Silicone Intraocular Lens Research Articles

Application of Silicone in Ophthalmology: A Review.

This paper reviews the latest trends and applications of silicone in ophthalmology, especially related to intraocular lenses (IOLs). Silicone, or siloxane elastomer, as a synthetic polymer, has excellent biocompatibility, high chemical inertness, and hydrophobicity, enabling wide biomedical applications. The physicochemical properties of silicone are reviewed. A review of methods for mechanical and in vivo characterization of IOLs is presented as a prospective research area, since there are only a few available technologies, even though these properties are vital to ensure medical safety and suitability for clinical use, especially if long-term function is considered. IOLs represent permanent implants to replace the natural lens or for correcting vision, with the first commercial foldable lens made of silicone. Biological aspects of posterior capsular opacification have been reviewed, including the effects of the implanted silicone IOL. However, certain issues with silicone IOLs are still challenging and some conditions can prevent its application in all patients. The latest trends in nanotechnology solutions have been reviewed. Surface modifications of silicone IOLs are an efficient approach to further improve biocompatibility or to enable drug-eluting function. Different surface modifications, including coatings, can provide long-term treatments for various medical conditions or medical diagnoses through the incorporation of sensory functions. It is essential that IOL optical characteristics remain unchanged in case of drug incorporation and the application of nanoparticles can enable it. However, clinical trials related to these advanced technologies are still missing, thus preventing their clinical applications at this moment.

Fellow eye data for intraocular lens calculation in eyes undergoing combined phacovitrectomy.

To evaluate whether the intraocular lens (IOL) calculation of the fellow eye (FE) can be used in eyes undergoing combined phacovitrectomy. In this retrospective, consecutive case series, we enrolled patients who underwent combined phacovitrectomy with silicone oil removal and IOL implantation at the Goethe-University. Preoperative examinations included biometry (IOLMaster 700; Carl Zeiss). We used the IOL calculation of the FE (FE group) to calculate the prediction error compared with the IOL calculation using only the axial length (AL) of the FE (AL-FE group), as well as using the AL of the operated eye (OE group) in addition to the measurable biometric parameters. IOL calculation was performed using the Barrett Universal II formula. We compared the mean (MAE) and median absolute prediction error (MedAE) with each other. Furthermore, the number of eyes with ±0.50, ±1.00 and ±2.00 dioptres (D) deviation from the target refraction was compared. In total, 79 eyes of 79 patients were included. MedAE was lowest in the OE group (0.41 D), followed by FE group (1.00 D) and AL-FE group (1.02 D). Comparison between the AL-FE and FE groups showed no statistically significant difference (p = 0.712). Comparing eyes within ±0.50 D of the target refraction, the OE group (63.3%) performed best, followed by the AL-FE group (27.8%) and the FE group (26.6%). Our results indicate no clinically relevant difference between using the IOL calculation of the FE versus using only the AL of the FE in addition to the measurable parameters for the IOL calculation. A two-step procedure should always be strived for.

A 3D in vitro model for assessing the influence of intraocular lens: Posterior lens capsule interactions on lens epithelial cell responses

Posterior Capsule Opacification (PCO), the most frequent complication of cataract surgery, is caused by the infiltration and proliferation of lens epithelial cells (LECs) at the interface between the intraocular lens (IOL) and posterior lens capsule (PLC). According to the “no space, no cells, no PCO” theory, high affinity (or adhesion force) between the IOL and PLC would decrease the IOL: PLC interface space, hinder LEC migration, and thus reduce PCO formation. To test this hypothesis, an in vitro hemisphere-shaped simulated PLC (sPLC) was made to mimic the human IOL: PLC physical interactions and to assess their influence on LEC responses. Three commercially available IOLs with different affinities/adhesion forces toward the sPLC, including Acrylic foldable IOL, Silicone IOL, and PMMA IOL, were used in this investigation. Using the system, the physical interactions between IOLs and sPLC were quantified by measuring the adhesion force and interface space using an adhesion force apparatus and Optical Coherence Tomography, respectively. Our data shows that high adhesion force and tight binding between IOL and sPLC contribute to a small interface space (or “no space”). By introducing LECs into the in vitro system, we found that, with small interface space, among all IOLs, acrylic foldable IOLs permitted the least extent of LEC infiltration, proliferation, and differentiation (or “no cells”). Further statistical analyses using clinical data revealed that weak LEC responses are associated with low clinical PCO incidence rates (or “no PCO”). The findings support that the in vitro system could simulate IOL: PLC interplays and predict IOLs’ PCO potential in support of the “no space, no cells, no PCO” hypothesis.

Secondary Piggyback Intraocular Lens for Correcting Refractive Surprise Post Silicone Oil Removal

Introduction : Pseudophakic refractive error can be caused by IOL malposition and inaccurate biometric examination. Treatment consists of IOL exchange, refractive laser correction, and secondary piggyback IOL. Secondary Piggyback IOL consist of customized IOL implantation on ciliary sulcus.
 Case Illustration : A Male, 62 years old, complains of blurry right eye. He underwent retinal surgery with silicone oil tamponade surgery 5 years ago and underwent silicone oil evacuation, phacoemulsification, and intraocular lens implantation one year later. The visual acuity of the right eye was 1/60 with BCVA of 0.2. He was diagnosed with Pseudophakia of both eyes and Hypermetropia Surprise of the right eye. He was planned to undergo piggyback intraocular lens implantation in the right eye (Figure 1). The visual acuity one week after operation of the patient's right eye was 0.32 (Figure 2).
 Discussion : Biometric examination in eye with silicon oil tamponade have longer axial length, causing pseudophakic refractive errors. Treatments consist of IOL replacement, refractive laser correction, and piggyback IOL implantation. IOL replacement has a high risk and requires quite high operator skills. Refractive laser correction is performed in small refractive errors. Piggyback IOL implantationis easier, safer, have more accurate IOL power, and reversible.
 Conclusion : Power of the intraocular lens is influenced by axial length, keratometry reading, lens thickness, and other parameters. Axial length measurement in patients with silicone oil tamponade requires greater accuracy to prevent pseudophakic refractive errors. IOL Piggyback implantation procedure is an alternative in person that can’t undergo laser correction or IOL exchange.

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

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

IOL's material and PCO

Posterior capsular opacification (PCO) is the most common of late post‐surgery complications and can lead to reduced visual acuity, diplopia, or glare. The different types of material used in intraocular lenses (IOLs) plays a significant role in possible post‐surgery complications, such as anterior capsule opacification (ACO) and phimosis, posterior capsule opacification (PCO), and the formation of IOL opacification. PCO incidence increases with time and varies from 10% to 50%. The incidence of PCO will rise in the nearest future since IOLs will stay longer in the eye, as people's lifespans are increasing. It was shown that hydrophilic IOLs had significantly more and denser PCO than hydrophobic or silicone IOLs. The higher incidence of PCO formation in hydrophilic than in hydrophobic IOLs should be considered as an important medical and health economic issue when choosing the IOL for implantation.

Accuracy of Intraocular Lens Power Estimation in Aphakic Eyes Filled with Silicone Oil

Purpose: To compare preoperative refractive power estimation and actual postoperative refraction after combined silicone oil removal and intraocular lens (IOL) sulcus implantation in silicone oil-filled aphakic eyes.Methods: Records of patients with silicone oil-filled aphakic eyes who received simultaneous silicone oil-removal and IOL sulcus implantation (Group1) and aphakic patients who received vitrectomy combined with IOL implantation (Group 2) were reviewed. Optical biometry including axial length measurements were obtained using IOL master<sup>®</sup> 700 and predicted refractive errors, actual postoperative refractive errors were examined retrospectively.Results: Predicted refractive errors, calculated by subtracting 1 diopter (D) from myopic lens power closest to plano based on sulcus implantation, were 0.50 ± 0.12 D in Group 1, 0.45 ± 0.20 D in Group 2. Six months after operation, mean refractive errors measured -0.76 ± 0.49 D in Group 1, -0.23 ± 0.49 D in Group 2, showing significant myopic shift (<i>p</i> < 0.001, <i>p</i> <0.001). Group 1 showed larger significant myopic shift compared to Group 2 (<i>p</i> = 0.001), especially in 3 eyes with insufficient filling of intravitreal silicone oil showing -1.5 D myopic shift.Conclusions: Ocular biometry of silicone oil-filled aphakic eyes undergoing simultaneous silicone oil removal and IOL sulcus implantation are difficult to measure, showing postoperative myopic shift compared to control. Incomplete intravitreal silicone oil filling showed larger refractive errors needing additional compensations.

Intraocular Lens Materials: A Detailed Assessment of Benefits and Drawbacks

Intraocular lenses (IOLs), which are used to repair vision in a large number of patients following cataract surgeries, are potentially the most significant single advancement in ophthalmology. The first IOLs were made by the only biomaterial available for implantation over decay which is a rigid plastic namely, polymethyl methacrylate (PMMA), The main drawback of PMMA is that it necessitates the largest incision in cataract surgery, with the corneal incision is as large as the optics of the IOLs. Because the essential intention of forward-thinking cataract surgery is to make the smallest incision possible, the IOLs must be adaptable and bend. This intention can be accomplished by enhancing the model and matter of IOLs. There are also some characteristics associated with IOLs materials that may have some impact such as (Refractive Index, Water content, Glistening, Etc.), The improvement of the first silicone IOLs used to overcome that problem but it is now rarely used and has been replaced with an Acrylic hydrogel material that provides a good performance; researchers are still evaluating suitable IOLs materials.

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

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. 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 5mN (milli Newton), 15mN, and 30mN and repeated three times. The lowest penetration depth (12µm) was observed with IOL B. However, IOL A, D, and F showed similar low penetration depths (20, 18, and 23µm, respectively). Lenses C and E showed slightly higher penetration depths of 36 and 39µm, respectively. The silicone lens (G) showed the greatest penetration depth of 54.6µm at a maximum load of 5mN. With higher maximal loads (15 and 30mN) the penetration depth increased significantly. Lens C, however, showed the same results at both 15 and 30mN 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 30s 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 37MPa. IOL B had the largest EIT of 37MPa, which could be caused by the low water content. 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.

Mechanical Removal of Calcifications on a Silicone Intraocular Lens with a Shielded Light Pipe in Asteroid Hyalosis

Calcific deposits on the posterior surface of a silicone intraocular lens (IOL) are a rare visually significant complication of asteroid hyalosis (AH). We report the novel use of a shielded light pipe to remove calcifications on a silicone lens.

Major clinical considerations of the use of hydrophobic intraocular lenses in patients with cataracts: a brief systematic review

Introduction: Every year about 1 to 2 million people become blind and the number of blind people is predicted to reach 90 million in 2020. A cataract is the biggest cause of blindness in the world, except in developed countries. It accounts for 47.8% of the world's cases of blindness. A cataract is a name given to any opacity of the lens, which does not necessarily affect vision, with phacoemulsification being the main choice of treatment, which consists of a posterior aspiration of the emulsified material. Objective: The objective of this study was to evaluate, through a systematic review, the visual acuity, with less recourse to correction, in patients undergoing phacoemulsification with bilateral implants of hydrophobic lenses. Methods: The systematic review rules of the PRISMA Platform were followed. The literature search was carried out from July to August 2022 in Scopus, PubMed, Science Direct, Scielo, and Google Scholar databases. Scientific articles from the last 3 years were selected. The quality of the studies was based on the GRADE instrument. The risk of bias was analyzed according to the Cochrane instrument. Results and Conclusion: A total of 23 articles were included in this study, with 6 articles being from the main current clinical studies on the use of intraocular lenses. Both PCO value and Nd: YAG capsulotomy rates were higher in the hydrophobic acrylic IOL group than in the long-term use silicone (intraocular lens) IOL group (more than 6 years) after implantation. This study indicates excellent postoperative visual acuity and refractive results in the eyes following implantation of the EyeCee® One. This is accompanied by a very little risk of intraoperative and postoperative complications. Furthermore, the Aktis SP IOL is a safe, effective, and stable lens that can be inserted through a 2.2 mm incision with satisfactory visual and refractive results, even in the late postoperative period. Therefore, by analyzing the histopathological composition of PCO using LECs, more information can be gained about the characteristics of IOLs that are important for biocompatibility. Finally, patients implanted with trifocal IOLs showed a significant improvement in visual acuity at different distances, providing broad absolute and relative depth of field values, with good patient satisfaction rates.

Posterior Capsule Opacification after Cataract Surgery via Implantation with Hydrophobic Acrylic Lens Compared with Silicone Intraocular Lens: A Systematic Review and Meta-Analysis.

Hydrophobic acrylic intraocular lens (IOL) is the most popular material in cataract surgery. Posterior capsule opacification (PCO) is a long-term complication of cataract surgery. It can impair vision and adversely affect the prognosis of IOL delamination. The objective of this study was to perform a systematic review and meta-analysis to provide an updated evaluation of long-term complications and visual function after implantation with hydrophobic acrylic and silicone intraocular lenses. PubMed, Embase, and Cochrane Library were searched from January 2000 until March 2021. Randomized controlled trials (RCTs) and retrospective studies were finally included. The main outcomes were PCO value and neodymium-doped yttrium aluminum garnet (Nd : YAG) capsulotomy rate. Subgroup analysis was performed to compare hydrophobic acrylic and silicone IOLs during the follow-up period. Sensitivity analysis was also performed. The meta-analysis included a total of 17 studies. When the follow-up period was considered, the results of the analysis revealed higher PCO value (Group 3: standardized mean difference (SMD), −0.59; 95% confidence interval (CI), −0.90 to −0.28) and Nd : YAG capsulotomy rate (Group 3: risk ratio (RR), 0.60; 95% CI, 0.40–0.89) for hydrophobic acrylic IOLs than silicone IOLs during a long-term (≥6 years) follow-up. In conclusion, both the PCO value and the Nd : YAG capsulotomy rates were higher in hydrophobic acrylic IOLs group than the silicone IOLs group at long-term use (more than 6 years) after implantation.

Different lens power calculation formulas for the prediction of refractive outcome after phacoemulsification with silicone oil removal

BackgroundFormulas predicting intraocular lens power have not been compared in silicone oil-tamponaded eyes. The study aims to compare six intraocular lens power assessment formulas in silicone oil-tamponaded eyes.MethodsThis prospective study included patients with silicone oil-tamponaded eyes scheduled for silicone oil removal, phacoemulsification, and intraocular lens implantation at Chongqing Aier Eye Hospital (June 2019 to December 2019). Implanted intraocular lens power was used to predict postsurgical spherical equivalence using SRK/T, Holladay 1, Holladay 2, Haigis, Hoffer Q, and Barrett Universal II, and assess those formula’s predictive accuracy with predictive error.ResultsThe analysis included 47 eyes in 47 patients (28 and 19 eyes with normal and long axial length, respectively). Postoperative spherical equivalence at 6 months in normal and long axial length eyes was − 0.6 ± 0.96 and − 0.8 ± 1.52 D, respectively. Predictive error values for SRK/T, Holladay 1, Holladay 2, Haigis, and Hoffer Q and Barrett Universal II were − 0.18 ± 0.92, − 0.15 ± 0.88, − 0.06 ± 0.94, − 0.15 ± 0.87, and − 0.05 ± 0.90 D and − 0.06 ± 0.90, respectively, for normal axial length eyes and 0.15 ± 1.16, 0.46 ± 1.17, 0.28 ± 1.11, − 0.04 ± 1.12, 0.49 ± 1.09 D and 0.11 ± 0.99, respectively, for long axial length eyes. For normal axial length eyes, predicted outcomes were similar to actual outcomes for all formulas. For long axial length eyes, predicted outcomes differed significantly from measured postsurgical values for Holladay 1, Holladay 2, and Hoffer Q (P < 0.05) but not SRK/T or Haigis or Barrett Universal II .ConclusionsThe formulas had comparable predictive accuracy in silicone oil-tamponaded eyes with normal axial length, but Haigis or SRK/T or Barrett Universal II may be preferable in long axial length eyes.Trial registrationChiCTR1900023215.

Clinical and histopathological findings in the dead bag syndrome.

To describe the findings of a recently described syndrome, the dead bag syndrome, in which the capsular bag appears to be clear many years postoperatively, becoming diaphanous and floppy and unable to support the intraocular lens (IOL) within it. John A. Moran Eye Center, University of Utah, Salt Lake City, Utah. Case series with clinicopathological correlation. Of 10 cases suspected to represent a dead bag syndrome, 8 IOLs and 7 capsular bags were removed because of subluxation or dislocation. The 7 capsular bags available for analysis were fixed in formalin and submitted to histopathological examination (hematoxylin-eosin and Masson trichrome stains). The associated explanted IOLs in 5 cases were also examined microscopically. Histopathologic examination of the 7 capsular bags showed capsular thinning and/or splitting. Lens epithelial cells (LECs) were completely absent on 2 specimens, whereas the other 5 specimens had rare LECs on the inner surface of the capsule. Explanted IOLs were 3-piece silicone IOLs or single-piece hydrophobic acrylic IOLs. 1 IOL optic showed a small amount of granular pigment deposition, but the optics of the other 4 IOLs were unremarkable. In this syndrome, there seems to be an absence of secondary proliferation of LECs and fibrotic changes. The capsule shows some signs of degradation, such as thinning and/or splitting. Weakness of zonular attachments seems to be an associated finding, with subsequent in-the-bag IOL dislocation. Further studies are necessary to ascertain the etiology of this condition.

Impact of Material and Lens Design on Repositioning Surgery of Toric Intraocular Lenses: A Single-Arm Meta-Analysis.

Aim To analyze the pooled incidence rate in repositioning surgery by considering different materials and designs. Methods All published studies investigating the repositioning surgery of toric intraocular lenses (IOLs) before September 1, 2020, were searched and evaluated. The R3.5.2 software was used to extract the data, and a single arm meta-analysis was performed. Results 19 cases from 18 published studies articles were included in the meta-analysis. The pooled incidence rate in repositioning surgery was 2% (I2 = 53%, Pheterogeneity<0.01). Plate and silicone IOLs had significantly higher incidence rates (6% for each) than loop (2%) and hydrophobic acrylate (2%). Incidence rates of Acrysof, Staar, TECNIS, PhysIOL SA, T-flex 623T, and Microsil 6116TU groups were 1% (95% CI [1%–2%]), 6% (95% CI [4%–9%]), 3% (95% CI [2%–4%]), 1.40% (1/71), 3.03% (1/33), and 4.76% (1/21), respectively. Conclusions The pooled incidence rate of repositioning surgery in IOLs was 2%. Materials and designs would be risk factors for the rotational stability of the toric IOLs. Pooled incidence rates of the hydrophobic acrylate and loop group were lower than those of the silicone and plate group. Product identity is the main driver of heterogeneity.

Effect of time and temperature-dependent changes of IOL material properties on IOL: Lens capsule interactions

Posterior Capsule Opacification (PCO) is the most common complication associated with Intraocular Lens (IOL) implantation. Based on the assumption that the interactions between an IOL and the lens capsule (LC) may influence the extent of PCO formation, a new in vitro model was developed to quantify the adhesion force of an IOL to simulated LC using a custom-designed micro-force tester. Using this system, we examined the influence of temperature (room temperature vs. body temperature) and incubation time (0 vs. 24 h) on the adhesion force between IOLs and LCs. The results show that, in line with clinical observations of PCO incidence, the adhesion force increased at body temperature and with increase in incubation time in the following order, Acrylic foldable IOLs > Silicone IOLs > PMMA IOLs. By examining the changes of surface properties as a function of temperature and incubation time, we found that acrylic foldable IOLs showed the largest increase in their hydrophilicity and reported the lowest surface roughness in comparison to other IOL groups. Coincidentally, using a newly established macromolecular dye imaging system to simulate cell migration between IOLs and LC, we observed that the amount of macromolecular dye infiltration between IOLs and LCs was in the following order: PMMA IOLs > Silicone IOLs > Acrylic foldable IOLs. These results support a new potential mechanism that body temperature, incubation time, surface hydrophilicity and smoothness of IOLs greatly contribute to their tight binding to LCs and such tight binding may lead to reduced IOL: LC space, cell infiltration, and thus PCO formation.

Stability of Various Types of Aspheric Intraocular Lenses After Implantation: A One-Year Retrospective Study.

ObjectiveThe aim of the present study was to evaluate the stability of four different types of aspheric intraocular lenses (IOLs) after implantation.MethodsThis retrospective study included 124 eyes implanted with four different types of aspheric IOLs including a one-piece four-loop fixed hydrophilic acrylic IOL, a one-piece flat fixed acrylic IOL, a one-piece two-loop fixed acrylic IOL, and a three-piece two-loop fixed silicone IOL. IOL decentration, tilt, and ocular coma‐like aberration (coma) at one-week, one-month, three-month, and one-year time points were evaluated postoperatively.ResultsIOL decentration, tilt, and coma in the AO, 36A, IQ, and KS-AiN implantation groups were statistically significantly different one week and one year postoperatively (p < 0.01). There were significant differences between each of the pairs of groups (p < 0.01), except for coma between the AO and 36A implantation groups one week postoperatively (p > 0.05). When comparing the different time points (ie, one week, one month, three months, and one year postoperatively), IOL decentration, tilt, and coma were significantly different in each group (p < 0.05). IOL decentration, tilt, and coma in each group increased over the period from one week to one year postoperatively. A positive linear correlation was observed between IOL decentration or tilt and coma one year postoperatively (p < 0.01).ConclusionOne-piece multi-point fixed acrylic IOLs demonstrate better stability when compared with three-piece two-point fixed silicone IOLs. IOL decentration, tilt, and coma increase gradually over time. Ocular coma‐like aberrations are influenced by the stability of IOLs.

Accuracy of Intraocular Lens Power Calculation in Children With Vitrectomized Eyes Undergoing Cataract Surgery

Purpose: To assess the predictability of desired postoperative refractive outcomes using the SRK-II formula for intraocular lens (IOL) power calculation in children undergoing cataract surgery in eyes with a previous pars plana vitrectomy (PPV). Methods: In this retrospective study, 68 eyes of 66 children who underwent cataract surgery and IOL implantation in eyes that had previous vitrectomy between January 2008 and December 2017 were included. Data were collected on preoperative and postoperative characteristics. The Mann-Whitney test, Kruskal-Wallis test, and multinominal logistic regression were used for comparing the results. Results: Absolute prediction error (APE) in the cohort was 1.29 ± 1.13. Desirable refractive outcome with insignificant prediction error of less than 0.50 diopters (D) was found in approximately one-third of the children. Patients were further subdivided by magnitude of APE as ≥ 0.50 to ≤ 1.00 D and &gt; 1.00 D. Age at the time of surgery, axial length, mean keratometry, silicone oil removal, IOL position, scleral buckle, and corneal suture did not affect APE and there was no significant difference between the groups ( P &gt; .05). Conclusions: The mean APE of the SRK-II formula for IOL power calculation in pediatric eyes that had vitrectomy is comparable to that reported in the literature for routine pediatric cataract surgeries. Factors such as age, axial length, corneal power, IOL position (bag/sulcus), scleral buckle, corneal suture, and silicone oil removal done prior to surgery or along with cataract surgery did not affect the APE. [ J Pediatr Ophthalmol Strabismus . 2021;58(2):126–131.]

An in vitro system to investigate IOL: Lens capsule interaction

Posterior capsule opacification (PCO) is the most common complication associated with intraocular lens (IOL) implantation. Unfortunately, current in vitro models cannot be used to assess the potential of PCO due to their failure to simulate the posterior curvature of the lens capsule (LC) and IOL, a factor known to affect PCO pathogenesis in clinic. To overcome such a challenge, a new system to study IOL: LC interaction and potentially predict PCO was developed in this effort. It is believed that the interactions between an IOL and the lens capsule may influence the extent of PCO formation. Specifically, strong adhesion force between an IOL and the LC may impede lens epithelial cell migration and proliferation and thus reduce PCO formation. To assess the adhesion force between an IOL and LC, a new in vitro model was established with simulated LC and a custom-designed micro-force tester. A method to fabricate simulated LCs was developed by imprinting IOLs onto molten gelatin to create simulated three dimensional (3D) LCs with curvature resembling the bag-like structure that collapses on the IOL post implantation. By pushing the LC mold vertically downward, while measuring the change in position of the bending bar with respect to its start position, the adhesion force between the IOLs and LCs was measured.An in vitro system that can measure the adhesion force reproducibly between an IOL and LC with a resolution of ~1 μN was established in this study. During system optimization, the 10% high molecular weight gelatin produced the best LC with the highest IOL: LC adhesion force with all test lenses that were fabricated from acrylic foldable, polymethylmethacrylate (PMMA) and silicone materials. Test IOLs exerted different adhesion force with the 3D simulated LCs in the following sequence: acrylic foldable IOL > silicone IOL > PMMA IOL. These results are in good agreement with the clinical observations associated with PCO performance of IOLs made of the same materials. This novel in vitro system can provide valuable insight on the IOL: LC interplay and its relationship to clinical PCO outcomes.

Comparison of the functional visual outcomes in pseudophakic patients implanted with different intraocular lenses

A good functional visual outcome after meticulous cataract surgery and intraocular lens implantation is the ultimate aim of every eye care practitioner. Combining the measurement of functional acuity contrast sensitivity testing along with visual acuity testing adds to our knowledge of visual performance. This study aims at assessing the functional visual outcome before and after cataract surgery with different IOL materials. Aims: To evaluate ,compare and analyse the visual outcome and contrast sensitivity functions in pseudophakic patients with hydrophobic acrylic, hydrophilic acrylic, spherical silicone and aspheric silicone intraocular lenses using the high contrast sensitivity Snellen's chart as well as low contrast sensitivity Sloan letter chart before and after cataract surgery Material and Methods: Retrospective, Randomised study, conducted over a period of 2 years from January 2004 to December 2005 at a tertiary eye care institute in Chennai. Results: The aspheric silicone IOL may provide an improvement in the quality of vision as measured by our clinical results of contrast sensitivity testing followed by the hydrophobic acrylic IOL and the hydrophilic Acrylic and the spherical silicone IOL. Keywords: Contrast Sensitivity, Functional Visual Acuity, Aspheric IOL, Pseudophakia