Light scattering and light transmittance in intraocular lenses explanted because of optic opacification

Material Analysis of Explanted Calcified Silicone Intraocular Lenses in Association with Asteroid Hyalosis

INTRODUCTION

The aim of this study was to analyze posterior surface opacification in explanted silicone intraocular lenses (IOLs) with clinicopathologic correlation to asteroid hyalosis.

METHODS

In a laboratory setup, 12 explanted silicone IOLs underwent laboratory analyses, including light microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy for elemental composition (EDX). Relevant clinical data were obtained for each case, including gender, age at IOL implantation, dates of implantation and explantation, as well as history of neodymium-dopped yttrium aluminum garnet (Nd:YAG) laser treatments or other opacification removal attempts. High-resolution optical coherence tomography (OCT) images were obtained in vitro with an anterior segment OCT device (Anterion, Heidelberg Engineering, Heidelberg, Germany).

RESULTS

Calcification located at the posterior optic surface of each lens was identified through SEM and EDX analyses, revealing deposits composed of hydroxyapatite. In all cases, IOL polishing using Nd:YAG laser had been attempted prior to IOL exchange. The clinical functional data showed that this type of IOL opacity led to increase in straylight and subjective symptoms of glare.

CONCLUSIONS

Silicone IOLs can develop posterior surface calcification in eyes with asteroid hyalosis. There are mechanical techniques of cleaning the IOL surface but in many cases, IOL explantation is the only sustainable way to reduce the patients' straylight levels and glare symptoms. Due to the risk of posterior surface calcification, silicone IOL implantation should be avoided in eyes with asteroid hyalosis.

Transmittance characteristics of transparent hydrophobic acrylic foldable intraocular lenses that were in vivo for a prolonged period of time: A UV visible spectrophotometric study

PURPOSE

To record experimental data on the spectral transmittance characteristics of transparent hydrophobic acrylic foldable IOLs, which were in vivo for a prolonged period of time and explanted under clinical indications and also to compare the data with that of corresponding control and crystalline lens along with review of the relevant literature.

METHOD

Material and make of each of the explanted intraocular lenses (IOLs) as well as pre-explantation clinical status of the eyes were confirmed from the medical record. The transmittance of wavelength from 185 to 900 nm of each of the selected IOLs was measured using Shimadzu UV 2600 UV visible (UV-Vis) spectrophotometer in double-beam configuration and probe version 2.16 software. The data obtained were statistically analyzed.

RESULTS

The mean transmittance of 12 clinically explanted IOLs at spectral range 300-700 nm was 49.5% ± SD 6.9%. This value was 10% and 38% less than the corresponding clear (59% ± SD 0.4%) and yellow (87.5% ± SD 0.4%) control, respectively. The mean transmittance of the analytes in the UV range was 43.3 ± SD 6.9%, and it was almost similar to the control. The data showed wide variations without good correlation, and it matches with the human crystalline lens at the age range of 50-60 years. All eyes were otherwise healthy, and none had age-related macular degeneration.

CONCLUSION

In comparison with fresh IOL with a yellow filter, light transmittance at the spectral range 300-700 nm was found decreased in all the IOLs, which were in vivo for an average period of 12.25 ± 4.4 years. All IOLs transmitted variable amounts of UV radiation. More data are required for further analysis on the subject.

The effect of hypotensive drugs on intraocular lenses clarity

OBJECTIVES

To assess the effect of hypotensive drugs on light absorbance, discoloration, opacification and precipitate formation of IOLs.

METHODS

In this laboratory study, four types of IOLs (two hydrophilic-acrylic-L1 and L2, and two hydrophobic-acrylic-B1 and B2) were soaked in solutions containing Timolol-maleate 0.5%, Dorzolamide 2%, Brimonidine-tartrate 0.2%, Latanoprost 0.005%, Brimonidine-tartrate/Timolol-maleate 0.2%/0.5% and Dorzolamide/Timolol-maleate 2%/0.5%. Non-treated IOLs and IOLs soaked in balanced salt solution (BSS) served as controls. All Treated lenses were sealed in containers and placed in an oven at 82 degrees Celsius for 120 days. Each IOL was examined using four different techniques: light microscopy imaging, light absorbance measurements at 550 nanometers through the optic's center, assessment of by a scanning electron microscope (SEM), and energy dispersive Xray spectrometry (EDX).

RESULTS

Ninety-eight IOLs were included. All BSS-soaked IOLs appeared clear with no significant discoloration or precipitate-formation. Light absorbance in these lenses was comparable to that of non-soaked, non-heated IOLs. No calcium or phosphate were detected in either of these groups. Light absorbance differed significantly between the four treated IOL types. The drops most affecting light absorbance differed between IOLs. Gross examination revealed brown and yellow discoloration of all IOLs soaked in Dorzolamide and Brimonidine-tartrate solutions, respectively. SEM demonstrated precipitates that differed in size, morphology and distribution, between different IOL-solution combinations. EDX's demonstrated the presence calcium and phosphor in the majority of precipitates and the presence of sulfur in brown discolored IOLs.

CONCLUSIONS

In vitro, interactions between hypotensive drugs and IOLs induce changes in light absorbance, discoloration and precipitate formation.

Clinical Characteristics of Patients with Intraocular Lens Calcification after Pars Plana Vitrectomy

AIM

To determine the clinical risk factors that may increase the occurrence of intraocular lens (IOL) calcification in patients who had undergone pars plana vitrectomy (PPV).

METHODS

The medical records of 14 patients who underwent IOL explantation due to clinically significant IOL opacification after PPV were reviewed. The date of primary cataract surgery, technique and implanted IOL characteristics; the time, cause and technique of PPV; tamponade used; additional surgeries; the time of IOL calcification and explantation; and IOL explantation technique were investigated.

RESULTS

PPV had been performed as a combined procedure with cataract surgery in eight eyes and solely in six pseudophakic eyes. The IOL material was hydrophilic in six eyes, hydrophilic with a hydrophobic surface in seven eyes and undetermined in one eye. The endotamponades used during primary PPV were C2F6 in eight eyes, C3F8 in one eye, air in two eyes and silicone oil in three eyes. Two of three eyes underwent subsequent silicone oil removal and gas tamponade exchange. Gas in the anterior chamber was detected in six eyes after PPV or silicone oil removal. The mean interval between PPV and IOL opacification was 20.5 ± 18.6 months. The mean BCVA in logMAR was 0.43 ± 0.42 after PPV, which significantly decreased to 0.67 ± 0.68 before IOL explantation for IOL opacification (p = 0.007) and increased to 0.48 ± 0.59 after the IOL exchange (p = 0.015).

CONCLUSIONS

PPV with endotamponades in pseudophakic eyes, particularly gas, seems to increase the risk for secondary IOL calcification, especially in hydrophilic IOLs. IOL exchange seems to solve this problem when clinically significant vision loss occurs.

Imaging Function and Relative Light Transmission of Explanted Opacified Hydrophilic Acrylic Intraocular Lenses

We evaluated the influence of intraocular lens (IOL) opacification on the optical performance of explanted hydrophilic acrylic IOLs. We performed a laboratory analysis of 32 Lentis LS-502-1 (Oculentis GmbH, Berlin, Germany) IOLs, explanted due to opacification, in comparison with six clear unused samples of the same IOL model. Using an optical bench setup, we obtained modulation transfer function (MTF), Strehl ratio, two-dimensional MTF, and United States Air Force (USAF) chart images. In addition, we assessed light transmission through the IOLs. The MTF values of opacified IOLs at 3-mm aperture were similar to those of clear lenses, with the median (interquartile range) values of 0.74 (0.01) vs. 0.76 (0.03) at the spatial frequency of 50 line pairs per millimeter in clear and opacified IOLs, respectively. The Strehl ratio of opacified lenses was not lower than that of clear lenses. The USAF-chart analysis showed a considerable reduction in brightness in opacified IOLs. The median (interquartile range) relative light transmission of opacified IOLs in comparison to clear lenses was 55.6% (20.8%) at the aperture size of 3 mm. In conclusion, the explanted opacified IOLs had comparable MTF values to those of clear lenses but significantly reduced light transmission.

In-Plane Phonon Anisotropy and Anharmonicity in Exfoliated Natural Black Arsenic

Group-VA two-dimensional layered materials in a puckered honeycomb structure exhibit strong in-plane anisotropy and have emerged as new platforms for novel devices. Here, we report on systematic Raman investigations on exfoliated b-As flakes on the A_g¹ and A_g² polarization dependence on their symmetry, excitation wavelength, and flake thickness. The intensity maximums of both phonons are corrected in the b-As armchair direction under 633 nm excitation regardless of the flake thickness upon considering optical birefringence effects and interference effects. The intensity ratio of A_g¹ to A_g² modes under 532 nm excitation is useful for b-As crystalline orientation identification. Temperature-dependent Raman investigations reveal the linearly anharmonic behaviors of both phonons in the range from 173 to 293 K and a slightly greater first-order temperature coefficient in the zigzag direction. Our findings give deep insight into the in-plane phonon anisotropy and anharmonicity of b-As and provide a step toward future device applications.

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.

A Novel Approach for Assessing Visual Impairment Caused by Intraocular Lens Opacification: High-Resolution Optical Coherence Tomography

PURPOSE

To quantify in vitro straylight induced by intraocular lens (IOL) localized opacification using an anterior segment optical coherence tomography (OCT) device.

DESIGN

Laboratory investigation.

METHODS

We obtained high-resolution OCT cross-section images of 44 explanted IOLs using a new in vitro application for an anterior segment OCT device, the Anterion (Heidelberg Engineering, Heidelberg, Germany). In 24 cases, the reason for IOL explantation was a centrally localized opacification, the sequela of a secondary ocular surgery. As a control, we used 20 IOLs removed after an IOL (sub-)luxation. Using image analysis, we found a threshold area value representing a metric for the amount of opacification in a region of interest in the IOL's central optic. We used a modified C-Quant straylight meter (Oculus, Wetzlar, Germany) to quantify light scattering. We derived a linear regression from calculating the correlation between the amount of opacification and straylight.

RESULTS

We visualized different amounts of IOL opacification using the OCT device. The opacified lenses showed a mean threshold area of 6.7% ± 3.3% and mean straylight was 95.1 ± 75.6 deg²/sr. The clear group's mean threshold area was 2.0% ± 0.8% and 5.0 ± 3.4 deg²/sr mean straylight. Straylight correlated statistically significantly with the threshold area, with a correlation coefficient of R² = 0.80, P < .001.

CONCLUSIONS

This high-resolution OCT imaging technique can be used to visualize IOL opacities. The amount of opacification correlated well with the straylight induced by the lens. Anterior segment OCT imaging might be used in the future as a tool for predicting the extent of visual impairment and aid clinicians to quantify patients' complaints.

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.

Physicochemical Analysis of Sediments Formed on the Surface of Hydrophilic Intraocular Lens after Descemet's Stripping Endothelial Keratoplasty

An intraocular lens (IOL) is a synthetic, artificial lens placed inside the eye that replaces a natural lens that is surgically removed, usually as part of cataract surgery. The opacification of the artificial lens can be related to the formation of the sediments on its surface and could seriously impair vision. The physicochemical analysis was performed on an explanted hydrophilic IOL and compared to the unused one, considered as a reference IOL. The studies were carried out using surface sensitive techniques, which can contribute to a better understanding of the sedimentation process on hydrophilic IOLs’ surfaces. The microscopic studies allowed us to determine the morphology of sediments observed on explanted IOL. The photoelectron spectroscopy measurements revealed the presence of organic and inorganic compounds at the lens surface. Mass spectroscopy measurements confirmed the chemical composition of deposits and allowed for chemical imaging of the IOL surface. Applied techniques allowed to obtain a new set of information approximating the origin of the sediments’ formation on the surface of the hydrophilic IOLs after Descemet’s stripping endothelial keratoplasty.

Straylight due to intraocular lens opacification in a patient with asteroid hyalosis

Purpose

To report a rare case of intraocular lens (IOL) calcification in the presence of asteroid hyalosis with in-vivo measurements of straylight before and after treatment.

Observations

A patient with asteroid hyalosis presented with complaints of disability glare due to calcifications on the posterior surface of the IOL. Straylight, measured with the C-Quant, was 8.2x elevated compared to normal (log(s) 2.08). Dissolution of the posterior face IOL deposits was performed with a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser, resulting in a significant decrease in straylight (log(s) 1.76), congruent with the patient's subjective improvement.

Conclusions and importance

To the best of our knowledge, this is the first report describing a patient with an opacified IOL due to asteroid hyalosis with in-vivo measurements of straylight before and after treatment. It illustrates that awareness of glare complaints in patients with an opacified IOL is important, documentation with C-Quant measurements may be helpful in indicating treatment, evaluating the treatment, and following up the patient, and treatment with a Nd:YAG laser may dissolve the opacifications to a clinically satisfactory level.

Light scattering levels from intraocular lenses extracted from donor eyes

PURPOSE

To assess light scatter levels of intraocular lenses (IOLs) extracted from donor eyes to understand straylight elevation documented earlier in pseudophakic population studies and identify potential sources of light scattering in IOLs.

SETTING

Rotterdam Ophthalmic Institute, Rotterdam, the Netherlands.

DESIGN

Experimental study.

METHODS

Light scattering in 74 donor IOLs was measured with the C-Quant device adapted for in vitro analysis of IOLs. Straylight was assessed at a 2.5-degree and 7.0-degree scatter angle, and results were compared with the straylight of a 20-year-old crystalline lens, a 70-year-old crystalline lens, and a lens with cataract. To identify potential changes to the IOL material, the IOLs were examined with a light microscope and a slitlamp.

RESULTS

At 2.5 degrees and 7.0 degrees, the straylight parameter was 5.78 deg²/steradian (sr) ± 4.70 (SD) and 5.06 ± 4.01 deg²/sr, respectively. Forty-one percent of IOLs showed lower straylight than the 20-year-old lens. In 14%, the scattering intensity was higher than in the 70-year-old lens; none showed straylight comparable to that of the cataractous lens. Increased straylight was associated with surface deposits, snowflake-like degeneration, and glistenings. The incidence of IOL-related complications differed between the IOL groups.

CONCLUSIONS

Microscopic structural alterations of IOLs play a major role in straylight elevations in pseudophakic eyes. A clear correlation with degeneration and/or alteration of implanted IOLs was found. Although these IOL-related complications would likely not affect visual acuity, they give rise to straylight and thus can cause disability glare and other symptoms.

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.

Serial intraocular lens opacifications of different designs from the same manufacturer: Clinical and light microscopic results of 71 explant cases

PURPOSE

To report clinical findings and light microscopic results of 71 opacified hydrophilic acrylic intraocular lenses (IOLs).

SETTING

Vivantes Klinikum Neukoelln, Ophthalmology Department, Berlin, Germany.

DESIGN

Retrospective case series.

METHODS

Sixty-three patients (71 eyes) were referred to the clinic because of vision-impairing IOL opacification between December 2012 and September 2016 after routine cataract surgery elsewhere. The explanted IOLs were analyzed with light microscopy at the John A. Moran Eye Center (University of Utah, Salt Lake City, Utah, USA). Medical records were reviewed for visual acuity, comorbidities, and complications. Clinical follow up was 6 months.

RESULTS

Seventy-one opacified 1-piece or 3-piece hydrophilic acrylic IOLs (Lentis) of different designs from 2009 to 2012 (LS-502-1, LS-402-1Y, LS 312-1Y, LS-313-1Y, L-402, L-312) were found. Morphological findings were surface, subsurface, or deep calcifications of the IOL material. Explantation was performed 4 years ± 1.2 (SD) after initial phacoemulsification. The mean patient age was 78.6 ± 8.2 years. Ocular and systemic comorbidities were found without statistical correlation: the most frequent were diabetes, uveitis, and glaucoma. The preoperative mean corrected distance visual acuity changed from 0.63 ± 0.47 logarithm of the minimum angle of resolution (logMAR) to 0.20 ± 0.28 logMAR postoperatively (P < .001).

CONCLUSIONS

Different designs of IOLs by the same manufacturer, implanted between 2009 and 2012, developed late calcification with significant visual loss after routine cataract surgery. No medical, surgical, or ophthalmologic trigger could be determined. A manufacture issue might be the reason for the opacification.

Intraocular lens power adjustment by a femtosecond laser: In vitro evaluation of power change, modulation transfer function, light transmission, and light scattering in a blue light-filtering lens

PURPOSE

To evaluate intraocular lens (IOL) power, modulation transfer function (MTF), light transmission, and light scattering of a blue light-filtering IOL before and after power adjustment by a femtosecond laser obtained through increased hydrophilicity of targeted areas within the optic, creating the ability to build a refractive-index-shaping lens within an existing IOL.

SETTING

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

DESIGN

Experimental study.

METHODS

Ten CT Lucia 601PY single-piece yellow hydrophobic acrylic IOLs were used in this study. The IOL power and MTF were measured with a power and modulation transfer function device. Light transmission was measured using a Lambda 35 UV-VIS spectrophotometer. Backlight scattering was assessed with a Scheimpflug camera within the IOL substance. All measurements were done with hydrated IOLs. The IOLs were also evaluated under light microscopy (LM) before and after laser adjustment.

RESULTS

After laser adjustment, a mean power change of -2.037 diopters was associated with a MTF change of -0.064 and a light transmittance change of -1.4%. Backlight scattering increased within the IOL optic in the zone corresponding to the laser treatment at levels that are not expected to be clinically significant. Treated areas within the optic could be well appreciated under LM without damage to the IOLs.

CONCLUSION

Power adjustment of a commercially available hydrophobic acrylic blue light-filtering IOL by a femtosecond laser produced an accurate change in dioptric power while not significantly affecting the quality of the IOL.

Further Enhancement of Intraocular Open-Capsule Devices for Prevention of Posterior Capsule Opacification

Purpose

We improve the intraocular open-capsule devices (IOCD) for the prevention of posterior capsule opacification (PCO).

Methods

A total of 45 New Zealand rabbit eyes were divided into six similar groups after crystalline lens evacuation. Each group was implanted with a hydrophilic intraocular lens (IOL) and a hydrophilic IOCD of different designs. In the first experiment (Part A), a square design ring with and without large apertures was compared to a round design ring without apertures. In the second experiment (Part B), a square design ring with large apertures was compared to square design IOCDs with small apertures of high and low density. PCO and Soemmering's ring were evaluated clinically, by the Miyake Apple view, and histologically. The results were compared to a control group of eyes implanted with a hydrophilic IOL only.

Results

All devices showed significant prevention of PCO and Soemmering's ring compared to the control group. Part A: the square design with apertures had the lowest level of peripheral lens epithelial cells proliferation (protrusions). Part B: modifying the size and density of the apertures had no influence on those protrusions.

Conclusions

The IOCD significantly reduced the rate of PCO and its precursor, Soemmering's ring. The rings with the square edges and apertures produced the best results. The study was underpowered to determine the influence of the apertures design.

Translational Relevance

The IOCD has the potential to prevent up to 80% of the PCO cases; the most common complication after cataract surgery. The design of the ring is important for its success.

Opacification of the C-flex 570C intraocular lens after sulcus fixation

PURPOSE

To report a case of diffuse intraocular lens (IOL) opacification in a patient who started complaining of blurred vision in his left eye over the course of three years after having phacoemulsification surgery combined with capsular bag fixation of a C-flex 570C IOL. The IOL had been repositioned in the ciliary sulcus following its subluxation.

METHOD

An IOL exchange was performed, and the explanted IOL was sent for histopathological analysis.

RESULTS

Scanning electron microscopy identified multiple crystalline-like deposits on both sides of the IOL. The optic was more extensively involved than the haptics. Energy-dispersive X-ray spectroscopy confirmed the predominance of calcium within the deposits.

CONCLUSIONS

The breakdown of the blood-aqueous barrier seems to be a key component of this calcification process. Ciliary sulcus fixation is not a suitable option for C-flex 570C IOLs.

Transparent Blend of Poly(Methylmethacrylate)/Cellulose Acetate Butyrate for the Protection from Ultraviolet

The use of transparent polymers as an alternative to glass has become widespread. However, the direct exposure of these materials to climatic conditions of sunlight and heat decrease the lifetime cost of these products. The aim of this study was to minimize the harm caused by ultraviolet (UV) radiation exposure to transparent poly(methylmethacrylate) (PMMA), which usually leads to changes in the physical and chemical properties of these materials and reduced performance. This was achieved using environmentally friendly cellulose acetate butyrate (CAB). The optical, morphological, and thermal properties of CAB blended with transparent PMMA was studied using UV-VIS spectrophotometry, scanning electron microscopy, X-ray diffraction, dynamic mechanical analysis, and thermal gravimetric analysis. The results show that CAB was able to reduce the effects of UV radiation by making PMMA more transparent to UV light, thereby preventing the negative effects of trapped radiation within the compositional structure, while maintaining the amorphous structure of the blend. The results also show that CAB blended with PMMA led to some properties commensurate with the requirements of research in terms of a slight increase in the value of the modulus and the glass transition temperature for the PMMA/CAB blend.

Late Opacification of a Hydrophilic Acrylic Intraocular Lens in Europe

Purpose

To describe the clinical and microscopic findings in 2 different patients of 2 cases of late opacification of the hydrophilic acrylic intraocular lens (IOL) Ioflex.

Methods

Two eyes of 2 patients (73 and 74 years old) had an uneventful phacoemulsification surgery with implantation of the Ioflex IOL (power +21.5 D). At 5 years after surgery, a dense IOL opacification was detected in both cases with significant visual degradation. The IOLs were explanted and analyzed by microscopy.

Results

In both cases, a satisfactory visual recovery was achieved (corrected distance visual acuity of 6/9 and 6/12). Microscopic examination of the explanted IOLs revealed multiple small granules on the surface/subsurface of the lens. Although histochemical or surface analyses were not performed, the aspect appears consistent with a process of calcification of this lens design. Other findings included few surface contaminants, such as fibers, crystals that may correspond to dry viscoelastic and/or salt solutions, as well as pigments and dust-like deposits.

Conclusions

Opacification of the posterior chamber hydrophilic acrylic IOL Ioflex probably related to calcification can appear several years after its implantation and requires IOL exchange due to the significant visual loss induced. More studies are required to understand the causes of this complication.

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.

Visual aberrations in a multifocal intraocular lens with injection-related scratches

We describe the case of a 70-year-old woman who had phacoemulsification and implantation of a single-piece hydrophobic acrylic multifocal intraocular lens (IOL). Following surgery, the patient experienced blurring, positive dysphotopsia, impaired night vision, and glare. After 2 years, optic damage likely related to the IOL injection procedure was noted. The IOL was successfully exchanged. The uncorrected distance visual acuity was 20/20, and the patient reported no further visual aberrations. Gross and microscopic examination revealed large linear scratches on the central part of the optic. Scheimpflug photography with densitometry analysis of the area of the anterior scratches revealed extremely high levels of surface backlight scattering (227 computer-compatible tape units). Modulation transfer function and Badal images of the explanted IOL and of a control IOL did not differ significantly. This report suggests that severe defects/damage such as those described would likely be clinically significant in IOLs with specialized optics and warrant immediate removal/exchange of a damaged multifocal IOL.

FINANCIAL DISCLOSURE

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

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.

Calcification of a hydrophilic acrylic intraocular lens: case report with laboratory analysis

We analyzed a single-piece plate-type hydrophilic acrylic posterior chamber intraocular lens (IOL) that was explanted due to a progressive loss of vision, which occurred 6 years after uncomplicated phacoemulsification. Gross and light microscopy, as well as anterior segment optical coherence tomography (OCT) revealed granular deposits below the IOL surface. Light scattering, as measured with Scheimpflug photography and densitometry analyses was found to be increased; spectrophotometry demonstrated a decrease in the light transmittance of the explanted lens. The granular deposits within the IOL material were found to be composed of calcium by histochemical methods (alizarin red and Von Kossa stains). To our knowledge this is the only report of calcification of this IOL design.