Etiology of surface light scattering on hydrophobic acrylic intraocular lenses

Differential Diagnosis of Changes in Intraocular Lenses

Differentiating between various intraocular lens (IOL) changes can be a challenge. In particular, certain IOL models carry the risk of late postoperative calcification. A major cause of IOL exchange surgery could be avoided if appropriate modifications were made during the IOL manufacturing process. The use of a hydrophilic acrylate carries the risk of IOL calcification, especially when a secondary procedure, such as a pars plana vitrectomy or other procedures using gas or air, is performed. In secondary IOL calcification, there is a wide range of opacification patterns, which are usually located in the centre on the anterior surface of the IOL or sometimes elsewhere. Often, granular deposits accumulate just below or on the surface of the IOL, leading to significant deterioration in visual quality and eventually requiring IOL exchange surgery. Therefore, in the case of eyes requiring secondary surgical intraocular intervention in the future, the use of hydrophilic IOLs should be critically evaluated. With regard to hydrophobic IOL materials, there are clear differences in the susceptibility to the formation of glistenings. Over time, there has been a significant decrease in glistening formation over the past 30 years due to optimisation of the material. With hydrophobic IOLs, special care should also be taken to avoid mechanical damage. In general, the only treatment option for functionally-impairing IOL opacification is surgical lens exchange, which carries potential risks of complications. In cases with a low degree of functional impairment, and especially in eyes with additional ocular diseases, it may be difficult to weigh the risk of additional surgery against the potential benefit. In some cases, it may be more appropriate not to perform an IOL exchange despite the IOL opacification. Recent visualisation methods that allow high-resolution analysis of the opacities in vivo and in vitro may be used in the future to estimate the functional effects of various IOL material changes on the optical quality.

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.

Geometric-phase intraocular lenses with multifocality

We demonstrate a new type of multifocal and extended depth of focus (EDOF) intraocular lenses (IOLs) embedding μm-thin geometric phase (GP) lens layers. As an emerging approach for lens phase design, the GP modulated IOLs outperform conventional diffractive IOLs in multifocality while completely avoiding the clinically undesirable demand for additional surface patterns to standard monofocal IOL designs. The number of foci and light splitting ratio of the GP IOLs are adjusted by changing the number of stacked GP layers and the thickness of each layer. Bifocal and trifocal GP IOLs are fabricated by radial alignment of anisotropic orientation in UV-curable liquid crystal polymers. After characterizing the defocus image and modulation transfer function of the GP IOLs, it is expected that GP IOLs will alleviate the most common problems associated with multifocal and EDOF IOLs, blurred vision and photic phenomena caused by light scattering and posterior capsule opacification.

Five-year clinical outcomes of rigid iris-fixated phakic intraocular lens in northern Chinese

PURPOSE

To investigate the 5-year clinic outcomes of rigid iris-fixated pIOL on the visual performance, complications and intraocular light scattering in northern Chinese.

METHODS

Thirty eyes implanted with iris-fixated phakic IOLs (pIOLs group) and 34 eyes with high myopia (myopia group) were involved in this study. At preoperatively, 6 months, 1, 3, and 5 years postoperatively, the uncorrected visual acuity (UCVA), best-spectacle corrected visual acuity (BSCVA), endothelial cell density (ECD), and intraocular pressure (IOP) were measured in pIOLs group. The objective scatter index (OSI), modulation transfer function cut off (MTF cut off), and Strehl ratio were measured by Optical Quality Analysis System and a pseudophakic dysphotopsia questionnaire (PDQ) was used to evaluate the subjects' satisfaction in pIOLs and myopia groups.

RESULTS

At 5 years postoperatively, an UCVA of 20/20 or better was found in 43.33% of eyes in pIOLs group. At 6 months, 1, 3, and 5 years postoperatively, the mean ECD decrease were 1.29% ± 0.45%, 2.59% ± 1.30%, 6.67% ± 2.26%, and 10.80% ± 3.48%. The value of OSI in pIOLs group was significantly higher than that in myopia group (P < 0.001). The PDQ results showed that the subjects in myopia group complained less with intolerance of bright lights than those in pIOLs group. The values of Strehl ratio and MTF cut off in pIOLs group were significantly lower than that in myopia group (P < 0.001).

CONCLUSIONS

Iris-fixated pIOL induce more intraocular light scattering. A significant decrease in ECD was observed at 5 years postoperatively. An annual evaluation of ECD is necessary for patients undergoing pIOL implantation.

Intraocular Scattering, Blinking Rate, and Tear Film Osmolarity After Exposure to Environmental Stress

Purpose

Dry environments, such as those in offices or aircraft cabins, can potentially generate ocular discomfort and alter the tear film. We compare light scatter, blinking rate, and tear osmolarity in young and older subjects after exposure to low humidity using a controlled environmental chamber.

Methods

Two groups of healthy subjects were recruited; younger (N = 13, 27 ± 6 years) and older (N = 23, 71 ± 7 years). Measurements were carried out before and after 90-minute exposure to low relative humidity (5%) and constant temperature (23 degrees). Ocular light scatter was measured using a double-pass instrument (OQAS, Visiometrics, Spain). Blinking rate was monitored using an infrared video camera. Tear osmolarity was measured using the TearLab system (Escondido, CA, USA).

Results

Ocular light scatter increased by a factor of 10% after exposure to low humidity in the older group (P = 0.03) but did not change significantly in the younger group. Blinking rate increased significantly (40% more blinks) in both groups but there was no difference between the groups. No significant differences in osmolarity were shown between two age groups or as result of environmental stress.

Conclusions

Exposure to dry environment increased light scatter in older subjects. Although more blinks were triggered in both younger and older groups to prevent corneal dehydration, there was no difference between the groups. Blink rate and osmolarity are not associated with the difference in light scatter.

Translational Relevance

Our work approaches a clinical care problem using basic research methods (measuring ocular scatter and blink ratio).

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.

Surface light scattering from 1-piece hydrophobic acrylic intraocular lenses with hydroxyethyl methacrylate: contralateral observation for 7 years

PURPOSE

To quantitatively and intraindividually compare surface light scattering for 7 years after implantation of Clareon and AcrySof intraocular lenses (IOLs).

SETTING

Miyata Eye Hospital, Miyazaki, Japan.

DESIGN

Retrospective comparative case series.

METHODS

Clinical records of eyes that had contralateral implantation of SN60WF and SY60WF IOLs were reviewed. Light scattering on the anterior surface of IOLs, corrected distance visual acuity (CDVA), and mesopic and photopic contrast sensitivities were examined at 1 year, 3 years, and 7 years postoperatively, and they were intraindividually compared.

RESULTS

34, 19, and 16 patients visited at 1 year, 3 years, and 7 years postoperatively, respectively. Surface light scattering in eyes with SY60WF IOL was significantly reduced, and the rate of increase was 2.74 computer compatible tapes per year. Although there were prominent increases in eyes with SN60WF IOL, no statistically significant difference was found in their CDVA and contrast sensitivities.

CONCLUSIONS

In eyes with Clareon IOLs, the development of surface light scattering was suppressed up to 7 years. The increase rate demonstrated that the visual acuity would be least deteriorated up to 12 years postoperatively, whereas the influence of straylight induced should be investigated.

Atomic force microscopy comparative analysis of the surface roughness of two posterior chamber phakic intraocular lens models: ICL versus IPCL

BACKGROUND

To compare the anterior surface roughness of two commercially available posterior chamber phakic intraocular lenses (IOLs) using atomic force microscopy (AFM).

METHODS

Four phakic IOLs were used for this prospective, experimental study: two Visian ICL EVO+ V5 lenses and two iPCL 2.0 lenses. All of them were brand new, were not previously implanted in humans, were monofocal and had a dioptric power of - 12 diopters (D). The anterior surface roughness was assessed using a JPK NanoWizard II® atomic force microscope in contact mode immersed in liquid. Olympus OMCL-RC800PSA commercial silicon nitride cantilever tips were used. Anterior surface roughness measurements were made in 7 areas of 10 × 10 μm at 512 × 512 point resolution. The roughness was measured using the root-mean-square (RMS) value within the given regions.

RESULTS

The mean of all anterior surface roughness measurements was 6.09 ± 1.33 nm (nm) in the Visian ICL EVO+ V5 and 3.49 ± 0.41 nm in the iPCL 2.0 (p = 0.001).

CONCLUSION

In the current study, we found a statistically significant smoother anterior surface in the iPCL 2.0 phakic intraocular lenses compared with the VISIAN ICL EVO+ V5 lenses when studied with atomic force microscopy.

Quantification of the In Vitro Predisposition to Glistening Formation in One Manufacturer's Acrylic Intraocular Lenses Made in Different Decades

Introduction

Foldable hydrophobic acrylic intraocular lenses (IOLs) are prone to develop a long-term postoperative material change called glistenings. The aim of this study was to investigate the changes in the predisposition for glistening formation in one type of hydrophobic acrylic IOL material from its introduction to the present day.

Methods

In a laboratory setup, an in vitro model was used to induce glistenings in hydrophobic acrylic IOLs manufactured by one company (Alcon, Fort Worth, TX, USA) in different years: 23 1990s-manufacture hydrophobic acrylic three-piece IOLs (MA30BA/MA60AC) that were explanted in 1996 and 1997, and five of each of the newer AcrySof IOL models (MA60AC, SA60AT, TFNT00 and SN60WF) from 2014 to 2017. Furthermore, five Clareon (SY60WF) IOLs were put through the same accelerated aging procedure. The number of microvacuoles per square millimeter (MV/mm²) was determined in the central part of each IOL optic and compared between the groups.

Results

The mean number of MV was highest in the 1990s-manufacture Alcon acrylic IOLs, with 1289 (± 738) MV/mm². The number decreased to 650 (± 101), 192 (± 105), 175 (± 112) and 47 (± 26) for MA60AC, SA60AT, TFNT00 and SN60WF, respectively. The lowest count was obtained in the Clareon group, with 1 (± 1) MV/mm².

Conclusions

A high number of glistenings was induced in the explanted IOLs from the 1990s. The propensity for glistening formation decreased considerably after that decade and now in current use. Even though in vitro glistening formation in today’s AcrySof material was low, the Clareon material was essentially glistenings-free.

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.

Scanning electron microscopic features of explanted degraded hydrophobic acrylic intraocular lenses which were in vivo for a prolonged period

Purpose:

To study and document electron microscopic features in explanted hydrophobic microvacuoles affected acrylic intraocular lenses (IOL) which were in vivo for an average duration of 11 years.

Methods:

Scanning electron microscopic (SEM; Hitachi S 3000 N EXAX Genesis VP SEM) study of five explanted hydrophobic acrylic IOL which had clinically evident microvacuoles prior to explantation, was done. The IOLs were in vivo for a prolonged period and needed explantation for various indications. Only those hydrophobic acrylic IOLs which fulfilled the inclusion criteria were included. The findings were compared with control specimens.

Results:

The IOLs were in vivo for an average duration of 11.6 ± 4.21 years. The cause of explantation of IOL was subluxation in four cases and low visual acuity in one case. Bulk degradation and microvacuoles on cut sections throughout the IOL optics and undulating surface patterns over both the surfaces of the IOL has been documented in all the specimens. No such findings were noted in the control specimens where the surface and texture were homogenous.

Conclusion:

SEM findings of the structural changes in explanted IOL documented in the study demonstrate that hydrophobic acrylic IOL is degradable in vivo. Microvacuoles are a clinical manifestation of the structural changes that occur at a microscopic and molecular level. These changes are not seen in IOLs which have not undergone intraocular implantation. To our knowledge, a similar study of this kind has not been done.

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.

An evaluation of glistening and stability of intraocular lens material manufactured by different methods

PURPOSE

To evaluate glistening and long-term stability of five commercially available intraocular lenses.

METHODS

This experimental study evaluated the SN60WF (Alcon), XY1 (Hoya), NS-60YG (NIDEK), ZCB00V (Johnson & Johnson Vision) and AN6KA (Kowa) intraocular lenses. To generate glistenings, intraocular lenses were immersed in physiological saline at 50°C for 2 h, then left in situ at 35°C and removed at regular intervals over 24 h. Stability of the intraocular lens material was assessed by immersing intraocular lenses into vials of purified water placed at 100°C for 115 days, which simulated 20-year ageing. Gas chromatography-mass spectrometry was used to detect leached compounds.

RESULTS

Almost no glistenings were observed for the AN6KA. Glistenings were observed in the remaining intraocular lenses after 3 h. The number of glistenings gradually disappeared by 6 h for all intraocular lenses except SN60WF (12 h). Only the NS-60YG and ZCB00V intraocular lenses had no changes in weight or dimensions. Gas chromatography-mass spectrometry detected phenethyl alcohol in XY1 and SN60WF, 2-phenoxyethanol in AN6K and no compounds in the remaining intraocular lenses. A peak shift due to the carbonyl group between 1600 and 1700 cm^-1 was detected for the SN60WF and AN6K intraocular lenses only.

CONCLUSION

SN60WF had the most numerous glistenings that resolved over a longer duration. The long-term stability test confirmed elution of the intraocular lens material-derived compounds and signs of degradation for the XY1, SN60WF and AN6K intraocular lenses. NS-60YG and ZCB00V showed no signs of deterioration due to ageing. Differing manufacturing methods likely play a role in the stability of intraocular lenses.

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.

Late postoperative opacification of a hydrophobic acrylic intraocular lens AcryNovaTMPC 610Y

PURPOSE

To report late postoperative opacification of a hydrophobic acrylic intraocular lens (IOL) AcryNovaTMPC 610Y as well as the clinical consequences in patients 10 years after uncomplicated cataract surgery.

MATERIALS AND METHODS

Medical records were reviewed of 23 patients (26 eyes) with AcryNovaTMPC 610Y implantated between years 2005 and 2007. Next clinical examination was performed 10 years after surgery. We assessed best corrected distance visual acuity (BCDVA), contrast sensitivity (CSV-1000E) and relative opacity of IOL material, (OCULUS Pentacam HR). Results of BCDVA and Pentacam were analysed statistically. One explanted IOL was analysed using anterior segment OCT in vitro and spectroscopic method EDX (Energy-dispersive X-ray spectroscopy).

RESULTS

Opacification led to a statistically significant reduction in the best corrected distance visual acuity (BCDVA) = (0,95 ± 0,10) versus (0,87 ± 0,20) and to increase of IOL opacity only in some lenses but statistically significant in the average (6,37 ± 2,16)% versus value of (14,22 ± 5,87)%. In the explanted IOL we have documented structural changes of primarily hydrophobic raw material leading to property of hydrophilic one.

CONCLUSION

Some batches of AcryNovaTMPC 610Y were produced from raw material of poor quality which is the cause of its structural changes and its progressive opacification.

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.

Reversible opacification of hydrophobic acrylic intraocular lens- two cases report

Background

The opacification of the intraocular lens (IOL) can cause significant visual deterioration. It is known that opacity of hydrophobic acrylic IOLs is rare. We report 2 cases of reversible optic opacification of hydrophobic acrylic intraocular lenses (Tecnis ZCB00, Abbott), observed within 2 months after uneventful cataract surgery.

Case presentation

Case 1: Uneventful cataract surgery was performed on the left eye of an 86-year-old diabetic man with chronic open-angle glaucoma. A hydrophobic acrylic intraocular lens (IOL; Tecnis ZCB00, Abbott, Lake Bluff, IL) was implanted in the bag. Eye drops containing 0.5% levofloxacin and 1.0% prednisolone were used after surgery along with topical anti-glaucoma medications. At 7 weeks postoperative, cloudy, concentric IOL opacification developed, accompanied by decreased visual acuity and increased intraocular pressure. However, the opacification completely disappeared after 9 weeks.

Case 2: Uneventful cataract surgery was performed on the left eye of a 72-year-old woman. A hydrophobic acrylic IOL (Tecnis ZCB00) was implanted in the bag. At 2 weeks postoperative, cloudy, concentric IOL opacification developed, accompanied by ocular discomfort. After 4 weeks, opacification and discomfort completely disappeared.

Conclusions

We observed two cases of completely reversible opacification of hydrophobic acrylic IOLs. The exact nature of the transient opacity remains unclear, but an inflammatory origin cannot be completely ruled out.

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.

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.

Light scattering and light transmittance in a series of calcified single-piece hydrophilic acrylic intraocular lenses of the same design

PURPOSE

To evaluate light scattering and light transmittance of Ioflex hydrophilic acrylic intraocular lenses (IOLs) explanted because of clinically significant opacification secondary to calcification.

SETTING

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

DESIGN

Experimental study.

METHODS

Seven explanted and 8 control Ioflex IOLs were studied. Gross and light microscopy of all the IOLs were performed. Light scattering was measured with a Scheimpflug camera, and light transmittance was assessed with a spectrophotometer. Analyses were performed at room temperature in the hydrated state, and findings of the explanted and control IOLs were compared.

RESULTS

Light scattering was 219.71 computer compatible tape (CCT) ± 2.62 (SD) for explanted IOLs and 4.75 ± 2.50 CCT for controls. The mean light transmittance in the visible light spectrum was 75.94% to 87.25% for explanted IOLs and 97.54% to 98.97% for controls. The most striking finding was variable degrees of light transmittance between 290 nm and 350 nm (ultraviolet-A and B radiation) in the explanted and control IOLs with expiration dates in 2009/2010 but 0% transmittance in this region in all controls with expiration dates in 2011/2012.

CONCLUSIONS

Light scattering was extremely high and transmittance was significantly reduced in calcified IOLs. Differences in transmittance observed in the 290 to 350 nm region between IOLs with different expiration dates were related to use of different hydrophilic acrylic raw material suppliers in the manufacture of the IOLs, highlighting the complexity of IOL calcification investigations.