Numerical Study of Customized Artificial Cornea Shape by Hydrogel Biomaterials on Imaging and Wavefront Aberration

The blindness caused by cornea diseases has exacerbated many patients all over the world. The disadvantages of using donor corneas may cause challenges to recovering eye sight. Developing artificial corneas with biocompatibility may provide another option to recover blindness. The techniques of making individual artificial corneas that fit the biometric parameters for each person can be used to help these patients effectively. In this study, artificial corneas with different shapes (spherical, aspherical, and biconic shapes) are designed and they could be made by two different hydrogel polymers that form an interpenetrating polymer network for their excellent mechanical strength. Two designed cases for the artificial corneas are considered in the simulations: to optimize the artificial cornea for patients who still wear glasses and to assume that the patient does not wear glasses after transplanting with the optimized artificial cornea. The results show that the artificial corneas can efficiently decrease the imaging blur. Increasing asphericity of the current designed artificial corneas can be helpful for the imaging corrections. The differences in the optical performance of the optimized artificial corneas by using different materials are small. It is found that the optimized artificial cornea can reduce the high order aberrations for the second case.

Comparative analysis of the clinical outcomes between wavefront-guided and conventional femtosecond LASIK in myopia and myopia astigmatism

AIM: To compare the clinical outcomes of wavefront guided femtosecond LASIK (WFG LASIK) and conventional femtosecond LASIK (NWFG LASIK) in eyes with myopia and myopia astigmatism. METHODS: This was a retrospective, nonrandomized, comparative investigation enrolling 236 eyes of 122 patients (18-50y) with low & moderate and high myopia. The WFG group including 97 eyes (50 patients) undergone WFG LASIK and the NWFG group including 139 eyes (72 patients) undergone conventional LASIK. Mean efficacy index, high order aberrations (HOAs), pupil size and the quality of visual questionnaire were evaluated 6mo postoperatively. RESULTS: There is no difference between WFG group (-0.054±0.049 in logMAR) and NWFG group (-0.040±0.056) in uncorrected distance visual acuity (UDVA) postoperatively. The myopia astigmatism is higher in WFG group than that in NWFG group (P<0.05). However, the mean efficacy index (MEI) in the WFG group (1.09±0.106) is better than that in the NWFG group (1.036±0.124; P<0.001). Increased HOAs were observed in NWFG group (0.30±0.196) than that in WFG group (0.146±0.188; P<0.001). The pupil size is larger in WFG group (5.15±0.76 mm) than that in NWFG group (4.32±0.52 mm). The patients are satisfied with the clinical surgery, yet WFG group showed better visual quality using the questionnaire survey. Meanwhile, high myopia would result in worse MEI, HOAs and visual quality than low & moderate myopia. CONCLUSION: WFG and NWFG FS-LASIK are both effective and safe procedures to correct low & moderate and high myopia, but WFG FS-LASIK gives a better postoperative MEI, aberrometric control and predictable outcome. Meanwhile, WFG FS-LASIK is better than NWFG FS-LASIK in correction of myopia astigmatism. Low & moderate myopia allow better clinical outcomes than high myopia using any surgical method.

Effect of intracorneal ring segment implantation on high order aberrations comparing patients with eccentric versus central keratoconus

Purpose: To assess potential differences between central and eccentric cones in the aberrometric corneal profile and in visual and keratometric outcomes 6 months after intracorneal ring segment (ICRS) implantation for keratoconus. Methods: This study compared two groups consisting of 12 patients each, with central or eccentric keratoconus who were treated with femtosecond laser-assisted Keraring implantation. Uncorrected (UDVA) and corrected (CDVA) distance visual acuity, keratometric readings and higher order aberrations (HOAs) including high order aberrations root mean square (HOARMS), coma, spherical aberration and trefoil were measured preoperatively and 6 months after ICRS implantation. Results: Trefoil and spherical aberration were significantly reduced after ICRS implantation compared to preoperative values in eccentric keratoconus (Trefoil, p = 0.0049; Spherical aberration, p < 0.0001). In central keratoconus spherical aberration was reduced not significantly after ICRS implantation compared to preoperative values ( p = 0.087). Coma showed a significant reduction in central ( p = 0.0001) and in eccentric keratoconus ( p = 0.0001). The reduction of spherical aberration in central keratoconus was significantly positively correlated to improvement in UDVA (Pearson’s correlation coefficient, r = −0.66; p = 0.02). In eccentric keratoconus there was a significant positive correlation between reduction of trefoil and improvement in UDVA (Spearmans R, r = −0.69; p = 0.01). Conclusion: Patients both with central and eccentric keratoconus benefit from ICRS implantation. Specifically, our data provide a slightly higher gain in visual performance for eccentric cones 6 month after ICRS implantation, which is accentuated by a greater reduction in spherical aberration and trefoil. Improvements in UDVA are positively correlated with reductions in HOAs.

Wavefront aberrations induced from biomechanical effects after customized myopic laser refractive surgery in finite element model

Purpose A customized myopic refractive surgery was simulated by establishing a finite element model of the human eye,after which we studied the wavefront aberrations induced by biomechanical effects and ablation profile after wavefront-guided LASIK surgery. Methods Thirty myopia patients (i.e., 60 eyes) without other eye diseases were selected. Their ages, preoperative spherical equivalent, astigmatism, and wavefront aberration were then obtained, in addition to the mean spherical equivalent error range − 4 to -8D. Afterward, wavefront-guided customized LASIK surgery was simulated by establishing a finite element eye model, followed by the analysis of the wavefront aberrations induced by the surface displacement from corneal biomechanical effects, as well as customized ablation profile. Finally, the preoperative and induced aberrations were statistically analyzed. Results Comatic aberrations were the main wavefront abnormality induced by biomechanical effects, and the wavefront aberrations induced by the ablation profile mainly included coma and secondary-coma, as well as sphere and secondary-sphere aberrations. Overall, the total high-order aberrations (tHOAs), total coma (C31), and sphere () increased after wavefront-guided customized LASIK surgery. According to our correlation analyses, coma, sphere, and total high-order aberrations were significantly correlated with decentration. Additionally, the material parameters of ocular tissue were found to affect the postoperative wavefront aberrations. When the material parameters of the sclera remained constant but those of cornea increased, the induced wavefront aberrations were reduced. Conclusion All biomechanical effects of cornea and ablation profile had significant effects on postoperative wavefront aberrations after customized LASIK refractive surgery; however, the effects of the ablation profile were more notorious.Additionally,the characteristics of biomechanical materials have influence on the clinical correction effect.

Relationship between Axial Length and Corneo-Scleral Topography: A Preliminary Study

The main objective of the current study was to investigate further the relationship of the overall length of the eye with a great variety of anterior segment parameters, including scleral geometry. A total of 64 eyes of 32 participants with ages from 12 to 52 years were included in this prospective non-randomized single-center study. All participants underwent a complete eye examination, including an analysis of corneo-scleral shape with a Fourier-domain profilometer. A strong negative correlation was found between axial length and temporal-nasal ocular sagittal height difference for different chord lengths. For the right eye, a consistent and stable linear model was obtained to predict the axial length from the spherical equivalent, the corneal diameter, the high-order aberrations root mean square, and the minimum sagittal height for 13- and 14-mm chord. For the left eye, a model was obtained to predict the axial length from the spherical equivalent and the mean corneal curvature, including other parameters such as corneal diameter or high-order aberrations, depending on the chord length, considered for estimating the sagittal height values. More studies with larger samples are needed to confirm these preliminary outcomes.

The Effect of Corneal Collagen Cross-Linking on Higher Order Aberrations in Keratoconus

Purpose: To assess the changes in ocular high order aberrations after collagen cross linking for keratoconus. Patients and Methods: This study included 30 eyes with confirmed KCN. Baseline evaluation focused on: UDVA and BSCVA using logMAR notation, MRSE, corneal topography using Orbscan IIZ and wave-front aberrometry using Zywave II. CXL was performed per ‘Dresden protocol’ through a 30-minutes exposure to 370 nm UVA with an irradiance of 3 mW/cm 2. Patients had comprehensive ophthalmic evaluation after 6 months with special attention to: UDVA, BSCVA, MRSE, corneal topography and wave-front aberrometry changes. Results: The mean age was 25.5±5.84 (20:31) years. After 6 months, there was a significant decrease in corneal thickness from 493.2± 24.17µ to 486.7±24.26µ (P<0.05) and a significant decrease in K max from 47.4±1.17D to 46.1±1.17D (P<0.05). BSCVA improved from preoperative value (0.00:0.5 logMAR (median 0.3)) to 6 months’ value (0.1:1.00 logMAR (median 0.2) (P <0.05). Preoperative MRSE was -7.25: -0.5D (median -2.85D) and at 6 months was -6.25: -0.5D (median - 2.125D) (P<0.05). A significant correlation was found at 6 months between changes in both BSCVA and: K max (P<0.001), corneal thickness (P<0.05), vertical coma (P<0.001) and trefoil (P<0.001). Conclusions: Improvement in HOA was detected after CXL for KCN. The changes in total, vertical coma and vertical trefoil aberrations were significantly correlated with postoperative improvement in BSCVA. Thus, improvement in HOA profile after CXL is one of the explanations of improvement in visual function after CXL in KCN.

Quality of Vision Following LASIK and PRK-MMC for Treatment of Myopia

ABSTRACT Introduction Femtosecond-assisted thin flap, laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy with mitomycin-C (PRK-MMC) are the two most common refractive surgical procedures used to enhance visual capability in the U.S military. The purposes of the study were to examine effects on quality of vision following LASIK and PRK-MMC using a novel computer-based quick contrast sensitivity function (qCSF) test. Materials and Methods This prospective clinical study included 58 active duty U.S. military service members who elected LASIK (n = 29) or PRK-MMC (n = 29) refractive surgery for myopia (nearsightedness) treatment. Monocular photopic and mesopic quality of vision of the right eyes in spectacle correction preoperatively and unaided right eyes at four postoperative follow-up visits (1 week, 2 weeks, 1 month, and 3 months) were examined using the qCSF device. Two qCSF parameters, area under a log CSF (AULCSF) between 1.5 and 18 cycles per degree, and CSF cutoff acuity (CSF Acuity), were collected using a 50-trial setting at a 4-m testing distance. General linear model (GLM) Repeated-measures Analysis of Covariance was used to examine effects on quality of vision following LASIK and PRK-MMC. Post hoc testing with Bonferroni correction was used for pairwise comparisons, and preoperative cylinder refraction was used as a covariate. Two-tailed independent t-test was used to compare preoperative and postoperative parameters between LASIK and PRK-MMC. Pearson’s correlation, Bland–Altman plots, and multiple linear regression were used to examine the relationship among the qCSF and other vision tests. Results Quality of vision, AULCSF, and CSF Acuity returned to the preoperative baseline at postoperative 2 weeks under mesopic condition and at postoperative 1 month under photopic condition after PRK-MMC. In comparison, photopic and mesopic quality of vision were not significantly different from the baseline at any of the four postoperative visits following LASIK. Changes of CSF Acuity from the baseline after LASIK were significantly better under photopic than mesopic condition by 0.067 ± 0.014 logarithm of the minimum angle of resolution (logMAR); P &lt; .001). Quality of vision was not significantly different between the LASIK and PRK-MMC groups at postoperative 1 and 3 months. When predicting photopic AULCSF (overall model fit R2 = 0.47), 5% contrast acuity (beta = −0.43), visual acuity in 100% contrast (beta = −0.18), and residual refraction in spherical equivalent (beta = 0.20) were significant predictors (P ≤ .001), while high-order aberrations (beta = −0.07, P = .22) were not significant predictors. Visual acuity (beta = −0.12, P = .07) and high-order aberrations (beta = −0.04, P = .58) were not significant predictors of mesopic AULCSF. Bland–Altman plots show that photopic CSF Acuity and visual acuity had a mean difference of 0.19 ± 0.01 logMAR with limits of agreement (LOAs) at −0.01 and 0.39 logMAR. Photopic CSF Acuity and 5% contrast acuity had a mean difference of −0.06 ± 0.01 logMAR with LOAs at −0.33 and 0.21 logMAR. Conclusion Quality of vision recovers at postoperative 1 week after LASIK and at postoperative 1 month after PRK-MMC. The standard black-on-white high-contrast, chart-based visual acuity test is weak in predicting quality of vision. The qCSF detects mild-to-moderate visual changes and is suitable for quality of vision assessment following refractive eye surgery.

Comparison of posterior capsule opacification between Clareon CNA0T0 and Tecnis ZCB00 intraocular lenses

Introduction: The purpose is to compare posterior capsule opacification (PCO) and its impact on vision between Clareon CNA0T0 (Alcon) and Tecnis ZCB00 intraocular lenses (IOLs) (Johnson&Johnson) 1, 6, and 12 months after implantation. Methods: A prospective observational study was performed at the Nuestra Señora de Gracia Hospital (Zaragoza, Spain). Fifty eyes (50 patients) with Tecnis IOL (group 1) and 60 eyes (60 patients) with Clareon IOL (group 2) were enrolled. One, 6, and 12 months after age-related cataract surgery by five different surgeons, the following tests were performed: mesopic corrected distance visual acuity (CDVA), CSV1000-E test, KR-1W wavefront analyzer, OQAS II, Catquest-9SF questionnaire and mydriatic slit-lamp pictures. PCO intensity was quantified and the area of opacification was measured using ImageJ (NIH). Results: Mean age was 71.20 ± 6.79 years in group 1, and 71.73 ± 8.17 years in group 2 ( p = 0.72); mean axial length was 23.46 ± 1.14 and 23.53 ± 0.91 mm, respectively ( p = 0.72); mean IOL power was 21.69 ± 2.26 D and 21.28 ± 2.44 D, respectively ( p = 0.37). One month after surgery there were differences in intensity of PCO (0.73 ± 0.60 and 1.05 ± 0.71, respectively, p = 0.02). Six months after surgery statistical differences were found in VA with 20% CS in mydriatic conditions (0.26 ± 0.21 logMAR (20/36) and 0.18 ± 0.17 logMAR (20/30), respectively, p = 0.04). Twelve months after surgery, no differences were detected between groups. As for the evolution of PCO within the Clareon group, high order aberrations ( p < 0.05) and the Strehl ratio ( p = 0.02) decreased. Conclusion: There are no differences in slit-lamp pictures or visual function between both IOLs during the first 12 months after implantation.