
Astigmatism ; Contact Lenses ; Corneal Topography ; Humans ; Korea ; Radius

PURPOSE: To introduce a new convenient and accurate method to measure the angle kappa using ultrasound biomicroscopy (UBM) and corneal topography. METHODS: Data from 42 eyes (13 males and 29 females) were analyzed in this study. The angle kappa was measured using Orbscan II and calculated with UBM and corneal topography. The angle kappa of the dominant eye was compared with measurements by Orbscan II. RESULTS: The mean patient age was 36.4 ± 13.8 years. The average angle kappa measured by Orbscan II was 3.98°± 1.12°, while the average angle kappa calculated with UBM and corneal topography was 3.19°± 1.15°. The difference in angle kappa measured by the two methods was statistically significant (p < 0.001). The two methods showed good reliability (intraclass correlation coefficient, 0.671; p < 0.001). Bland-Altman plots were used to demonstrate the agreement between the two methods. CONCLUSIONS: We designed a new method using UBM and corneal topography to calculate the angle kappa. This method is convenient to use and allows for measurement of the angle kappa without an expensive device.
Corneal Topography* ; Humans ; Male ; Methods ; Microscopy, Acoustic* ; Ultrasonography*

PURPOSE: To investigate the changes in corneal higher-order aberration (HOA) during amblyopia treatment and the correlation between HOA and astigmatism in hyperopic amblyopia children. METHODS: In this retrospective study, a total of 72 eyes from 72 patients ranging in age from 38 to 161 months were included. Patients were divided into two groups based on the degree of astigmatism. Corneal HOA was measured using a KR-1W aberrometer at the initial visit and at 3-, 6-, and 12-month follow-ups. Correlation analysis was performed to assess the association between HOA and astigmatism. RESULTS: A total of 72 patients were enrolled in this study, 37 of which were classified as belonging to the higher astigmatism group, while 35 were assigned to the lower astigmatism group. There was a statistically significant difference in success rate between the higher and lower astigmatism groups. In both groups, all corneal HOAs were significantly reduced during amblyopia treatment. When comparing the two groups, a significant difference in coma HOA at the 12-month follow-up was detected (p = 0.043). In the Pearson correlation test, coma HOA at the 12-month follow-up demonstrated a statistically significant correlation with astigmatism and a stronger correlation with astigmatism in the higher astigmatism group than in the lower astigmatism group (coefficient values, 0.383 and 0.284 as well as p = 0.021 and p = 0.038, respectively). CONCLUSIONS: HOA, particularly coma HOA, correlated with astigmatism and could exert effects in cases involving hyperopic amblyopia.
Aberrometry ; Adolescent ; Amblyopia/*physiopathology ; Astigmatism/*physiopathology ; Child ; Child, Preschool ; Corneal Topography ; Corneal Wavefront Aberration/diagnosis/*physiopathology ; Eyeglasses ; Follow-Up Studies ; Humans ; Hyperopia/*physiopathology/therapy ; Retrospective Studies ; Visual Acuity/physiology