Influence of glistenings on the optical quality of acrylic foldable intraocular lens

3D monitoring of the microphase separations inside the intraocular lens

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

Nano-Indentation to Determine Mechanical Properties of Intraocular Lenses: Evaluating Penetration Depth, Material Stiffness, and Elastic Moduli

INTRODUCTION

Intraocular lenses (IOL) should remain in the eye for life after implantation into the capsular bag during cataract surgery. The material must meet various requirements. It is crucial that the material has the best biocompatibility, and it should be flexible and soft for best possible implantation process but also sufficiently stable and stiff for good centering in the eye and posterior capsule opacification prevention.

METHODS

In this laboratory experiment, we used nano-indentation for the mechanical assessment of three hydrophobic acrylic (A, B, C), three hydrophilic acrylic (D, E, F), and one silicone (G) intraocular lens. We wanted to determine whether some react more sensitively to touching/handling than others. The indentation elastic modulus and the creep were obtained from the force displacement curve. For measuring penetration depth and testing of possible damage to the intraocular lenses, the samples were measured at room temperature. A 200-µm-diameter ruby spherical tipped indenter was used for all the tests. Indentations were made to three different maximum loads, namely 5 mN (milli Newton), 15 mN, and 30 mN and repeated three times.

RESULTS

The lowest penetration depth (12 µm) was observed with IOL B. However, IOL A, D, and F showed similar low penetration depths (20, 18, and 23 µm, respectively). Lenses C and E showed slightly higher penetration depths of 36 and 39 µm, respectively. The silicone lens (G) showed the greatest penetration depth of 54.6 µm at a maximum load of 5 mN. With higher maximal loads (15 and 30 mN) the penetration depth increased significantly. Lens C, however, showed the same results at both 15 and 30 mN with no increase of penetration depth. This seems to fit well with the material and manufacturing process of the lens (lathe-cut). During the holding time of 30 s at constant force all six acrylic lenses showed a significant increase of the creep (CIT 21-43%). Lens G showed the smallest creep with 14%. The mean indentation modulus (EIT) values ranged from 1 to 37 MPa. IOL B had the largest EIT of 37 MPa, which could be caused by the low water content.

CONCLUSION

It was found that results correlate very well with the water content of the material in the first place. The manufacturing process (molded versus lathe-cut) seems to play another important role. Since all included acrylic lenses are very similar, it was not surprising that the measured differences are marginal. Even though hydrophobic materials with lower water content showed higher relative stiffness, penetration and defects can also occur with these. The surgeon and scrub nurse should always be aware that macroscopic changes are difficult to detect but that defects could theoretically lead to clinical effects. The principle of not touching the center of the IOL optic at any time should be taken seriously.

Current State of the Art and Next Generation of Materials for a Customized IntraOcular Lens according to a Patient-Specific Eye Power

Intraocular lenses (IOLs) are commonly implanted after surgical removal of a cataractous lens. A variety of IOL materials are currently available, including collamer, hydrophobic acrylic, hydrophilic acrylic, PHEMA copolymer, polymethylmethacrylate (PMMA), and silicone. High-quality polymers with distinct physical and optical properties for IOL manufacturing and in line with the highest quality standards on the market have evolved to encompass medical needs. Each of them and their packaging show unique advantages and disadvantages. Here, we highlight the evolution of polymeric materials and mainly the current state of the art of the unique properties of some polymeric systems used for IOL design, identifying current limitations for future improvements. We investigate the characteristics of the next generation of IOL materials, which must satisfy biocompatibility requirements and have tuneable refractive index to create patient-specific eye power, preventing formation of posterior capsular opacification.

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

Background

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

Materials and methods

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

Results

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

Conclusion

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

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.

Glistening Formation on a Single-Piece Prehydrated Hydrophobic Acrylic Intraocular Lens in a Diabetic Patient

PURPOSE

To report a case of intraocular lens (IOL) glistening after uneventful cataract surgery and in-the-bag implantation of an enVista MX60 IOL (Bausch & Lomb, Rochester, NY) in a patient with uncontrolled diabetes mellitus.

METHODS

Case report.

RESULTS

A 76-year-old woman with non-insulin-dependent diabetes mellitus underwent uncomplicated phacoemulsification with in-the-bag implantation of an enVista MX60 IOL. After 6 months, glistening formation within the IOL optic was observed. In the fellow pseudophakic eye, an acrylic hydrophilic Akreos Adapt AO IOL (Bausch & Lomb) was implanted without complications.

CONCLUSIONS

IOL glistening can develop with the enVista MX60 IOL, even after uneventful cataract surgeries in certain situations (eg, uncontrolled diabetes mellitus). Increased vascular permeability due to uncontrolled diabetes mellitus might have been responsible for the postoperative IOL glistening formation. [J Refract Surg. 2016;32(10):710-712.].

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.

Glistening in glaucomatous eyes: visual performances and risk factors

PURPOSE

To analyse risk factors and visual performances of glaucomatous eyes with glistening in the intra-ocular lens (IOL).

METHODS

Prospective study performed between November 2010 and April 2011 and involving 67 consecutive glaucomatous eyes (47 patients), who previously had a phacoemulsification with a hydrophobic acrylic IOL implanted in the capsular bag. Glistening was classified in three groups of severity grade: G0 (<50 microvacuoles per mm(2) ), G1 (50-150 microvacuoles per mm(2) ), and G2 (>150 microvacuoles per mm(2) ). All eyes underwent a best-corrected visual acuity evaluation (BCVA, LogMAR scale), a complete clinical examination, a visual field test, a contrast sensitivity evaluation and a wavefront analysis of high-order aberrations (HOAs) using a Shack-Hartmann aberrometer. Eyes with a posterior capsular opacification and a BCVA>0.30 LogMAR were excluded.

RESULTS

Twenty six eyes (38.8%) had a grade 0, 12 eyes (17.9%) a grade 1 and 29 eyes (43.3%) a grade 2 of glistening severity grade. The mean follow-up after cataract surgery was 35.2 ± 24.2 months and was significantly higher for G1 and G2 groups (p < 0.001). A higher number of topical glaucoma medication were associated with a higher glistening severity grade (p < 0.05). G1 and G2 groups had significantly lower mean contrast sensitivity values at high spatial frequencies and significantly higher loss variance (LV) values of the visual field test (p < 0.05). There was no significant difference in mean BCVA between groups (p = 0.455).

CONCLUSIONS

In glaucomatous eyes, glistening increased with time was associated with the number of topical glaucoma medications daily instilled and altered visual performances. It should be a consideration for glaucoma patients who are more likely to develop glistening within the IOL optic.

Analysis of glistenings in hydrophobic acrylic intraocular lenses on visual performance

AIM

To assess patients' visual performance with glistenings in one piece soft hydrophobic acrylic intraocular lenses (IOLs) (Alcon) 2 years postoperatively.

METHODS

This cross section trial included 120 eyes with one piece IOL at 2 years postoperatively. Glistening was classified in 4 groups, ranging from 0 (none) to 3 (most evident) according to their severity in IOLs optics observed under a slit lamp. All eyes underwent a uncorrected and best-corrected visual acuity evaluation (UCVA and BCVA, LogMAR scale), a complete clinical examination, a contrast sensitivity (CS) evaluation by F.A.C.T chart, and a visual field test by Humphrey Field Analyzer ‖ (HFA). One-way ANOVA was used for quantitative data, while Pearson χ (2) test was used for qualitative data to analyze the visual function of 4 glistening groups.

RESULTS

Totally 120 eyes were enrolled with 30 eyes in each glistening group. There was no statistical correlation between glistening grades and patients' age, IOLs power, postoperative UCVA and BCVA (P>0.05). Quantificationally, CS values among each group were not statistically different. However, qualitative analysis showed there were more eyes in grade 3 group than in grade 0 group having abnormally declined CS at high spatial frequency (10% vs 36.7% at 18 cpd, P=0.029; 6.7% vs 26.7% at 12 cpd, P=0.013). Mean deviation (MD) of the visual field test was -2.14±2.31, -1.97±2.23, -3.02±3.17, -4.12±3.38 in group 0 to 3 respectively. There was a significant decrease in the most serious glistenings group (P =0.018).

CONCLUSION

Glistenings may potentially have an impact on contrast sensitivity at high spatial frequency and MD in visual field test.

Evaluation of in vitro glistening formation in hydrophobic acrylic intraocular lenses

Purpose

To evaluate the impact of continuous manufacturing process improvements on glistening formation in AcrySof hydrophobic acrylic intraocular lenses (IOLs) by comparing lenses manufactured in 2003 with lenses manufactured in 2012.

Methods

Glistenings were experimentally created as aqueous-filled microvacuoles utilizing an accelerated laboratory method by immersing the lens in water at 45°C for 24 hours and then reducing the temperature to 37°C for 2.5 hours. To determine the impact of continuous improvements on glistening formation, AcrySof IOLs (Alcon Laboratories, Inc) Model SB30 AL manufactured in 2003 were compared with AcrySof IOLs Model SN60 WF manufactured in 2012.

Results

Glistenings were present in all lenses after the accelerated microvacuole test method. The mean microvacuole density for IOLs manufactured in 2003 was 315.7 microvacuoles per square millimeter (MVs/mm²) with a glistening severity less than 100 MVs/mm² in 1.0% of the IOLs. The mean microvacuole density for IOLs manufactured in 2012 was 39.9 MVs/mm² with a glistening severity less than 100 MVs/mm² in 95.2% of the IOLs. Laboratory-induced microvacuole density was significantly lower in IOLs manufactured in 2012 (mean 39.9 MVs/mm²) relative to IOLs manufactured in 2003 (mean 315.7 MVs/mm²) as indicated by the Wilcoxon test of significance (P < 0.0005).

Conclusion

AcrySof IOLs recently manufactured in 2012 demonstrated a significant reduction in glistening density (87% reduction in mean density) as a result of continuous manufacturing process improvements compared with IOLs manufactured in 2003.

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).

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.

Quantification of glistenings in intraocular lenses using a ballistic-photon removing integrating-sphere method

An alternative method for quantification of glistenings in intraocular lenses (IOLs) using an integrating sphere with an adjustable back aperture to remove ballistic photons is presented. Glistenings in soft IOLs have been known for more than a decade; however, their severity and visual impact are still under investigation. A number of studies have been made to quantitatively describe glistenings in IOLs. Quantization and precise grading of IOLs will provide needed information to evaluate the severity and visual impact of glistenings in patients. We investigated the use of a simple modification of an integrating-sphere method to eliminate ballistic photons to quantitatively measure scattered light from glistenings in IOLs. The method described in this paper provides a simple and effective way to quantitatively characterize glistenings in vitro. It may be especially useful to quantify scattering associated with low-grade glistenings where the density of the scattering centers is low. Finally, the modified integrating-sphere method may also be generally applicable to quantitatively characterize scattering from other optical media.

Impact on visual function from light scattering and glistenings in intraocular lenses, a long-term study

PURPOSE

To investigate the impact on visual function from light scattering and glistenings in intraocular lenses (IOLs) in patients who had cataract surgery 10 years previously.

SETTING

Eye clinic, Norrlands university hospital, Umeå, Sweden.

METHODS

One hundred and three patients, who had phacoemulsification with implantation of Acrysof(®) MA60BM IOLs 10 years previously, were evaluated with best corrected visual acuity (VA), and low contrast visual acuity (LCVA) 10% and 2.5%. The light scattering from the IOLs was measured by Scheimpflug photography. The degree of glistenings was also quantified at the slit-lamp. Eyes with coexisting pathology that could affect VA and LCVA were excluded.

RESULTS

The patients were divided into various groups according to the degree of light scattering and grade of glistenings. In two subsets of patients, paired data from the patients' eyes were analysed. It was not possible to detect any significant impact on visual function, best corrected visual acuity (BCVA) and LCVA 10% and 2.5% in eyes with a more pronounced light scattering or a higher grade of glistenings seen at the slit-lamp. The correlation between IOL dioptric power and both the total light scattering of the IOL, and the subjective grading of the intensity of the glistenings at the slit-lamp was statistically significant (r(P)=0.25; p=0.012; r(S)=0.23; p=0.019, respectively).

CONCLUSION

Most patients in this case series operated 10 years previously had severe glistenings and a high level of light scattering from their intraocular lenses. No detectable impact on BCVA, LCVA 10% and 2.5% was found.

Osmotic cavitation of elastomeric intraocular lenses

In recent years, traditional rigid materials have been replaced with softer elastomers in intraocular lenses to minimize the size of the required surgical incision, thereby reducing patient recuperation time. However, water-filled cavities that may impact visual acuity are found in many of these new implants. We demonstrate that the cavitation observed in vivo can occur due to an osmotic pressure difference between the aqueous solution within the cavity and the external media in which the lens is immersed. By reducing the osmolarity of the external solution from 300 to 0mM, we observe an increase in cavity volume of almost a factor of 30. Further, we have developed a model for cavity growth assuming the controlling factor is diffusion of hydrophilic molecules from the polymer matrix into the cavity. We find that the experimental observations are consistent with the model and suggest that oligomeric species generated during polymerization are responsible for the observed cavitation.

Unusual pattern of glistening formation on a 3-piece hydrophobic acrylic intraocular lens

A 3-piece hydrophobic acrylic intraocular lens (IOL) was explanted from the left eye of a 68-year-old patient 26 days after implantation because of glistenings that impaired fundus visualization. The effect of the glistenings on the patient's visual function was unknown because of retinal issues. The fluid-filled vacuoles within the IOL optic were different from those described in clinical and experimental studies. They were initially observed 4 days after surgery and were very large. The glistening formation was reproduced experimentally by immersing the explanted IOL in balanced salt solution at 37 degrees C and analyzing the IOL at room temperature for up to 2 weeks. An IOL of the same design was used as a control. Although both IOLs were subjected to the same laboratory conditions, gross and light microscopic analyses confirmed that the pattern of the glistening formation differed between them. Analyses of the explanted IOL and the control IOL under differential scanning calorimetry, as well as by attenuated total reflection Fourier transform infrared spectroscopy, revealed slight differences between the IOLs.

Equilibrium water content and glistenings in acrylic intraocular lenses

PURPOSE

To investigate the possible relationship between temperature and water absorption in acrylic intraocular lenses (IOLs).

SETTING

Laboratory setting, Miyata Eye Clinic, Hiroshima, Japan.

METHODS

The equilibrium water content (amount of water absorbed per weight of the resin x 100) in 2 hydrophobic acrylic IOLs (AcrySof MA60BM [Alcon] and Sensar AR40 [AMO]) was calculated at 30 degrees C, 40 degrees C, and 50 degrees C. The 2 IOLs were also subjected to 3 changes in temperature: from 37 degrees C to 35 degrees C, 39 degrees C to 35 degrees C, and 41 degrees C to 35 degrees C. They were incubated in physiological saline at the higher temperature for 2 hours and at the lower temperature for 30 days before being examined for glistening formation.

RESULTS

The water content was higher in the AR40 IOL than in the MA60BM IOL at all temperatures. A temperature-dependent increase in water content was seen in both IOLs, greater in the MA60BM. With a temperature change from 37 degrees C to 35 degrees C, glistening formation was not observed in either IOL. With a temperature change from 39 degrees C to 35 degrees C, glistenings were observed in the MA60BM IOL, and with a temperature change from 41 degrees C to 35 degrees C, they were observed in both IOLs.

CONCLUSION

The change in the equilibrium water content caused by temperature changes between 30 degrees C and 40 degrees C is an important factor in glistening formation, and thus an IOL featuring less temperature-dependent water absorption is less likely to form glistenings.

Comparison of Wavefront Aberrations and Optical Quality of Eyes Implanted With Five Different Intraocular Lenses

PURPOSE

We compared corneal and total higher order wavefront aberrations in 25 pseudophakic eyes implanted with five different types of intraocular lenses to obtain an objective evaluation of the optical quality of these pseudophakic eyes. Five IOLs per type were studied.

METHODS

Implanted lenses were the Pharmacia Tecnis Z9000 with negative spherical aberration, Pharmacia 911 Edge, Alcon Acrysof SA60AT and MA60BM, and Allergan Sensar AR40e. Eyes were examined using the Topcon KR-9000PW topographer/aberrometer, which obtains simultaneous coaxial measurements of corneal and ocular aberrations, and displays the calculated Point Spread Function (PSF) and Modulation Transfer Function (MTF).

RESULTS

Corneal spherical aberration was positive in all tested eyes. For a 4-mm optical zone, ocular spherical aberration was 0.0054+/-0.0172 microm root-mean-square (RMS) in eyes implanted with the Tecnis lens, and was 0.0562 to 0.0974 microm RMS in eyes implanted with the four other conventional IOLs. A myopic refractive shift with mydriasis of -0.08 D occurred with the Tecnis IOL; it was -0.57 to -0.90 D with the conventional IOLs. Coma did not show a substantial reduction with any of the IOLs. Total wavefront aberrations showed nonsignificant reduction with the Tecnis lens. The PSF and the MTF also showed nonsignificant improvements over conventional IOLs.

CONCLUSIONS

The optical quality of pseudophakic eyes can be measured in vivo by aberrometers. Different IOLs resulted in measurably different outcomes. In this preliminary study, compensation of the spherical aberration observed with the Tecnis lens confirmed the theoretical predictions associated with this lens and resulted in no myopic shift in refraction with mydriasis.

Limitation of Scheimpflug videophotography system in quantifying posterior capsule opacification after intraocular lens implantation

PURPOSE

To assess the applicability of Scheimpflug videophotography system for the quantitative comparison of posterior capsule opacification after intraocular lens (IOL) implantation of different materials.

DESIGN

Retrospective, nonrandomized, interventional case series.

METHODS

Three groups (n = 15 eyes, each) underwent cataract surgery with implantation of acrylic, silicone, or hydrogel IOL. One year after surgery, the scatter light density at the anterior IOL surface level was measured using EAS-1000. Another three groups (n = 32 eyes, each) received acrylic, silicone, or hydrogel lens. One week after surgery, the scatter light density at the posterior capsule was measured.

RESULTS

Scatter light density at the anterior IOL surface 1 year after implantation was 7.5 +/- 3.0 computer-compatible tape (CCT) steps in the acrylic group, 6.0 +/- 2.3 CCT steps in the silicone group, and 5.0 +/- 3.2 CCT steps in the hydrogel group; the density in the acrylic group was significantly greater than that in the hydrogel group (P =.026). Scatter light density at the posterior capsule level 1 week after surgery was 28.3 +/- 8.9 CCT steps in the acrylic group, 22.2 +/- 2.0 CCT steps in the silicone group, and 26.7 +/- 6.7 CCT steps in the hydrogel group; there was a significant difference between the acrylic and silicone groups (P =.0005) and between the silicone and hydrogel groups (P =.008).

CONCLUSIONS

The IOL material significantly influences the scatter light density measurements of Scheimpflug videophotography system, and thus the intensity of posterior capsule opacification quantified by this system cannot be directly compared with different optic materials.

Clinical performance of Alcon SA30AL and SA60AT single-piece acrylic intraocular lenses

PURPOSE

To report the clinical performance characteristics of single-piece acrylic Alcon SA30AL and SA60AT intraocular lenses (IOLs).

SETTING

A private practice in Marshalltown, Iowa, USA.

METHODS

In a review of 2630 consecutive cases operated on from January 2000 through July 2001, ease of IOL insertion and integrity of the haptic architecture were evaluated in a prospective fashion at implantation. Subgroups of cases were studied prospectively to evaluate 3 factors: same-day incision competence after implantation (postoperative intraoperative pressure [IOP], 107 cases); 2- to 5-week A-constant validation (200 cases); 1-day, 2-week, and 1- and 5-month descriptions of optic centration with respect to pupil and capsule anatomy (79 cases); and a 1-day versus 9-month photographic comparison of IOL centration (70 cases). A retrospective evaluation of the population's diagnostic codes tabulated complications including increased postoperative iritis, cystoid macular edema, neodymium:YAG (Nd:YAG) laser intervention for posterior capsule opacification, and pseudophakic dysphotopsia. A retrospective review of a subgroup of 140 consecutive cases was done to categorize postoperative optic clarity.

RESULTS

Overall, the IOLs were easy to implant with no haptic or optic damage using a forceps or the Monarch injector. Subgroup studies confirmed good performance in the following parameters: There were no cases of incision incompetence evidenced by an abnormally low postoperative IOP. The lowest postoperative IOP was 6 mm Hg, with the overall mean IOP increasing to 29 mm Hg from the 17 mm Hg measured a mean of 102 minutes after surgery. The manufacturer's published A-constant was almost identical to that obtained in review (118.4 versus 118.38 for the SA30AL and 118.35 for the SA60AT). In verbal descriptions, IOL optic centration was assessed to be within 0.4 mm of perfect in 75 (95%) of 79 cases. Slitlamp photographs showed that 52 (98%) of 53 IOLs were in the same position 9 months after surgery as on the day of surgery. One IOL optic appeared to rotate 14 degrees. There were no cases of decentration greater than 1.0 mm in either optic centration subgroup. Given a normal postoperative topical steroid regimen, there were no cases of substantially increased or prolonged iritis. There were 17 cases (0.65%) of macular edema. An Nd:YAG laser posterior capsulotomy was performed in 0.64% (13/2044) in the SA30AL group over a mean of 9 months (range 2 to 23 months) and in 0.34% (2/586) in the SA60AL group over a mean of 5.5 months (range 5 to 6 months). Pseudophakic dysphotopsia was diagnosed in 26 eyes of 18 patients (1% of 2630 cases), with 1 patient requiring an IOL exchange. Optic glistenings were observed in 11 (11%) of 100 SA30AL cases at a mean follow-up of 8 months. No glistenings in 40 cases were seen in the SA60AT group at a mean follow-up of 3 months.

CONCLUSIONS

The single-piece acrylic lenses performed well in all regards. Although not as intense as observed with the earlier 3-piece designs, pseudophakic dysphotopsia occurred in a few patients with the single-piece acrylic lens. Intraocular lens exchanges with single-piece IOLs may be accomplished with less difficulty early rather than late.

Glistenings in foldable intraocular lenses

PURPOSE

To evaluate the formation of glistenings in foldable intraocular lenses (IOLs) of various materials after cataract surgery.

SETTING

University Eye Clinic of Trieste, Trieste, Italy.

METHODS

In this prospective study, 273 patients were randomized to have implantation of 1 of 7 types of foldable IOLs in the capsular bag after phacoemulsification. The IOLs were the CeeOn Edge 911A (Pharmacia & Upjohn Co.), ACR6D (Corneal), AcrySof (Alcon), SI-40NB (AMO), Hydroview H60M (Storz), Sensar (AMO), and Stabibag (Ioltech). The presence of glistenings in the IOL optic was assessed by slitlamp evaluation 7, 30, 90, 180, 360, and 720 days after surgery. The glistenings were graded at each control.

RESULTS

Glistenings were observed in all IOL groups. The percentage of patients with glistenings ranged from 40.0% to 67.5%, with the percentage increasing up to 90 days after surgery and then becoming stable in most groups. The AcrySof group had a continuous increase over time. The mean grade of glistenings increased up to 180 days after surgery and then became stable in most groups. The AcrySof and 911A groups had a continuous increase over time.

CONCLUSIONS

Glistening formation was observed in 7 different foldable IOLs. The AcrySof group had a higher percentage and a greater density of glistenings.

Survey of intraocular lens material and design

Modern cataract surgery is constantly evolving and improving in terms of lens material and design. Researchers and physicians strive to obtain better refractive correction with smaller wound size and minimizing host cell response to limit the proliferation of lens epithelial cells leading to opacification of the lens capsule. Intraocular lens material varies in water content, refractive index, and tensile strength. Intraocular lens design has undergone revisions to prohibit lens epithelial cell migration and reflection of internal and external light. The evolution of intraocular lens and extracapsular cataract surgery has lead to faster postoperative recovery and better visual outcomes.