Surface scattering in implanted hydrophobic intraocular lenses

Visual Performance of a Violet-Filtering Intraocular Lens versus a Blue-Filtering Intraocular Lens of New/Old Manufacturing Processes

This article compares the visual performance of a violet light-filtering colored lens (ZCB00V) and blue light-filtering intraocular lens (IOL; SN60WF) before and after modifying the manufacturing process for glistening suppression. In this retrospective study, conducted at Saneikai Tsukazaki Hospital, Himeji, Japan, a consecutive sample of 8943 eyes of 5119 patients were included and implanted with blue-filtering IOLs before and after modifying the manufacturing process (SN60WF-J (1318 eyes) and SN60WF-Q,A (1418 eyes), respectively), noncolored UV-cut IOLs (ZCB00 (1418 eyes)), and ZCB00V (3717 eyes). For each patient, the corrected distance visual acuity (CDVA) at 3 months postoperative (3MCDVA) and the area under log contrast sensitivity function (AULCSF) were measured. The 3MCDVA was -0.076 ± 0.1, -0.11 ± 0.13, -0.10 ± 0.17, and -0.11 ± 0.13, for SN60WF-J, SN60WF-Q,A, ZCB00, and ZCB00V, respectively. The SN60WF-J group revealed significant differences as compared to the other three groups (all p < 0.05). The mesopic AULCSF was 2.59 ± 0.20, 2.68 ± 0.19, -2.69 ± 0.18, and 2.76 ± 0.19, respectively, whereas the photopic AULSCF was 2.63 ± 0.23, 2.76 ± 0.25, -2.77 ± 0.25, and 2.88 ± 0.25. The SN60WF-J and ZCB00V groups exhibited significant differences as compared to the other three groups, whereas no significant differences were noted between the SN60WF-Q,A and the ZCB00 groups (all p < 0.05). The violet-filtering lens offers higher visual acuity and contrast sensitivity than the clear and blue-filtering lens. It was also found that the above functions were improved by modifying the manufacturing process.

Clinical outcomes of new multifocal intraocular lenses with hydroxyethyl methacrylate and comparative results of contrast sensitivity, objective scatter, and subjective photic phenomena

Background

We investigate the performance of new hydrophobic diffractive multifocal intraocular lenses (IOL) with hydroxyethyl methacrylate (HEMA) and compare their optical quality, contrast sensitivity, and subjective photic phenomena.

Methods

Medical records of patients who underwent routine simple cataract surgery and insertion of an existing multifocal IOL (TFNT, TF group) or a new multifocal IOL (CNWT, CN group) were retrospectively reviewed. Clinical data was collected 2 months postoperatively and included optical quality analysis system (OQAS) indices, contrast sensitivity, and subjective degrees of photic phenomena.

Results

One hundred thirty-five eyes of 135 patients were included (CN group, 71; TF group, 64). There was no significant difference between the two groups in the visual acuity and defocus curve. The indices of OQAS did not show a significant difference between groups. Contrast sensitivity was significantly better in the CN group at all degrees, including the area under the log contrast sensitivity function (p = 0.01). The subjective photic phenomena survey showed better results for the CN group, with the proportion of patients reporting no photic phenomena as 9.9% and 3.1% in the CN and TF groups, respectively. The proportion of patients who reported severe photic phenomena was 11.3% in the CN group and 25.0% in the TF group. Although the follow-up period was only 2 months, glistening, surface scattering, and posterior capsule opacity were not observed in any patient.

Conclusions

The new multifocal IOL with HEMA is safe, and provides stable visual acuity as well as superior contrast sensitivity and lower subjective photic phenomena, over the prior IOL.

Quantitative evaluation of microvacuole formation in five intraocular lens models made of different hydrophobic materials

In this laboratory study, we assessed the resistance to microvacuole (glistening) formation in hydrophobic intraocular lenses (IOLs). Glistenings were induced in five lenses each of five different hydrophobic acrylic IOL models, using an established in vitro laboratory model: 800C (Rayner, Worthing, UK), AcrySof SN60WF (Alcon, Fort Worth, USA), Tecnis ZCB00 (Johnson & Johnson Vision, Santa Ana, USA), Vivinex XY1 (Hoya, Tokyo, Japan) and CT Lucia 611P (Zeiss, Oberkochen, Germany). We evaluated the number of microvacuoles per square millimeter (MV/mm2) in the central part of each IOL. Results were analyzed statistically, and mean glistening numbers were ranked, with the highest in the SN60WF which had 66.0 (±45.5) MVs/mm, followed by the 611P with 30.7 (±8.4) MVs/mm2. The 800C and XY1 showed comparable values of 2.0 (±3.6) and 2.7 (±2.4) MVs/mm2, respectively. ZCB00 had the lowest number with 0.9 (±0.6) MVs/mm2. This study shows that the resistance to glistening formation differs depending on the hydrophobic acrylic copolymer composition of the IOL material. Some IOLs from current clinical use are still prone to develop glistenings whereas others, including the ZCB00, 800C and XY1 show high resistance to microvacuole formation.

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.

Changes in Opacification of Hydrophobic Acrylic Intraocular Lenses According to Temperature and Hydration

Purpose

To investigate optic opacification of hydrophobic acrylic intraocular lens (IOL) depending on hydration and temperature conditions.

Methods

IOL (Acrysof^® MA60BM Alcon, Fort Worth, Texas, USA) extracted from a 55-year-old male who underwent binocular cataract 11 years ago were used for the analysis. On slit lamp examination, the binocular IOL optics showed homogenous opacification. After extraction of the IOLs, the IOL opacification disappeared during dry storage at 4°C. To investigate the changes in IOL opacification according to temperature and hydration, an extracted IOL was stored in either dry conditions or normal saline at 4°C, room temperature, or 37°C for 24 hours, and then the degree of haziness was examined. To investigate the impact of an opaque optic on visual function, light transmission was performed using an ultraviolet-visible spectrophotometer (U-3000, Hitachi High-Technologies Corp., Tokyo, Japan).

Results

The extracted IOL optics at 4°C, room temperature, and 37°C were transparent at dry conditions. When the dried IOL was immersed in normal saline at room temperature and 37°C, opacification appeared. However, when the dried IOL was immersed in normal saline at 4°C, opacification of the IOL did not appear. When compared with the control, light transmission of the extracted IOLs from the right and left eyes stored in 37°C normal saline decreased by 4.7% at 453 nm and by 5.1% at 482 nm, respectively.

Conclusion

In acrylic hydrophobic IOLs, optic opacification can occur depending on temperature and hydration conditions.

Glistening formation in a new hydrophobic acrylic intraocular lens

Background

The formation of fluid-filled microvacuoles, termed glistenings, is a common complication of intraocular lenses (IOLs) made from hydrophobic acrylate. Using our well-established in-vitro laboratory method, we evaluated a new IOL material’s resistance to glistening formation.

Methods

An in-vitro stress test for glistening induction was performed on 20 samples of hydrophobic acrylic IOLs: ten of the new Eyecryl ASHFY600 (Biotech Vision Care, Ahmedabad, India) compared with ten samples of AcrySof IQ SN60WF (Alcon, Fort Worth, USA). The number of microvacuoles per square millimetre (MV/mm²) was evaluated in five sections of each IOL. The results for each model were compared and rated on a modified Miyata Scale for grading glistening severity.

Results

In all cases, glistening number was higher in the central section of the IOL optic than in the periphery. Mean number of MV/mm² was highest in the central part of the AcrySof IQ SN60WF, with 41.84 (±27.67) MVs/mm². The lowest number of glistenings was found in the five sections of the Eyecryl ASHFY600 with 0.52 (±0.24) MVs/mm². Mean value of the Eyecryl ASHFY600 IOL, using the Miyata Scale, was Zero.

Conclusion

In this in-vitro laboratory study, the new hydrophobic acrylic IOL showed a high resistance to microvacuole formation. Results from this in-vitro study suggest that glistening numbers will be low in clinical use in the Eyecryl ASHFY600.

Evaluation of clarity characteristics in a new hydrophobic acrylic IOL in comparison to commercially available IOLs

PURPOSE

To perform in vitro assessments of surface haze and roughness, subsurface nanoglistenings (SSNGs), and glistenings of a new hydrophobic acrylic intraocular lens (IOL) in comparison to commercially available IOLs.

SETTING

Universities of Utah and Alcalá, and Alcon Vision, LLC.

DESIGN

Experimental study.

METHODS

The IOLs used were Clareon CNA0T0, Tecnis ZCB00 and Tecnis OptiBlue ZCB00V, Eternity W-60, enVista MX60, and Vivinex XY1. Surface haze was assessed by the pixel intensity units (PIU) from cross-sectional slitlamp images, and it was correlated to atomic force microscopy roughness. For SSNGs, the IOLs were artificially aged up to 10 years, followed by Scheimpflug densitometry (computer-compatible tape unit [CCTU]) measurements. For glistenings, the IOLs were immersed in a water bath and subjected to temperature changes before analysis.

RESULTS

The surface haze (n = 10, PIU) was 4.25 ± 0.87 (SD) (CNA0T0), 9.50 ± 1.66 (ZCB00), 39.48 ± 1.97 (ZCB00V), 46.68 ± 3.16 (W-60), 44.70 ± 4.00 (MX60), and 4.42 ± 0.71 (XY1) (P < .001), which showed a strong correlation with surface roughness measurements (R = 0.94, P = .006). The densitometry (n = 10, CCTU at 10 years) was 7.30 ± 1.36 (CNA0T0), 11.88 ± 3.10 (ZCB00), 38.12 ± 2.24 (ZCB00V), 48.13 ± 9.44 (W-60), 20.20 ± 3.84 (MX60), and 6.75 ± 6.66 (XY1) (P < .001), with no significant differences between CNA0T0 vs. ZCB00 and XY1. The glistenings density (n = 30) was the lowest for the CNA0T0, W-60, and MX60 IOLs.

CONCLUSIONS

The new Clareon CNA0T0, which is manufactured from a hydrophobic acrylic material, exhibited among the lowest levels of surface haze and roughness, SSNGs, and glistenings compared with other commercially available hydrophobic acrylic IOLs.

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.

Experimental study of the mechanisms leading to the formation of glistenings in intraocular lenses by Raman spectroscopy

The phenomenon of glistenings, often appearing in intraocular lenses (IOLs) of patients after some time from the surgical operation, is potentially able to induce a poor quality of vision and, therefore, frustrate IOL implantation itself. In this paper, we combine optical microscopy with micro-Raman spectroscopy to get a deeper insight on the mechanism ruling, at microscopic scale, glistening formation. In particular, we have analyzed two types of IOLs, characterized by a different internal hydrophobicity but a similar polymer hydration coefficient. Raman imaging of single microvacuoles reveals that water creeps into the polymeric network, which traps water. Finally, applying the Principal Component Analysis (PCA) to Raman data, we provide information on the probable mechanism leading to water trapping in the two kinds of analyzed IOLs.

Suppression of surface light scattering in intraocular lenses manufactured using an improved production process

PURPOSE

To clinically examine the suppression of surface light scattering after implantation of an intraocular lens (IOL) manufactured using an improved production process.

SETTING

Miyata Eye Hospital, Miyazaki, Japan.

DESIGN

Comparative case series.

METHODS

The prospective case series comprised eyes receiving hydrophobic acrylic Acrysof SN60WF IOLs that were manufactured before and after the improvement. Light scattering on the anterior IOL surface was examined up to 3 years postoperatively using an EAS-1000 anterior segment analyzer. The changes during the postoperative period were evaluated and the 2 IOLs compared. The corrected distance visual acuity (CDVA) and contrast sensitivity under photopic and mesopic conditions were also examined 3 years postoperatively.

RESULTS

The case series comprised 24 eyes (received IOL before improvement) and 27 eyes (received IOL after improvement). After the improvement, the IOLs showed no increase in surface light scattering up to 2 years, while there were increases after 2 years in the other IOLs. The light scattering with the improved IOL was significantly reduced at all observations (P < .048, t test with Holm correction). No difference was found in the CDVA and contrast sensitivity.

CONCLUSIONS

The improvement in the production process effectively decreased and slowed the development of surface light scattering. The slower increase in the improved IOL 3 years postoperatively showed that the development of water aggregates would not be completely prevented.

FINANCIAL DISCLOSURE

None of the authors has a financial or proprietary interest in any material or method mentioned.

Steam-like clouding observed on anterior surface of intraocular lens developed soon after implantation

Purpose

To report our findings in three cases of a clouding of the anterior surface of an implanted intraocular lens that developed within 14 days after implantation.

Observations

Three eyes were implanted with the same model IOL and a steam-like clouding developed on the anterior surface of the IOL. The clouding occurred on days 4, 7, and 14 after the implantation in an area of the IOL that was in contact with the aqueous humor. The clouding was accompanied by a reduction of vision in all cases but without any other abnormalities such as inflammation. The clouding was resolved by irrigation and aspiration of the anterior chamber in 2 cases at 2 and 34 days after the onset, and a spontaneous disappearance in 1 case at 14 days after the onset of the clouding. After the disappearance of the clouding, the visual acuity improved, and there were no recurrences. The solution used to irrigate the anterior chamber was collected and examined to confirm the absence of cellular materials. Elemental analyses confirmed that sodium and chloride were the predominant ions. The IOL implanted was the XACT lens (Advanced Vision Science, USA) which is a hydrophobic acrylic IOL and is characterized by having higher water content compared to other IOLs. In addition, it is packaged in 0.9% saline to maintain the pre-hydrated condition. These aspects may be related to the cause of the clouding. This IOL was implanted in 3271 eyes in our clinic, and 3 of them (0.09%) developed this clouding.

Conclusions and importance

We report our findings in 3 eyes that developed a clouding on the anterior surface of the lens soon after implantation. The clouding was localized to the area in contact with the aqueous. The cause of the clouding was not determined.

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.

Influence of surface light scattering in hydrophobic acrylic intraocular lenses on laser beam transmittance

The aim of this study was to experimentally examine the changes in the transmittances of photocoagulation lasers when surface light scattering increases in AcrySof intraocular lenses (IOLs). SA60AT IOLs (Alcon) were acceleratingly aging for 0, 3, 5, and 10 years to simulate surface light scattering, and the surface light-scattering intensities of both IOL surfaces were measured using a Scheimpflug photographer. The powers of laser beams that passed from a laser photocoagulator through the aged IOLs were measured at 532, 577, and 647 nm. Changes in the laser power and transmittance with the years of aging and the intensities of surface light scattering were examined. Although the intensity of surface light scattering increased with the years of aging, the laser power did not change with the years of aging (P > 0.30, Kruskal-Wallis test). There were no significant changes in the laser transmittance with the years of aging or the laser wavelength (P > 0.30 and 0.57, respectively). The intensity of surface light scattering revealed no significant association with the laser transmittance at any wavelength (P > 0.37, liner regression). The increases in the surface light scattering of the AcrySof IOLs would not influence retinal photocoagulation treatments for up to 10 years after implantation.

Effect of intraocular lens glistening size on visual quality

PURPOSE

To determine whether intraocular glistenings have an impact on light scatter and visual function.

SETTING

John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA.

DESIGN

Retrospective cohort study.

METHODS

Pseudophakic patients with visual acuity no worse than 0.02 logMAR and no ocular pathology were enrolled. All had received a single-piece high-refractive-index acrylic intraocular lens (IOL). All IOLs were photographed, and glistenings were analyzed for size and density. Outcome measures included logMAR corrected distance visual acuity (CDVA), mesopic 10% contrast logMAR CDVA with and without glare, and straylight determination with a straylight meter (C Quant log).

RESULTS

All 79 patients had glistenings within 2 diameter groups: 6 to 25 μm and over 25 μm. Linear regression for the nonstratified group was significant for IOL glistening size versus contrast visual acuity with glare. Linear regression for the 6 to 25 μm group was significant for a measure of severity index (%area) versus the straylight meter measurements, %area/size versus straylight meter measurements, IOL age versus CDVA, IOL age versus contrast visual acuity, and IOL age versus contrast visual acuity with glare. Linear regression for the over 25 μm group was significant for IOL age versus glistening size and %area/size versus contrast visual acuity, and density versus CDVA and contrast visual acuity with glare.

CONCLUSIONS

Glistening %area, at a key size, correlated with random light scatter. The age of the IOL likely affects glistening size and visual parameters.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Decreased visual acuity resulting from glistening and sub-surface nano-glistening formation in intraocular lenses: A retrospective analysis of 5 cases

Background

To report on five patients with decreased visual acuity due to glistening and severe sub-surface nano-glistening (SSNG) formation within their intraocular lenses (IOLs).

Design

Case reports and analysis of extracted IOLs.

Participants and samples

We report improved visual acuity when IOLs with severe glistening and SSNG were exchanged for clear IOLs in five patients.

Methods

Case reports.

Main outcome measures

The main outcome measure was visual acuity. The secondary outcome measure was light transmission. Explanted IOLs were subjected to investigation. Pre- and postoperative slit lamp images of the anterior eye and microscopic images of the extracted IOLs were taken and compared. Light transmission of the IOL was measured using a double beam type spectrophotometer. An integrated value of the percentage light transmittance in the visible light spectrum was calculated.

Results

We report on five patients whose visual acuity improved when IOLs were exchanged because of severe glistening and SSNG. All of the affected IOLs were MA60BM (Alcon, Forth Wroth Texas, USA) and the original implantation had occurred over a range of 6–15 years prior to the IOL exchange. Light transmission was decreased in all affected lenses compared to a similar control IOL.

Conclusions

Although only a few reports of cases in which glistening and SSNG have progressed to the level of decreased visual function have been published, the likelihood is that this phenomena will increase as the severity and incidence of these inclusions have been shown to increase with time. Appropriate evaluations of visual function in such patients are needed and consideration should be given to IOL exchange in symptomatic patients.

Determination of scattering in intraocular lenses by spectrophotometric measurements

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

Optical simulation for subsurface nanoglistening

PURPOSE

To determine whether subsurface nanoglistening in hydrophobic acrylic intraocular lenses (IOL) diminishes visual performance.

SETTING

Department of Ophthalmology, Kanazawa Medical University, Uchinada, Ishikawa, Japan.

DESIGN

Experimental study.

METHODS

The effect of subsurface nanoglistenings was simulated using optical design software Lighttools and Code V with the Liou-Brenann model eye and an acrylic IOL. Peak irradiance of the retina, forward light scattering, and modulation transfer function (MTF) were evaluated. During optical simulation, particle diameters were set at 100 nm, 150 nm, and 200 nm and volume ratios at 0%, 0.05%, 0.1%, 0.2%, 0.5%, and 1.0%.

RESULTS

Peak irradiance decreased as subsurface nanoglistening volume ratio and particle size increased. At a volume ratio of 0.05%, the peak irradiance of subsurface nanoglistening particles 100 nm, 150 nm, and 200 nm in diameter decreased 0.7%, 1.8%, and 2.9%, respectively, compared with those at volume ratio 0% (no subsurface nanoglistenings). At a volume ratio of 0.1%, the peak irradiance of subsurface nanoglistening particles 100 nm, 150 nm, and 200 nm decreased 1.5%, 3.6%, and 5.7%, respectively. Forward light scattering increased with increased size of subsurface nanoglistening particle and volume ratio. The MTF was not altered by changes in subsurface nanoglistening particle size or volume ratio.

CONCLUSIONS

Subsurface nanoglistenings increased forward scattering slightly and reduced irradiance but significantly diminished retinal image. The effect of subsurface nanoglistenings on visual function in the absence of severe retinal disease was minimal.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Laboratory analyses of two explanted hydrophobic acrylic intraocular lenses

Two three-piece hydrophobic acrylic intraocular lenses (IOLs) were explanted from two patients at 7 and 9 years, respectively, after implantation, because of poor fundus visualisation and/or a clinically significant decrease in visual acuity related to their opacified IOLs. In addition to light microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy, confocal laser scanning microscopy was used for the first time to observe the explanted IOLs. The clinical aspect seemed to correspond to the phenomenon of surface light scattering, while laboratory analyses showed dense glistenings in the central layer of the IOL optic, which had no change next to the surface. Further studies on these phenomena are needed.

Evaluation of the impact of light scatter from glistenings in pseudophakic eyes

PURPOSE

To study the impact of light scatter from glistenings in pseudophakic eyes using ray tracing in a model eye

SETTING

Department of Research, Advanced Vision Science, Inc., Goleta, California, USA.

DESIGN

Mathematical modeling and simulation.

METHODS

A pseudophakic eye model was constructed in Zemax using the Arizona eye model as the basis. The Mie scattering theory was used to describe the intensity and direction of light as it scatters for a spherical particle immersed in a given media (intraocular lens [IOL]). The modeling and evaluation of scatter and modulation transfer function (MTF) were performed for several biomaterials with various size and density of glistenings under scotopic, mesopic, and photopic conditions.

RESULTS

As predicted by the Mie theory, the amount of scatter was a function of the relative difference in refractive index between the media and the scatterer, the size of the scatterer, and the volume fraction of the scatterer. The simulation demonstrated that an increase in density of glistenings can lead to a significant drop in the MTF of the IOL and the pseudophakic eye. This effect was more pronounced in IOLs with smaller cavitations, and the observation was consistent for all tested biomaterials.

CONCLUSIONS

Mathematical modeling demonstrated that glistenings in IOLs will lead to reduction in the MTF of the IOL and the pseudophakic eye. The loss in MTF was more pronounced at high densities and small cavitation sizes across all biomaterials. Inconsistent and poor clinical quantification of glistenings in IOLs may explain some inconsistencies in the literature.

Light scattering and light transmittance of cadaver eye-explanted intraocular lenses of different materials

PURPOSE

To evaluate light scattering and light transmittance in cadaver eye-explanted intraocular lenses (IOLs) manufactured from different materials.

SETTING

John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.

DESIGN

Experimental study.

METHODS

Forty-nine pseudophakic cadaver eyes were selected according to IOL material/type and implantation duration, and the IOLs were explanted. Hydrophobic acrylic, hydrophilic acrylic, poly(methyl methacrylate) (PMMA), and silicone IOLs were included. Gross and light microscopy was performed for all IOLs. Light scattering was measured with an EAS 1000 Scheimpflug camera, and light transmittance was assessed using a Lambda 35 UV/Vis spectrophotometer (single-beam configuration with an RSA PE-20 integrating sphere). Analyses were performed at room temperature in the hydrated state and compared with analyses of controls.

RESULTS

The highest levels of surface light scattering were measured for 3-piece hydrophobic acrylic, which was also the IOL type with the longest implantation duration among the Acrysof hydrophobic acrylic IOLs. Hydrophilic acrylic, PMMA, and silicone IOLs exhibited relatively low light-scattering levels. The lowest light-scattering levels were observed with PMMA IOLs (1-piece looped and 3-piece) and plate silicone IOLs, which represent the IOL types with the longest implantation duration in this series. Light transmittance values measured for all IOL types appeared to be similar to the values of the corresponding control IOLs.

CONCLUSIONS

The phenomenon of surface light scattering (nanoglistenings) is more particularly related to hydrophobic acrylic IOLs and increases with implantation time. No significant effect of surface light scattering on IOL light transmittance was found.

Effects of glistenings in intraocular lenses

Glistenings consist of multiple microvacuoles in intraocular lenses (IOLs) that cause retinal stray light and may affect quality of vision. For four IOL types, the microvacuole particle size distribution and particle volume density was measured using confocal light microscopy and dark field microscopy, and the corresponding extinction coefficient γ was determined. The light scatter contribution induced by microvacuoles was measured as function of both angle and extinction, and was verified by calculations using Mie theory. Two IOL types possessed significant glistenings having stray light levels higher than that of a healthy 20 year old crystalline lens corresponding to γ ≥ 0.08 mm(-1).

Etiology of surface light scattering on hydrophobic acrylic intraocular lenses

PURPOSE

To study the etiology of surface light scattering on hydrophobic acrylic intraocular lenses (IOLs).

SETTING

Alcon Research Laboratories, Fort Worth, Texas, USA.

DESIGN

Experimental study.

METHODS

Intraocular lenses were obtained from clinical explantations (n = 5), from human cadavers (n = 8), and from finished-goods inventory (controls). Surface light scattering was measured and imaged with the IOLs in various hydration states (dry, short-term wetted, and long-term hydrated) before and after proteins were quantified and removed. Selected IOL samples were analyzed with x-ray photoelectron spectroscopy, scanning electron microscopy (SEM) with energy-dispersion x-ray analysis, Fourier-transform infrared spectroscopy with attenuated total reflectance, and cryogenic SEM with a focused ion beam.

RESULTS

No inorganic deposits or organic changes were observed on any IOL surface. Under clinically relevant hydrated conditions, surface light-scattering intensity was independent of proteinaceous biofilm state (P≥.11). Instead, the hydration state of the IOLs significantly contributed to the intensity of surface light scattering (P<.001); clinically explanted and cadaver-eye IOLs (but not control IOLs) exhibited minimal scatter when dry, intermediate scatter when wetted, and maximum scatter when hydrated. Subsurface nanoglistenings with diameters less than a micron and with locations up to 120 μm from the surface of the IOLs were characterized by SEM with a focused ion beam and were identified as the source of the hydration-related surface light scattering.

CONCLUSION

Surface light scattering on hydrophobic IOLs was predominantly caused by hydration-related subsurface nanoglistenings within the acrylic IOL material.

Long-term effect of surface light scattering and glistenings of intraocular lenses on visual function

PURPOSE

To investigate the long-term effect of surface light scattering and glistenings of various intraocular lenses (IOLs) on visual function and optical aberrations after cataract surgery.

DESIGN

Case-control study.

METHODS

Thirty-five eyes that underwent implantation of a hydrophobic acrylic, silicone, or polymethyl methacrylate (PMMA) IOL more than 10 years ago were recruited. The scattering light intensity of the surface and internal matrix of the optic was measured using Scheimpflug photography. Visual acuity (VA) was measured using VA charts, and contrast VA and that with glare (glare VA) were examined using a contrast sensitivity tester. Ocular higher-order aberrations (HOAs) were measured using a Hartmann-Shack aberrometer.

RESULTS

Mean scattering light intensity of the surface and internal matrix of the optic was significantly higher in the acrylic group than in the silicone and PMMA groups (P < .0001). Mean uncorrected VA, photopic and mesopic contrast VA and glare VA, and HOAs did not differ significantly among groups, although mean corrected VA in the acrylic group was significantly better than that in the other groups (P = .0023). Scattering light intensity of the surface and internal matrix did not correlate with VA, contrast VA, or glare VA, and did not correlate with ocular and internal optic HOAs in the acrylic group.

CONCLUSIONS

At more than 10 years postoperatively, visual function, including contrast sensitivity, and ocular HOAs were comparable among eyes that received acrylic, silicone, and PMMA IOLs. Surface scattering and glistenings with the acrylic IOLs were not significantly correlated with visual function and optical aberrations.

Effect on visual acuity of increased surface light scattering in intraocular lenses

PURPOSE

To assess the long-term increase in surface light scattering of foldable hydrophobic acrylic intraocular lenses (IOLs) and to evaluate its effect on visual acuity.

SETTING

Miyata Eye Hospital, Miyazaki, Japan.

DESIGN

Cross-sectional study.

METHODS

The clinical records of patients who received an Acrysof IOL (study group) or a Sensar AR40 or AR40e IOL (control group) were reviewed retrospectively. Surface light scattering of IOLs was measured 1 year postoperatively or later. The corrected distance visual acuity (CDVA) at the surface-light-scattering examination was compared with the CDVA 1 month after IOL implantation. The changes in CDVA over time were compared with the increase in surface light scattering.

RESULTS

The study evaluated 466 eyes of 337 patients. Surface light scattering in the study group continued to increase up to 15 years postoperatively. The light scattering was higher on the anterior IOL surface after 4.5 years. Increased surface light scattering had no significant impact on CDVA; however, there were more cases with decreased CDVA when the surface light scattering exceeded 50 computer-compatible tape steps.

CONCLUSION

Surface light scattering with the implanted foldable hydrophobic acrylic IOL continuously increased during the postoperative years and was a risk for decreased visual acuity.

Clinical evaluation of the transparency of hydrophobic acrylic intraocular lens optics

PURPOSE

To clinically evaluate postoperative changes in the transparency of hydrophobic acrylic intraocular lenses (IOLs).

SETTING

Department of Ophthalmology, Dokkyo Medical University, Tochigi, Japan.

DESIGN

Case-control study.

METHODS

Eyes having phacoemulsification were randomly assigned to have implantation of 1 of 3 hydrophobic acrylic IOL models. The IOLs were photographed at 0 degree and 90 degrees 1 week, 6 months, and 1 year after implantation using a Nidek EAS-1000 anterior chamber analyzer in slit mode. The images were used to determine the intensity of light scattering in the surface and middle regions of the IOL optic.

RESULTS

The study comprised 65 eyes of 57 patients with a mean age of 72.5 years. The rate of increase in light-scattering intensity was similar in the middle and surface regions of the Tecnis ZA9003 aspheric IOL. The increase in light-scattering intensity in both regions of the AF-1 VA-60BB spherical IOL was greater than that in the aspheric IOL at all the measurement points. The intensity of light scattering was highest and tended to increase over time in both regions of the AcrySof SA60AT spherical IOL; the rate of increase in intensity was higher in the surface region than in the middle region, and the difference was significantly greater at 6 months and 1 year than at 1 week.

CONCLUSION

Our results suggest that AcrySof SA60AT and AF-1 VA-60BB IOLs are likely to develop glistenings over time and that the former may develop whitening.