Outcomes of manual arcuate keratotomy with compression sutures for high regular postkeratoplasty astigmatism.

PURPOSE: To report functional and refractive outcomes of manual arcuate keratotomy (AK) with compression sutures for high regular postkeratoplasty astigmatism.Setting: not specified (review). DESIGN: Retrospective analysis. METHODS: This study included 90 eyes with high regular postkeratoplasty astigmatism (>4 diopters, D) who received AK with compression sutures between 2010 and 2022. Functional and refractive outcomes were assessed by evaluating topographic indices and by performing vector astigmatism and Fourier analysis. RESULTS: At last follow-up (mean=13.7±16.6 months), BCDVA improved from 0.59±0.28 logMAR to 0.34±0.25 logMAR. Cylinder magnitude decreased from 9.91±2.88 D to 5.42±3.35 D. Surface Asymmetry Index, Irregular Astigmatism Index, Corneal Eccentricity Index were equal to preoperative values, whereas Surface Regularity Index approached normal values at last follow-up. Fourier analysis indicated a decrease in the regular astigmatic component, whereas non-regular components (asymmetry and higher-order irregularity) remained stable. In vector astigmatism analysis, Target Induced Astigmatism magnitude was 9.92±2.86 D and Surgically Induced Astigmatism magnitude was 10.16±4.86 D (Correction Index of 0.91±0.48) with a Difference Vector of 5.42±3.35 D at last follow-up. Correction of astigmatism magnitude was adequate in 40% of the eyes, under-corrected in 30% and over-corrected in 30%. Angle of Error was <|22.5°| in 88% resulting in a low risk of off-axis treatment. CONCLUSION: AK with compression sutures is a simple, relatively effective and safe surgical procedure for astigmatism reduction after keratoplasty. In case of regular astigmatism, the procedure does not increase corneal irregularities. The remaining refractive error might be further corrected by spectacles, contact lenses or toric IOL implantation (in-the-bag / add-on), thus reducing the need for repeat keratoplasty.

Prediction of Visual Acuity in Pseudophakic Cataract Population Based on Residual Refraction.

PURPOSE: The purpose of the study was to design a simple, handy prediction for the effect of spherical and cylindrical refractive error on the visual acuity degradation at different distances and validate this model on a clinical dataset. METHODS: This study examined 70 eyes from 35 patients' post-cataract surgery with aberration-free intraocular lenses. Biometric and corneal data were analysed, and subjective refraction and visual acuity were evaluated by two experienced optometrists. The study computed the spherical equivalent (SEQ), and defocus equivalent via vector addition (DEQ vec), as the sum of absolute values (DEQ abs). Predictive models were developed using univariate regression, with confidence intervals (BCa 95%) calculated through non-parametric bootstrapping (10,000 cycles). RESULTS: Various calculated equivalents included -0.44 D for spherical equivalent (SEQ), 0.70 D for defocus equivalent based on vector calculation (DEQ vec), and 0.89 D for defocus equivalent based on absolute values (DEQ abs). Uncorrected and corrected visual acuity averaged 0.07 logMAR and -0.04 logMAR, respectively. The absolute defocus equivalent (DEQ abs) exhibited the smallest confidence interval (BCa 95%) at 0.07. CONCLUSION: The defocus equivalent based on the addition of absolute values (DEQ abs) emerged as the most practical predictor for the described applications. Notably, it offers the advantage of easy calculability through a simple equation: VA loss = DEQ abs ⋅ 0.23. In 95% of cases, this predicted loss would have an accuracy of ±0.03 lines.

Refractive Astigmatism Outcomes of Femtosecond Laser-Assisted Arcuate Keratotomies Combined with Femtosecond Laser-Assisted Cataract Surgery: Two-Year Results.

PURPOSE: To evaluate the effectiveness and stability of refractive astigmatism reduction after penetrating femtosecond laser-assisted arcuate keratotomy performed at the time of femtosecond laser-assisted cataract surgery. METHODS: Non-randomized retrospective data analysis of all patients that underwent femtosecond laser-assisted cataract surgery with femtosecond laser-assisted arcuate keratotomy over a 4-year period with a non-toric monofocal intraocular lens (2017-2021) at a tertiary care academic center. Postoperative visual acuity, manifest refraction, and predicted residual refractive error were also recorded at 1 month, 3-6 months, 12-18 months, and 2 years postoperatively. Preoperative keratometric astigmatism was compared to postoperative refractive astigmatism using vector calculations and the ASCRS double-angle plot tool. RESULTS: This study comprised 266 eyes (179 patients) that met inclusion criteria. The mean preoperative keratometric astigmatism magnitude was 0.99 ± 0.53 D. At 1 month, 3-6 months, 12-18 months, and 2 years postoperatively, the mean refractive cylinder was 0.49 ± 0.45 D, 0.49 ± 0.45 D, 0.55 ± 0.54 D, and 0.52 ± 0.46 D, respectively. Horizontal against-the-rule astigmatism showed a higher tendency toward undercorrection than vertical with-the-rule astigmatism, which had a slightly higher tendency toward overcorrection. With-the-rule astigmatism had smaller difference vectors between target-induced astigmatism and surgically induced astigmatism. CONCLUSIONS: Femtosecond laser-assisted arcuate keratotomy performed at the time of femtosecond laser-assisted cataract surgery was an effective option for correcting low-to-moderate corneal astigmatism for up to 2 years.

Vector analysis of corneal astigmatism in cataractous eyes based on IOLMaster 700 biometry.

PURPOSE: The purpose of this study was to investigate the effect of the corneal back surface by comparing the keratometric astigmatism (K, derived from the corneal front surface) of a modern optical biometer against astigmatism of Total Keratometry (TK, derived from both corneal surfaces) in a large population with cataractous eyes. The results were then used to define linear prediction models to map K to TK. METHODS: From a large dataset containing bilateral biometric measurements (IOLMaster 700) in 9736 patients prior to cataract surgery, the total corneal astigmatism was decomposed into vectors for K, corneal back surface (BS), and TK. A multivariate prediction model (MV), simplified model with separation of vector components (SM) and a constant model (CM) were defined to map K to TK vector components. RESULTS: The K centroid (X/Y) showed some astigmatism with-the-rule (0.1981/-0.0211 dioptre (dpt)) whereas the TK centroid was located around zero (-0.0071/-0.0381 dpt against-the-rule) and the BS centroid showed systematic astigmatism against-the-rule (-0.2367/-0.0145 dpt). The respective TK-K centroid was located at -0.2052/-0.0302 dpt. The MV model showed the same performance (i.e. mean absolute residuum) as the SM did (0.1098 and 0.1099 dpt respectively) while the CM performed only slightly worse (0.1121 dpt mean absolute residuum). CONCLUSION: In cases where tomographic data are unavailable statistical models could be used to consider the overall contribution of the back surface to the total corneal astigmatism. Since the performance of the CM is sufficiently close to that of MV and SM we recommend using the CM which can be directly considered e.g. as surgically induced astigmatism.

Performance of a simplified strategy for formula constant optimisation in intraocular lens power calculation.

PURPOSE: To investigate the performance of a simple prediction scheme for the formula constants optimised for a mean refractive prediction error. METHODS: Analysis based on a dataset of 888 eyes before and after cataract surgery with IOL implantation (Hoya Vivinex). IOLMaster 700 biometric data, power of the implanted lens and postoperative spherical equivalent refraction were used to calculate the optimised constants (.)opt for SRKT, HofferQ, Holladay and Haigis formula with an iterative nonlinear optimisation. For detuning start values by ±1.5 from (.)opt, the predicted formula constants (.)pred were calculated and compared with (.)opt. Formula performance metrics mean (MPE), median (MEDPE), mean absolute (MAPE), median absolute (MEDAPE), root mean squared (RMSPE) and standard deviation (SDPE) of the formula prediction error were analysed for (.)opt and (.)pred. RESULTS: (.)pred - (.)opt showed a 2nd order parabolic behaviour with maximal deviations up to 0.09 at the tails of detuning and a minimal deviation up to -0.01 for all formulae. The performance curves of different metrics of PE as functions of detuning variations show that the formula constants for zeroing MPE and MEDPE yield almost identical formula constants, optimisation for MAPE, MEDAPE and RMSPE yielded formula constants very close to (.)opt, and optimisation for SDPE could result in formula constants up to 0.5 off (.)opt which is unacceptable for clinical use. CONCLUSION: This simple prediction scheme for formula constant optimisation for zero mean refraction error performs excellently in our monocentric dataset, even for larger deviations of the start value from (.)opt. Further studies with multicentric data and larger sample sizes are required to investigate the performance in a clinical setting further.

Long-term astigmatism after intraocular pressure sensor implantation and nonpenetrating glaucoma surgery: EYEMATE-SC trial.

PURPOSE: To investigate long-term astigmatism after combined nonpenetrating glaucoma surgery (NPGS) and implantation of the first miniaturized suprachoroidal intraocular pressure (IOP) sensor EYEMATE-SC. SETTING: The study was conducted in 5 medical centers in 2 different countries. DESIGN: Retrospective multicenter clinical study. METHODS: Astigmatism of patients instrumented with the EYEMATE-SC IOP sensor was assessed over a follow-up period of 3 years. Refraction and corrected distance visual acuity (CDVA) were obtained preoperatively, after 6 months, 1, 2, and 3 years. A canaloplasty-operated patient cohort served as control. Astigmatism was evaluated using 3-dimensional power vector analysis involving the spherical equivalent M, and the Jackson crossed cylinder projections J 0 and J 45 . Exclusion criteria included neovascular and angle-closure glaucoma, myopia, axial length outside 22 to 26 mm, other ocular diseases, prior glaucoma surgery, other ocular surgery within 6 months (cataract surgery within 3 months) before NPGS, serious generalized conditions, and other active medical head/neck implants. RESULTS: Multivariate analysis indicated no changes in astigmatism along the observation period in both the EYEMATE-SC (n = 24) and the canaloplasty (n = 24) group ( P > .05 or nonsignificant after Bonferroni correction). Astigmatism was unchanged between the EYEMATE-SC and the canaloplasty group at all timepoints ( P > .05). CDVA did not change along the observation period of 3 years in each of both groups ( P > .05). CONCLUSIONS: Despite its suprachoroidal localization, this study indicated that the miniaturized EYEMATE-SC IOP sensor did not negatively affect long-term astigmatism after combined implantation with NPGS.

Leaving trusted paths: Estimating corneal keratometric index in cataract surgery eyes with zero-power implants.

PURPOSE: This study aimed to estimate the corneal keratometric index in the eyes of cataract surgery patients who received zero-power intraocular lenses (IOLs). METHODOLOGY: This retrospective study analyzed postoperative equivalent spherical refraction and axial length, mean anterior curvature radius and aqueous humor refractive index to calculate the theoretical corneal keratometric index value (nk). Data was collected from 2 centers located in France and Germany. RESULTS: Thirty-six eyes were analyzed. The results revealed a mean corneal keratometric index of 1.329 ± 0.005 for traditional axial length (AL) and 1.331 ± 0.005 for Cooke modified axial length (CMAL). Results ranged from minimum values of 1.318/1.320 to maximum values of 1.340/1.340. CONCLUSION: The corneal keratometric index is a crucial parameter for ophthalmic procedures and calculations, particularly for IOL power calculation. Notably, the estimated corneal keratometric index value of 1.329/1.331 in this study is lower than the commonly used 1.3375 index. These findings align with recent research demonstrating that the theoretical corneal keratometric index should be approximately 1.329 using traditional AL and 1.331 using CMAL, based on the ratio between the mean anterior and posterior corneal curvature radii (1.22).

Repeatability of biometric measures from the IOLMaster 700 in a cataractous population.

PURPOSE: The purpose of this study was to investigate the repeatability of biometric measures and also to assess the interactions between the uncertainties in these measures for use in an error propagation model, using data from a large patient cohort. METHODS: In this cross-sectional non-randomised study we evaluated a dataset containing 3379 IOLMaster 700 biometric measurements taken prior to cataract surgery. Only complete scans with at least 3 successful measurements for each eye performed on the same day were considered. The mean (Mean) and standard deviations (SD) for each sequence of measurements were derived and analysed. Correlations between the uncertainties were assessed using Spearman rank correlations. RESULTS: In the dataset with 677 eyes matching the inclusion criteria, the within subject standard deviation and repeatability for all parameters match previously published data. The SD of the axial length (AL) increased with the Mean AL, but there was no noticeable dependency of the SD of any of the other parameters on their corresponding Mean value. The SDs of the parameters are not independent of one another, and in particular we observe correlations between those for AL, anterior chamber depth, aqueous depth, lens thickness and corneal thickness. CONCLUSIONS: The SD change over Mean for AL measurement and the correlations between the uncertainties of several biometric parameters mean that a simple Gaussian error propagation model cannot be used to derive the effect of biometric uncertainties on the predicted intraocular lens power and refraction after cataract surgery.

Comparison of Pre- and Post-DMEK Keratometry and Total Keratometry Values for IOL Power Calculations in Eyes Undergoing Triple DMEK.

PURPOSE: To evaluate prediction accuracy of pre- and post-DMEK keratometry (K) and total keratometry (TK) values for IOL power calculations in Fuchs endothelial corneal dystrophy (FECD) eyes undergoing DMEK with cataract surgery (triple DMEK). METHODS: Retrospective cross-sectional multicenter study of 55 FECD eyes (44 patients) that underwent triple DMEK between 2019 and 2022 between two centers in USA and Europe. Swept-source optical coherence tomography biometry (IOLMaster 700) was used for pre- and post-DMEK measurements. K and TK values were used for power calculations with ten formulae (Barrett Universal II (BUII), Castrop, Cooke K6, EVO 2.0, Haigis, Hoffer Q, Hoffer QST, Holladay I, Kane, and SRK/T). Mean error, mean absolute error (MAE), standard deviation, and percentage of eyes within ±0.50/±1.00 diopters (D) were calculated. Studied formulae were additionally adjusted using a method published previously (IOLup1D Method), which increases the IOL power by 1D. While both eyes from the same patient were considered for descriptive statistics, we restricted to one eye per individual (44 eyes for statistical comparisons. RESULTS: MAEs for all formulae were lower for post-DMEK K and TK than pre-DMEK K and TK by an average of 0.24 and 0.47 D, respectively. The lowest MAE was 0.49 D for Kane using post-DMEK TK, and the highest MAE was 1.05 D for BUII using pre-DMEK TK. Most IOLup1D formulae had lower MAEs than pre-DMEK K and TK formulae. CONCLUSIONS: The IOLup1D Method should be used instead of pre-DMEK K and TK values for triple DMEK in FECD eyes. Using post-DMEK TK values for cataract surgery after DMEK provides better refractive accuracy than any of the three studied methods used for triple DMEK procedures.

Impact of uncertainties in biometric parameters on intraocular lens power formula predicted refraction using a Monte-Carlo simulation.

PURPOSE: The purpose of this study was to investigate the uncertainty in the formula predicted refractive outcome REFU after cataract surgery resulting from measurement uncertainties in modern optical biometers using literature data for within-subject standard deviation Sw. METHODS: This Monte-Carlo simulation study used a large dataset containing 16 667 preoperative IOLMaster 700 biometric measurements. Based on literature Sw values, REFU was derived for both the Haigis and Castrop formulae using error propagation strategies. Using the Hoya Vivinex lens (IOL) as an example, REFU was calculated both with (WLT) and without (WoLT) consideration of IOL power labelling tolerances. RESULTS: WoLT the median REFU was 0.10/0.12 dpt for the Haigis/Castrop formula, and WLT it was 0.13/0.15 dpt. WoLT REFU increased systematically for short eyes (or high power IOLs), and WLT this effect was even more pronounced because of increased labelling tolerances. WoLT the uncertainty in the measurement of the corneal front surface radius showed the largest contribution to REFU, especially in long eyes (and low power IOLs). WLT the IOL power uncertainty dominated in short eyes (or high power IOLs) and the uncertainty of the corneal front surface in long eyes (or low power IOLs). CONCLUSIONS: Compared with published data on the formula prediction error of refractive outcome after cataract surgery, the uncertainty of biometric measures seems to contribute with ⅓ to ½ to the entire standard deviation. REFU systematically increases with IOL power and decreases with axial length.

Short-Term Effect of Rose Bengal Photodynamic Therapy (RB-PDT) on Collagen I, Collagen V, NF-κB, LOX, TGF-ß and IL-6 Expression of Human Corneal Fibroblasts, In Vitro.

PURPOSE: To investigate collagen I, collagen V, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), lysyl oxidase (LOX), transforming growth factor ß1 (TGF-ß1) and interleukin-6 (IL-6) expression in healthy and keratoconus human corneal fibroblasts (HCFs and KC-HCFs), 24 h after Rose Bengal photodynamic therapy (RB-PDT). METHODS: HCFs were isolated from healthy human corneal donors (n = 5) and KC-HCFs from elective penetrating keratoplasties (n = 5). Both cell cultures underwent RB-PDT (0.001% RB concentration, 0.17 J/cm2 fluence) and 24 h later collagen I, collagen V, NF-κB, LOX, TGF-ß1 and IL-6 mRNA and protein expression have been determined using qPCR and Western blot, IL-6 concentration in the cell culture supernatant by ELISA. RESULTS: TGF-ß1 mRNA expression was significantly lower (p = 0.02) and IL-6 mRNA expression was significantly higher in RB-PDT treated HCFs (p = 0.01), than in HCF controls. COL1A1, COL5A1 and TGF-ß1 mRNA expression was significantly lower (p = 0.04; p = 0.02 and p = 0.003) and IL-6 mRNA expression was significantly higher (p = 0.02) in treated KC-HCFs, than in KC-HCF controls. TGF-ß1 protein expression in treated HCFs was significantly higher than in HCF controls (p = 0.04). IL-6 protein concentration in the HCF and KC-HCF culture supernatant after RB-PDT was significantly higher than in controls (p = 0.02; p = 0.01). No other analyzed mRNA and protein expression differed significantly between the RB-PDT treated and untreated groups. CONCLUSIONS: Our study demonstrates that RB-PDT reduces collagen I, collagen V and TGF-ß1 mRNA expression, while increasing IL-6 mRNA and protein expression in KC-HCFs. In HCFs, RB-PDT increases TGF-ß1 and IL-6 protein level after 24 h.

Limitations of constant optimization with disclosed intraocular lens power formulae.

PURPOSE: To investigate the effect of formula constants on predicted refraction and limitations of constant optimization for classical and modern intraocular lens (IOL) power calculation formulae. SETTING: Tertiary care center. DESIGN: Retrospective single-center consecutive case series. METHODS: This analysis is based on a dataset of 888 eyes before and after cataract surgery with IOL implantation (Hoya Vivinex). Spherical equivalent refraction predSEQ was predicted using IOLMaster 700 data, IOL power, and formula constants from IOLCon ( https://iolcon.org ). The formula prediction error (PE) was derived as predSEQ minus achieved spherical equivalent refraction for the SRKT, Hoffer Q, Holladay, Haigis, and Castrop formulae. The gradient of predSEQ (gradSEQ) as a measure for the effect of the constants on refraction was calculated and used for constant optimization. RESULTS: Using initial formula constants, the mean PE was -0.1782 ± 0.4450, -0.1814 ± 0.4159, -0.1702 ± 0.4207, -0.1211 ± 0.3740, and -0.1912 ± 0.3449 diopters (D) for the SRKT, Hoffer Q, Holladay, Haigis, and Castrop formulas, respectively. gradSEQ for all formula constants (except gradSEQ for the Castrop R) decay with axial length because of interaction with the effective lens position (ELP). Constant optimization for a zero mean PE (SD: 0.4410, 0.4307, 0.4272, 0.3742, 0.3436 D) results in a change in the PE trend over axial length in all formulae where the constant acts directly on the ELP. CONCLUSIONS: With IOL power calculation formulae where the constant(s) act directly on the ELP, a change in constant(s) always changes the trend of the PE according to gradSEQ. Formulae where at least 1 constant does not act on the ELP have more flexibility to zero the mean or median PE without coupling with a PE trend error over axial length.

VIVEX: A Formula for Calculating Individual Vitreous Volume: A New Approach Towards Tailored Patient Dosing Regime in Intravitreal Therapy.

INTRODUCTION: Personalized medicine and patient-tailored drug dosing have been substantiated through thousands of clinical studies, demonstrating their safety and efficacy. The principle: "as much as necessary, as little as possible" is widely spread. Quantities and doses are therefore adjusted individually. This is not the case for intravitreal injections in the context of retinal diseases. Intravitreal injections are not adjusted in relation to the vitreous volume. The vitreous body is described as "approx. 4 cm3" in the literature. METHODS: In this retrospective observational study, we included 72 eyes of patients who had undergone magnetic resonance imaging (MRI) of the orbit and biometry measurements of the anterior chamber depth (ACD) and axial length. After segmentation of the volume data, the vitreous volume was extracted by voxel integration, and a simple prediction model was derived to determine the vitreous volume from the axial length (AL) measurement with AL3·π/6·(0.76 + 0.012·(AL-24). This is the volume of a sphere AL3·π/6 and a correction term 0.76 + 0.012·(AL-24) to account for the portion of the vitreous in the entire globe and the proportional increase of the vitreous portion for long (myopic) eyes. RESULTS: Emmetropic eyes with an axial length of 22.50-23.50 mm had a vitreous volume of around 4.5-5.5 cm3. Myopic eyes with an axial length of 30.00 mm had a calculated vitreous volume of 9.0-10.0 cm3. Hypermetropic eyes with an axial length of 20.00 mm showed a vitreous volume of 3.0-4.0 cm3. CONCLUSIONS: By implementing the new calculation formula on the IOLCON website, it will be easy to get the exact individual vitreous volume. The data could be used by retinal surgeons prior to surgery. The knowledge of anatomical dimensions and exact individual vitreous volume seems to be important for gas and silicone oil fillings. With the newly derived knowledge, multicentric studies can evaluate the impact of the dose in intravitreal therapies. Patient-tailored dosing could prevent side effects and improve effectiveness.

Evaluation of corneal power from an AS-OCT thick lens model and ray tracing: reliability of the keratometer index.

PURPOSE: To investigate and compare different strategies of corneal power calculations using keratometry, paraxial thick lens calculations and ray tracing. SETTING: Tertiary care center. DESIGN: Retrospective single-center consecutive case series. METHODS: Using a dataset with 9780 eyes of 9780 patients from a cataractous population the corneal front (Ra/Qa) and back (Rp/Qp) surface radius/asphericity, central corneal thickness (CCT), and entrance pupil size (PUP) were recorded using the Casia 2 tomographer. Beside keratometry with the Zeiss (PK Z ) and Javal (PK J ) keratometer index, a thick lens paraxial formula (PG) and ray tracing (PR) was implemented to extract corneal power for pupil sizes from 2 mm to 5 mm in steps of 1 mm and PUP. RESULTS: With PUP PK Z /PK J overestimates the paraxial corneal power PG in around 97%/99% of cases and PR in around 80% to 85%/99%. PR is around 1/6 or 5/6 diopters (D) lower compared with PK Z or PK J . For a 2 mm pupil PR is around 0.20/0.91 D lower compared with PK Z /PK J and for a 5 mm pupil PR is comparable with PK Z (around 0.03 D lower) but around 0.70 to 0.75 D lower than PK J . CONCLUSIONS: "True" values of corneal power are mostly required in lens power calculations before cataract surgery, and overestimation of corneal power could induce trend errors in refractive outcome with axial length and lens power if compensated with the effective lens position.

Evaluation of statistical correction strategies for corneal back surface astigmatism with toric lenses: a vector analysis.

PURPOSE: To compare actual and formula-predicted postoperative refractive astigmatism using measured posterior corneal power measurements and 4 different empiric posterior corneal astigmatism correction models. SETTING: Tertiary care center. DESIGN: Single-center retrospective consecutive case series. METHODS: Using a dataset of 211 eyes before and after tIOL implantation (Hoya Vivinex), IOLMaster 700 (IOLM) or Casia2 (CASIA) keratometric and front/back surface corneal power measurements were converted to power vector components C0 (0/90 degrees) and C45 (45/135 degrees). Differences between postoperative and Castrop formula predicted refraction at the corneal plane using the labeled parameters of the tIOL and the keratometric or front/back surface corneal powers were recorded as the effect of corneal back surface astigmatism (BSA). RESULTS: Generally, the centroid of the difference shifted toward negative C0 values indicating that BSA adds some against the rule corneal astigmatism (ATR). From IOLM/CASIA keratometry, the average difference in C0 was 0.39/0.32 diopter (D). After correction with the Abulafia-Koch, Goggin, La Hood, and Castrop nomograms, it was -0.18/-0.24 D, 0.27/0.18 D, 0.13/0.08 D, and 0.17/0.10 D. Using corneal front/back surface data from IOLM/CASIA, the difference was 0.18/0.12 D. CONCLUSIONS: The Abulafia-Koch method overcorrected the ATR, while the Goggin, La Hood, and Castrop models slightly undercorrected ATR, and using measurements from the CASIA tomographer seemed to produce slightly less prediction error than IOLM.

Monte-Carlo simulation for calculating phakic supplementary lenses based on a thick and thin lens model using anterior segment OCT data.

BACKGROUND: Phakic lenses (PIOLs, the most common and only disclosed type being the implantable collamer lens, ICL) are used in patients with large or excessive ametropia in cases where laser refractive surgery is contraindicated. The purpose of this study was to present a strategy based on anterior segment OCT data for calculating the refraction correction (REF) and the change in lateral magnification (ΔM) with ICL implantation. METHODS: Based on a dataset (N = 3659) containing Casia 2 measurements, we developed a vergence-based calculation scheme to derive the REF and gain or loss in ΔM on implantation of a PIOL having power PIOLP. The calculation concept is based on either a thick or thin lens model for the cornea and the PIOL. In a Monte-Carlo simulation considering, all PIOL steps listed in the US patent 5,913,898, nonlinear regression models for REF and ΔM were defined for each PIOL datapoint. RESULTS: The calculation shows that simplifying the PIOL to a thin lens could cause some inaccuracies in REF (up to ½ dpt) and ΔM for PIOLs with high positive power. The full range of listed ICL powers (- 17 to 17 dpt) could correct REF in a range from - 17 to 12 dpt with a change in ΔM from 17 to - 25%. The linear regression considering anterior segment biometric data and the PIOLP was not capable of properly characterizing REF and ΔM, whereas the nonlinear model with a quadratic term for the PIOLP showed a good performance for both REF and ΔM prediction. CONCLUSION: Where PIOL design data are available, the calculation concept should consider the PIOL as thick lens model. For daily use, a nonlinear regression model can properly predict REF and ΔM for the entire range of PIOL steps if a vergence calculation is unavailable.

Human corneal epithelial cell and fibroblast migration and growth factor secretion after rose bengal photodynamic therapy (RB-PDT) and the effect of conditioned medium.

PURPOSE: To investigate human corneal epithelial cell and fibroblast migration and growth factor secretion after rose bengal photodynamic therapy (RB-PDT) and the effect of conditioned medium (CM). METHODS: A human corneal epithelial cell line (HCE-T), human corneal fibroblasts (HCF) and keratoconus fibroblasts (KC-HCF) have been used. Twenty-four hours after RB-PDT (0.001% RB concentration, 565 nm wavelength illumination, 0.17 J/cm2 fluence) cell migration rate using scratch assay and growth factor concentrations in the cell culture supernatant using ELISA have been determined. In addition, the effect of CM has been observed. RESULTS: RB-PDT significantly reduced migration rate in all cell types, compared to controls (p≤0.02). Migration rate of HCE-T cultures without RB-PDT (untreated) was significantly higher using HCF CM after RB-PDT, than using HCF CM without RB-PDT (p<0.01). Similarly, untreated HCF displayed a significantly increased migration rate with HCE-T CM after RB-PDT, compared to HCE-T CM without treatment (p<0.01). Furthermore, illumination alone and RB-PDT significantly decreased keratinocyte growth factor (KGF) concentration in HCF and KC-HCF supernatant, and RB-PDT significantly decreased soluble N-Cadherin (SN-Cad) concentration in HCF supernatant, compared to controls (p<0.01 for all). In HCE-T CM, RB-PDT increased hepatocyte growth factor (HGF) and basic fibroblast growth factor (FGFb) concentration (p≤0.02), while decreasing transforming growth factor ß (TGF-ß) concentration (p<0.01). FGFb concentration increased (p<0.0001) and TGF-ß concentration decreased (p<0.0001) in HCF CM, by RB-PDT. Epidermal growth factor (EGF), HGF, and TGF-ß concentration decreased (p≤0.03) and FGFb concentration increased (p<0.01) in KC-HCF CM, using RB-PDT. CONCLUSIONS: HCE-T, HCF and KC-HCF migration rate is reduced 24 hours after RB-PDT. In contrast, HCE-T migration is enhanced using HCF CM after RB-PDT, and HCF migration rate is increased through HCE-T CM following RB-PDT. Modulation of EGF, KGF, HGF, FGFb, TGF-ß and N-Cadherin secretion through RB-PDT may play an important role in corneal wound healing.

EDOF intraocular lens design: shift in image plane vs object vergence.

BACKGROUND: To compare 2 different design scenarios of EDOF-IOLs inserted in the Liou-Brennan schematic model eye using raytracing simulation as a function of pupil size. METHODS: Two EDOF IOL designs were created and optimized for the Liou-Brennan schematic model eye using Zemax ray tracing software. Each lens was optimized to achieve a maximum Strehl ratio for intermediate and far vision. In the first scenario, the object was located at infinity (O1), and the image plane was positioned at far focus (I1) and intermediate focus (I2) to emulate far and intermediate distance vision, respectively. In the second scenario, the image plane was fixed at I1 according to the first scenario. The object plane was set to infinity (O1) for far-distance vision and then shifted closer to the eye (O2) to reproduce the corresponding intermediate vision. The performance of both IOLs was simulated for the following 3 test conditions as a function of pupil size: a) O1 to I1, b) O1 to I2, and c) O2 to I1. To evaluate the imaging performance, we used the Strehl ratio, the root-mean-square (rms) of the spot radius, and the spherical aberration of the wavefront for various pupil sizes. RESULTS: Evaluating the imaging performance of the IOLs shows that the imaging performance of the IOLs is essentially identical for object/image at O1/I1. Designed IOLs perform dissimilarly to each other in near-vision scenarios, and the simulations confirm that there is a slight difference in their optical performance. CONCLUSION: Our simulation study recommends considering the difference between object shift and image plane shift in design and test conditions to achieve more accurate pseudoaccommodation after cataract surgery.

Prediction of corneal power vectors after cataract surgery with toric lens implantation-A vector analysis.

BACKGROUND: Intraocular lenses are typically calculated based on a pseudophakic eye model, and for toric lenses (tIOL) a good estimate of corneal astigmatism after cataract surgery is required in addition to the equivalent corneal power. The purpose of this study was to investigate the differences between the preoperative IOLMaster (IOLM) and the preoperative and postoperative Casia2 (CASIA) tomographic measurements of corneal power in a cataractous population with tIOL implantation, and to predict total power (TP) from the IOLM and CASIA keratometric measurements. METHODS: The analysis was based on a dataset of 88 eyes of 88 patients from 1 clinical centre before and after tIOL implantation. All IOLM and CASIA keratometric and total corneal power measurements were converted to power vector components, and the differences between preoperative IOLM or CASIA and postoperative CASIA measurements were assessed. Feedforward neural network and multivariate linear regression prediction algorithms were implemented to predict the postoperative total corneal power (as a reference for tIOL calculation) from the preoperative IOLM and CASIA keratometric measurements. RESULTS: On average, the preoperative IOLM keratometric / total corneal power under- / overestimates the postoperative CASIA keratometric / real corneal power by 0.12 dpt / 0.21 dpt. The prediction of postoperative CASIA real power from preoperative IOLM or CASIA keratometry shows that postoperative total corneal power is systematically (0.18 dpt / 0.27 dpt) shifted towards astigmatism against the rule, which is not reflected by keratometry. The correlation of postoperative CASIA real power to the corresponding preoperative CASIA values is better than those as compared to the preoperative IOLM keratometry. However, there is a large variation from preoperative IOLM or CASIA keratometry to the postoperative CASIA real power of up to 1.1 dpt (95% confidence interval). CONCLUSION: One of the challenges of tIOL calculation is the prediction of postoperative total corneal power from preoperative keratometry. Keratometric power restricted to a front surface measurement does not fully reflect the situation of corneal back surface astigmatism, which typically adds some extra against the rule astigmatism.

P42-A105†Sterile donor tomography for improvement of refractive results after keratoplasty.

PURPOSE: To evaluate the efficiency of using anterior segment optical coherence tomography (AS-OCT) as a non-invasive and sterile screening method in the eye bank to detect corneal grafts with curvature and/or thickness anomalies, thus improving the graft selection for corneal transplantation. METHODS: 1222 donor corneal tissues mounted in sterile organ culture flasks were imaged using an AS-OCT (CASIA 2 - Tomey, Nagoya, Japan) between January 2018 and September 2022. The corneal tissues were preserved at least 12 hours in organ culture medium 2 (containing 6% dextran T-500) before the measurement in order to allow deswelling prior to the examination. Depth scans were performed sterilely through the organ culture flask from the posterior surface of the corneal tissues within a 7 mm central zone to create 3D volume data. The volume data set was imported to MATLAB (MathWorks Inc., Natick, Massachusetts, USA) and, after preprocessing the data and defining the region of interest (ROI), the edge of the front and back surfaces of the corneal tissues was detected. Subsequently, the adaptation of a sphero-cylindrical surface model was carried out with raytracing. The radii of curvature for the front and back surfaces and the central corneal thickness were determined according to the method proposed by Mäurer, Eppig, Langenbucher et al at the Institute of Experimental Ophthalmology, Homburg/Saar, Germany. RESULTS: The mean steep/flat front surface radius was 7.46 ± 0.29 (6.07 - 9.29)/7.69 ± 0.24 (6.70 - 9.50) mm, the corresponding values for the back surface being 6.48 ± 0.32 (5.30 - 8.00)/6.80 ± 0.31 (5.81 - 8.00) mm and the mean central thickness was 611.5 ± 85.6 (378.5 - 1457.2) µm. Anomalies (beyond ± 2 or ± 3 standard deviations SD) were found in 111 or 41 corneas (9.1% or 3.4%) for anterior surface curvature, 135 or 38 for corneas (11.0% or 3.1%) for the posterior surface, and 53 or 15 corneas (4.3% or 1.2%) for central corneal thickness. CONCLUSION: The AS-OCT provides an objective, sterile and semi-automated screening method to identify corneal morphological and refractive alterations (e.g. keratoconus, status post keratorefractive surgery) to further optimize corneal donor selection in the eye bank. Corneal donors with curvature or thickness anomalies +/- 3 SD (eminence-based) do not have to be discarded but can be used for posterior lamellar keratoplasty, especially DMEK in Germany.