Accommodative intraocular lenses: where are we and where we are going

Real-World Clinical Results with the Hoya Vivinex Impress Intraocular Lens with Enhanced Depth of Focus

BACKGROUND

In cataract surgery, intraocular lenses (IOLs) with enhanced depth of focus are an option to correct presbyopia. The purpose of this quality assurance analysis was to evaluate visual acuity and patient satisfaction after implantation of the Hoya Vivinex Impress IOL.

METHODS

The Hoya Vivinex Impress IOL was implanted in patients undergoing cataract surgery at the Pallas Klinik, Olten, Switzerland. Five weeks postoperatively, a clinical examination and a survey on patient satisfaction were conducted.

RESULTS

A total of 17 eyes (9 patients; mean age 64 years) underwent cataract surgery with implantation of a Hoya Vivinex Impress IOL. Five weeks postoperatively, mean uncorrected distance visual acuity (UDVA) was 0.2 logMAR, uncorrected intermediate visual acuity (UIVA) was 0.0 logMAR, and uncorrected near visual acuity (UNVA) was 0.2 logMAR. The mean distance-corrected visual acuity results were 0.0 logMAR, 0.1 logMAR, and 0.3 logMAR, respectively. Reading the newspaper without glasses was possible for 33.4% of patients. Visual disturbances such as halos and glares were not reported.

CONCLUSION

Cataract surgery with Hoya Vivinex Impress IOL implantation revealed good distance and intermediate vision and, in some patients, functional near vision as well as a high patient satisfaction.

Outcomes and predictive factors in multifocal and extended depth of focus intraocular lens implantation

PURPOSE OF REVIEW

Options for addressing presbyopia with intraocular lens (IOL) implantation have become more varied and sophisticated. We reviewed recent literature on multifocal and extended depth of focus (EDOF) IOLs in order to provide insight on their respective advantages, with emphasis on the visual outcomes of each design.

RECENT FINDINGS

Increased patient age, spectral domain optical coherence tomography (SD-OCT) abnormalities, abnormal optical axis measurements, and better preoperative visual acuity have been implicated as predictors of worse postoperative vision or visual quality in multifocal IOLs. Despite differences in objective outcomes, patient-reported outcomes such as satisfaction are consistently similar between multifocal and EDOF IOLs. EDOFs may have slightly lower rates of spectacle independence than trifocals, but there is more support for their use in the setting of with other ocular conditions.

SUMMARY

Multifocal and EDOF IOLs are both viable options for patients who wish to preserve near vision. Given their similar objective performance in many aspects, enabling patients to make informed decisions based on their expectations and visual requirements is critical to postoperative satisfaction. Evidence for advanced technology IOL implantation in pediatric patients remains inconclusive.

Estimation of the full shape of the crystalline lens from OCT: validation using stretched donor lenses

Quantifying human crystalline lens geometry as a function of age and accommodation is important for improved cataract and presbyopia treatments. In previous works we presented eigenlenses as a basis of 3-D functions to represent the full shape of the crystalline lens ex vivo. Also, we presented the application of eigenlenses to estimate the full shape of the lens in vivo from 3-D optical coherence tomography (OCT) images, where only the central part of the lens -visible through the pupil- is available. The current work presents a validation of the use of eigenlenses to estimate in vivo the full shape of dis-accommodated lenses. We used 14 ex vivo crystalline lenses from donor eyes (11-54 y/o) mounted in a lens stretcher, and measured the geometry and the power of the lenses using a combined OCT and ray tracing aberrometry system. Ex vivo, the full extent of the lens is accessible from OCT because the incident light is not blocked by the iris. We measured in non-stretched (fully accommodated) and stretched (mimicking in vivo dis-accommodated lenses) conditions. Then, we simulated computationally in vivo conditions on the obtained ex vivo lenses geometry (assuming that just the portion of the lens within a given pupil is available), and estimated the full shape using eigenlenses. The mean absolute error (MAE) between estimated and measured lens' diameters and volumes were MAE = 0.26 ± 0.18 mm and MAE = 7.0 ± 4.5 mm3, respectively. Furthermore, we concluded that the estimation error between measured and estimated lenses did not depend on the accommodative state (change in power due to stretching), and thus eigenlenses are also useful for the full shape estimation of in vivo dis-accommodated lenses.

Objective method for visual performance prediction

We propose, implement, and validate a new objective method for predicting the trends of visual acuity through-focus curves provided by specific optical elements. The proposed method utilized imaging of sinusoidal gratings provided by the optical elements and the definition of acuity. A custom-made monocular visual simulator equipped with active optics was used to implement the objective method and to validate it via subjective measurements. Visual acuity measurements were obtained monocularly from a set of six subjects with paralyzed accommodation for a naked eye and then that eye compensated by four multifocal optical elements. The objective methodology successfully predicts the trends of the visual acuity through-focus curve for all considered cases. The Pearson correlation coefficient was 0.878 for all tested optical elements, which agrees with results obtained by similar works. The proposed method constitutes an easy and direct alternative technique for the objective testing of optical elements for ophthalmic and optometric applications, which can be implemented before invasive, demanding, or costly procedures on real subjects.

Estimation of the full shape of the crystalline lens in-vivo from OCT images using eigenlenses

Quantifying the full 3-D shape of the human crystalline lens is important for improving intraocular lens power or sizing calculations in treatments of cataract and presbyopia. In a previous work we described a novel method for the representation of the full shape of the ex vivo crystalline lens called eigenlenses, which proved more compact and accurate than compared state-of-the art methods of crystalline lens shape quantification. Here we demonstrate the use of eigenlenses to estimate the full shape of the crystalline lens in vivo from optical coherence tomography images, where only the information visible through the pupil is available. We compare the performance of eigenlenses with previous methods of full crystalline lens shape estimation, and demonstrate an improvement in repeatability, robustness and use of computational resources. We found that eigenlenses can be used to describe efficiently the crystalline lens full shape changes with accommodation and refractive error.

Accommodative movements of the choroid in the optic nerve head region of human eyes, and their relationship to the lens

The ciliary muscle (CM) powers the accommodative response, and during accommodation the CM pulls the choroid forward in the region of the ora serrata. Our goal was to elucidate the accommodative movements of the choroid in the optic nerve region in humans and to determine whether these movements are related to changes in the lens dimensions that occur with aging, in the unaccommodated and accommodated state. Both eyes of 12 human subjects (aged 18-51 yrs) were studied. Homatropine (1 drop/5%) was used to relax the ciliary muscle (unaccommodated or "resting" eye) and pilocarpine was used to induce the maximum accommodative response (2 drops/4%) (accommodated eye). Images of the fundus and choroid were collected in the region of the optic nerve (ON) via Spectralis OCT (infrared and EDI mode), and choroidal thickness was determined. Ultrasound biomicroscopy (UBM; 50 MHz, 35 MHz) images were collected in the region of the lens/capsule and ciliary body. OCT and UBM images were collected in the resting and accommodated state. The unaccommodated choroidal thickness declined significantly with age (p = 0.0073, r = 0.73) over the entire age range of the subjects studied (18-51 years old). The choroidal thickness was significantly negatively correlated with lens thickness in the accommodated (p = 0.01) and the unaccommodated states (p = 0.005); the thicker the lens the thinner the choroid. Choroid movements around the optic nerve during accommodation were statistically significant; during accommodation the choroid both thinned and moved centrifugally (outward/away from the optic nerve head). The accommodative choroid movements did not decline significantly with age and were not correlated with accommodative amplitude. Measurement of the choroidal thickness is possible with the Spectralis OCT instrument using EDI mode and can be used to determine the accommodative changes in choroidal thickness. The choroidal thickness decreased with age and during accommodation. It may be that age-related choroidal thinning is due to changes in the geometry of the accommodative apparatus to which it is attached (i.e., ciliary muscle/lens complex) such that when the lens is thicker, the choroid is thinner. Accommodative decrease in choroidal thickness and stretch of the retina/choroid may indicate stress/strain forces in the region of the optic nerve during accommodation and may have implications for glaucoma.

Recent Advances of Intraocular Lens Materials and Surface Modification in Cataract Surgery

Advances in cataract surgery have increased the demand for intraocular lens (IOL) materials. At present, the progress of IOL materials mainly contains further improving biocompatibility, providing better visual quality and adjustable ability, reducing surgical incision, as well as dealing with complications such as posterior capsular opacification (PCO) and ophthalmitis. The purpose of this review is to describe the research progress of relevant IOL materials classified according to different clinical purposes. The innovation of IOL materials is often based on the common IOL materials on the market, such as silicon and acrylate. Special properties and functions are obtained by adding extra polymers or surface modification. Most of these studies have not yet been commercialized, which requires a large number of clinical trials. But they provide valuable thoughts for the optimization of the IOL function.

Natural Antioxidant Activities of Plants in Preventing Cataractogenesis

A cataract is a condition that causes 17 million people to experience blindness and is the most significant cause of vision loss, around 47.9%. The formation of cataracts is linked to both the production of reactive oxygen species (ROS) and the reduction of endogenous antioxidants. ROS are highly reactive molecules produced by oxygen. Examples of ROS include peroxides, super-oxides, and hydroxyl radicals. ROS are produced in cellular responses to xenobiotics and bacterial invasion and during mitochondrial oxidative metabolism. Excessive ROS can trigger oxidative stress that initiates the progression of eye lens opacities. ROS and other free radicals are highly reactive molecules because their outer orbitals have one or more unpaired electrons and can be neutralized by electron-donating compounds, such as antioxidants. Examples of natural antioxidant compounds are vitamin C, vitamin E, and beta-carotene. Numerous studies have demonstrated that plants contain numerous antioxidant compounds that can be used as cataract preventatives or inhibitors. Natural antioxidant extracts for cataract therapy may be investigated further in light of these findings, which show that consuming a sufficient amount of antioxidant-rich plants is an excellent approach to cataract prevention. Several other natural compounds also prevent cataracts by inhibiting aldose reductase and preventing apoptosis of the eye lens.

Assessing accommodative presbyopic biometric changes of the entire anterior segment using single swept-source OCT image acquisitions

BACKGROUND/OBJECTIVES

To evaluate biometric changes throughout the anterior chamber during accommodation and presbyopia using single image acquisition swept-source anterior-segment optical coherence tomography (AS-OCT).

SUBJECT/METHODS

Anterior-segment images were obtained using a new swept-source AS-OCT device (ANTERION, Heidelberg Engineering) from healthy volunteers (n = 71) across two centers in this prospective observational case series. In one image acquisition, cornea through posterior lens, including the ciliary muscle on both sides of the right eye, was imaged. Subjects undertook no accommodative effort and -1, -3, and -5 D of target vergence. Two-way repeated measures ANOVA modeling was performed for ciliary muscle measurements, lens parameters, aqueous depth (AD), and pupil diameter (PD). The first ANOVA factor was accommodative stimuli, and the second factor included age and refractive status.

RESULTS

Maximum ciliary muscle thickness increased with accommodative stimuli (p < 0.001), while the distance from the scleral spur to the maximal point on the ciliary muscle and posterior ciliary muscle thickness (CMT2) decreased (p < 0.001-0.002). Older individuals showed no accommodative changes for ciliary muscle parameters, lens thickness, lens vault, PD, and AD (p = 0.07-0.32). Younger- and middle-aged eyes showed statistically significant accommodative structural alterations for these endpoints (p < 0.001-0.002), but with different patterns, including early loss of CMT2 contraction in middle-aged eyes. Within the middle-aged group, myopic eyes maintained better capacity for accommodative structural change.

CONCLUSIONS

Swept-source AS-OCT demonstrated multiple simultaneous anterior-segment biometric alterations in single acquisition images, including early loss of posterior ciliary muscle function and better maintained capacity for anterior-segment structural change in myopia.

Citation network analysis of the various types of multifocal intraocular lenses

BACKGROUND AND OBJECTIVE

The implantation of multifocal intraocular lens (IOL) has increased in recent years, allowing patients to achieve good quality vision at all distances, independence from use of glasses, and consequently, an increase in quality of life. The main purpose of this study was to analyse the links between publications and authors via citation networks, as well to as identify the different research areas and determine the most cited publications.

MATERIAL AND METHODS

The publication search was performed through the Web of Science database, using the terms «Multifocal intraocular lens», «Bifocal intraocular lens», «Trifocal intraocular lens», «Diffractive intraocular lens», «Refractive intraocular lens», «Accommodative intraocular lens» and «Extended depth of focus intraocular lens», for a time interval from 1989 to August 2020. The software used to analyse the publications was the Citation Network Explorer.

RESULTS

A total of 1293 publications were found, with 11,730 citations generated in the network, and 2019 had the highest number of publications of any year. The most cited publication was «European multicenter study of the AcrySof ReSTOR apodized diffractive intraocular lens» by Kohnen et al., published in 2006. Four groups about different research areas in this field were found using the Clustering functionality: visual quality, IOL designs, ocular aberrations, or defocus curves.

CONCLUSIONS

The citation network offers an objective and comprehensive analysis of the main articles on the different designs and classes of multifocal IOL.

Biofabrication of Artificial Stem Cell Niches in the Anterior Ocular Segment

The anterior segment of the eye is a complex set of structures that collectively act to maintain the integrity of the globe and direct light towards the posteriorly located retina. The eye is exposed to numerous physical and environmental insults such as infection, UV radiation, physical or chemical injuries. Loss of transparency to the cornea or lens (cataract) and dysfunctional regulation of intra ocular pressure (glaucoma) are leading causes of worldwide blindness. Whilst traditional therapeutic approaches can improve vision, their effect often fails to control the multiple pathological events that lead to long-term vision loss. Regenerative medicine approaches in the eye have already had success with ocular stem cell therapy and ex vivo production of cornea and conjunctival tissue for transplant recovering patients' vision. However, advancements are required to increase the efficacy of these as well as develop other ocular cell therapies. One of the most important challenges that determines the success of regenerative approaches is the preservation of the stem cell properties during expansion culture in vitro. To achieve this, the environment must provide the physical, chemical and biological factors that ensure the maintenance of their undifferentiated state, as well as their proliferative capacity. This is likely to be accomplished by replicating the natural stem cell niche in vitro. Due to the complex nature of the cell microenvironment, the creation of such artificial niches requires the use of bioengineering techniques which can replicate the physico-chemical properties and the dynamic cell-extracellular matrix interactions that maintain the stem cell phenotype. This review discusses the progress made in the replication of stem cell niches from the anterior ocular segment by using bioengineering approaches and their therapeutic implications.

Presbyopia Treatments by Mechanism of Action: A New Classification System Based on a Review of the Literature

Presbyopia, a loss of accommodative ability associated with aging, is a significant cause of vision impairment globally. At the clinical level, it is a frustrating and difficult issue that negatively impacts patients’ quality of life. Less appreciated is the fact that loss of accommodative ability and its current treatments methods may present safety concerns, for example, increasing the risk of falls. Therefore, a more complete understanding of treatment options with respect to how they relate to the natural ability of the eye is needed to improve decision making and to aid clinicians in individualizing treatment options. This article reviews the options for expanding functional through focus—a term coined to describe the ability of the eye to see at all distances with minimal latency—by how they vary the refractive power over time, across the visual field, between eyes, or across a range of distances.

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Factors Affecting Posterior Capsule Opacification in the Development of Intraocular Lens Materials

Posterior capsule opacification (PCO) is the most common complication arising from the corrective surgery used to treat cataract patients. PCO arises when lens epithelial cells (LEC) residing in the capsular bag post-surgery undergo hyper-proliferation and transdifferentiation into myofibroblasts, migrating from the posterior capsule over the visual axis of the newly implanted intraocular lens (IOL). The developmental pathways underlying PCO are yet to be fully understood and the current literature is contradictory regarding the impact of the recognised risk factors of PCO. The aim of this review is firstly to collate the known biochemical pathways that lead to PCO development, providing an up-to-date chronological overview from surgery to established PCO formation. Secondly, the risk factors of PCO are evaluated, focussing on the impact of IOLs’ properties. Finally, the latest experimental model designs used in PCO research are discussed to demonstrate the ongoing development of clinical PCO models, the efficacy of newly developed IOL technology, and potential therapeutic interventions. This review will contribute to current PCO literature by presenting an updated overview of the known developmental pathways of PCO, an evaluation of the impact of the risk factors underlying its development, and the latest experimental models used to investigate PCO. Furthermore, the review should provide developmental routes for research into the investigation of potential therapeutic interventions and improvements in IOL design in the aid of preventing PCO for new and existing patients.

Presbyopia - A Review of Current Treatment Options and Emerging Therapies

Presbyopia is a common age-related vision disorder characterized by a progressive inability to focus on near objects. If uncorrected or under-corrected, presbyopia can significantly impact patients' quality of life. Presbyopia represents an area of considerable unmet need due to its rising prevalence worldwide as the population ages, the high proportion of under-treated individuals in some parts of the world, and the limitations of currently available corrective methods. Progressive or bifocal spectacles are associated with peripheral blur, a restricted visual field and impaired depth perception, which have been linked to an increased risk of falls in the elderly. Contact lens options can be difficult to maintain due to the development of age-related dry eye symptoms and reduced manual dexterity. Other corrective methods involve surgical interventions that modify the optics of the cornea, replace the crystalline lens, or attempt to restore active accommodation. While patients undergoing surgery report satisfactory outcomes post-operatively, many of them eventually require reading glasses. Non-invasive therapies with novel mechanisms of action are currently being investigated; these include miotic agents and UNR844, a lipoic acid choline ester. In this narrative review, available evidence on presbyopia prevalence, quality of life impact and risk factors are described, with a focus on observational studies in non-clinical settings. The diagnosis pathway and patient journey in presbyopia are outlined, and various treatment options are analyzed. The data reviewed herein reveals significant gaps in the provision of vision correction for this common condition, with a paucity of effective, non-invasive treatment options broadly accessible to presbyopic individuals.

A numerical investigation of changes in lens shape during accommodation

The purpose of this study was to investigate how the mechanical properties and geometry of the lens influence the changes in lens shape during accommodation. To do so, ex vivo stretching tests of the isolated lens were simulated via finite element analysis. In these tests, the lens is stretched from the accommodated state to the non-accommodated state. Several key characteristics of the lens were studied: the stiffness gradient of the lens material, the distribution of the capsule thickness, the mechanical properties of the capsule and the material comprising the lens, nucleus and cortex, and the influence of two different age-related lens geometries (17 and 29 y/o subjects). To determine the effects on the changes in lens shape during accommodation, changes in the anterior and posterior radius, the lens and nucleus thicknesses and the equatorial lens diameter were analysed. The results suggest that multiple factors exert statistically significant influences on how the lens changes its shape, but two factors predominate over the rest: the stiffness ratio between the nucleus and cortex and the stiffness of the capsule, specifically the posterior surface.

Measurement properties of reading tests in subjects with maculopathy

PURPOSE

A reliable reading test provides a standardized measure of the visual component of reading performance. This study evaluated reproducibility, agreement and feasibility of five Dutch language continuous text reading tests used in clinical practice and research in visually impaired participants.

METHODS

In 42 participants with macular pathologies (mean age 77 years), the Colenbrander Reading Card (Colenbrander), International Reading Speed Texts (IReST), Laboratory of Experimental Ophthalmology (LEO) charts, 'de Nederlanders' (NED) and the Radner Reading Charts (Radner) were evaluated. The coefficient of repeatability was calculated for different reading parameters, and agreement between the reading tests was determined.

RESULTS

Between the reading tests, the differences found in repeatability for reading performance were mainly within the limit of one line (0.1 logMAR). Exceptions were the inter-session repeatability for critical print size: Colenbrander (0.35 logMAR), LEO (0.34), Radner (0.23). The highest agreement was found between the LEO and Radner; Reading acuity bias 0.03 logMAR (SD 0.10), CPS 0.03 (0.12).

CONCLUSION

This study shows that reading performance results obtained with reading tests are not always reliable and reading parameters could not always be properly assessed in participants with maculopathies. Therefore, choices regarding which reading test to use especially for research purposes should be based on both the feasibility and reliability of the reading test. The NED (a historical test) was the least feasible, and it is recommend that this test is no longer used. To allow standardized and comparable analysis of reading performance a highly standardized reading test, like the Radner is recommended.

Simulating Outcomes of Cataract Surgery: Important Advances in Ophthalmology

As the human eye ages, the crystalline lens stiffens (presbyopia) and opacifies (cataract), requiring its replacement with an artificial lens [intraocular lens (IOL)]. Cataract surgery is the most frequently performed surgical procedure in the world. The increase in IOL designs has not been paralleled in practice by a sophistication in IOL selection methods, which rely on limited anatomical measurements of the eye and the surgeon's interpretation of the patient's needs and expectations. We propose that the future of IOL selection will be guided by 3D quantitative imaging of the crystalline lens to map lens opacities, anticipate IOL position, and develop fully customized eye models for ray-tracing-based IOL selection. Conversely, visual simulators (in which IOL designs are programmed in active elements) allow patients to experience prospective vision before surgery and to make more informed decisions about which IOL to choose. Quantitative imaging and optical and visual simulations of postsurgery outcomes will allow optimal treatments to be selected for a patient undergoing modern cataract surgery.

Citation network analysis of the various types of multifocal intraocular lenses

BACKGROUND AND OBJECTIVE

The implantation of multifocal intraocular lens (IOL) has increased in recent years, allowing patients to achieve good quality vision at all distances, independence from use of glasses, and consequently, an increase in quality of life. The main purpose of this study was to analyse the links between publications and authors via citation networks, as well to as identify the different research areas and determine the most cited publications.

MATERIAL AND METHODS

The publication search was performed through the Web of Science database, using the terms «Multifocal intraocular lens», «Bifocal intraocular lens», «Trifocal intraocular lens», «Diffractive intraocular lens», «Refractive intraocular lens», «Accommodative intraocular lens» and «Extended depth of focus intraocular lens», for a time interval from 1989 to August 2020. The software used to analyse the publications was the Citation Network Explorer.

RESULTS

A total of 1293 publications were found, with 11730 citations generated in the network, and 2019 had the highest number of publications of any year. The most cited publication was «European multicenter study of the AcrySof ReSTOR apodized diffractive intraocular lens» by Kohnen et al., published in 2006. Four groups about different research areas in this field were found using the Clustering functionality: visual quality, IOL designs, ocular aberrations, or defocus curves.

CONCLUSIONS

The citation network offers an objective and comprehensive analysis of the main articles on the different designs and classes of multifocal IOL.

Use of presbyopia-correcting intraocular lenses in patients with prior corneal refractive surgery

PURPOSE OF REVIEW

Corneal refractive surgery has achieved spectacle-free vision for millions of patients, but this aging population is now developing cataracts. Many of these patients may wish to avoid reliance on glasses after cataract surgery. Presbyopia-correcting intraocular lenses (IOLs) offer a solution, but corneal changes after refractive surgery may compound higher order aberrations and dysphotopic symptoms associated with these IOLs. This review aims to discuss potential factors that could aid in determining suitable postkeratorefractive candidates for presbyopia-correcting IOLs.

RECENT FINDINGS

Studies investigating which preoperative measures influence outcomes are lacking. The few studies that have examined presbyopia-correcting IOLs in postkeratorefractive patients report that satisfactory outcomes are possible. However, recommendations for preoperative thresholds appear limited to expert opinion and studies involving virgin corneas.

SUMMARY

As the number of presbyopia-correcting IOLs and postkeratorefractive patients grows, continued investigation into relevant preoperative factors and appropriate IOLs is required to make evidence-based decisions. The current literature shows that with rigorous counseling and appropriate patient selection, presbyopia-correcting IOLs can provide postkeratorefractive patients with satisfactory results and spectacle independence. In addition, the development of postoperative modifiable IOLs may prove to be the preferred option.

Future Intraocular Lens Technologies

The future of intraocular lens (IOL) technology has already begun with a number of recent innovations. The postoperative change of refractive power will lead to a customized fine-tuning that provides patients with the individual vision they expect and with as much spectacle independence as possible. The latest-generation (2.0) Light-Adjustable Lens (RxSight) was recently introduced into clinical practice, with the first results being very encouraging. Other methods of altering the power of an already implanted IOL are under development. The same can be said about the correction of presbyopia, the so-called last frontier in refractive surgery. Extended depth-of-focus IOLs have been introduced, as has the technology of the pinhole IOL. The latter has therapeutic potential beyond the refractive aspect and has already proven helpful in cases of iris defects and irregular corneas. Several technologies are currently being tested to achieve-finally-an accommodative IOL. One such concept uses the (remaining) strength of the ciliary muscle, whereas another is triggered by the pupil reaction when shifting focus from far to near. Not an IOL itself, but rather a high-tech innovation that so far has mostly been implanted during cataract surgery, is a microelectronic sensor that measures habitual intraocular pressure (IOP) at any given time and promises to revolutionize the management of glaucoma patients. The last generation of this device (Eyemate; Implandata Opthalmics Products GmbH) is implanted during small-incision cataract surgery; the latest development is an even smaller sensor that will be inserted suprachoroidally before, in the near future, such a device will be part of a capsular ring. These IOP sensors are a prime example that IOL technology will continue to be a driving force in ophthalmology, with a positive impact far beyond cataract surgery.

Lens-based surgical correction of presbyopia. Where are we in 2020?

INTRODUCTION

Presbyopia is the progressive and irreversible loss of accommodation due to aging. It is one of the main causes of loss of quality of life in people from 45 years of age, due to the, often novel, dependence on spectacles. The eagerness to correct it by ophthalmologists impulsed by the desire of millions of people who suffer from it, has become one of the main drivers for the development of intraocular lens (IOL) technology over the last twenty years.

MATERIAL AND METHODS

This review briefly presents the different alternatives that have allowed us to improve the crystalline lens surgical approach of presbyopia; from monofocal lenses and monovision technique, accommodative, refractive, and diffractive multifocal lenses, and finally the most recent extended depth of focus/field lenses known as EDOFs.

RESULTS

Each IOL has its advantages, limitations and disadvantages. Furthermore, there is no single lens that suits the needs of all patients.

CONCLUSIONS

It is necessary to know the variety of lenses available, and to have an in-depth understanding of their optical properties, as well as the impact that these will have later on their clinical performance and on the visual quality of the patients. This should help us to select the best alternative for each of them.

Refractive surgery beyond 2020

Refractive surgery refers to any procedure that corrects or minimizes refractive errors. Today, refractive surgery has evolved beyond the traditional laser refractive surgery, embodied by the popular laser in situ keratomileusis or 'LASIK'. New keratorefractive techniques such as small incision lenticule extraction (SMILE) avoids corneal flap creation and uses a single laser device, while advances in surface ablation techniques have seen a resurgence in its popularity. Presbyopic treatment options have also expanded to include new ablation profiles, intracorneal implants, and phakic intraocular implants. With the improved safety and efficacy of refractive lens exchange, a wider variety of intraocular lens implants with advanced optics provide more options for refractive correction in carefully selected patients. In this review, we also discuss possible developments in refractive surgery beyond 2020, such as preoperative evaluation of refractive patients using machine learning and artificial intelligence, potential use of stromal lenticules harvested from SMILE for presbyopic treatments, and various advances in intraocular lens implants that may provide a closer to 'physiological correction' of refractive errors.

A Novel Concept of Correcting Presbyopia: First Clinical Results with a Phakic Diffractive Intraocular Lens

Purpose

To evaluate the effect of a novel technique to correct presbyopia. A phakic IOL (presbyopic IPCL; implantable phakic contact lens) with a diffractive optic is implanted and its impact on visual acuity, refraction, patient satisfaction in patients striving for spectacle-independence is evaluated.

Design

Retrospective noncomparative open-label clinical trial.

Methods

Sixteen eyes of 8 patients (average age 47 years) had a presbyopic IPCL implanted in the posterior chamber. The visual acuity on different distances, refractive status, corneal topography, endothelial cell density, anterior chamber depth, white-to-white, mesopic pupil size and intraocular pressure (IOP) were measured before implantation of this novel phakic IOL with diffractive optic and four weeks after surgery.

Results

At follow-up four weeks after surgery, 9 of the 16 eyes were emmetropic and uncorrected distance visual acuity was at least 0.8. Near vision was excellent in all patients without the need to wear reading glasses. There was neither a significant change in IOP nor a significant surgical impact on endothelial cells. Patient satisfaction was high. There was no major complaint of halos or glare.

Conclusion

The presbyopic IPCL can provide the presbyopic patient with good visual acuity and spectacle-independence for far and near distance. We found this novel technique to have a good safety profile during the surgical procedure and our short follow-up period. Further long-term follow-up is mandatory.

Risk of falls and injuries requiring hospitalisation after first-eye cataract surgery in elderly Australians

PURPOSE

To investigate the impact of the type of the intraocular lenses (IOLs) in first-eye cataract surgery in elderly people on the risk of hospitalisation due to falls and injuries.

METHODS

A retrospective cohort study was conducted using the Australian Government Department Veterans' Affairs claims data. All people aged 65 years and above who had first cataract surgery between January 2007 and July 2017 were identified. Two cohorts were established depending on the type of IOL-monofocal and multifocal. The risk of injuries and falls requiring hospitalisation in the first 3 months post the surgery was assessed using Cox proportional hazard models with age at entry as primary time scale and adjusting for gender, comorbidities and prior history of falls.

RESULTS

There were 45 728 people across the two cohorts with the majority receiving monofocal lenses (97%), followed by multifocal lenses (3%) at the time of first cataract surgery. The risk of injury and falls was lower (but not significant) in the multifocal cohort compared to monofocal cohort (adjusted hazard ratio (aHR) 0.56, 95% CI 0.26-1.17). The risk was also lower (but not significant) when stratifying by age group at the time of the surgery.

CONCLUSIONS

Regardless of age, multifocal lenses did not appear to be associated with the higher risk of serious injuries and falls after first-eye cataract surgery compared to monofocal lenses.

Optimization of the Light Sword Lens for Presbyopia Correction

Purpose

We propose and evaluate the modifications of a light sword lens (LSL) to obtain better performance for distance vision while maintaining good operation for near and intermediate vision.

Methods

The modifications consisted of assigning angular or circular windows for distance vision while rescaling the LSL profile in the remaining area of the element. The objective performance of the redesigned LSLs was verified numerically by the Strehl ratio and experimentally using correlation coefficients and Michelson contrast. Subjective assessments were provided by monocular visual acuity (VA) and contrast sensitivity (CS) through-focus curves for six patients with paralyzed accommodation. The tested object vergence range was [-4.0, 0.0] diopters (D). All experiments were conducted in a custom-made monocular visual simulator.

Results

Computational simulations and objective experiments confirmed the better performance of the modified LSL for the imaging of distant objects. The proposed angular and radial modulations resulted in flat VA and CS through-focus curves, indicating more uniform quality of vision with clearly improved distance vision. The VA provided by the modified LSL profiles showed a maximal improvement of 1.5 lines of acuity with respect to the VA provided by the conventional LSL at distance vision.

Conclusions

Optimized LSLs provide better imaging of distant objects while maintaining a large depth of focus. This results in comparable and acceptable quality for distance, intermediate, and near vision. Therefore, the modified LSLs appear to be promising presbyopia correctors.

Translational Relevance

The new design of LSL reveals an improved performance for all ranges of vision and becomes a promissory element for a real presbyopia correction in clinical applications.

Model of the light sword intraocular lens: in-vitro comparative studies

This work presents the first models of light sword intraocular lenses (LS IOLs) with angularly modulated optical power. We performed an experimental, comparative study with multifocal and extended depth of focus intraocular lenses, which are available on the market. The measurements conducted in an original optical bench were utilised for an analysis of point spread functions, elongated foci, modulation transfer functions and the areas defined by them. The LS IOL models perform homogeneous imaging in the whole range of designed defocus. The proposed concept of extended depth of focus seems to be promising for the development of presbyopia-correcting intraocular lenses capable of regaining fully functional vision.

Optimized multielement accommodative intraocular lens with a four-freeform-surface Alvarez lens and a separate aspheric lens

This paper proposes an accommodative intraocular lens (IOL), which consists of a two-element Alvarez lens and an aspheric lens for changing focal power and refractive power, respectively. The four-freeform-surface Alvarez lens is optimized for a multiple field of view; further, the aspheric lens also corrects the aberrations induced by the corneal asphericity of the human eye over the whole range of accommodation. A simulation using optical design software demonstrates its excellent performance in that the values of the modulation transfer function at 100 cycles/mm all reach ∼0.4 with a ±5° field of view for 3 and 5 mm pupils.

Electrically variable liquid crystal lenses for ophthalmic distance accommodation

We present the example of a specific design of an electrically tunable liquid crystal lens (TLCL) with floating electrode to analyze experimentally the potential of using TLCLs in intraocular implants. An optimized voltage-frequency driving technique is demonstrated to achieve high optical powers (up to 4 diopters) with very low aberrations (below 0.1μm) for an optical aperture of 3mm. In addition, the continuous character of distance accommodation and the absence of granularity across the aperture of the lens (pixel-free) make this component an excellent choice for various ophthalmic applications.

Contributions of shape and stiffness to accommodative loss in the ageing human lens: a finite element model assessment

Ageing changes to the various components of the accommodative system of the eye lens contribute to the loss of focusing power. The relative contributions of each ageing component, however, are not well defined. This study investigates the contribution of geometric parameters and material properties on accommodation, simulated using models based on human lenses aged 16, 35, and 48 years. Each model was tested using two different sets of material properties and a range of zonular fiber angles and was compared to results from in vivo measurements. The geometries and material parameters of older and younger lens models were interchanged to investigate the role of shape and material on accommodative capacity. Results indicate that geometry has the greater role in accommodation.

Advances and challenges of intraocular lens design [Invited]

Phacoemulsification technique with intraocular lens implantation has been a common treatment for cataract patients. With rising demand among the public, new technologies for lens design have emerged to minimize intraocular aberrations, improving visual quality to the largest extent. This paper systematically reviews the development of materials applied in lens manufacturing, the different categories of intraocular lenses, and respective design principles. The advantages and potential drawbacks of intraocular lenses are illustrated in the paper, and prospective research to improve the design are presented in the end.

Premium intraocular lenses: The past, present and future

Purpose

To present potential benefits as well as limitations of premium intraocular lens (IOL) use, and provide insight in future of premium cataract surgery.

Methods

Bibliographic research was performed in PubMed/Medline database, and the most recently updated papers were evaluated. Keywords used were: premium intraocular lens, multifocal intraocular lens, toric intraocular lens, toric multifocal intraocular lens, accommodative intraocular lens, and the respective brand names.

Results

Multifocal IOLs provide uncorrected distance visual acuity (UDVA) of 0.03 logMAR in 82.3%–95.7% of patients and overall spectacle independence in 81%–85% of patients. Toric IOLs provide UDVA of 0.3 logMAR in 70%–95% of patients, residual astigmatism of 1 D or less is noted in 67%–88% of patients, and spectacle independence is reported in 60%–85% of patients. Toric multifocal IOLs provide UDVA of 0.3 logMAR in 92%–97% of patients, and spectacle independence is reported in 79%–90% of patients. Accommodative IOLs represent intensively developing field in ophthalmology, and the results are still variable depending on the IOL model.

Conclusions

Premium IOL technology and advanced surgical techniques have significantly improved postoperative visual outcomes. Future developments will potentiate development of new premium IOL designs that will provide spectacle independence and excellent visual outcomes after cataract surgery.