Corneal Edema after Cataract Surgery.

This systematic review investigates the prevalence and underlying causes of corneal edema following cataract surgery employing manual phacoemulsification. A comprehensive search encompassing databases such as PubMed, Embase, ProQuest, Cochrane Library, and Scopus was conducted, focusing on variables encompassing cataract surgery and corneal edema. Two independent reviewers systematically extracted pertinent data from 103 articles, consisting of 62 theoretical studies and 41 clinical trials. These studies delved into various aspects related to corneal edema after cataract surgery, including endothelial cell loss, pachymetry measurements, visual performance, surgical techniques, supplies, medications, and assessments of endothelial and epithelial barriers. This review, encompassing an extensive analysis of 3060 records, revealed significant correlations between corneal edema and endothelial cell loss during phacoemulsification surgery. Factors such as patient age, cataract grade, and mechanical stress were identified as contributors to endothelial cell loss. Furthermore, pachymetry and optical coherence tomography emerged as valuable diagnostic tools for assessing corneal edema. In conclusion, this systematic review underscores the link between corneal edema and endothelial cell loss in manual phacoemulsification cataract surgery. It highlights the relevance of factors like patient demographics and diagnostic modalities. However, further research is essential to unravel the complexities of refractive changes and the underlying mechanisms.

Intra-ocular lens optical changes resulting from the loading of dexamethasone.

To study the optical changes on hydrogel-silicone intraocular lenses (IOLs) resulting from loading them with dexamethasone. We used prototype hydrogel(pHEMA)-silicone IOLs and loaded the matrices with an anti-inflammatory drug (dexamethasone). The optical properties we analyzed experimentally were a) modulation transfer function (MTF); b) spectral transmission; c) diopter power. These determinations were performed on drug-loaded IOLs, IOLs that had released the drug, and IOLs that had not been drug-loaded. Loading a hydrogel-silicone IOL with dexamethasone results in impairment of its optical qualities, in particular its MTF and spectral transmission, but not dioptric power. However, once the drug has been released, it almost recovers its initial optical properties.

Light transmission and ultraviolet protection of contact lenses under artificial illumination.

PURPOSE: To determine the spectral transmission of contact lenses (CLs), with and without an ultraviolet (UV) filter to evaluate their capacity for protection under UV radiation from artificial illumination (incandescent, fluorescent, xenon (Xe) lamps, or white LEDs (light-emitting diode)). METHODS: The transmission curves of nine soft CLs were obtained by using a PerkinElmer Lambda 35 UV-vis spectrophotometer. A CIE standard was used for the emission spectra of incandescent and fluorescent lamps, and Xe lamps and white LEDs were measured by using an International Light Technologies ILT-950 spectroradiometer. RESULTS: Five of the nine soft CLs analysed state that they incorporate UV filters, but the other four do not specify anything in this regard. The spectral transmission of all the CLs studied is excellent in the visible region. The CLs with UV filters filter out this radiation more or less effectively. Xe lamps emit a part in the UV region. Incandescent, fluorescent and white LEDs do not emit at all in the UV. CONCLUSIONS: Incorporating UV filters is important when the illumination is from a Xe lamp since this light source emits in the UV region. This, however, does not occur with incandescent and fluorescent lamps or white LEDs. The CLs that do incorporate UV filters meet all the standard requirements that the U.S. FDA (Food and Drug Administration) has for UV-blocking CLs Class II (OcularScience, CooperVision and Neolens), and AcuvueMoist and HydronActifresh400 even comply with the stricter Class I. The CLs without UV filters let UVA, UVB and even some UVC through.

Refractive changes in nuclear, cortical and posterior subcapsular cataracts. Effect of the type and grade / Cambios refractivos en las cataratas nuclear, cortical y subcapsular posterior. Efecto del tipo y grado

Purpose: To determine the effect of main morphological types and grades of age-related cataracts on refractive error. Methods: We measured 276 subjects with optical compensation prior to the development of cataract. We evaluated 224 eyes with nuclear cataract, 125 with cortical cataract, and 103 with posterior subcapsular (PSC) cataract classified with LOCSIII. We measured visual acuity (VA) with their spectacles and best-corrected visual acuity (BCVA) with chart in decimal scale to obtain the optimal compensation with cataract. We evaluated the differences between compensations. Results: A significant myopic shift was observed in nuclear cataract from low to mild grade (p = 0.031), the same as for PSC cataract from mild to advanced grade (p = 0.025). No significant changes were found for cortical cataract (p = 0.462). Regarding astigmatism, we observed power changes in cortical cataract from low to mild grade (p = 0.03) and axis changes in PSC from low to mild grade (p = 0.02) and in nuclear cataract from mild to advanced grade (p = 0.02). Conclusions: Cataract produces changes in patient’s compensation which depend on severity and type of cataract. For nuclear and PSC cataract, we observed that the higher the grade of severity, the greater the myopic shift. Power astigmatic changes were found in cortical cataract and axis changes in PSC and nuclear cataract (AU)

Objetivo: Determinar el efecto sobre el error refractivo de los principales tipos morfológicos y grados de catarata asociada a la edad. Métodos: Medimos a 276 sujetos con compensación óptica, previamente a la aparición de la catarata. Evaluamos 224 ojos con catarata nuclear, 125 con catarata cortical, y 103 con catarata subcapsular posterior (CSP), clasificados con el sistema LOCSIII. Medimos la agudeza visual (AV) con sus gafas, y la mejor agudeza visual corregida (MAVC) con un test en escala decimal, para obtener la compensación óptima con la catarata. Evaluamos las diferencias entre las compensaciones. Resultados: Se observó un cambio considerable en la catarata nuclear, al pasar del grado bajo al leve (p = 0,031), al igual que en la catarata subcapsular posterior al pasar de grado leve a avanzado (p = 0,025). No se observaron cambios en la catarata cortical (p = 0,462). En cuanto al astigmatismo, observamos cambios de potencia en la catarata cortical al pasar de grado bajo a leve (p = 0,03) y cambios en el eje en la catarata subcapsular posterior al pasar de grado bajo a leve (p = 0,02), y en la catarata nuclear al pasar de grado leve a avanzado (p = 0,02). Conclusiones: La catarata produce cambios en la compensación del paciente, que depende de su severidad y tipo. En la catarata nuclear y subcapsular posterior, observamos que cuanto mayor era el grado de severidad, mayor era el cambio miópico. Se hallaron cambios de potencia astigmática en la catarata cortical, y cambios en el eje en la catarata subcapsular posterior y nuclear (AU)

Determination of scattering in intraocular lenses by spectrophotometric measurements.

This study presents a method for measuring scattering in explanted intraocular lenses (IOLs). Currently, determining scattering in IOLs is usually performed by Scheimpflug cameras and the results are expressed in the units used by this apparatus. The method we propose uses a spectrophotometer and this makes it possible to measure the total transmission of the IOL by using an integrating sphere; the direct transmission is determined by the double-beam mode. The difference between these two transmissions gives a value of the scattering in percentage values of light lost. In addition, by obtaining the spectral transmission curve, information about the most scattered wavelengths is also obtained. The IOL power introduces errors when directly measured, particularly with high powers. This problem can be overcome if a tailor-made cuvette is used that shortens the distance between the IOL and the condensing lens of the spectrophotometer when the IOL powers are below 24 diopters. We checked the effectiveness of this method by measuring the scattering of three explanted IOLs from cornea donors. This method, however, does not make it possible to ascertain whether the scattering measured is caused by surface light scattering or internal light scattering.

Effect of the color of the intraocular lens on optical and visual quality.

Purpose: To analyze the optical quality of intraocular lenses (IOL) with an orange (PC440Y) and a yellow (SN60AT) filter, and correlate these results with the visual quality of patients with these implants. Setting: Fisabio Oftalmologνa Mιdica, Valencia, Spain. Design: Randomized prospective study. Materials and Methods: The IOL optical quality was determined using the modulation transfer function (MTF) and the spectral transmission. The visual quality of 87 eyes with cataract (51 with orange filter and 36 with yellow filter) was determined by best corrected visual acuity (BCVA) and contrast sensitivity function (CSF) under photopic and mesopic conditions. To analyze the results, we use a Student's t-test. Results: Orange lens filtered more of the blue spectrum (cut-off wavelength of 370 nm) than the yellow lens (390 nm). The MTF of the yellow lens was better than the orange lens (average modulation of 0.676 for natural and 0.672 for orange). The patients' BCVA was 0.02 + 0.10 logMAR for both lenses. The CSF obtained with the yellow lens was slightly better, although without statistically significant differences (P > 0.05). Conclusions: Both lenses are of good optical quality. The patients' visual quality was similar with both lenses, and optical quality was also similar. The color of the lens does not affect the visual quality of the patient.

Simulating images seen by patients with inhomogeneous sensitivity losses.

PURPOSE: We aim to simulate how colored images are perceived by subjects with local achromatic and chromatic contrast sensitivity losses in the visual field (VF). METHODS: The spatiochromatic corresponding pair algorithm, introduced in a previous article (J Opt Soc Am (A) 2004;21:176-186), has been implemented with a linear model of the visual system. Spatial information is processed separately by the chromatic and achromatic mechanisms by means of a multiscale model, with sensors selective to frequency, orientation, and spatial position, whose mechanism-dependent relative weights change with the spatial location of the image. These weights have been obtained from perimetric data from a patient with Leber's Hereditary Optic Neuropathy and an age-matched sample of normal subjects, using achromatic, red-green, and blue-yellow gratings of different spatial frequencies. Distortion contours for each mechanism have been derived from the images simulating the perception of these subjects at different locations in the VF. RESULTS: The images simulating the perception of normal subjects at different locations of the VF show a fast decrease in image quality with eccentricity. The same analysis carried out with the Leber's Hereditary Optic Neuropathy patient reveals worse overall image quality throughout the VF, plus a color vision defect resembling red-green dichromacy at fovea and trichromatic anomaly in the rest of the VF. CONCLUSIONS: In the present article, we show that implementing the algorithm with a spatial vision model that considers the changes in contrast sensitivity with spatial location of the stimulus may reveal the local effects that are suffered, in general, by pathological subjects, and that are ignored by simpler spatial vision models.

Lens opacities in Valencia, Spain.

PURPOSE: To evaluate the most common lens opacities in Valencia (Spain), analyzed by gender, grade, and type of cataracts. The results are compared with other studies performed at other geographical latitudes and on different races. METHODS: A total of 1951 eyes of patients diagnosed with cataracts, aged between 30 and 96 years, were evaluated in accordance with age, gender, type and degree of the cataract, bilaterality, and symmetry of this disease. Lens Opacities Classification System III was used to classify the cataract and the degree was graded as mild or moderate to advanced. RESULTS: The most common type of cataract is corticonuclear in the elderly and subcapsular in younger subjects. The most common are nuclear (28.4%) followed by cortical (6.2%), if combined cataracts are ruled out. There is a greater incidence of cortical cataracts in women (70%) and subcapsular cataracts in men (70%). CONCLUSIONS: The results suggest the existence of a gender factor in cataract formation and coincide with those obtained in similar studies performed in areas at a similar latitude (40º N) and with different race population. The geographical location (intensity and length of exposure to solar radiation) seems to be a determining factor in the formation of a specific type of cataract, more than race, although there are other factors that contribute in the formation of a specific type of cataract.

Images perceived after chromatic or achromatic contrast sensitivity losses.

PURPOSE: We simulate how subjects with losses in chromatic and achromatic contrast sensitivity perceive colored images by using the spatiochromatic corresponding pair algorithm. METHODS: This is a generalized version of the algorithm by Capilla et al. (J Opt Soc Am (A) 2004;21:176-186) for simulating color perception of color deviant subjects, which incorporates a simple spatial vision model, consisting of a linear filtering stage, with a band-pass achromatic filter and two low-pass chromatic ones, for the red-green and blue-yellow mechanisms. These filters, except for the global scaling, are the subject's contrast sensitivity functions measured along the cardinal directions of the color space. In its present form, the algorithm would serve to simulate alterations both in the spectral sensitivities and in the contrast sensitivities of the visual mechanisms. RESULTS: After a preliminary theoretical study on the effect of frequency selective and overall reductions in the contrast sensitivity function of a single mechanism, we present cases of real subjects with glaucoma and diabetes, suffering alterations of different magnitude in the three mechanisms. CONCLUSIONS: The simulations allow us to learn about the different types of distortions that can be experienced by a subject with impaired contrast sensitivities (blur, haloes, color shifts, local or global contrast, brightness and colorfulness reductions, etc.) and highlight the difficulties arising when trying to predict the quality of the final image from the losses in the individual mechanisms.