Systematic review of potential causes of intraocular lens opacification

Intraocular lens (IOL) opacification is an infrequent complication of cataract surgery. Surface analysis has demonstrated that the opacification of IOLs is related to calcium or phosphate precipitation on or within the lenses, but the associated mechanisms are unknown, and the scientific literature is heterogeneous and limited to case series and retrospective studies. The purpose of this systematic review was to analyse the most frequent conditions associated with opacification of IOLs reported by studies. A search was carried out using the PubMed MEDLINE, Web of Science and Scopus databases. The quality of the studies selected was evaluated using the Pierson tool. The search provided a total of 811 articles, of which 39 were selected following the inclusion and exclusion criteria. The most common opacified lenses were hydrophilic IOLs according to our analysis. The mean time of appearance of lens opacification was 14.93 ± 17.82 months. The most frequent conditions associated with opacification of the IOLs were Descemet Stripping with Automated Endothelial Keratoplasty (DSAEK/DSEK) and diabetes mellitus (DM), followed by pars plana vitrectomy (PPV), blood hypertension (HT), and glaucoma. Concerning the quality analysis, the mean score was 7.00 ± 1.43 (scoring range from 0 to 10), indicating an acceptable quality of the case reports and retrospective studies. In conclusion, DSAEK/DSEK, DM, PPV, glaucoma and hypertension are conditions with potential risk of IOL opacification after cataract surgery, especially when implanting hydrophilic acrylic IOLs.Ministry of Economy, Industry and Competitiveness of Spain, Grant/Award Number: RYC‐2016‐20471

Tribological performance of silicon nitride and carbon black Ionanofluids based on 1-ethyl-3-methylimidazolium methanesulfonate

Development of nano-lubricants by the dispersion of nano-particles in current lubricants has contributed to improving energy efficiency reducing wear and friction. During the last two decades, ionic liquids have evolved as novel lubricants or lubricant additives, especially for high vacuum and high temperature. Nevertheless, the number of experimental studies regarding the tribological properties of Ionanofluids, defined as dispersions of nano-particles in ionic liquids, is limited. 1-Ethyl-3-methylimidazolium methanesulfonate, [EMIM][MS], is a promising candidate for lubrication applications due to its wide liquid range, high thermal conductivity, low friction coefficients and low compressibility in comparison with commercial mineral and synthetic hydrocarbon based lubricants. In this work, Ionanofluid lubricants based on dispersions of nano-additives (silicon nitride and carbon black) at mass concentration between 0.10 and 1.0 wt% in [EMIM][MS] were designed. The nearly spherical morphology of the nano-additives, silicon nitride and carbon black, was described by using scanning electron microscopy. The stabilities of the resulting nano-particle dispersions in the ionic liquid were analyzed by dynamic light scattering measurements of size for one month. Tribological characterization was performed by a rotational rheometer coupled with a tribology cell with ball-on-three-pins configuration (100Cr6 steel) in sliding conditions at 298.15 and 353.15 K. Afterwards, the wear track morphology of the worn pins was analyzed by a 3D optical profiler and Raman spectroscopy. The dispersions at the optimal nano-additive concentrations for lubrication reached friction coefficient decreases of up to 16% and wear tracks with a volume 28 times lower. Additionally, the density and dynamic viscosity of [EMIM][MS] and the optimal Ionanofluids for lubrication applications measured with a rotational Stabinger visco-densimeter in the 278.15 to 373.15 K temperature range showed small increases with almost no dependence on temperature.This work was supported by the “Ministerio de Economía y Competitividad” (Spain) and the ERDF program through ENE2017-86425-C2-1/2-R projects, and by the “Xunta de Galicia” (ED431E 2018 08, ED431D 2017 06 and GRC ED431C 2016 001/034). J.P.V. acknowledges the FPI Program of the “Ministerio de Economía y Competitividad”.S

Long-Term Efficacy, Visual Performance and Patient Reported Outcomes with a Trifocal Intraocular Lens: A Six-Year Follow-up

(1) Background: To evaluate the efficacy at 6 years postoperative after the implantation of a trifocal intraocular lens (IOL) AT Lisa Tri 839MP. The secondary objective was to evaluate the contrast sensitivity defocus curve (CSDC), light distortion analysis (LDA), and patient reported outcomes (PROs). (2) Methods: Sixty-two subjects participated in phone call interviews to collect data regarding a visual function questionnaire (VF-14), a patient reported spectacle independence questionnaire (PRSIQ), and questions related to satisfaction and decision to be implanted with the same IOL. Thirty-seven of these subjects were consecutively invited to a study visit for measurement of their visual acuity (VA), CSDC, and LDA. (3) Results: The mean monocular distance corrected VA was −0.05, 0.08, and 0.05 logMAR at far and distances of 67 cm and 40 cm, respectively. These VAs were significantly superior to those reported in previous literature (p < 0.05). The total area under the CSDC was 2.29 logCS/m−1 and the light distortion index 18.82%. The mean VF-14 score was 94.73, with 19.4% of subjects requiring spectacles occasionally for near distances, and 88.9% considering the decision of being operated again; (4) Conclusions: Long-term AT LISA Tri 839MP IOL efficacy results were equal or better than those reported 12 months postoperatively in previous studies. The spectacle independence and satisfaction rates were comparable to those reported in short-term studies.This research was funded by grant support from Carl Zeiss Meditec AG

Contrastación de hipótesis en diseños multivariados split-plot con matrices de dispersión arbitrarias

El presente trabajo examina diversos procedimientos para contrastar hipótesis nulas globales, correspondientes a datos obtenidos mediante diseños multivariados split-plot cuando se incumple el supuesto de homogeneidad de las matrices de dispersión. Un examen de estos procedimientos para un amplio número de variables confirma, por un lado, la robustez del procedimiento multivariado de Welch-James dado por Johansen (1980) para probar el efecto principal de los ensayos y, por otro, la robustez de la generalización multivariada del procedimiento de Brown-Forsythe (1974) para probar la interacción de los grupos x los ensayos. Nuestros resultados también ponen de relieve que las diferencias de potencia eran pequeñas en aquellas condiciones en que tanto el procedimiento de Welch-James como de Brown-Forsythe controlaban las tasas de error de Tipo I

Above-average defocus curves in photopic and mesopic vision with multifocal intraocular lenses after laser assisted in situ keratomileusis

Letter to the Edito

New Approach for the Calculation of the Intraocular Lens Power Based on the Fictitious Corneal Refractive Index Estimation

Purpose. To identify the sources of error in predictability beyond the effective lens position and to develop two new thick lens equations. Methods. Retrospective observational case series with 43 eyes. Information related to the actual lens position, corneal radii measured with specular reflection and Scheimpflug-based technologies, and the characteristics of the implanted lenses (radii and thickness) were used for obtaining the fictitious indexes that better predicted the postoperative spherical equivalent (SE) when the real effective lens position (ELP) was known. These fictitious indexes were used to develop two thick lens equations that were compared with the predictability of SRK/T and Barrett Universal II. Results. The SE relative to the intended target was correlated to the difference between real ELP and the value estimated by SRK/T (ΔELP) (r = −0.47, p = 0.002), but this only predicted 22% of variability in a linear regression model. The fictitious index for the specular reflection (nk) and Scheimpflug-based devices (nc) were significantly correlated with axial length. Including both indexes fitted to axial length in the prediction model with the ΔELP increased the r-square of the model up to 83% and 39%, respectively. Equations derived from these fictitious indexes reduced the mean SE in comparison to SRK/T and Barrett Universal II. Conclusions. The predictability with the trifocal IOL evaluated is not explained by an error in the ELP. An adjustment fitting the fictitious index with the axial length improves the predictability without false estimations of the ELP

From Presbyopia to Cataracts: A Critical Review on Dysfunctional Lens Syndrome

Dysfunctional lens syndrome (DLS) is a term coined to describe the natural aging changes in the crystalline lens. Different alterations in the refractive properties and transparency of the lens are produced during the development of presbyopia and cataract, such as changes in internal high order aberrations or an increase in ocular forward scattering, with a potentially significant impact on clinical measures, including visual acuity and contrast sensitivity. Objective technologies have emerged to solve the limits of current methods for the grading of the lens aging, which have been linked to the DLS term. However, there is still not a gold standard or evidence-based clinical guidelines around these new technologies despite multiple research studies have correlated their results with conventional methods such as visual acuity or the lens opacification system (LOCS), with more scientific background around the ocular scattering index (OSI) and Scheimpflug densitometry. In either case, DLS is not a new evidence-based concept that leads to new knowledge about crystalline lens aging but it is a nomenclature change of two existing terms, presbyopia and cataracts. Therefore, this term should be used with caution in the scientific peer-reviewed literature.The author David P. Piñero has been supported by the Ministry of Economy, Industry and Competitiveness of Spain within the program Ramón y Cajal, RYC-2016-20471

Corneal biomechanics after laser refractive surgery: Unmasking differences between techniques

The hypothesis that small-incision lenticule extraction provides better preservation of corneal biomechanics than previous laser refractive techniques has led to a growth in the interest in clinical and experimental research in this field. This hypothesis is based on the fact that corneal layers with greater stiffness are preserved with this new technique. However, this hypothesis is controversial because clinical research has shown a great disparity in the outcomes. In this review, we performed an in-depth analysis of the factors that might affect corneal biomechanics in laser refractive surgery procedures from a macrostructural to a microstructural viewpoint. New advances in algorithms with current devices or the introduction of new devices might help unmask the possible advantages of small-incision lenticule extraction in corneal biomechanics

Biometric Factors Associated with the Visual Performance of a High Addition Multifocal Intraocular Lens

Purpose/Aim: To evaluate the impact of ocular parameters on the visual performance achieved with the multifocal intraocular lens (IOL) Bi-Flex M 677MY. Materials and Methods: About 26 subjects were included in the current study. Several physiological variables were retrieved from the 3-month follow-up visit, including pupil diameter and distance from pupil center to the vertex normal of the anterior cornea (µ). These variables were also obtained in the preoperative visit. Binocular and monocular visual acuity defocus curves were measured at 1 and 3 months after surgery, respectively. The monocular Area Under the Curve (AUC) was computed along the total range (Total Area Under the Curve (TAUC), +1.00 to −4.00 D) and for the ranges of Far (Far Area Under the Curve (FAUC), +0.50 to −0.50 D), (Intermediate Area Under the Curve (IAUC), −1.00 to −1.50 D) and Near vision (Near Area Under the Curve (NAUC), −2.00 to −4.00 D). Correlations between these areas and the postoperative physiological variables were assessed. Results: The mean µ was reduced from 0.21 to 0.10 mm after surgery, as well as pupil diameters, either photopic (−7.4%) or mesopic (−8.1%) (p < 0.05). The mean AUCs were 2.08 ± 0.74 for TAUC, 0.57 ± 0.17 for FAUC, 0.16 ± 0.09 for IAUC, and 0.81 ± 0.29 for NAUC. Significant correlations were found between NAUC and corneal power (r = −0.39, p = 0.05) as well as between IAUC and temporal decentration of the lens from vertex normal (ρ = −0.41, p = 0.04). Conclusions: The visual performance at near distance with the IOL evaluated improved in eyes with less corneal power. On the other hand, a slight temporal IOL decentration from vertex normal also improved intermediate visual acuity. The binocular defocus curve was similar to other trifocal IOLs