Lens Material Research Articles

Uptake and release of polyhexamethylene biguanide (PHMB) from hydrogel and silicone hydrogel contact lenses using a radiolabel methodology

PurposeThe purpose of this study was to evaluate the uptake and release of radiolabelled polyhexamethylene biguanide (PHMB) on reusable daily wear contact lenses (CLs) over 7 days. MethodsThree silicone hydrogel (SH) contact lens materials (lotrafilcon B, balafilcon A, senofilcon A) and two conventional hydrogel (CH) materials (etafilcon A, omafilcon A) were examined. In experiment 1 (1-day study), CLs were soaked in 2 mL of phosphate buffered solution (PBS) containing radiolabelled 14C PHMB (1 µg/mL) for 8 h. The release kinetics of 14C PHMB from the CLs was measured at t = 0.25, 0.5, 1, 2, 4, 8, and 24 h in fresh 2 mL PBS. In experiment 2 (7-day study), the CLs were soaked in the 14C PHMB (1 µg/mL) solution for 8 h followed by a 16-hour release in 2 mL PBS. The lens cycle was repeated daily for 7 days. After both experiments, the residual amount of PHMB remaining within the lenses was extracted to determine the total uptake of PHMB. ResultsIn experiment 1, the total uptake of PHMB for etafilcon A was significantly greater than senofilcon A (p = 0.01). There were no significant differences in total uptake of PHMB between other lens materials (p > 0.05). Etafilcon A released more PHMB compared to all other lens types over a 24-hr period (p < 0.001). In experiment 2, all CL materials continued to sorb more PHMB over time (p < 0.001). By day 7, the amount of PHMB sorbed by etafilcon A was significantly greater than senofilcon A (p = 0.02). After day 2, the CH materials released significantly more PHMB than the SH materials (p < 0.01). ConclusionThe CL materials continued to sorb PHMB with no signs of saturation after 7 days. All lens materials released a consistent amount of PHMB each day. Radioactive labelling provides a sensitive method of assessing the uptake and release of PHMB from CL materials.

Antimicrobial Efficacy of Multipurpose Solutions Paired with Five Lens Materials Against Clinical Strains of Fusarium

Purpose: To evaluate the antimicrobial effectiveness of multipurpose lens care solutions (MPS) paired with five commercially available contact lens materials according to ISO 18259 and ISO 14729. Solution and lens pairings were challenged with clinical strains of the fungal pathogen Fusarium isolated from microbial keratitis according to ISO 18259. Solution efficacy with lenses in cases was compared to baseline efficacy in test tubes at the recommended disinfection time (DT) per ISO 14729.

Antimicrobial Efficacy of Multipurpose Solutions Paired with Five Lens Materials Against Clinical Strains of Bacteria and Fungi

Purpose: To evaluate the antimicrobial effectiveness of multipurpose lens care solutions (MPS) paired with five commercially available contact lens materials according to ISO 18259:2014 and ISO 14729:2001. Solution and lens pairings were challenged with bacteria and fungi isolated from microbial keratitis according to ISO 18259. Solution efficacy with lenses in cases was compared to baseline efficacy in test tubes at the recommended disinfection time (DT) per ISO 14729.

Assessment of a novel silicone hydrogel daily disposable lens among physically active subjects

Purpose: Physical exercise can change the body’s hydration status and blink rate that results in hyperosmotic tears. Increased osmolarity is related to contact lens (CL) dryness. Maintaining ocular surface homeostasis while wearing CLs is complex and has led to innovations in lens material and design. This study evaluated wear experiences of subjects that actively take part in regular sport or physical activity (PA) and subjects that don’t (NPA) while wearing a novel kalifilcon A (KA) daily disposable silicone hydrogel lens (DDSH) containing moisturizers and osmoprotectants.

HEVL and UV Transmittance Properties of a New Contact Lens Material

Purpose: A new contact lens material that provides both Class 1 ultra-violet (UV) blocking and high-energy visible light (HEVL) filtration was evaluated. The UV and HEVL transmittance properties of the new contact lens material were compared to existing contact lens materials (senofilcon A, senofilcon C, comfilcon A, and samfilcon A) and were also compared to Crizal® Prevencia® and DuraVision® BlueProtect spectacle lenses.

Effect of Daily Disposable Contact Lens Solutions in Stabilizing the Activity of a Tear Film Protein

Purpose: Interactions between tear proteins and the interface of contact lenses (CL) can be complex and can influence CL wear success. Tear proteins, including lysozyme, function to maintain the balance of ocular surface homeostasis, evidenced by research of its conformation relative to stabilizing the tear film, its lubricating properties, and the potential impact of denatured lysozyme to corneal cells. A novel silicone hydrogel daily disposable CL, kalifilcon A, has integrated multiple moisturizers infused into the lens material to help stabilize the tear film. This in vitro study investigates the ability of daily disposable CL solutions to stabilize lysozyme in its native state.

Surface characterization of a new contact lens water gradient using fluorescent staining

Purpose: A fluorescently labelled C-reactive protein (CRP) was used to characterize a new contact lens material (lehfilcon A) with a water gradient surface containing embedded phosphoryl choline (PC) groups. The uniformity and functionality of these groups were verified before and after on-eye wear.

Surface softness comparison of worn contact lenses by nanoindentation

Purpose: This study was designed to measure surface softness of a new contact lens material (NCLM) with biologically inspired water gradient surface after 30 days of daily wear (DW) and 6 nights/7 days extended wear (EW). These values were compared with fresh lenses and other contact lens benchmarks.

4D printed thermochromic Fresnel lenses for sensing applications

The conventional manufacturing processes for optical sensors fabrication have limitations in terms of ease of fabrication, design freedom, mechanical flexibility, cost requirements, etc. Therefore, adapting additive manufacturing (3D printing) is highly desirable because it opens up a variety of design and manufacturing possibilities. We have demonstrated that the 3D fabrication process using computer-aided design may be used to fabricate 4D functionalized photonic devices such as Fresnel lenses. We have introduced spectral color variation as the fourth dimension to 3D printed lenses in response to temperature as an external stimulus. The digital light processing (DLP) 3D printing process parameters were optimized to print the needed features with precise geometric dimensions of the lenses. Thermochromic pigment powders were mixed in the liquid monomer resins to print tinted Fresnel lenses used for selective color focusing and temperature sensing applications. The focusing ability and thermal sensing of printed lenses were assessed using customized setups that included normalized power intensity and transmission spectra measurements. Contact angle measurements were used to determine surface wettability, revealing the hydrophilic nature of the lens material. 3D printing offers custom-built optical devices and the ability to optimize the materials for both active and passive optical sensing applications, making them more promising than traditional Fresnel lenses.

Clinical Performance Evaluation of a New Silicone Hydrogel Material

Purpose: This study evaluated the clinical performance of a new silicone hydrogel (SiHy) material, with a core lens material containing 55% water that gradually transitions to nearly 100% water at the outer surface.

Water gradient surface durability and wettability of worn new monthly contact lens material

Purpose: A new contact lens material (lehfilcon A) was designed with a unique phosphorylcholine water gradient surface. This study evaluates the durability and wettability of this water gradient surface contact lens after on-eye wear.

Lens wear adaptation in neophytes wearing monthly replacement soft lenses

Purpose: Many eye care professionals (ECP’s) still advocate a gradual adaptation to lens wear in neophyte soft contact lens wearers, however this approach has limited supportive evidence. This study aimed to ascertain whether this adaptation period, given modern advancements in soft lens materials, was necessary for monthly disposable soft contact lenses, in both hydrogel and silicone hydrogel materials.

ИССЛЕДОВАНИЕ ОПТИЧЕСКИХ СПЕКТРОВ ПРОПУСКАНИЯ И ПАРАМЕТРОВ ОБРАБОТКИ ПОВЕРХНОСТИ ИНТРАОКУЛЯРНЫХ ЛИНЗ

Manufacturers of intraocular lenses are constantly improving the parameters of artificial lenses,functionally bringing them closer to their natural counterpart. In this work, an experimental study of anumber of important physical and technical parameters of intraocular lenses of the world's leadingmanufacturers, affecting the quality of vision of operated patients, was carried out. The transmissionspectra of optical radiation of intraocular lenses in the range of 200–800 nm were investigated. In theshort-wavelength part, the measurement results showed a high efficiency of the protective properties ofintraocular lenses from ultraviolet radiation. It is shown that radiation with a wavelength of up to350 nm is completely absorbed by the lens material, and the transmission of waves with a wavelength of400 nm is 20 %. Further, up to a wavelength of 550 nm, an increase in the transmittance of the studiedintraocular lens to 100 % is observed, after which it gradually decreases to the end of the visible rangeto 85%. The work also investigated the influence of the quality of the surface treatment of intraocularlenses on the likelihood of secondary cataract development in the long-term period. Accordingto postoperative statistics, the likelihood of secondary cataract is 20–35 %. The appearance ofareas of optical opacity is due to various factors, one of which is the quality of the surface treatmentof intraocular lenses. The smoothness of the surface profile of the lens depends on the model,manufacturing technology and material of the artificial lens. The study of the quality of surfacetreatment of soft and hard intraocular lenses was carried out by atomic force microscopy. Ananalysis of the results of scanning the surface of intraocular lenses and a statistical analysis of630 clinical cases of secondary cataract in the long-term postoperative period (6 months or more)showed their relationship. If the height of irregularities (protrusions) on the lens surface increasesto 70 nm or more, the likelihood of secondary cataract in the postoperative period increases from6 to 15 %.

Evaluation of daily disposable senofilcon A contact lenses in a symptomatic population

PurposeTo evaluate the comfort performance of ACUVUE OASYS® 1-Day with HydraLuxe™ Technology among symptomatic contact lens wearers by using Contact Lens User Experience (CLUE) comfort scores and Contact Lens Dry Eye Questionnaire 8 (CLDEQ-8) discomfort and dryness scores. MethodsThree clinical trials evaluated comfort and dryness when refitting symptomatic contact lens wearers to ACUVUE OASYS® 1-Day with HydraLuxe™ lenses. This analysis combined the CLUE comfort and CLDEQ-8 scores obtained at baseline and 2-week follow-up and compared average scores between visits. Subjects were grouped by habitual lens modality (daily disposable or daily wear reusable) and habitual lens material (silicone hydrogel or hydrogel). The analysis included data from 107 subjects. ResultsSignificant increases in mean CLUE comfort scores between baseline and 2–week follow-up occurred in all subject groups across habitual lens modality and material, indicating an improvement in overall comfort. CLUE comfort score improved clinically (≥5-point increase) among 75.7% of subjects (81/107). Similarly, significant decrease in mean CLDEQ-8 scores between baseline and 2-week follow-up occurred in all subject groups, indicating a decrease in the prevalence of dryness and discomfort symptoms. CLDEQ-8 score improved clinically (≥3-point reduction) among 82.2% of subjects (88/107). A majority of subjects (57.0%) became asymptomatic (CLDEQ-8 score ≤ 11 points) after 2 weeks of bilateral wear. ConclusionRefitting symptomatic contact lens patients to ACUVUE OASYS® 1-Day with HydraLuxe™ can improve overall comfort and reduce symptoms of dryness and discomfort, irrespective of the previous lens modality or habitual lens material.

Anterior capsular contraction syndrome with hyperopic shift

PurposeTo present a case of anterior capsular contraction syndrome with hyperopic shift two weeks after an uncomplicated combined cataract surgery and pars plana vitrectomy. ObservationsA 55-year-old man, with no known risk factors, who developed anterior capsular contraction syndrome with hyperopic shift two weeks after an uncomplicated combined cataract surgery and pars plana vitrectomy. Hyperopic shift was caused by posterior displacement of the intraocular lens with anterior flexion of the haptics. Manual peeling of the anterior capsule using the can-opener approach and microscissors successfully restored vision and corrected refractive errors. Conclusions and ImportanceAnterior capsular contraction syndrome is a complication of cataract surgery and is known to be affected by zonular weakness, pre-existing systemic and ocular conditions, intraocular lens materials, and intraoperative complications. Careful maneuver with surgery or laser can effectively restore vision and correct refraction.

Designing a Solar Heat Storage System using Heat Pipe and Phase-Change Material (PCM)

Phase change material (PCM) is used as a storage medium in a thermal heating system. The PCM's ability to store heat for a long time is suitable for combining with solar energy. PCM can absorb or release large amounts of latent heat at relatively constant temperatures. However, the PCM has poor thermal conductivity. The superconductive heat pipe is suitable to enhance the heat transfer in the PCM. The study aims to prove the concept of a unique thermal storage system that combines solar Fresnel lens, heat pipe, and phase change materials technologies. This study presented a detailed design and testing of the combined system under an actual outdoor environment. Four Fresnel lenses refracted the sunlight and focused on a heat collector. The lenses can be manually adjusted according to the sun's position. The heat is transferred to the PCM storage tank via a finned heat pipe. The testing results showed that the paraffin wax (PCM) has a melting temperature between 54 -59 °C. The highest temperature recorded in the paraffin wax tank was 121 °C which is suitable for many future applications. The system could store the heat up to 730 kJ by using 2 kg of paraffin. During the solidification of PCM (discharging), the system retained 120 kJ of heat for almost 7 hours with minimal heat loss. The system was proven to function well for storing the heat after the sunset, and it can be used for a passive power generation system, such as using thermoelectric cells.

Study of Myopia Correction Using Nanoporous Polymer Gas Permeable Contact Lenses

Ophthalmic treatments using contact lenses are now used by more and more specialists around the world. Improving contact lens (CL) materials is a condition that is constantly evolving. Contact lens materials are usually composed of polymer hydrogel or silicone hydrogel. The materials used for night contact lenses are gas permeable and they gradual flatten the center of the cornea which decreases the progression of myopia or myopic astigmatism. The aim of this study is to identify, in correlation with the chemical interactions between structural components of contact lenses and their biocompatibility with the surface layer and microtopography of the cornea or sclera, different incidents that occur in patients who have used rigid gas permeable contact lenses. The study was performed on a group of 10 patients who had a follow-up period between 4 and 6 years, who presented regularly for eye examinations. The following clinical parameters were analyzed: ocular refraction before and after wearing night contact lenses, types of contact lens materials, appearance of corneal topography, biomicroscopic examination of the anterior segment of the eye, keratometry, ocular comfort, as well as other incidents regarding this type of lenses. Difficulties caused by wearing contact lenses at night arose due to poor hygiene and maintenance in two cases or due to interruption of lens wear in one case.

Development of an enzymatic method for the evaluation of protein deposition on contact lenses

The aim of this study was to evaluate a new digestion method to quantify protein deposition on contact lenses. Four silicone hydrogel and one hydrogel contact lens material were incubated in lactoferrin, lysozyme, immunoglobulin A, and bovine serum albumin solutions at approximate physiological concentrations and temperature. Immobilized trypsin was used to digest the protein deposits from the contact lens surfaces. The total protein absorbed to lenses was extracted and digested using sequencing grade trypsin. The tryptic peptides were quantified using selected reaction monitoring mass spectrometry. The concentration of surface protein deposits was either lower than or the same as the total protein for all lens types and proteins. Immobilised trypsin can digest protein deposits from the surface of contact lenses. This ability to analyse the amount of protein at a contact lens surface may help in elucidating the effect of surface deposition on clinical outcomes during lens wear.

Design of foldable, responsively drug-eluting polyacrylic intraocular lens bulk materials for prevention of postoperative complications.

Posterior capsular opacification (PCO), resulting from undesired intracapsular cell proliferation, is the most common complication of intraocular lens (IOL) implantation after cataract surgery. In recent years, IOLs have been developed into a drug delivery platform. Compared with traditional eye drops, drug-loaded IOLs have the characteristics of independent patient compliance and no other operation except surgical implantation. In this work, a series of poly(glycidyl methacrylate-co-2-(2-ethoxyethoxy)ethyl acrylate) (PGE) acrylic intraocular lens materials were synthesized as drug delivery platforms. The PGE synthesized with 10% crosslinking agent has excellent optical, foldable, and thermomechanical properties. An aldehyde group was subsequently introduced into the PGE chains, and an antiproliferative drug (doxorubicin) was immobilized onto the PGE chains via an H+-sensitive imine bond. The IOL exhibits H+-dependent Dox release behavior in a simulated pathological environment. The in vitro and in vivo systematical evaluations indicate that such a responsively drug-eluting PGE IOL can effectively prevent PCO.

Femtolaser-assisted phacoemulsification of intumescent cataract

To optimize the technique of intumescent cataract phacoemulsification by involving the use of femtosecond lasers. Group 1 included 29 patients (30 eyes) with mature intumescent cataract, who underwent femtolaser-assisted phacoemulsification using a new, optimized technique. Group 2 included 20 patients (20 eyes), in whom the femtolaser stage was performed using the standard technique. Patients of groups 1 and 2 were almost identical in all preoperative parameters. The optimized femto-capsulorhexis technique included: preoperative assessment of intralenticular pressure, staining of the anterior capsule of the swelling lens with trypan blue, introduction of a viscoelastic with high molecular weight into the anterior chamber to balance intraocular and intralenticular pressures, increasing the laser energy when performing anterior capsulorhexis up to 10 mJ. In group 1, there was a non-penetration of the anterior capsule in 2 eyes, in one of them in the 30° sector, in the second - in the 45° sector. Leakage of lens material into the anterior chamber and the floating anterior capsule were not observed in patients of group 1. In group 2, non-penetration of the anterior capsule was observed in 6 eyes, in the 45-60° sector - in 2 eyes, in the 90° sector - in 3 eyes, in the 180° sector - in 1 eye. Floating anterior capsule was observed in 5 cases. Leakage of lens material into the anterior chamber was observed in 9 eyes. The optimized technique of femtolaser-assisted intumescent cataract phacoemulsification eliminates leakage of lens material into the anterior chamber and allows performing anterior capsulorhexis of given size and shape.