Natural Lens Research Articles

Twelve-month clinical outcomes after implantation of a new, modular, anterior shape-changing fluid optic intraocular lens.

To report the initial safety and effectiveness profile for an anterior shape-changing, modular IOL, Juvene IOL (JIOL), for the treatment of aphakia and presbyopia after removal of the natural crystalline lens due to cataract. 2 private practices in Monterrey and Tijuana, Mexico. Exploratory prospective multicenter open-label noncomparative clinical trial. A convenience sample of patients aged 50 to 80 years with planned cataract surgery was recruited to undergo unilateral or bilateral implantation with the JIOL. Patients were required to complete an informed consent and be able to dilate to at least 6.0 mm pharmacologically, be in good overall health, and have no significant eye health history to qualify. Visual acuities, defocus curves, and contrast sensitivity were measured for all patients 12 months postoperatively. 51 of 58 eyes completed the 12-month visit. Intraoperative complication rates were extremely low (n = 1; missed base lens tab). The most frequent adverse events (AEs) were prolonged inflammation (N = 6) and cystoid macular edema (N = 4); all AEs were resolved without sequelae by the 12-month visit. The mean monocular logMAR corrected distance visual acuity, distance-corrected intermediate visual acuity, and distance-corrected near visual acuity were 0.01, 0.08, and 0.24, respectively. Defocus testing showed visual acuity > 20/40 from approximately +1.00 through -2.00 diopters. Binocular implantation (n = 16) provided superior performance over monocular implantation. The JIOL offers a new solution to treat presbyopia, providing clear functional vision performance across a range of distances with an acceptable initial safety profile.

Suppression of natural lens fluorescence in fundus autofluorescence measurements: review of hardware solutions.

Fluorescence lifetime imaging ophthalmoscopy (FLIO), a technique for investigating metabolic changes in the eye ground, can reveal the first signs of diseases related to metabolism. The fluorescence of the natural lens overlies the fundus fluorescence. Although the influence of natural lens fluorescence can be somewhat decreased with mathematical models, excluding this influence during the measurement by using hardware enables more exact estimation of the fundus fluorescence. Here, we analyze four 1-photon excitation hardware solutions to suppress the influence of natural lens fluorescence: aperture stop separation, confocal scanning laser ophthalmoscopy, combined confocal scanning laser ophthalmoscopy and aperture stop separation, and dual point confocal scanning laser ophthalmoscopy. The effect of each principle is demonstrated in examples. The best suppression is provided by the dual point principle, realized with a confocal scanning laser ophthalmoscope. In this case, in addition to the fluorescence of the whole eye, the fluorescence of the anterior part of the eye is detected from a non-excited spot of the fundus. The intensity and time-resolved fluorescence spectral data of the fundus are derived through the subtraction of the simultaneously measured fluorescence of the excited and non-excited spots. Advantages of future 2-photon fluorescence excitation are also discussed. This study provides the first quantitative evaluation of hardware principles to suppress the fluorescence of the natural lens during measurements of fundus autofluorescence.

Multichannel Delivery in Healthcare: The Impact of Telemedicine Centers in Southern India

Telemedicine is increasingly used across the developing world to expand access to healthcare, to improve outcomes, and to reduce costs. One common model is that of telemedicine centers, which are small primary care facilities run by midlevel (nonphysician) providers who conduct a preliminary examination and then facilitate a telemedicine visit with a remote physician in real time. However, the impact of this channel of care delivery—particularly on existing physical healthcare-delivery channels—has not been thoroughly examined. We use data from one of the largest tele-ophthalmology implementations in the world to examine this issue. Using a quasi-experimental difference-in-differences approach, we find that opening a nearby telemedicine center generates a 31% increase in the overall network visit rate from the population within 10 km of the new center, 62% of which is driven by new patients, suggesting a substantial increase in access. The rate of eyeglasses prescriptions to correct for simple refractive errors increases by 18.5%, whereas the rate of cataract surgery to replace the natural lens in a patient’s eye with an artificial lens remains unchanged. The increase in access and treatment rates does not significantly impact the direct costs incurred by patients, but reduces their indirect costs (measured as travel distance) by 30% (12 km). Finally, we find significant spatial heterogeneity in these effects, which vary with the distance of patients to facilities. These results have important implications for the design of telemedicine networks and the portfolio of healthcare services provided through them. This paper was accepted by Stefan Scholtes, healthcare management. Supplemental Material: The data files and online appendix are available at https://doi.org/10.1287/mnsc.2022.4488 .

Accommodation

Accommodation is the natural increase or decrease of the refraction of the eye lens as a function of the fixation distance. It relies on the proper elasticity of the natural eye lens. The evaluation of accommodation and the coupled convergent eye movements enables us to make the diagnosis of certain eye-related conditions and allows the differential diagnostic from some of the "neuroophthalmic diseases". This may avoid some unnecessary diagnostic procedures and reduce patient anxiety in terms of having a health threatening disease.

Patient with cataract – observations after 2 years of the pandemic and future prospects

Cataract is a disease in which the natural lens becomes completely or partially cloudy. During the pandemic, there was a significant decrease in the number of cataract surgeries performed compared to previous years, due to fear of the disease and the safety of the procedures performed. Cataract surgery should be performed in patients whose visual acuity deterioration has an impact on the performance of life or work activities. Due to the pandemic, some patients report to a more advanced stage of cataract, which leads to a reduction in their quality of life. Such surgery can be associated with a higher risk of surgical complications and longer recovery time. The development of new intraocular lens technologies, increased life expectancy, as well as changing lifestyles and increased activity of the elderly contribute to the increasing choice of premium intraocular lenses by patients. These lenses enable patients to achieve satisfactory uncorrected visual acuity not only for distance, but also for near and intermediate distances.

Comparing color vision impairment in natural lens and artificial lens groups

Comparing color vision impairment in natural lens and artificial lens groups

A white daisy on intraocular lens

We report two patients with precipitation of Pseudo-exfoliative material (PXF) material on intraocular lens (IOL), a rare entity, years after uneventful cataract surgery. The PXF material was present on the anterior surface of the IOL optic in a characteristic radiating spoke-like manner, a pattern resembling shape of a white daisy flower. Emphasis is given on differentiating features between PXF deposition on natural lens and PXF deposition on IOL. Furthermore, how opacification of IOL is different from PXF on IOL is briefly explained. In the first case, PXF deposits were not found elsewhere except on anterior IOL surface and in the second patient, pupillary involvement was also noted along with settling on IOL optic. The fellow eyes in both the patients did not have PXF. PXF on IOL is a vital sign and should not be overlooked as it can be the only clue warranting thorough glaucoma evaluation.

Pupil steering holographic display for pre-operative vision screening of cataracts.

Cataract is the most common cause of preventable blindness and vision loss where the only treatment is surgical replacement of the natural lens with an intraocular lens. Computer-generated holography (CGH) enables to control phase, size, and shape of the light beam entering through the eye-pupil. We developed a holographic vision simulator to assess visual acuity for patients to experience the postoperative corrected vision before going through surgery. A holographically shaped light beam is directed onto the retina using small non-cataractous regions of the lens with the help of a pupil tracker. A Snellen chart hologram is shown to subjects at desired depth with myopia and hyperopia correction. Tests with 13 patients demonstrated substantial improvements in visual acuity and the simulator results are consistent with the post-operative vision tests. Holographic simulator overperforms the existing vision simulators, which are limited to static pinhole exit pupils and incapable of correcting aberrations.

Visual Performance of Refractive Intraocular Lenses within the Human Eye

The most effective treatment for cataracts is to remove the cloudy crystalline natural lens and implant an intraocular lens (IOL) in its place. These refractive (IOL) provide the same focusing as do the natural lens. Two refractive IOLs are designed and analyzed in this paper—these IOL are made of (PMMA, and Acrylic). The quality of the retinal image is analyzed and compared with the healthy eye, which is based on the (Liou-Brennan) eye model) LBEM). Polychromatic Point Spread Function (PSF), Modulation Transfer Function (MTF), spot diagram, Encircled Energy (EE), and monochromatic aberration are used as acceptable criteria within the Zemax software.

Impact of ultraviolet radiation on the retina

Light has acrucial role in the visual process. For nonvisible radiation in the short-wave spectrum, there are natural mechanisms that protect the human retina from damaging ultraviolet (UV) radiation. Here, the dose (=energy) makes the poison. Damage caused by UV light mainly affects the outer retina, particularly the photoreceptors and the retinal pigment epithelium. While retinal damage due to increased UV radiation exposure can potentially still occur up to the age of20, in adulthood, exposure of the retina to UV radiation can no longer be assumed, due to decreasing transmission properties of the natural lens. The natural lens, modern intraocular lenses, and wearing of sunglasses with appropriate filter function, particularly in childhood and adolescence, provide arelevant reduction in UV radiation exposure of the retina.

The use of soft contact lens for intraocular foreign body removal to avoid inadvertent cataract formation.

Ocular injuries carry a significant morbidity worldwide. Visual outcomes vary depending on the mechanism of injury, the damage on arrival and the surgical technique used. The presence of an intraocular foreign body further complicates matters, due to its constituents, the infectious potential, and/or damage to intraocular structures. Another described problem is the inadvertent cataract formation due to contact with the natural lens during removal of the foreign body. The purpose of this paper is to describe a case with a mechanical foreign body lodging in the posterior chamber without harming the lens. The surgical challenge was to remove it without causing cataractous changes. Therefore, a soft contact lens was used to form a protective layer between the foreign body and the natural lens of the eye allowing successful removal of the foreign body.

Age-related changes in crystalline lens tilt and decentration: swept-source OCT study.

To investigate the age-related tilt and decentration of crystalline lenses using a swept-source optical coherence tomography biometer (SS-OCT) (CASIA2, Tomey Corp.). Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China. Cross-sectional study. The direction and magnitude of the crystalline lens were evaluated in 230 participants with ages ranging from 7 to 90 years using SS-OCT. The participants were divided into 4 age groups, and the differences among the groups were analyzed. Multiple linear regression was used to investigate the main factors influencing crystalline lens tilt and decentration. The natural crystalline lens tilted toward the inferotemporal direction with a mean magnitude of 4.3 ± 1.5 degrees (range 0.7 to 8.95 degrees). The mean decentration toward the superotemporal direction was 0.17 ± 0.12 mm (range 0.03 to 1.15 mm). There was mirror symmetry between the right and left eyes. There were statistically significant differences in the crystalline lens tilt and decentration among the age groups. Multiple linear regression showed that changes in crystalline lens tilt depended on angle α (P < .01) and anterior chamber depth (ACD; P = .008), whereas crystalline lens decentration depended on angle κ (P = .003), age (P < .01), and angle α (P = .002). Although there was a statistically significant difference in crystalline lens tilt and decentration among age groups, the variation in the crystalline lens position was partially affected by age. The crystalline lens tilt was greater in eyes with wider angle α and shallower ACD, whereas crystalline lens decentration was greater in younger eyes with wider angles κ and α.

Retinal image size in pseudophakia.

Approaches are developed to determine relative retinal magnifications in anisometropic patients undergoing cataract surgery; these can be used to balance between full spectacle corrections with equal intraocular lens (IOL) powers and a pure IOL power correction. The analysis started from the original and pseudophakic Navarro eye models, where in the latter case an IOL replaced the natural lens. A third model was a simplified Navarro-IOL model with a single surface cornea and a thin lens. These models were manipulated by altering vitreous length, corneal power and lens position. Retinal image sizes were determined for both full IOL corrections and full spectacle corrections by raytracing and approximate equations. Relative magnification (RM) was determined as the ratio of retinal image size of an eye to that of the appropriate standard eye. For raytracing and full IOL correction, vitreous length led to RM change of 5%/mm, while for corneal power and IOL position this was -0.4%/D and 1.4%/mm, respectively. For raytracing and spectacle correction, effects were 0%/D (vitreous depth), -1.6%/D (corneal power) and +1.0%/mm (IOL position). For full IOL correction, the approximate RM calculations were highly accurate. For spectacle correction, the approximate RM calculations were exact for vitreous length changes, reasonably accurate for corneal power changes but very inaccurate for changes in anterior chamber depth. Relative magnification approximations may be useful to assess the risk of aniseikonia in anisometropic patients targeted for postoperative emmetropia. Some of these patients would be corrected best by a combination of spectacles and IOLs.

The Economic Impact of Presbyopia.

Presbyopia is the world's number one cause of vision loss with more than 1 billion individuals affected globally. The total global costs associated with correcting near vision impairment due to uncorrected presbyopia have been estimated at $30.8 billion for a comprehensive eye care model. Both cost to the patient and cost to society, which is greater in low-income countries relative to high-income areas, should be considered. Ultimately, surgical correction of the nonaccommodating dysfunctional natural lens may provide the "cure" for presbyopia. Presbyopia-correcting intraocular lenses (IOLs) may provide better visual acuity and fewer adverse effects. Patients are pursuing cataract surgery at a younger and younger age. Although this expands the viable pool for lens exchange, this younger group of patients has extreme demands and has a much more scrutinizing frame of reference for comparison (a milder cataract). Thus, they are at a much higher risk for dissatisfaction and have a much higher chance of noticing potential adverse effects from multifocal IOLs. Setting appropriate expectations and thoroughly educating patients preoperatively helps create a partnership with the patient and a strong foundation for a successful surgical outcome. A cure for presbyopia has always been considered the holy grail of ophthalmology. In 2021, ophthalmologists are moving closer to achieving this goal while also creating a safer, more productive, cost-effective solution to presbyopia on an individual and on a global level. [J Refract Surg. 2021;37(6 Suppl):S17-S19.].

APPLICATION OF MICRORELIEF PLANARIZATION BY PHOTORESIST FOR CHARACTERIZATION OF DIFFRACTIVE ORIGINALS AT PRODUCTION OF BIFOCAL INTRAOCULAR LENS «MIOL-ACCORD»

Bifocal diffraction-refractive intraocular lenses (BDRIOL) are widely used in ophthalmology for replacing natural lenses that have been clouded by cataracts. In Russia, the REPER-NN company has developed a manufacturing technology for such BDRIOLS which based on the frontal polymerization of a liquid photopolymer placed between two transparent quartz matrices. The direct measurement of the light energy distribution over the foci after the manufactured quartz diffraction matrix is complicated by the fact that the diffraction relief depth corresponds to the polymer lens operation in the intraocular fluid and is therefore significantly greater than is required when working in air. We have developed a method for the energy distribution measuring over the foci of the BDRYOL diffraction component which based on the time planarization of the matrix relief by a photoresist layer. The diffraction relief filling with a material with a refractive index of a given value higher than refractive index of fused quartz makes it possible to achieve light focusing conditions equivalent to working in the intraocular environment, and also to measure the light energy distribution across the foci under conditions close to the calculated light wavelength in the visible range. The primary task at the moment is to obtain such a photoresist refractive index, which will provide the relief depth of the intraocular lens diffraction component, corresponding to the work in the vitreous body of the eye. The work is devoted to the selection of drying conditions and the method of measuring the photoresist refractive index.

Lens coating could help prevent cataract surgery complication

Cataracts can be corrected by replacing the opaque natural lens with an artificial one. But the surgery has a common complication called posterior capsule opacification, the formation of cloudy sca...

Lens regeneration: scientific discoveries and clinical possibilities.

In the process of exploring new methods for cataract treatment, lens regeneration is an ideal strategy for effectively restoring accommodative vision and avoiding postoperative complications and has great clinical potential. Lens regeneration, which is not a simple repetition of lens development, depends on the complex regulatory network comprising the FGF, BMP/TGF-β, Notch, and Wnt signaling pathways. Current research mainly focuses on in situ and in vitro lens regeneration. On the one hand, the possibility of the autologous stem cell in situ regeneration of functional lenses has been confirmed; on the other hand, both embryonic stem cells and induced pluripotent stem cells have been induced into lentoid bodies in vitro which are similar to the natural lens to a certain extent. This article will briefly summarize the regulatory mechanisms of lens development, describe the recent progress of lens regeneration, explore the key molecular signaling pathways, and, more importantly, discuss the prospects and challenges of their clinical applications to provide reference for clinical transformations.

Predicting Spatial Displacement Based on Intraocular Image Design Using Convolution Neural Network – Preliminary Findings

The main global cause for blindness is due to cataract. The common treatment for cataract is to have the cloudy natural lens to be removed and replace with an artificial intraocular lens (IOL). Success in the post cataract surgery depends on the design and quality of the IOL implanted on the eye. ISO11979-3 is the standard adhered to by many lens manufacturers, to test the mechanical stability of their lenses that were produced. This compression test experiments on the lab are very costly and time consuming. Alternatively, we propose to use the convolution neural network (CNN) to predict the spatial displacement response based on the intraocular image designs. Due to limited number of images in the datasets, data augmentation was performed to tranform these images and increase the sample size to 240. On top of this, the ResNet-50 deep learning network architecture was utilized to transfer the learning done on over millions of images. The final RMSE value for the training set, validation set and testing set were at 0.47mm, 2.93mm and 2.92mm respectively. The model predictabillity is well within the range recommended by the standard between 0.15 to 1.98 mm.

Lens in Primary Congenital Glaucoma Eyes Treated by Combined Angle and Filtering Surgery.

To report on the changes in the natural crystalline lens in primary congenital glaucoma (PCG) eyes that had undergone previous combined angle-filtering surgery with antimetabolites. The pediatric ophthalmology unit of the ophthalmology department of Alexandria Main University Hospital. A retrospective chart review. A retrospective chart review of patients presenting with and operated (by combined angle-filtering surgery with antimetabolites) for PCG in the period from 2005 to 2018. Any lens pathology was noted as well as the management and the outcome. The records of 422 children (613 eyes) were reviewed. Lens pathology was noted in 54 (8.8%) eyes. Abnormalities in lens clarity (cataract) were detected in 31 (56%) eyes, and abnormalities in lens position (subluxation) were detected in 24 (44%) eyes. Management options included observation (in 28 eyes), lensectomy for aphakia (in 14 eyes), lensectomy with in the bag intraocular lens (IOL) implantation (in 11 eyes), and lensectomy with iris-fixated IOL (in 1 eye). Elevation of intraocular pressure (IOP) occurred in only 4 eyes (of 26 operated eyes, 15.3%) after lens extraction. Changes in the natural crystalline lens clarity and/or position occurred in 8.8% (54 of 613) of PCG eyes operated by combined angle-filtering surgery with antimetabolites. Lens extraction was a relatively safe procedure with only 15% (4 of 26) of eyes suffering an elevation of IOP after lens extraction.

Distributions of crystalline lens tilt and decentration and associated factors in age-related cataract.

To investigate the characteristics and factors associated with crystalline lens tilt and decentration measured by CASIA2 anterior segment optical coherence tomography. Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China. Cross-sectional study. 1097 eyes of 1097 patients who planned to undergo cataract surgery were enrolled. All patients underwent a general ophthalmologic examination. Lens thickness (LT), front curvature radius (FCR), back curvature radius, lens equator diameter (LED), tilt, and decentration of preoperative crystalline lenses were measured by CASIA2. Univariate and multivariate regression analyses were performed to evaluate the relationships between the tilt and decentration of crystalline lens with related factors. The natural crystalline lenses showed a mean tilt of 5.16 degrees toward the inferotemporal direction and a mean decentration of 0.22 mm toward the temporal direction. Of the total 1097 eyes, 119 eyes (10.85%) had a tilt greater than 7 degrees, and 89 eyes (8.11%) had a decentration more than 0.4 mm. Multivariate regression analysis showed that larger decentration, thicker LT, shorter axial length (AL), and FCR were associated with greater lens tilt (P < .001, P = .007, P = .006, and P = .003, respectively). In addition, greater tilt, older and thinner LT were correlated with larger decentration (all P < .001). Preoperative crystalline lens had a certain degree of tilt and decentration in age-related cataract. The greater tilt of the crystalline lens was, the larger decentration of it was. In addition, AL, FCR, LT, and age also correlated with tilt and decentration.