Effect of intraocular lens glistening size on visual quality

3D monitoring of the microphase separations inside the intraocular lens

Glistenings often occur after implanting the intraocular lens (IOL) due to the formation of numerous microvacuoles (MVs) and may lead to deterioration of vision quality. Previous studies showed the formation of MVs was associated with the hydrophobicity of IOL materials. Yet, the mechanism remains an open question due to the complexity of IOL polymer networks. In this study, two commercialized IOLs with similar hydrophobicity are found distinct in the formation of MVs. The 3D growth kinetics of MVs during cooling processes are captured for the first time by digital holographic microscopy (DHM) and the components of MVs are measured by DHM and Raman spectroscopy. The results reveal that the growth of MVs stems from the microphase separation of water and surrounding IOL polymers. A polymer swelling model is thus proposed to describe the microphase separation process which is found dependent on the elasticity of IOL polymer networks. The total volume of MVs is determined by the IOL hydrophobicity, while the elastic force of IOL polymer networks determines the number density and size of MVs. This study demonstrates an approach for characterizing the phase separation of crosslinked polymeric materials in biosystems and sheds lights on the refinement of IOL materials. STATEMENT OF SIGNIFICANCE: Glistenings due to the formation of numerous microvacuoles (MVs) in intraocular lens (IOL) can occur after IOL implantation, which may induce poor quality of vision. However, the underlying mechanism of MVs formation is still an open question. This study establishes an in-situ 3D imaging platform to monitor growth kinetics of the MVs in IOLs, which allows to uncover the mechanism of glistenings formation resulting from the microphase separation. The findings imply the material hydrophobicity influences the total volume of MVs, while the local elasticity of IOL polymer networks determines the number density and the size of MVs. This study offers a new approach for characterizing phase separation in crosslinking biosystems and sheds lights on the refinement of IOL materials.

Comparative study of the glistening between four intraocular lens models assessed by OCT and deep learning

PURPOSE

To evaluate the glistening in 4 different models of intraocular lenses (IOLs) using optical coherence tomography (OCT) and deep learning (DL).

SETTING

Centro Internacional de Oftalmología Avanzada (Madrid, Spain).

DESIGN

Cross-sectional study.

METHODS

325 eyes were assessed for the presence and severity of glistening in 4 IOL models: ReSTOR+3 SN6AD1 (n = 41), SN60WF (n = 110), PanOptix TFNT (n = 128) and Vivity DFT015 (n = 46). The presence of glistening was analyzed using OCT, identifying the presence of hyperreflective foci (HRF) in the central area of the IOL. A manual and an original DL-based quantification algorithm designed for this purpose was applied.

RESULTS

Glistening was detected in 22 (53.7%) ReSTOR SN6AD1, 44 (40%) SN60WF, 49 (38.3%) PanOptix TFNT, and 4 (8.7%) Vivity DFT015 IOLs, when any grade was considered. In the comparison of the different types of IOLs, global glistening measured as total HRF was 17.3 ± 25.9 for the ReSTOR+3; 9.3 ± 15.7 for the SN60WF; 6.9 ± 10.5 for the PanOptix; and 1.2 ± 2.6 for the Vivity ( P < .05). There was excellent agreement between manual and DL-based quantification (≥0.829).

CONCLUSIONS

It is possible to quantify, classify and compare the glistening severity in different IOL models using OCT images in a simple and objective manner with a DL algorithm. In the comparative study, the Vivity presented the lowest severity of glistening.

Glistening on intraocular lenses: A review

The glistening in intraocular lenses (IOLs) is a phenomenon in which tiny water-filled microvacuoles (MVs) form within the IOL material, causing light to scatter and create a sparkling or shimmering effect. The presence of glistening is common in many types of IOL materials and models and has been extensively studied in recent years to determine its incidence, risk factors, evolution, and possible clinical relevance. Classically, it has been studied in vitro in the laboratory or by means of photography obtained with a slit lamp, but these were techniques that required either specific technology or an expert explorer, complex image processing, and required a lot of time. In recent years, proposals based on the Scheimpflug camera and optical coherence tomography have emerged to try to simplify the analysis of glistening in IOLs. It has been described that the manufacturing process, the hydrophobic acrylic material, or the time since surgery are risk factors for the appearance of glistening. In addition, many issues related to this phenomenon are still unknown, such as not knowing from what number of points or their size they may have relevance to visual function since different optical phenomena related to glistening have been described on the IOLs.

Reply to Stanojcic et al. Comment on "Fernández-Vigo et al. Objective Classification of Glistening in Implanted Intraocular Lenses Using Optical Coherence Tomography: Proposal for a New Classification and Grading System. J. Clin. Med. 2023, 12, 2351"

We appreciate the comments made by Stanojcic et al. [...].

Objective Classification of Glistening in Implanted Intraocular Lenses Using Optical Coherence Tomography: Proposal for a New Classification and Grading System

Purpose: To propose a classification of the glistening in intraocular lenses (IOL) using swept-source optical coherence tomography (SS-OCT) by means of a simple, objective and reproducible method that allows the quantification of the presence and severity of glistening. Methods: A cross-sectional study on a sample of 150 eyes of 150 patients who underwent cataract surgery in at least 600 days before the exam and attended a routine examination. Each subject was examined by SS-OCT after pupil dilation, identifying the presence of glistening or hyperreflective foci (HRF) in the central area of the IOL. The degree of glistening was classified into four categories: 0: ≤5 HRF; 1: 6 to 15 HRF; 2: 16 to 30 HRF; and 3: >30 HRF. The intra and interobserver reproducibility (intraclass correlation coefficient, ICC) in the quantification and classification of the glistening were calculated. The correlation between the horizontal and vertical scan of the IOL was also assessed. Results: Glistening was present in the IOL in 42.7% of the patients. The mean number of HRF or glistening microvacuoles was 10.4 ± 26.2 (range 0 to 239). In total, 63.3% of the IOLs had a grade 0, 20% grade a 1, 6.7% grade a 2 and 10% a grade 3. The intraobserver and interobserver reproducibility were very high, both for the absolute quantification of the glistening (ICC ≥ 0.994) and for the severity scale (ICC ≥ 0.967). There was an excellent correlation in the quantification of the IOL glistening between the horizontal and vertical scans (R ≥ 0.834; p < 0.001). Conclusions: The use of SS-OCT makes it possible to identify, quantify and classify IOL glistening in a simple, objective and reproducible way. This technique could provide relevant information for the study of the glistening on IOLs.

Outcomes of a multicenter U.S. clinical trial of a new monofocal single-piece hydrophobic acrylic IOL

PURPOSE

To evaluate the safety and effectiveness of the CT LUCIA 611P intraocular lens (IOL) in patients with cataracts.

SETTING

23 surgeons at 15 different clinical sites.

DESIGN

Prospective single-arm clinical trial.

METHODS

The study was conducted under an Investigational Device Exemption for premarket approval of a new hydrophobic acrylic IOL in the United States. Patients were followed for 12 months, and the main measured variables included uncorrected (UDVA) and corrected (CDVA) distance visual acuities, manifest refraction, and adverse events.

RESULTS

In total, 339 eyes of 339 patients were implanted with the study device, of which 310 (91.4%) reached the 12-month visit. The percentage of eyes within ±0.50 diopter (D) and ±1.00 D of emmetropia was 85.8% (266/310) and 96.8% (300/310), respectively. Manifest refraction spherical equivalent (MRSE) remained stable over the first year with the mean 12-month MRSE of -0.03 ± 0.45 D. The mean 12-month UDVA and CDVA were 0.09 ± 0.15 (≈20/25) and -0.02 ± 0.09 (≈20/19) logMAR, respectively. Of all patients, 99.4% (308/310) achieved postoperative CDVA ≥20/40. The incidence of Nd:YAG capsulotomy within the first year was 3.5% (11/310). Only 2 eyes had IOL tilt present at the 12-month postoperative visit with no associated visual symptoms. There were 2 cases of IOL decentration; one required removal of the IOL, whereas the other had no visual side effects related to decentration. There were no findings of glistening at any visit.

CONCLUSIONS

The CT LUCIA 611P IOL demonstrated excellent safety, efficacy, and stability of refractive outcomes. No significant issues related to the biocompatibility of the IOL material were observed.

Microscopic Characteristics of Late Intraocular Lens Opacifications

CONTEXT.—

The increases in overall life expectancy and in lens surgeries performed on younger patients have resulted in a significant increase in the anticipated duration of artificial intraocular lenses (IOLs) in the eye. Thus, the physicochemical properties of the IOL become a critical issue, and several types of postoperative IOL opacifications have been reported.

OBJECTIVE.—

To describe the microscopic characteristics of opacified IOLs. Glistenings and subsurface nanoglistenings are fluid-related phenomena developing mainly in hydrophobic acrylic IOLs and are associated with aqueous influx into the IOL matrix. Calcification presents in hydrophilic acrylic or silicone IOLs as deposits of hydroxyapatite or other phases of calcium. Snowflake degeneration is less common, and it manifests in older polymethyl methacrylate IOLs.

DATA SOURCES.—

PubMed and ScienceDirect databases were searched for the following keywords: intraocular lens, IOL, cataract surgery, phacoemulsification, opacification, glistening, subsurface nanoglistenings, calcification, snowflake degeneration. English-language articles published up to October 15, 2019 were included in the study. The manuscript contains mainly a literature review; however, it was supplemented with original investigations from the David J. Apple International Laboratory for Ocular Pathology.

CONCLUSIONS.—

Glistenings and subsurface nanoglistenings should be evaluated in a hydrated state and at room temperature; they manifest as microvacuoles sized from 1.0 to greater than 25.0 μm and less than 200 nm, respectively. Calcification deposits are situated on or underneath the surface of the IOL and can be stained with a 1% alizarin red solution or with the von Kossa method. Snowflake degeneration manifests as "particles" or "crystals," causing whitish IOL discoloration. Scanning electron microscopy or energy dispersive X-ray spectroscopy may improve the diagnostic accuracy.

In vitro glistening formation in IOLs: automated method for assessing the volumetric density and depth distribution of microvacuoles

PURPOSE

To develop a method to measure the depth profile of microvacuoles (MVs) in intraocular lenses (IOLs) and to characterize, after accelerated aging, the glistening of an acrylic hydrophobic IOL.

SETTING

University of Milano-Bicocca, Milan, Italy.

DESIGN

In vitro study.

METHODS

A heat treatment was applied in vitro to Basis V IOLs exposed to deionized water (24 hours at 45 ± 1°C, rapid cooling, and 24 hours at 24 ± 1°C). Thirty images (area 1.2 mm) of each IOL were acquired by a microscope, focusing on sequential planes every 23 ± 2 μm. By tracking the traces of each MV in consecutive images, the coordinates of the MV centroids along the IOL thickness were construed by an automated procedure, and in the generated single-focus stacked image, MVs were counted by an automated method.

RESULTS

MV density was found normally distributed along the IOL depth profile (Jarque-Bera test). In focus-stacked images, the MV automated counting was found accurate within 5% vs manual counting, and MV volume density of the order of 10 mm was estimated. It was observed that stacks of 15 images provided a 4% lower MV volume density compared with the stacking of 30 images.

CONCLUSIONS

The assessment of the number of MVs by the acquisition of a single image of an IOL was influenced by the distance of the selected plane from the IOL surface. The decrease in MV density approaching the IOL edges can be explained as a consequence of the diffusion of water toward the external environment after accelerated aging.

A review of late intraocular lens opacifications

PURPOSE OF REVIEW

Phacoemulsification cataract surgery is one of the most commonly performed surgical procedure worldwide. In the majority of cases, intraocular lenses (IOLs) are implanted. Due to the increasing life expectancy and the fact that cataract surgery is performed in earlier stages, the anticipated IOL duration in the eye has increased over the last decades. The aim of this study was to review the types and describe the characteristics of late intraocular lens opacifications.

RECENT FINDINGS

Calcification was the most commonly reported type of opacification in hydrophilic IOLs; it usually negatively impacted the visual function and required IOL explantation. Glistening manifested in hydrophobic acrylic lenses and was frequent in some IOL models. In most cases glistening and subsurface nanoglistenigs do not lead to a decline in visual acuity or require IOL exchange. Current studies indicate that fluid-related phenomena may induce straylight, leading to a decrease of comfort and quality of vision.

SUMMARY

Several reports on late IOL opacifications have been published in recent years. In some cases, particularly in glistening, the development of the opacifications might be related to IOL aging. The influence of the fluid-related microvacuoles on the quality of vision requires further research.

A narrative review of intraocular lens opacifications: update 2020

The opacifications of intraocular lenses (IOLs) can significantly impact patients visual quality. Despite the identification of specific risk factors, manufacturing changes, opacifications are not eliminated. Likewise, more attention in recent studies was paid to possible new risk factors, however one of the most important purposes of the studies remains opacifications effect on visual performance, which could be disturbed in different aspects. The aim of this review is to discuss the main risk factors of IOLs opacification in particular IOL types, and its impact on vision quality. Different risk factors were discussed in the study, including the material of IOLs, the impact of the breakdown of blood-aqueous barrier (BAB), and certain surgeries that can be associated with opacification formation. Glistenings occur more often in a hydrophobic material, however, the changes in water content of the IOLs can significantly reduce the formation of glistenings. The studies showed a significant effect of intraocular injection of exogenous air or gas during Descemet-stripping endothelial keratoplasty, Descemet-stripping automated endothelial keratoplasty, Descemet membrane endothelial keratoplasty, and pars plana vitrectomy on calcification formation. It raises a concern, as the incidence of these surgeries is increasing. Visual acuity decreases significantly after the calcification in IOLs occurs, and it usually causes IOLs exchange. However, disability glare seems to be more affected in patients with IOLs, which were affected by glistenings than visual acuity. Disability glare is associated with increased levels of straylight, which was widely evaluated in recent studies and it was reported to be a susceptible measurement to detect the presence of IOLs pathology. For future researches, it should be noticed that disability glare and straylight are more appropriate in evaluating IOLs opacification effect on visual quality than visual acuity. While reviewing the main risk factors of IOLs opacifications particular attention must be paid on calcification occurrence in hydrophilic acrylic IOLs after surgeries with intraocular injection of exogenous air or gas.

The assessment of the impact of glistening on visual performance in relation to tear film quality

Background

The aim of our case control study was to evaluate the impact of glistening and tear film quality on visual performance after implantation of two different hydrophobic acrylic intraocular lenses (IOLs).

Materials and methods

In our retrospective study we included cataract patients operated between January 1, 2011 and December 31, 2012, with follow-up controls between January 2016 and December 2019. Z-Flex 860FAB (Medicontur) and AcrySof IQ SN60WF (Alcon) monofocal IOLs were implanted during standard phacoemulsification. Best corrected distance visual acuity (BCDVA) and contrast sensitivity were monitored over the post-operative period of up to 6 years. Glistening was evaluated semi-quantitatively with slit-lamp biomicroscopy and quantitatively using Pentacam HR (Oculus). Using HD Analyzer OQAS (Visiometrics), total intraocular light diffusion was interpreted with the objective scatter index (OSI) and tear film quality was evaluated with the tear film related objective scatter index (TF-OSI).

Results

26 eyes implanted with the Z-Flex and 25 eyes with the AcrySof IQ IOLs were included in the analysis. The slit-lamp evaluation of patients with the Z-Flex IOL (0.57 ± 0.60) revealed significantly less glistening (p<0.0001), compared to the AcrySof IQ group (1.82 ± 0.90), and these observations were confirmed by the Pentacam HR analyses, as well (Z-Flex group: 35.1 ± 1.63, Acrysof IQ: 39.6 ± 3.69, p<0.0001). TF-OSI differed between the two sets of patients remarkably (1.53 ± 1.03 vs. 2.51 ± 1.76 for AcrySof IQ and Z-Flex groups, respectively, p = 0.043). Both groups of patients provided similar results of BCDVA and contrast sensitivity.

Conclusion

Glistening and tear film quality both contribute to visual performance outcomes after cataract surgery. In our study the advantage of less glistening in the Z-Flex IOL might have been masked by the adverse effects of the more pronounced tear film insufficiency of these patients, compared to the AcrySof IQ group. Among other factors, tear film quality should also be taken into consideration when comparing the impact of glistening on visual quality of patients implanted with different IOLs.

Comparison of the Visual Performance after Implantation of Three Aberration-correcting Aspherical Intraocular Lens

PURPOSE

To compare the visual performance after implantation of three aberration-correcting aspherical intraocular lens (IOL).

MATERIALS AND METHODS

Seventy-seven eyes of 77 cataract patients were divided into three groups: 26 eyes implanted with a non-constant aberration IOL (LUCIA 601P IOL, Zeiss Company, Germany); 26 eyes implanted with a spherical aberration -0.18μm IOL (CT ASPHINA 509M, Zeiss Company, Germany) and 27 eyes implanted with a spherical aberration -0.27μm IOL (AMO Tecnis ZCB00, Johnson & Johnson Surgical Vision, USA). Three months after operation, the distance visual acuity, wavefront aberrometry, contrast sensitivity, intraocular stray light, IOL decentration, and tilt were evaluated.

RESULTS

Three months postoperatively, no statistically significant differences were found in uncorrected distance visual acuity and corrected distance visual acuity (p≥.83). The RMS for total ocular coma was statistically significantly lower in the Lucia group (p=.03) and spherical aberration was statistically significantly lower in the Tecnis group (p<.01). No statistically significant differences were observed among the three lenses in higher order aberration (p=.85) and in contrast sensitivity under both photopic and mesopic lighting conditions (p≥.05). The intraocular stray light was statistically significantly better in the Lucia group (p=.04). No statistically significant differences were observed with respect to IOL decentration (p=.75) and tilt (p=.89).

CONCLUSIONS

Cataract surgery with non-constant aberration IOL resulted in lower coma and better intraocular stray light than with the spherical aberration -0.18μm and -0.27μm IOLs despite equivalent postoperative levels of visual acuity and contrast sensitivity.

Experimental and analytical quantification of light scattering from vacuoles in intraocular lenses

PURPOSE

To develop an advanced test methodology for quantification of scattered light from intraocular lenses (IOLs) and to evaluate the correlation between IOL vacuole characteristics and measured scattered light.

SETTING

U.S. Food and Drug Administration, Optical Therapeutics and Medical Nanophotonics Laboratory, Silver Spring, Maryland, USA.

DESIGN

Experimental and analytical study.

METHODS

Twenty-four IOLs containing vacuoles were evaluated using a digital microscopy approach for identifying and characterizing the vacuoles present. A scanning light scattering profiler (SLSP) was used to evaluate and quantify the amount of scattered light from each IOL and from a 25th control IOL without any vacuoles. A variety of IOLs and vacuoles were also modeled in a Zemax simulation of the SLSP, and the simulated scattered light was modeled.

RESULTS

The scattered light as measured with SLSP was well correlated with vacuole characteristics, specifically density and size, as measured under the digital microscope for the 24 vacuole-containing IOLs. Additional correlations were found between vacuole sizes, orientations, and the angle at which light was scattered most severely. These correlations were also present in the Zemax model.

CONCLUSIONS

Vacuole optical characteristics can be well correlated with measured scatter, demonstrating an ability to predict scattered light based solely on microscope evaluation. Furthermore, the quantitative amount of scatter predicted with Zemax simulations trended closely with the experimentally measured trends.

Visual and refractive outcomes and glistenings occurrence after implantation of 2 hydrophobic acrylic aspheric monofocal IOLs

PURPOSE

To compare the Clareon IOL with the Tecnis PCB00 IOL in terms of visual performance, refractive outcomes, glistenings occurrence, and quality-of-life outcomes.

SETTING

Guy's and St Thomas' NHS Foundation Trust, London, United Kingdom.

DESIGN

Single-center, single-masked, prospective, randomized controlled trial.

METHODS

One hundred thirty-nine patients with bilateral cataracts were randomized to receive the Clareon (C IOL) or Tecnis (T IOL) IOL. Visual acuity, refraction, central corneal thickness (CCT), endothelial cell loss, contrast sensitivity, mesopic gap acuity, evaluation of glistenings, and rates of perioperative and postoperative complications were recorded. Quality-of-life outcomes were measured with the EuroQOL-5 dimensions questionnaire and the patient-reported outcome measures (PROMs) questionnaire. Optimized A-constants were available for the T IOL but not for the C IOL.

RESULTS

Seventy-one patients (140 eyes) received the C IOLs and 68 patients (134 eyes) received the T IOLs. Data were analyzed for the first implanted eye. At 12 months, mean uncorrected distance visual acuity (logarithm of the minimum angle of resolution) was 0.02 ± 0.10 and 0.01 ± 0.08 (mean ± SD; P = .49; 95% CI, -0.02 to 0.04) in the C IOL and T IOL groups, respectively. Corrected distance visual acuity was -0.02 ± 0.09 and -0.03 ± 0.06, respectively (P = .45; 95% CI, -0.02 to 0.04). The increase in CCT was 14 ± 19 and 16 ± 28 μm, respectively (P = .63; 95% CI, -10.16 to 6.16). Mean absolute refraction spherical equivalent error from target refraction was 0.41 ± 0.28 for the C IOL and 0.25 ± 0.2 for the T IOL groups (P = .002; 95% CI, 0.08 to 0.24). Glistenings were minimal (median grade 0), with no difference in grades between groups (P = .2). PROMs improved postoperatively and were similar in both groups.

CONCLUSIONS

There were no differences in visual outcomes between the Clareon IOL and Tecnis PCB00 IOL. Glistenings were rarely observed in either IOL with no difference in grades. There was no difference in perioperative or postoperative complications. Surgeon optimization of the A-constant for the Clareon IOL is recommended.

Comparison of glistenings formation and their effect on forward light scatter between the Acrysof SN60WF and Eternity Natural Uni NW-60 intraocular lenses

Aims

To compare the characteristics of glistenings and forward light scatter between the Alcon Acrysof SN60WF and Santen Eternity Natural Uni NW-60 intraocular lenses (IOLs).

Methods

Five Acrysof SN60WF and five Eternity Natural Uni NW-60 IOLs were studied. All IOLs were single piece blue blockers with the same dioptric power (20D) and optic diameter (6.0 mm). Glistenings were induced by a thermal accelerated ageing process. Glistenings were objectively quantified using bespoke image processing software. The angular distribution of forward light scatter was measured using an optical bench system and the straylight parameter calculated from the light scatter function.

Results

The median increase in the number of glistenings was 15 and 525 for the Eternity and Acrysof IOLs, respectively, which was statistically significantly different (p=0.012). Median glistenings diameter was 23.8 μm (Acrysof) and 32.8 μm (Eternity). Four (80%) of the Acrysof lenses had straylight values higher than a 20-year-old CIE standard glare observer and in two cases the straylight exceeded that of the 70-year-old CIE standard glare observer. None of the Eternity lenses had straylight values that exceeded the value for the 20-year-old CIE standard glare observer.

Conclusions

The Eternity Natural Uni NW-60 IOLs resisted the induction of glistenings more than the Acrysof SN60WF IOLs. Although the Acrysof IOLs developed smaller glistenings than the Eternity IOLs, there were sufficient numbers to produce a higher straylight parameter.

Quantitative Multiparameter Evaluation of Vacuoles in Intraocular Lenses Employing a High-Magnification Digital Microscopy Method

As small imperfections with micrometric sizes, fluid-filled vacuoles, also referred to as glistenings, in intraocular lenses (IOLs) have been known to induce significant unwanted light scattering that in several cases presumably cause complaints and sometimes lead to IOL explantation and replacement. This unwanted scatter is of particular concern for patients viewing bright light in reduced-light conditions such as when driving at night, as the scattered light toward the retina can cause temporary blindness. In this study, we have developed and implemented an accurate test methodology based on a high-magnification digital microscopy approach for quantitative multiparameter evaluation and classification of IOL vacuoles depending on their critical optical characteristics including vacuole size, density, shape, and orientation within the IOL material. Using the multiparameter database developed by evaluating vacuole characteristics, we established a classification grading system that can be used to evaluate vacuole effects on light scattering.

Clinical and material degradations of intraocular lenses: A review

PURPOSE

To review the published scientific literature concerning clinical and material degradations of intraocular lenses after implantation in cataract surgery.

METHODS

A search was undertaken using the following databases: CENTRAL (including Cochrane Eyes and Vision Trials Register; The Cochrane Library: Issue 2 of 12 February 2019), Ovid MEDLINE (R) without Revisions (1996 to February week 2, 2019), Ovid MEDLINE (R) (1946 to February week 2, 2019), Ovid MEDLINE (R) Daily Update 19 February 2019, MEDLINE and MEDLINE non-indexed items, Embase (1980-2019, week 7), Embase (1974-2019, 19 February), Ovid MEDLINE (R) and Epub Ahead of Print, in-Process & Other Non-Indexed Citations and Daily (1946 to 19 February 2019), Web of Science (all years), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrial.gov) and the WHO International Clinical Trials Registry Platform (www.who.int/ictrp/search/en). Only published articles in English were selected. Search terms/keywords included 'IOL' or 'intraocular lens', combined with 'opacification', degradation, glistenings, nanoglistenings, whitening, transmittance, light scatter, discolouration/discoloration, performance, quality, material, biocompatibility, calcification, explantation and ultraviolet/UV radiation. Relevant in-article references not returned in our searches were also considered.

RESULTS

After review of the available articles, the authors included 122 publications in this review, based on the quality of their methodology and their originality. The studies included in this review were randomized controlled trials, cohort studies, case-controlled studies, case series, case reports, laboratory studies and review papers. Differing material degradations of intraocular lenses have been described and their associated pathophysiology studied. Reported anomalies include photochemical alterations, water vacuoles, internal and surface calcific deposits, surface coatings and discolouration. The nature of such changes has been shown to depend on the type of intraocular lenses material used and/or manufacturing processes and storage conditions employed. Changes in the intraocular lens can also be influenced by surgical technique, coexisting ocular pathologies and topical and systemic medications. The clinical significance of these degradations is variable, with some resulting in significant visual disturbance and the need for intraocular lens explantation and others producing only minimal visual impairments. Failure to recognize the precise nature of the problem may lead to unnecessary laser capsulotomy procedures.

CONCLUSION

Clinical degradations of intraocular lenses are uncommon but have been reported following the implantation of intraocular lenses made of differing biomaterials. Their correct identification and thorough investigation to determine the underlying cause is necessary for optimal patient management and the prevention of such problems. Choosing a lens made of a particular material may be important in patients with certain ocular conditions.

Polarized glasses may help in symptomatic cases of intraocular lens glistenings

Intraocular lens (IOL) glistening is a relatively common phenomenon. Although most of the patients remain asymptomatic, a small percentage of patients can develop unwanted optical side effects. We report 6 symptomatic patients with IOL glistening. All patients underwent an implantation of a hydrophobic acrylic mononofocal, multifocal or toric IOL in external clinics for visually significant cataract at least 6 months prior. Patients had very reasonable corrected visual acuity (0.8-1.0 decimal), but significantly had reduced contrast sensitivity and modulation transfer function, complained of visual phenomena and expressed dissatisfaction with their visual status. Patients indicated the symptoms were not present immediately after surgery, but gradually developed postoperatively. Slit-lamp examination revealed moderate-to-severe glistening in all cases. No other pathology that would be responsible for the visual symptoms was present. Patients reported improvement in side effects with the use of edge filter (blue-light blocking) eyeglasses and polarized sunglasses with an increase in contrast sensitivity by aproximately 1 line on Pelli-Robson chart. The use of specific eyewear seems to be a promising alternative to avoid explant of an IOL in symptomatic patients with glistenings and very good visual acuity. In conclusion, we believe that long-term optical clarity is crucial for the choice of an IOL.

Effects of intraocular lens glistenings on visual function: a prospective study and presentation of a new glistenings grading methodology

Objective

To investigate the effect of intraocular lens (IOL) glistenings on visual performance and evaluate a new glistenings grading methodology.

Methods and Analysis

Thirty-four patients (34 eyes) were recruited. Corrected distance visual acuity (CDVA), mesopic gap acuity (MGA), functional contrast sensitivity (FCS) and forward light scatter were measured (Advanced Vision and Optometric Tests, City Occupational, London, UK). The IOL centre was imaged and glistenings density graded by three observers using the Miyata scale and a new system. Inter-rater reliability, association between the two grading scales, and correlations between glistenings grades and visual performance parameters were evaluated.

Results

The intraclass correlation coefficient between graders for the new grading system was 0.769 (95% Confidence Interval [CI] 0.636 to 0.868). There was a significant association between the Miyata scale and the new grading system for all graders (r_s=0.533–0.895, p≤0.001). There was no association between CDVA or MGA and glistenings grade (r_s=− 0.098, p=0.583 and r_s=0.171, p=0.359, respectively). There was no association between FCS at mesopic light levels and glistenings grade (r_s=−0.032, p=0.864), or the straylight parameter and glistenings grade (r_s=0.021, p=0.916). No association was found between the integrated straylight parameter and glistenings grade (r_s=0.078, p=0.701).

Conclusion

The new glistenings grading scale was highly reproducible. In this cohort, glistenings in the same hydrophobic acrylic IOL after cataract surgery were not associated with changes in visual function, as assessed by a series of tests not previously used in glistenings research.

Glistening Formation and Light Scattering in Six Hydrophobic-Acrylic Intraocular Lenses

PURPOSE

To study the glistening formation in various hydrophobic-acrylic intraocular lens (IOL) models, and to evaluate the effect of glistenings on light scattering in these IOLs.

DESIGN

Laboratory investigation.

METHODS

The susceptibility of the hydrophobic-acrylic material to develop glistenings was evaluated in 6 IOL models. Accelerated lens aging was induced by immersing the IOLs in a solution at 45 C for 24 hours and cooled to 37 C for 2.5 hours. Light microscopy and image acquisition were performed. Glistening statistics-that is, microvacuoles' (MV) number and size-were derived from image analysis. Light scattering was measured using a clinical device featuring an adaptation for in vitro IOL assessment.

RESULTS

The number of glistenings differed among the studied IOLs and ranged from 0 to 3532 MV/mm². In 1 model, glistenings were found only at the periphery, with diffuse light scattering observed centrally despite the absence of microvacuoles. The mean size of glistenings ranged from 5.2 to 10.2 μm. The mean straylight parameter of the IOLs increased from 0.6 to 5.0 deg²/sr after accelerated aging. Straylight elevation demonstrated a proportional relationship with the glistening number.

CONCLUSIONS

We showed that hydrophobic-acrylic lenses differ in their resistance to glistenings, as one group proved to be glistening-free, but the other models revealed varying grades of glistenings. Moreover, we demonstrated that the presence of glistenings results in increased straylight, and that straylight proportionally depends on the glistenings number irrespective of the IOL model. However, more research is needed to confirm that the relationship we found holds for all hydrophobic-acrylic IOLs.

Long-term clinical results and scanning electron microscopic analysis of the aspheric, hydrophobic, acrylic intraocular lens CT LUCIA 611P(Y)

Purpose

The aim of this study was to evaluate the clinical outcomes of a novel designed hydrophobic, acrylic, monofocal, fully preloaded intraocular lens (IOL; CT LUCIA 611P) 1 year after implantation. Scanning electron microscopic analysis regarding the optic-haptic junction and sharp edges of the IOL was performed.

Patients and methods

This is a noninterventional, observational prospective study of cataract patients who underwent implantation of the CT LUCIA 611P. Ninety-six eyes of 54 subjects were enrolled. Follow-up included visual acuity assessment, slit lamp examination with special focus on appearance of glistenings and evaluation of posterior capsule opacification (PCO). Scanning electron microscopic analysis of the new designed optic-haptic junction and edges of the IOL was performed.

Results

Best-corrected distance visual acuity increased from mean 0.48 logMAR (range 0.86-0.34) preoperatively to mean 0.02 logMAR (range 0.14 to -0.10) 1 year after surgery. Thirty-eight of 42 subjects' eyes (90.5%), which underwent bilateral surgery with implantation of the IOL, never required glasses for distance again, while 4 (9.5%) required glasses only in rare cases (eg, driving at night). The spherical equivalent was within ±0.50 D in 88 of 96 subjects (91.7%) and within ±0.75 D in 96.9% of cases. Target refraction ±1.00 D was achieved in 100% of subject eyes. No glistenings were reported in any case. From the surgeons' perspective, the wider, thicker optic-haptic transition of the IOL resulted in significantly increased stiffness, which enabled improved centering of the IOL and enhanced rotational stability and refractive predictability and stability and PCO prevention.

Conclusion

The results of this long-term observational study demonstrate the safety and efficacy of the IOL. Because of the completely new designed thicker and stiffer optic-haptic junction regarding improved characteristics of the IOL (stability in the capsular bag), some special attention has to be addressed to the slightly different behavior of the lens during implantation and unfolding process.

Intraocular light scatter in patients on topical intraocular pressure-lowering medication

PURPOSE:

To quantify ocular light scattering in patients under treatment with intraocular pressure-lowering eye-drops.

METHODS:

In this prospective, observational, cross-sectional case series study, 160 eyes of 160 patients with primary open angle glaucoma or primary ocular hypertension were consecutively recruited from our Glaucoma Department over 7 months. In total, 46 eyes of 46 healthy volunteers matched for age and sex served as the control group. The variables recorded in a single visit were as follows: drug and number of drops per day, treatment duration, OXFORD corneal staining grade, lower tear meniscus height as measured by spectral domain optical coherence tomography, ocular redness and non-invasive tear breakup time measured with the Oculus Keratograph 5M, ocular surface disease index questionnaire score and objective scatter index through a double-pass technique (Optical Analysis System II).

RESULTS:

Objective scatter index was higher in the patient group (3.1, interquartile range = 1.8-5.47) than in the control group (1.95; interquartile range = 0.7-5; p = 0.017). In a multiple linear regression model, non-invasive tear breakup time was identified as the most influential variable on light scatter (mean ratio = -1.015; p = 0.003; 95% confidence interval = -1.025 to -1.005). No correlation with objective scatter index was observed for number of daily eye-drops, preservative concentration or treatment duration.

CONCLUSION:

Participants on anti-glaucoma medication showed a significantly higher objective scatter index than control group individuals. In the treated patient group, a lower non-invasive tear breakup time was associated with a higher objective scatter index. This suggests that lubricating eye-drops to improve tear breakup time could also improve vision quality in these patients by diminishing light scattering.

Biomaterial Influence on Intraocular Lens Performance: An Overview

There is strong evidence that the IOL material is the factor having the greatest impact on posterior capsule opacification (PCO), anterior capsule opacification (ACO) development, and glistening formation after cataract surgery, even though there are other IOL features—such as haptic material and design and edge and optic design—that also have some influence. We reviewed the published literature describing the adverse events that are mainly related to the intraocular lens (IOL) material, such as PCO, ACO, and the subsequent capsule contraction, as well as glistening formation. The adverse events presented in this overview are the most common ones in clinical practice, and therefore, they are generally included in the clinical protocols for IOL evaluation.

Influence of intraocular lens subsurface nanoglistenings on functional visual acuity

To investigate the influence of intraocular lens subsurface nanoglistenings (SSNGs) on functional visual acuity (FVA), thirty-nine eyes of 29 patients were examined in this study. The SSNG group comprised 19 eyes of 14 patients (75.7± 5.4 years, mean ± standard deviation), and the control group comprised 20 eyes of 15 patients (73.6 ± 6.5 years). The SSNGs were diagnosed on the basis of the typical whitish IOL appearance upon slit-lamp examination and results of densitometry regarding surface light scattering using Scheimpflug images. The FVA measurement system (AS-28; Kowa, Aichi, Japan) was used to examine changes in continuous visual acuity (VA) over time, and visual function parameters such as FVA, visual maintenance ratio (VMR), maximum VA, minimum VA, standard deviation of VA, and number of blinks were assessed. The results were compared between the SSNG and control groups, and correlations of FVA parameters with the intensity of surface light scattering, time after surgery, and age were also evaluated. There were significant differences in VMR (P = 0.035) and standard deviation of VAs (P = 0.031) between the two groups, although no significant differences were found in baseline VA, FVA, maximum VA, minimum VA, and number of blinks. None of the FVA parameters showed any significant correlations with the intensity of surface light scattering, time after surgery, or age. There is a possibility that VA is unstable during a continuous gazing task in patients with SSNGs.

Intraocular lens optics and aberrations

PURPOSE OF REVIEW

This review outlines concepts in intraocular lens (IOL) optics and aberrations important both for current IOLs and for new IOLs in development.

RECENT FINDINGS

Optical aberrations make a significant impact on the laboratory and clinical performance of IOLs, especially under mesopic and low-contrast conditions. Minimizing or correcting these aberrations can potentially improve visual function. Strategic management of aberrations can have clinical utility for extended depth of focus and presbyopia correction.

SUMMARY

All IOLs affect ocular aberrations in some manner. It is important for clinicians and researchers to understand the implications how any residual aberrations could affect visual quality, visual side-effects, and depth of focus.