Purpose: The aim of this study was to determine the mechanisms leading to the refractive shift and intraocular lens calculation error induced by Descemet membrane endothelial keratoplasty (DMEK), using ocular biometry and corneal elevation tomography data. Methods: This is a retrospective, monocentric cohort study. Eyes which underwent uncomplicated DMEK surgery with available pre-DMEK and post-DMEK Scheimpflug rotating camera data (Pentacam, Oculus, Wetzlar, Germany) were considered for inclusion with an age-matched control group of healthy corneas. Cataract surgery data were collected for triple-DMEK cases. DMEK-induced refractive shift (DIRS) and intraocular lens calculation error (DICE) were calculated. Pearson r correlation coefficient was calculated between each corneal parameter variation and both DIRS and DICE. Results: DIRS was calculable for 49 eyes from 43 patients. It was 30.61% neutral, 53.06% hyperopic (36.73% > 1D), and 16.32% myopic (6.12% > 1 D). DICE was calculable for 30 eyes of 26 patients: It was 46.67% neutral, 40.00% hyperopic (10.00% > 1D), and 13.33% myopic (3.33% > 1D). DIRS and DICE were mainly associated with variations in PRC/ARC ratio, anterior average radii of curvature (ARC), posterior average radii of curvature (PRC), and posterior Q. Conclusions: Our results suggest that ARC variations, PRC/ARC ratio variations, PRC variations, and posterior Q variations are the most influential parameters for both DIRS and DICE. We suggest that a distinction between those different phenomenons, both currently described as “hyperopic shift” in the literature, should be made by researchers and clinicians.

To ascertain the theoretical impact of optical design variations of the intraocular lens (IOL) on the accuracy of IOL power formulas based on a single lens constant using a thick lens eye model. This impact was also simulated before and after optimization. We modeled 70 thick-lens pseudophakic eyes implanted with IOLs of symmetrical optical design and power comprised between 0.50 D and 35 D in 0.5-step increments. Modifications of the shape factor resulting in variations in the anterior and posterior radii of an IOL were made, keeping the central thickness and paraxial powers static. Geometry data from three IOL models were also used. Corresponding postoperative spherical equivalent (SE) were computed for different IOL powers and assimilated to a prediction error of the formula due to the sole change in optical design alone. Formula accuracy was studied before and after zeroization on a uniform and non-uniform realistic IOL power distribution. The impact of the incremental change in optic design variability depended on the IOL power. Design modifications theoretically induce an increase in the standard deviation (SD), Mean Absolute Error (MAE), and Root Mean Square (RMS) of the error. The values of these parameters reduce dramatically after zeroization. While the variations in optical design can affect refractive outcomes, especially in short eyes, the zeroization of the mean error theoretically reduces the impact of the IOL’s design and power on the accuracy of IOL power calculation.

The high prevalence of cataracts necessitates the development of advanced technologies in ophthalmic microsurgery. A research team has introduced an innovative hydrodynamic scheme designed to increase the safety of phacoemulsification procedures. This system detects occlusion by monitoring the vacuum levels in the aspiration line; when a critical threshold is reached and sustained, the system detects the occlusion and gradually reduces the vacuum to a predetermined value, all while maintaining occlusion. This study aimed to investigate morphological changes in the corneal tissue of rabbit eyes following experimentally induced post-occlusion waves using this novel hydrodynamic scheme. A total of 32 eyes from 16 white laboratory rabbits were studied. Both the conventional technology and the new hydrodynamic model were employed, using phaco needles of different diameters. The corneal samples were subjected to histological examination under light microscopy. The results showed that the least corneal damage occurred in group 4, where the innovative hydrodynamic scheme was combined with a fine needle (diameter = 0.9 mm). These findings suggest that this novel system can significantly reduce corneal trauma during phacoemulsification.

Purpose: To evaluate visual outcomes of high hyperopic laser in situ keratomileusis (LASIK), using corneal aspherization to control the induced spherical aberration. Setting: Fondation Ophtalmologique Adolphe de Rothschild, Paris, France. Design: Prospective interventional case series. Methods: Prospective interventional study of consecutive high hyperopes (≥+3 diopters [D] of spherical equivalent [SE]) undergoing LASIK with the WaveLight FS200 femtosecond and EX500 excimer laser platform. An aspheric ablation profile (planned change in corneal asphericity ΔQ = +0.2) was delivered using the Custom-Q nomogram on an optical zone of ≥6.5 mm centered near the corneal vertex. Uncorrected corrected distance visual acuity (UDVA) and corrected distance visual acuity, as well as changes in SE, corneal asphericity (ΔQ), and higher-order aberrations, were analyzed preoperatively and on day 1, 1, 3, 6, and 12 months. Results: 117 eyes of 63 patients (mean age of 30.1 ± 5.6 years) were included. Preoperatively and at 12 months postoperatively, the mean SE was 5.1 ± 1.1 D and 0.00 ± 0.7 D, respectively. 88% of eyes achieved 0 logMAR or better UDVA at 12 months. 1 month postoperatively, there was a statistically significant induction of positive spherical aberration decreasing progressively and significantly until the last visit (preop SA4 = 0.09 ± 0.11 μm, day 1 SA4 = 0.30 ± 0.32 μm, 12 months SA4 = 0.08 ± 0.21 μm, P = .056). 2 eyes needed enhancement at 12 months. Conclusions: LASIK for high levels of hyperopia showed good outcomes mainly due to aspheric-customized ablation profile with a change of ΔQ = +0.2 in corneal asphericity.