Hydrogel Lens Wear Research Articles

International trends in prescribing silicone hydrogel contact lenses for daily wear (2000–2023): An update

PurposeIntroduced around the turn of the 21st century, silicone hydrogel contact lenses alleviated hypoxic anterior eye complications due to their high oxygen transmissibility. The purpose of this work is to update earlier surveys by describing international trends in silicone hydrogel daily wear contact lens fitting between 2000 and 2023. MethodAn annual contact lens prescribing survey was sent to eye care practitioners in up to 71 countries between 2000 and 2023. Data relating to 260,144 daily wear soft contact lens fits undertaken in 20 countries returning reliable longitudinal data were analysed in respect of silicone hydrogel daily wear contact lens fitting. ResultsThere has been a dramatic increase in silicone hydrogel daily wear lens fits (p < 0.0001), increasing from 2.8 % of all daily wear soft lens fits in 2000 to 73.7 % in 2023. Of all daily wear soft contact lenses prescribed to males, 44.6 % were silicone hydrogel lenses, compared with 43.5 % for females (p = 0.0146). The mean age of those wearing silicone hydrogel daily wear lenses was 32.0 ± 14.5 years, compared to 30.4 ± 13.6 years for those wearing daily wear hydrogel lenses (p < 0.0001). Between 2019–2023, the average percentage of fits was – (a) material type: silicone hydrogel – 73 %; mid-water content hydrogels – 13 %; high water content hydrogels – 9 %; and low water content hydrogels – 5 %, and (b) lens design: spherical – 44 %, toric – 32 %, multifocal – 17 %, monovision – 4 %, and ‘other’ – 3 %. ConclusionThe dramatic increase in silicone hydrogel contact lens prescribing for daily wear has been commensurate with the introduction of multiple lens brands and an ongoing expansion of lens designs, parameters and replacement frequency options. The balance between silicone hydrogel and hydrogel lens prescribing is perhaps starting to approach an equilibrium.

Wear Experience of a Water Surface Daily Disposable Contact Lens in Existing Silicone Hydrogel Planned Replacement Lens Wearers.

PurposeThe health benefits of silicone hydrogel lens materials and a daily replacement modality have been demonstrated in previous studies; however, existing planned replacement lens wearers may resist changing to a new lens replacement schedule. The purpose of this study is to evaluate the wear experience of satisfied planned replacement silicone hydrogel wearers when refit into a silicone hydrogel daily disposable lens.Patients and MethodsIn this open-label, non-comparison study, satisfied wearers of two week planned replacement contact lenses were evaluated for inclusion criteria and refit with optimized prescriptions in their habitual lenses. At a follow-up visit one week later, participants were refit with the study daily disposable lenses and completed visual analog scale (VAS) surveys of initial quality of vision, comfort, and satisfaction. Participants returned for a final visit after two weeks of wearing the study daily disposable lenses. At the final visit, VAS surveys for both overall and end of day (EOD) vision, comfort, and dryness were completed. Overall median and interquartile range (IQR) were assessed for all surveys in the study.ResultsThirty individuals completed the study (29.1 ± 7.8 years old; 19 female). Median (IQR) results for the initial impression VAS surveys were 92.50(11.75) for quality of vision, 92.50(18.00) for comfort, and 93.00(18.00) for satisfaction. Final VAS survey results revealed median scores of 87.50(25.00) for EOD quality of vision and 82.50(51.25) for EOD comfort. The median overall quality of vision was 91.00(17.00) and overall comfort was 93.00(28.50). Median (IQR) overall dryness was 28.50(49.00) and median EOD dryness was 30.50(64.25).ConclusionThe findings of this study suggest that providers can successfully refit satisfied wearers of early generation silicone hydrogel planned replacement lenses into a new generation silicone hydrogel daily disposable lens while maintaining satisfaction.

The risk of vision loss in contact lens wear and following LASIK.

To compare the risk of vision loss following contemporary laser-assisted in situ keratomileusis (LASIK) with different types and modality of use of contact lenses. Data from a previously published study were used to derive the incidence of vision loss (≥ 2 line loss of best corrected spectacle acuity) following microbial keratitis for different contact lens types and wearing modality, stratified by duration of lens wear. A literature search on vision loss following LASIK was performed between 2003 and 2019. The prevalence of vision loss at six months post-surgery was captured from clinical trials published after 2003. A proportion meta-analysis was applied to derive the prevalence of vision loss following LASIK. A least-squares fitting of cumulative vision loss (P, /10000 wearers) over time (t, years) using an exponential model estimated the years of contact lens wear to which the risk of vision loss with LASIK was equivalent. Vision loss following LASIK occurred in 66 (95% confidence interval [CI] 34-108) per 10000 wearers. As a conservative estimate based on the lower confidence interval of the estimated equivalent years of contact lens wear, daily wear contact lenses and extended overnight silicone wear hydrogel contact lens need to be worn for 103 (95% [CI] 103-391) and 25 (95% [CI] 25-79) years respectively, to equal the rate of vision loss equivalent to a one-off LASIK procedure. The risk of vision loss to the individual is low with either contact lens wear or refractive surgery. Contact lens wear does not pose a higher risk of vision loss than LASIK surgery for the most common wear modalities.

Brittle or Ductile? Abrasive Wear of Polyacrylamide Hydrogels Reveals Load-Dependent Wear Mechanisms

Cartilage and hydrogels are composed of an elastic network that retains a large volume of water allowing them to efficiently maintain smooth sliding interfaces while under high compressive loads. For hydrogels to be viable candidates to replace osteoarthritic cartilage, a study of their robust long-term use and surface failure mechanism is necessary. In this work, a sandpaper covered probe attached to a microtribometer with a reciprocating stage was used to wear 7.5 wt% polyacrylamide hydrogels under a range of speeds (1 mm/s, 2 mm/s, and 3 mm/s) and normal loads (1 mN, 5 mN, 10 mN, and 20 mN). The subsequent wear scars were imaged using a 3D laser scanning confocal microscope. For all sliding speeds of the 1 mN and 5 mN loading conditions, microcutting, which is characteristic of brittle materials, contributed more to the measured wear volume. For the 10 mN and 20 mN loading conditions, microplowing, which is characteristic of ductile materials, contributed more to the measured wear volume. We found that the mechanical wear of hydrogels is a competition between ductile fracture and brittle fracture, and the dominant mechanism is dependent upon load, but not speed for the range of speeds tested. The different wear behavior between the lower loads (1 mN and 5 mN) and higher loads (10 mN and 20 mN) suggests that there is a critical load between 5 and 10 mN that marks the shift from more brittle fracture to more ductile fracture. This work is the beginning of developing more accurate predictions of the wear behavior of hydrogels and cartilage based on the nature of the materials.

Characterizing wear behaviors of edible hydrogels by kernel-based statistical modeling

Hydrogels are used in multiple industries; although hydrogel deformation and wear behaviors can be a good indicator for their functionality, there are no available models for characterizing hydrogel deformation–wear behaviors. This study characterized wear behaviors of casein (3–5% w/w, 200 mM NaCl), κ-carrageenan (0.8–1.2% w/w, 100 mM NaCl), and whey protein gels (13% w/w, 50–150 mM NaCl) at room temperature (20 °C) under several normal forces (0.1–1.5 N). A kernel-based model was used to characterize hydrogel wear behavior by separating the deformation–wear process deformation-dominant, constant wear rate, and failure regions. Higher normal force and lower polymer concentration showed higher constant wear rates and lower durability. The kernel model was able to characterize hydrogel wear-deformation behaviors and is useful for industrial applications.

Characterizing and modeling wear-recovery behaviors of acid-induced casein hydrogels

Hydrogels are soft materials with applications in multiple industries, but their fundamental wear behaviors are relatively unknown. Studies on hydrogel wear behaviors generally use empirical measurements. Additionally, it can be difficult to measuring hydrogel wear rates by traditional mass loss measurements because wear debris cannot always be removed without disturbing intact sample. Therefore, the objective of study was to develop a method for more precise calculation of soft material wear rates. The method developed compared creep-recovery and wear-recovery behaviors of casein hydrogels to separate deflection of the material under an applied load from the amount of material removed. Casein hydrogels were prepared at different concentrations (8%, 10%, and 15% w/w) and pH (2.3, 3.6, 4.8), and tested under a range of normal loads (0.3, 0.4, 0.5 N). Wear-recovery behaviors were fit to an exponential model. Maximum penetration depth during wear and creep, creep-recovery, and wear-recovery increased with lower casein concentration and higher normal force and pH. Exponential models for casein gel wear-recovery behaviors indicated good fit (R2 > 0.99). This wear measurement method is useful for developing food products with specific oral and industrial processing behaviors.

Lubrication and Wear Protection of Micro-Structured Hydrogels Using Bioinspired Fluids.

We report the fabrication and the use of a bioinspired synovial fluid acting as a lubricant fluid and antiwear agent at soft and porous chitosan hydrogel tribopairs. This synthetic synovial fluid is composed of sodium hyaluronate (HA) and a bottle-brush polymer (BB) having a polycationic attachment group and polyzwitterionic pendant chains. The 2.5%w/w chitosan hydrogel plugs are organized in a bilayered structure exposing a thin and dense superficial zone (SZ), covering a porous deep zone (DZ), and exhibiting microchannels perpendicularly aligned to the SZ. Using a low-load tribometer, the addition of HA lubricating solution at the hydrogel-hydrogel rubbing contact drastically decreased the coefficient of friction (CoF) from μ = 0.20 ± 0.01 to 0.04 ± 0.01 on the DZ configuration and from μ = 0.31 ± 0.01 to 0.08 ± 0.01 on the SZ surface when increasing the HA concentration from 0 to 1000 μg/mL and its molecular mass from 10 to 1500 kDa, similar to what was found when using the BB polymer alone. When combining the BB polymer and the 1500 kDa HA, the CoF remained stable at μ = 0.04 ± 0.01 for both studied contact configurations, highlighting the synergistic interaction of the two macromolecules. Hydrogel wear was characterized by assessing the final gel surface roughness by the means of an interferometer. Increasing HA concentration and molecular weight plus the addition of the BB polymer led to a dramatic surface wear protection with a final gel surface roughness of the hydrogels similar to the untested gels. In brief, the BB polymer in combination with high molecular weight HA is a potential lubricating fluid as well as a wear resistant agent for soft materials lubrication and wear protection.

Tear Film Osmolarity in Response to Long-Term Orthokeratology Treatment.

To compare tear film osmolarity (TFO) measurements in non-contact lens (CL) wearers and wearers of hydrogel or overnight orthokeratology (OK) CLs, and to assess possible effects of long-term OK on TFO. Overall, 108 subjects with moderate myopia participated in 2 experiments, and TFO was measured using the TearLab osmolarity system. In experiment 1, TFO measurements were made in 77 right eyes of 23 non-CL wearers, 26 hydrogel wearers, and 28 OK wearers. Subjects in the last 2 groups had worn their CL for at least 3 years. In experiment 2, 31 individuals (habitual soft CL wearers) were enrolled for prospective long-term follow-up of OK treatment. These subjects were fitted with Paragon-CRT (n=16) or Seefree (n=15) lenses, and TFO readings were taken at baseline and after 1 month and 1 year of lens wear and after 1 month of OK treatment interruption. Values of TFO were within the normal limits in all 3 subject groups, although significantly lower osmolarities (P<0.01) were observed in non-CL wearers (281.7±5.9 mOsm/L) compared with hydrogel (291±16.5 mOsm/L) or OK lens wearers (301.7±10.8 mOsm/L). In experiment 2, TFO differed significantly at baseline between the Paragon-CRT and Seefree groups (P<0.05), and a significant decrease in TFO compared with baseline (P<0.01) was observed in the Paragon-CRT group after 1 month of cessation of lens wear. Higher TFO values were observed in lens wearers (hydrogel or OK) than non-CL wearers. After interruption of OK treatment, TFO returned to similar values to those found in non-CL wearers.

Ocular surface and tear film status among contact lens wearers and non-wearers who use VDT at work: comparing three different lens types.

To analyze differences in the ocular surface appearance and tear film status of contact lens wearers and non-wearers in a group of visual display terminals (VDT) workers and additionally to assess differences between lens materials. Cross-sectional study of 236 office workers, of whom 92 were contact lens wearers. Workers provided information on their contact lenses (conventional hydrogel, silicone hydrogel or rigid gas permeable lenses) and exposure to VDT at work. Ocular surface and tear film status were determined by the presence of bulbar, limbal and lid redness, lid roughness and corneal staining type, and by Schirmer's and tear break-up time tests (TBUT). A generalized linear model was used to calculate the crude (cRR) and age- and sex-adjusted (aRR) relative risk to measure the association between ocular surface and tear film abnormalities and contact lens use and type. The aRR of ocular surface abnormalities was higher in contact lens wearers compared to non-wearers: bulbar redness (aRR 1.69; 95% CI 1.25-2.30), limbal redness (aRR 2.87; 1.88-4.37), lid redness (aRR 2.53; 1.35-4.73) and lid roughness (aRR 7.03; 1.31-37.82). VDT exposure > 4h/day increased wearers' risk of limbal and lid redness. Conventional hydrogel wearers had the highest risk of ocular surface abnormalities, followed by silicone hydrogel wearers. Both contact and non-contact lens wearers had a high prevalence of altered TBUT (77.3 and 75.7% respectively) and Schirmer (51.8 and 41.3%). Regular contact lens use during VDT exposure at work increases risk of bulbar, limbal and lid redness, and lid roughness, especially in soft contact lens wearers. The high prevalence of altered TBUT and Schirmer's results in all participants suggests that VDT use greatly affects tear film characteristics.

Changes in Tear Cytokines Following a Short Period of Daily and Overnight Silicone Hydrogel Lens Wear

Background and Objective: To investigate changes in ocular surface inflammatory markers after daily and overnight silicone hydrogel contact lens wear in healthy wearers.&#x0D; Material and Methods: Twenty-six experienced soft contact lens subjects were evaluated at baseline, after 1-day of silicone hydrogel lens wear, and after 1-night of wear. Basal tears were collected at each visit and tear cytokine concentrations were quantified using multiplex [interleukin (IL)-1β, IL-6, IL-10, IL-12(p70), IL-17A and tumor necrosis factor (TNF)-α] or ELISA (IL-8) kits. A historical control group of 27 non-contact lens wearers was used to compare absolute concentrations and diurnal variations in tear cytokine concentrations. Changes in cytokine concentrations were analyzed using linear mixed models. Linear regression with bootstrapping was used to assess whether changes in IL-1β concentrations were associated with changes in other cytokines.&#x0D; Results: IL-8 concentrations decreased after 1 day of silicone hydrogel contact lens wear and returned to baseline levels the next morning (p=0.04). This same diurnal fluctuation was seen in non-contact lens wearers (p=0.03). With daily contact lens wear, there was a significant positive correlation between the changes in IL-1β and IL-8, TNF-α, IL-10 and IL-12(p70) (all p&lt;0.03). With overnight contact lens wear, there were significant positive correlations between the changes in IL-1β and IL-6, IL-17A and TNF-α (all p&lt;0.01).&#x0D; Conclusion: A short period of daily and overnight silicone hydrogel lens wear does not significantly alter the inflammatory status in adapted soft contact lens wearers.

Comparison of Corneal Thickness and Endothelial Cell Morphology in Myopic Patients with Daily Wear Hydrogel (Nelfilcon A) and Silicon Hydrogel (Lotrafilcon B) Contact Lenses: A Pilot Study

Background: To compare corneal thickness and endothelial cell morphology in myopic patients wearing 1 month hydrogel conventional and silicon hydrogel contact lenses in daily wear.Methods: This is a prospective, single blind, randomized study. Seventeen (34 eyes) myopic patients were randomly assigned to receive either nelfilcon A or lotrafilcon B. Central corneal thickness (CCT), coefficient of variation (CV), and percentage of six-sided cell (6A) were examined using specular noncon robo Konan microscope. Changes in CCT, CV, and 6A were evaluated before contact lenses fitting as well as 1 week and 1 month after the treatment. Patients were also evaluated for any subjective side effects and complications during the treatment period. Results: There were 64.7% subjects with history of contact lens wearers and 52.9% of them was hydrogel wearers. After 1 month daily wear of nelfilcon A and lotrafilcon B, no statistically differences changes in CCT (p=0.285; Mann Whitney test), CV (p=0.587; unpaired t-test), and 6A (p=0.353; unpaired t-test). General linear model analysis in follow up evaluation with test of within subject effect revealed decreased in CCT (p=0.001) and CV (p=0.001), also increased in 6A (p=0.022) in all subjects.Conclusion: There were no statistically difference in CCT, CV, and 6A between daily wear of nelfilcon A and lotrafilcon B. Subjects with history of contact lens wearers gained advantages in oxygen availability, which decrease corneal thickness and improve endothelial cell morphology. Â Keywords: nelfilcon A, lotrafilcon B, simple myopic, corneal thickness, endothelial cell morphology

Effect of poly(vinyl alcohol) (PVA) wear particles generated in water lubricant on immune response of macrophage

Abstract To develop a novel biotribological material for artificial cartilage implant with a lubricity supplement of the joint surface, we focused on two types of poly(vinyl alcohol) (PVA) hydrogel: repeated freeze–thawing (PVA-FT) and cast-drying (PVA-CD) gels. Here we observed the morphology of wear particles generated during a reciprocating wear test and assessed macrophage immune responses by applying hydrogel wear particles. As a result, PVA-CD had a significantly lower total amount of wear than did PVA-FT. The size distributions of PVA-FT and -CD wear particles were similar. Most of the particles were nanoparticles up to approximately 50 nm in diameter. Considering the particle volume distribution, there were very few micron- and submicron-sized wear particles around 1 μm in diameter. In SEM observations of dried PVA wear particles, both distributions of wear particles of PVA-FT and -CD were similar. Micron-sized wear particles were chiefly formed by close packing of 20- to 50-nm-sized particles. Biochemical and immunological evaluations revealed no cytotoxic effects of wear particles on macrophages. Cytokine synthesis of both wear particle-stimulated groups was significantly lower than that of the lipopolysaccharide-stimulated positive control. Therefore, it is suggested that PVA wear particles do not affect the macrophage immune response.

One-month evaluation of corneal staining with dual disinfectant multipurpose solutions

Purpose: To assess corneal staining in silicone hydrogel lens wearers using dual disinfectant multipurpose solutions (MPS) for 30 days.

Risk factors for microbial bioburden during daily wear of silicone hydrogel contact lenses.

To assess risk factors associated with substantial microbial bioburden of lids, conjunctivae, contact lenses, and storage cases during daily wear of silicone hydrogel contact lenses. Two hundred eighteen patients were fit to lotrafilcon A lenses, randomized to use either a multipurpose solution or a hydrogen peroxide care system, and followed up for 1 year. Lenses, lens transport saline, lids, conjunctivae, and storage cases were cultured and considered to have substantial microbial bioburden when they harbored high levels of commensal or pathogenic organisms. Univariate and multivariate logistic regression analyses were conducted to examine which demographic covariates were associated with significant bioburden at each location while controlling for solution use. In multivariate analyses, smoking trended toward an association with lens bioburden (odds ratio [OR]=2.15, 95% confidence interval [CI]: 0.95-4.88). Clerical occupations were found to be associated with more frequent overall storage case contamination (OR=3.51, 95% CI: 1.15-10.70) and, specifically, higher gram-positive storage case contamination (OR=5.57, 95% CI: 1.82-17.06). The peroxide system was associated with more frequent storage case contamination (OR=7.6, 95% CI: 3.79-15.19). Coagulase-negative staphylococci (CNS) were the most frequently cultured organisms within storage cases, and in multivariate analyses, CNS were more frequently found in storage cases of peroxide users (OR=6.12, 95% CI: 2.91-13.09). Clerical occupations were associated with increased microbial bioburden of storage cases during daily wear of silicone hydrogel lenses. Smoking may increase the risk of lens contamination. Storage cases are most frequently contaminated with normal skin flora, and peroxide cases were associated with more frequent contamination. However, the solution type was not associated with lid or lens contamination nor with corneal infiltrative events in this study.

Corneal Inflammatory Events with Daily Silicone Hydrogel Lens Wear

This study aimed to determine the probability and risk factors for developing a corneal inflammatory event (CIE) during daily wear of lotrafilcon A silicone hydrogel contact lenses. Eligible participants (n = 218) were fit with lotrafilcon A lenses for daily wear and followed up for 12 months. Participants were randomized to either a polyhexamethylene biguanide-preserved multipurpose solution or a one-step peroxide disinfection system. The main exposures of interest were bacterial contamination of lenses, cases, lid margins, and ocular surface. Kaplan-Meier (KM) plots were used to estimate the cumulative unadjusted probability of remaining free from a CIE, and multivariate Cox proportional hazards regression was used to model the hazard of experiencing a CIE. The KM unadjusted cumulative probability of remaining free from a CIE for both lens care groups combined was 92.3% (95% confidence interval [CI], 88.1 to 96.5%). There was one participant with microbial keratitis, five participants with asymptomatic infiltrates, and seven participants with contact lens peripheral ulcers, providing KM survival estimates of 92.8% (95% CI, 88.6 to 96.9%) and 98.1% (95% CI, 95.8 to 100.0%) for remaining free from noninfectious and symptomatic CIEs, respectively. The presence of substantial (>100 colony-forming units) coagulase-negative staphylococci bioburden on lid margins was associated with about a five-fold increased risk for the development of a CIE (p = 0.04). The probability of experiencing a CIE during daily wear of lotrafilcon A contact lenses is low, and symptomatic CIEs are rare. Patient factors, such as high levels of bacterial bioburden on lid margins, contribute to the development of noninfectious CIEs during daily wear of silicone hydrogel lenses.

Consequences of Wear Interruption for Discomfort With Contact Lenses

To establish whether increased end-of-day discomfort during soft contact lens wear is associated with short-term changes occurring to the lens itself. Twenty-seven subjects wore hydrogel lenses (Focus Dailies; Alcon) bilaterally for 10 hours on two separate days. Comfort was reported using 1-100 numerical rating scales (1 = intolerable discomfort, 100 = lens cannot be felt). Day 1 ratings were taken before lens insertion and at 0.05, 5, and 10 hours post-insertion. Day 2 ratings occurred at similar times, but lenses were removed after the 5-hour assessment and either reinserted (n = 14) or newly replaced (n = 12). An additional rating was taken 5 minutes after re-insertion. Wear then continued to the 10-hour point. In a separate study, 24 different subjects repeated these procedures using a silicone hydrogel lens (AirOptix Aqua; Alcon) with wear taking place on 3 days to permit lens replacement to be with existing as well as new lenses in all subjects. For hydrogel lenses, comfort scores (mean ± 95% CI) reported after 10 hours were 79.4 ± 8.3 when lenses were worn un-replaced, compared with 73.2 ± 9.2 for replacement with the existing lens. When replacement was with a brand new lens, the corresponding values were 72.9 ± 10.9 (un-replaced) versus 69.2 ± 12.8 (new lens replacement). For silicone hydrogel lenses, 10-hour comfort was 90.3 ± 3.2 (un-replaced) versus 92.2 ± 2.9 (replacement with existing lens) versus 90.0 ± 3.3 (replacement with new lens). Differences between replacement conditions were not significant in any case (analysis of variance, p > 0.05). Final comfort was not influenced by replacing lenses midway through the wearing period. Comfort decrements experienced by users of these daily contact lenses towards the later part of the wearing period are not caused by changes occurring to the lenses on this time scale. Possible alternative etiological factors include a fatigue-like response in one or more ocular tissues or stimulation of ocular surface nociceptors induced by the presence of the contact lens.

Specialist contact lens fitting

What is meant by the term ‘specialist contact lens fitting’? Or put another way, what would be considered non-specialist contact lens fitting? Is there such a thing as routine contact lens fitting? Soft or silicone hydrogel fitting for daily wear would probably be considered as routine contact lens fitting, but would extended or flexible wear remain in the same category or would they be considered a specialist fit? Different eras will classify different products as being ‘specialist’. Certainly twenty years ago soft toric contact lenses were considered as being speciality lenses but today would be thought of as routine lenses. Conversely, gas permeable lenses were thought of as mainstream twenty years ago but now are considered as speciality lenses. Although this would not be the same globally, as in some countries (such as Netherlands, France and Japan) gas permeable lens fitting remains popular and is not on the decline as in other countries (Canada, Australia and Sweden) [1]. Bandage soft lenses applied after surface laser refractive procedures would be considered as therapeutic lenses but in reality they are just plano thin hydrogel lenses worn constantly for 3–4 days to allow the underlying epithelium to convalesce and are then removed [2]. Some patients find that wearing hydrogel lenses during periods when they suffer from seasonal allergies actually improves their ocular comfort as the contact lens acts as a barrier to the allergen [3] and [4]. Scleral lenses have long been considered speciality lenses, apart from a time when they were the only lenses available but at that time all contact lens work would have been considered speciality practice! Nowadays we see the advent of mini-scleral designs and we see large diameter gas permeable lenses too. It is possible that these lenses increase the popularity of gas permeable lenses again and they become more main stream. So it would seem that the lines between routine and speciality contact lens fitting are not clear. Whether a lens is classed a specialist fit or not would depend on the lens type, why it was fitted, where in the world the fitting was being done and even the era in which it was fitted. This begs the question as to what would be considered entry level knowledge in contact lens fitting. This may not be an issue for most BCLA members or CLAE readers but certainly would be for bodies such as the College of Optometrists (UK) or the Association of British Dispensing Opticians when they are planning the final registration examinations for budding practitioners or when planning the level of higher level qualifications such as College Certificates or Diplomas. Similarly for training institutions when they are planning their course content. This becomes even trickier when trying to devise a qualification that spans across many countries, like the European Diploma in Optometry and Optics. How do we know if the training and examination level is correct? One way would be to analyse things when they go wrong and if patterns of malpractice are seen then maybe that could be used as an indicator to more training being needed. There were 162 Fitness to Practice Hearing at the General Optical Council between 2001 and 2010. Forty-seven of these were clinically related case, 39 fraud related, and 76 others. Of the clinical ones only 3 were contact lens related. So it would appear that as whole, in the profession, contact lens clinical skills are not being questioned too often (although it seems a few of us can’t keep our hands out the cookie jar!).

The effects of silicone hydrogel lens wear on the corneal epithelium and risk for microbial keratitis.

Previous studies using animal models and human clinical trials have demonstrated that the use of low-oxygen-transmissible contact lens materials produce corneal epithelial surface damage resulting in increased Pseudomonas aeruginosa (PA) adhesion and raft-mediated internalization into surface corneal epithelial cells. These findings led to the testable clinical predictions that (1) microbial keratitis (MK) risk is expected to be the greatest during the first 6 months of wear; (2) there is no difference between 6 and 30 night extended wear; and (3) that wear of hyperoxygen-transmissible lenses would reduce the reported incidence of infection. Subsequent epidemiologic studies have confirmed the first two predictions; however, increased oxygen transmissibility with silicone hydrogel (SiHy) lens wear has not altered the overall incidence of MK. In this review, more recent clinical and basic studies that investigate epithelial alterations and bacterial adhesion to corneal epithelial cells after the wear of SiHy lenses with and without concomitant exposure to chemically preserved multipurpose solutions (MPS) will be examined. The collective results of these studies demonstrate that even in the absence of lens-related hypoxia, MPS induce ocular surface changes during SiHy lens wear that are associated with a pathophysiologic increase in PA adherence and internalization in the corneal epithelium, and therefore, predict a greater risk for PA-MK. In addition, new data supporting an interactive role for inflammation in facilitating PA adherence and internalization in the corneal epithelium will also be discussed.

Silicone Hydrogel Lens–Solution Interaction and Inflammation

Daily wear of silicone hydrogel (SiHy) lenses using marketed lens care solutions results in varied levels of anterior eye inflammation. There are several pathways that may lead to corneal and conjunctival inflammation that include mechanical, allergic, and pathogen driven stimuli. The hypotheses and evidence for these various models of inflammation will be discussed in the context of SiHy lens designs and materials and lens care solution components.

Meta-analysis of the ocular biocompatibility of a new multipurpose lens care system

BackgroundThe purpose of this paper is to evaluate the biocompatibility of a novel multipurpose solution (MPS) with a dual disinfectant system containing polyaminopropyl biguanide and polyquaternium-1 (Biotrue®) by analysis of biomicroscopy signs and adverse events in six large clinical trials.MethodsData from six consecutive, prospective clinical trials conducted from February 2008 to March 2010 were combined for meta-analysis. Subjects used the new MPS daily for periods of 2 weeks to 6 months. Slit-lamp signs were graded at each follow-up visit using an ordinal scale (0, one; 1, trace; 2, mild; 3, moderate; 4, severe). Analysis for biocompatibility included tracking of greater than grade 2 slit-lamp findings and number of adverse events.ResultsA total of 1,567 subjects (3,134 eyes) and 81 clinical investigators participated in the six studies, with 1,499 subjects completing the studies. Based on subject days in the studies, there were 72,904 exposures to the MPS and 7,212 biomicroscopy examinations. The completion rate for the studies was 96.3%. Per observation incidence of any finding greater than grade 2 at the follow-up visits were: corneal staining 0.08%, limbal injection 0.04%, bulbar injection 0.04%, tarsal conjunctiva abnormality 0.09%, and neovascularization 0.01%. There were no other slit-lamp signs greater than grade 2 and no statistically significant difference between hydrogels and silicone hydrogels for any finding. There were no reports of adverse events during the trials.ConclusionAnalysis of over 72,000 daily exposures and 7,212 eye examinations showed that the novel MPS exhibited excellent biocompatibility in subjects using daily wear hydrogel or silicone hydrogel lenses.