Silicone Hydrogel Soft Contact Research Articles

Corneal confocal microscopy and dry eye findings in contact lens discomfort patients

To evaluate the corneal confocal microscopy and dry eye findings in patients with contact lens discomfort. The study included 3 groups of participants: Contact lens wearers using silicone hydrogel soft contact lenses who are symptomatic (CLD, n=15) or asymptomatic (ACL, n=11) and non-wearers as controls (n=14). Duration of contact lens wear, Ocular Surface Disease Index (OSDI) questionnaire responses, fluorescein tear break-uptime (FBUT), and corneal confocal microscopy findings were recorded. Mean age was 25.7±8.2 years and male/female ratio was 7/33. Demographic findings were similar regarding the groups. CLD patients had a longer lens use history than ACL (median 5 vs 2 years, p<0.001). OSDI scores were higher in CLD group than ACL or controls (p<0.001, p=0.002). FBUT was significantly lowest in CLD group, compared to controls and ACL (p<0.001, p=0.039). FBUT was also lower in ACL patients compared to controls (p=0.036). There was no difference between basal epithelium cell counts between all 3 groups. Anterior stromal activated keratocyte numbers were similar between contact lens using groups but was lower in controls (p=0.005). However, dendritiform cells in the sub-basal nerve layer were higher in CLD group compared to controls but similar to ACL (p<0.001, p=0.058). Graded sub-basal nerve tortuosity was more prominent in CLD group than the ACL (p=0.014). Patients with CLD had been wearing contact lenses for longer than those without symptoms. OSDI and FBUT scores were worse in CLD patients. In contact lens discomfort patients, there were increased dendritiform cells, indicating intensified inflammatory status of the cornea.

Theoretical fitting characteristics of typical soft contact lens designs.

To calculate theoretical fitting success rates (SR) for a range of typical soft contact lens (SCL) designs using a mathematical model. A spreadsheet mathematical model was used to calculate fitting SR for various SCL designs. Designs were evaluated using ocular topography data from 163 subjects. The model calculated SR based on acceptable edge strain (within range 0-6%) and horizontal diameter overlap (range 0.2-1.2mm). Where lenses had multiple base curves (BCs), eyes unsuccessful with the steeper BC were tested with the flatter BC and aggregate SR calculated. Calculations were based on typical, current, hydrogel and silicone hydrogel SCLs and allowed for appropriate on-eye shrinkage (1.0-2.3%). Theoretical results were compared with those from actual clinical trials. Theoretical success rates for one-BC lenses ranged from 60.7% (95% CI 7.2%) to 90.2% (95% CI 3.7%). With two-BC designs, most combinations showed a SR increase with a second BC (84.0%-90.2%). However, one of the two-BC combinations showed only negligible increase with a second BC (72.4%-73.0%). For designs with lower SR, the greatest contributor to failure was inadequate lens diameter. For a given design, differences in shrinkage (i.e. on-eye bulk dehydration) had a significant effect on success rate. In comparison with historical clinical data, there was a positive correlation between small lens fitting prevalence and discomfort reports (r=+0.95, P=<0.001) with a poor correlation between theoretical and actual tight/loose fittings. Mathematical modelling is a useful method for testing SCL design combinations. The results suggest that judicious choice of additional fittings can expand the range of fitting success.

The impact of silicone hydrogel contact lenses on the measurement of intraocular pressure using non-contact tonometry

Background/Aim. Measurement of intraocular pressure (IOP) over therapeutic silicone hydrogel soft contact lenses by a non-contact method of tonometry could be applied in opthalmologic practice but the results obtained are still controversial. The aim of this study was to evaluate the effect of spherically designed silicone hydrogel soft contact lenses and their power on values of IOP measured by using a noncontact tonometry method. Methods. We measured IOP with and without spherical silicone hydrogel soft contact lenses on 143 eyes of 80 subjects who did not have any ocular or systemic diseases. Results. The Wilcoxon statistical analysis test for ranking average values of IOP measured on 143 eyes over a spherical silicone hydrogel soft contact lenses showed significantly higher values compared to those measured with no contact lenses (15.81 ? 3.46 mm Hg vs 14.54 ? 3.19 mm Hg; respectively; Z = -5.224, p = 0.001). Refractive power analysis of the contact lenses of -9.00D to +6.00 D showed a significant difference of IOP in the range from 0.00D to -6.00D. Conclusion. Non-contact tonometry is not an accurate method of IOP measuring over spherical silicone hydrogel soft contact lenses which belong to therapeutic contact lenses.

Characterizing Contact Lens-Related Corneal Infiltrates: A Pilot Study.

Purpose:To document the time course and resolution of contact lens–related corneal infiltrative events (CIEs) comparing slit-lamp images with anterior segment ocular coherence tomography (AS-OCT) images.Methods:Six silicone hydrogel (SiHy) soft contact lens (SCL) wearers presenting with newly diagnosed symptomatic CIEs were monitored with slit-lamp images, detailed drawings, and AS-OCT until the resolution of the CIE. A final follow-up visit was completed 4 weeks after CIE resolution to determine whether scar formation was present. Positive controls were 2 SiHy SCL wearers with established (inactive) corneal scars, and negative controls were 2 SiHy SCL wearers with clear corneas. High- and low-contrast logMAR visual acuities were measured, and subjective symptom questionnaires were completed at all visits.Results:Clinical signs, vision, and symptoms improved in tandem with the resolution of the CIEs as measured by imaging methods. Calibrated measures of infiltrate width from a slit-lamp biomicroscope appear to be similar to calibrated images from AS-OCT.Conclusions:Although further studies are needed to develop standardized procedures, AS-OCT can be a useful tool to characterize the development, progression, and resolution of corneal infiltrates as an objective measure of resolution and scar formation.

Therapeutic outcomes of combined topical autologous serum eye drops with silicone–hydrogel soft contact lenses in the treatment of corneal persistent epithelial defects: A preliminary study

To evaluate the efficacy of the combination of topical 20% autologous serum eye drops (ASEs) and silicone-hydrogel soft contact lenses (SCLs) for the treatment of corneal persistent epithelial defects (PEDs), and to compare the recurrence of epithelial breakdown with or without continuous use of ASEs after silicone-hydrogel SCLs removal. We conducted a prospective interventional study of 21 eyes of 21 patients with PEDs treated with combined ASEs and silicone-hydrogel SCLs from September 2014 to August 2015. SCLs were removed after total re-epithelialization and patients were subsequently randomized divided into two groups: (1) with and (2) without continuous use of ASEs for an additional 2 weeks. PEDs healing rate and epithelial defect recurrence were evaluated. PEDs healed in all eyes within 3 weeks. Recurrence was noted in five eyes (50%) in patients without continued use of ASEs for 2weeks after total re-epithelialization and SCLs removal during a 3-month follow-up (odds ratio: 23.0; P<0.05). Recurrent epithelial defects were successfully treated with secondary SCLs application combined with autologous serum use. No adverse events were noted during the entire treatment period. The combined use of ASEs and silicone-hydrogel SCLs can successfully treat recalcitrant PEDs. Prolonged use of ASEs after total re-epithelialization can decrease recurrence rates.

Rate of change and predictive factors for increasing minus contact lens powers in young myopes

BackgroundUnderstanding the factors associated with myopic progression is critical to properly recruit subjects into clinical trials for control of myopia. The purpose of this study is to describe the rate of change in soft contact lens (SCL) power and the associated predictive factors in a young clinical population from the Contact Lens Assessment in Youth study.MethodsData from a retrospective chart review of myopic SCL wearers aged eight to 22 years were analysed for rate of progression of myopia and associated characteristics using multivariate methods.ResultsMyopic subjects (n = 912) with at least six months of follow‐up were observed (4,341 visits, mean follow‐up 25 months, 37 per cent hydrogel and 63 per cent silicone hydrogel SCLs). During observation, 36 per cent of subjects experienced a change in soft contact lens power of −0.50 D or more. Significant predictors of future increase in minus lens power were: ages eight to 13 years, shorter time to the first increase in minus power and hydrogel soft contact lens material. The mean annualised increase in minus decreased with age (−0.31D per year for eight to 13 year olds to −0.10 D per year for 20 to 22 year olds, p < 0.0001). Increases in minus were less common among users of silicone hydrogel materials than hydrogel daily disposable lenses after controlling for age (p = 0.039).ConclusionIn this retrospective chart review of young soft contact lens wearers, the mean annualised rate of increase in minus soft contact lens power decreased with age, longer time to first increase in power and was greater with hydrogel soft contact lenses. The rates observed were similar to progression rates in prospective myopia clinical trials that employed cylcoplegic autorefraction.

The influence of lens design and power on the zonal oxygen transmissibility of silicone hydrogel soft toric contact lenses

The influence of lens design and power on the zonal oxygen transmissibility of silicone hydrogel soft toric contact lenses

Dexamethasone diffusion across contact lenses is inhibited by Staphylococcus epidermidis biofilms in vitro.

This study was designed to measure the impact of bacterial biofilms on diffusion of an ocular therapeutic through silicone hydrogel bandage lenses in vitro. An assay was designed to study the passage of a commonly used steroid, dexamethasone, through silicone hydrogel soft contact lenses. Diffused dexamethasone was measured using a spectrophotometer over a period of 18 hours and quantified using a standard curve. This assay was performed with control and Staphylococcus epidermidis biofilm-coated contact lenses comprised of lotrafilcon A and methafilcon. Biofilms were formed in brain heart infusion broth supplemented with D-glucose. The presented data validate a simple in vitro model that can be used to measure the penetration of a topical therapeutic through silicone hydrogel soft contact lenses. Using this model, we measured a reduction in dexamethasone diffusion up to 88% through S. epidermidis biofilm-coated silicone hydrogel lenses compared with control lenses. The results of this in vitro study demonstrate that bacterial biofilms impede dexamethasone diffusion through silicone hydrogel contact lenses and warrant future studies regarding the clinical benefit of using ocular therapeutics in the setting of bandage contact lens use for corneal epithelial defects.

Extended latanoprost release from commercial contact lenses: in vitro studies using corneal models.

In this study, we compared, for the first time, the release of a 432 kDa prostaglandin analogue drug, Latanoprost, from commercially available contact lenses using in vitro models with corneal epithelial cells. Conventional polyHEMA-based and silicone hydrogel soft contact lenses were soaked in drug solution ( solution in phosphate buffered saline). The drug release from the contact lens material and its diffusion through three in vitro models was studied. The three in vitro models consisted of a polyethylene terephthalate (PET) membrane without corneal epithelial cells, a PET membrane with a monolayer of human corneal epithelial cells (HCEC), and a PET membrane with stratified HCEC. In the cell-based in vitro corneal epithelium models, a zero order release was obtained with the silicone hydrogel materials (linear for the duration of the experiment) whereby, after 48 hours, between 4 to 6 of latanoprost (an amount well within the range of the prescribed daily dose for glaucoma patients) was released. In the absence of cells, a significantly lower amount of drug, between 0.3 to 0.5 , was released, (). The difference observed in release from the hydrogel lens materials in the presence and absence of cells emphasizes the importance of using an in vitro corneal model that is more representative of the physiological conditions in the eye to more adequately characterize ophthalmic drug delivery materials. Our results demonstrate how in vitro models with corneal epithelial cells may allow better prediction of in vivo release. It also highlights the potential of drug-soaked silicone hydrogel contact lens materials for drug delivery purposes.

Survey on Bandage Contact Lens Practice in the United Kingdom

Purpose: To determine the opinion regarding the prescribing practices of bandage contact lenses (BCL) amongst members of the Bowman Club (UK Cornea Society).Methods: In June 2011, followed by a reminder in July, a questionnaire was sent out to all 128 members of the Bowman Club. The survey included 19 questions regarding indications, preferred type, methods of insertion, concomitant medication, complications related to BCL use among other questions.Results: The survey was completed anonymously by 52 (40.6%) consultant ophthalmologists either online (88.5%) or by post (11.5%). The most common indication is pain relief by 51 (98%), followed by promotion of epithelial healing by 49 (94.2%) respondents. Silicon hydrogel soft contact lens is the most commonly used BCL by 39 (75%) consultants. There was a higher incidence of secondary corneal ulcers reported if consultants were using non-sterile (51.9%) versus sterile (15.4%) insertion technique as well as use (26.9%) versus no use of topical prophylactic antibiotic (40.4%).Conclusions: This is the first survey on practice pattern of BCL use amongst consultant ophthalmologists with expertise in the management of a subspecialty in Ocular Surface Diseases in the UK. It demonstrates that the most common indication for BCL use is pain relief, with silicone hydrogel soft contact lenses being the most frequently used. Secondary corneal ulcers were more frequently seen by consultants that neither use sterile insertion technique nor prophylactic topical antibiotics.

In vitro and in vivo delivery of the secretagogue diadenosine tetraphosphate from conventional and silicone hydrogel soft contact lenses

PurposeTo evaluate the possible use of soft contact lenses (CL) to improve the secretagogue role of diadenosine tetraphosphate (Ap4A) promoting tear secretion. MethodsTwo conventional hydrogel CL (Omafilcon A and Ocufilcon D) and two silicone hydrogel (SiH) CL (Comfilcon A and Balafilcon A) were used. Ap4A was loaded into the lenses by soaking in a 1mM Ap4A solution during 12h. In vitro experiments were performed by placing the lenses in multi-wells during 2h containing 1ml of ultrapure water. 100μl aliquots were taken at time zero and every minute for the first 10min, and then every 15min. In vivo experiments were performed in New Zealand rabbits and both the dinucleotide release from SiH and tear secretion were measured by means of Schirmer strips and high-pressure liquid chromatography (HPLC) analysis. ResultsAp4A in vitro release experiments in hydrogel CL presented a release time 50 (RT50) of 3.9±0.2min and 3.1±0.1min for the non-ionic and the ionic CL, respectively. SiH CL released also Ap4A with RT50 values of 5.1±0.1min for the non-ionic and 2.7±0.1min for the ionic CL. In vivo experiments with SiH CL showed RT50 values of 9.3±0.2min and 8.5±0.2min for the non-ionic and the ionic respectively. The non-ionic lens Ap4A release was able to induce tear secretion above baseline tear levels for almost 360min. ConclusionThe delivery of Ap4A is slower and the effect lasts longer with non-ionic lenses than ionic lenses.

Incidence and Epidemiologic Associations of Corneal Infiltrates With Silicone Hydrogel Contact Lenses

Contact lens-associated corneal infiltrative events (CIEs) are presumed sterile events that have complicated contact lens wear for more than 30 years. There is consistent evidence that silicone hydrogel soft contact lenses increase CIE risk by twofold compared with low Dk hydrogel materials. The incidence of CIEs during silicone hydrogel extended wear ranges from 2% to 6% for symptomatic events and from 6% to 25% when asymptomatic events are included. For daily wear, with silicone hydrogels, the incidence of CIEs ranges from 2% to 3% for symptomatic events and from 7% to 20% when asymptomatic events are included. Despite the increased rate of CIEs with silicone hydrogels, the benefits of these lenses largely outweigh this risk for many patients. Most risk factors for CIEs observed with silicone hydrogels are consistent with CIE risk factors reported earlier with hydrogel lenses, such as bacterial bioburden on lens surfaces, and young age among others. Limiting the transfer of bacterial bioburden from the skin to lenses, lens cases and eventually to the eye is an obvious step forward for the prevention of CIEs across all lens types.

Quality of Vision with Spectacles, Special Silicone Hydrogel and Gas Permeable Contact Lenses in Keratoconic Patients

ABSTRACT Purpose To evaluate optical quality and visual function in keratoconus patients corrected with RGP contact lenses and a novel special design of silicone hydrogel contact lens. Materials and methods Twelve eyes of six patients with keratoconus were enrolled to experience a new soft contact lens (Soft-K) for keratoconus made of a silicone-hydrogel material and the outcomes were compared to the performance with gas permeable lenses and spectacles. The three situations were compared for monocular and binocular high (100%) and low contrast (10%) ETDRS LogMAR visual acuity and contrast sensitivity function (CSF). Results On average, there was an improvement of more than two lines in visual acuity over spectacle correction and this is statistically significant for both gas permeable (GP) and Soft-K lens (p &lt; 0.001). Visual acuity was not significantly different between GP and Soft-K lens for high contrast acuity but was slightly higher with GP lens for low contrast under binocular conditions. Monocular CSF showed a marked improvement with the Soft-K lens and GP, compared to spectacles correction, particularly for medium and high frequencies; conversely. Conclusion Soft-K silicone hydrogel soft contact lens produces a clinical and statistically significant improvement in visual acuity and contrast sensitivity function over spectacle correction. How to cite this article González-Méijome JM, Peixoto-de- Matos SC, Queiros A, Jorge JM, Diaz-Rey A. Quality of Vision with Spectacles, Special Silicone Hydrogel and Gas Permeable Contact Lenses in Keratoconic Patients. Int J Kerat Ect Cor Dis 2013;2(2):56-59.

Contact Lens Dry Eye Questionnaire-8 (CLDEQ-8) and Opinion of Contact Lens Performance

To report on the development and validation of a short form of the Contact Lens Dry Eye Questionnaire (the CLDEQ-8) to enable it to reflect status of and change in overall opinion ("opinion") of soft contact lenses (SCLs). Item reduction for the CLDEQ was achieved by correlation with overall opinion of SCLs at follow-up visits in a sample of 38 SCL wearers at one academic clinical site. The CLDEQ-8 score (frequency plus late day intensity of dryness, discomfort, and "blurry vision"; frequency of "closing eyes to rest them" and "removing CLs to relieve discomfort") was then tested in 379 SCL wearers in a multicenter study with analysis stratified by opinion ratings at baseline and 2 weeks postrandomization to new silicone hydrogel SCLs. The sum of CLDEQ-8 scores (maximum 37) was correlated with opinion by Spearman's rank correlation coefficient and analyzed for change in opinion by analysis of variance (ANOVA). The CLDEQ-8 scores in the validation sample were highly correlated with habitual baseline opinion (-0.44, p < 0.0001) and responsive to change in opinion postrandomization (-0.58, p < 0.0001). Baseline CLDEQ-8 scores by opinion status were as follows: Fair: 17.4 ± 8.7, Good 13.7 ± 6.4, Very Good 9.1 ± 4.7, and Excellent 6.4 ± 3.7 (ANOVA, F = 291.1, p < 0.0001). After 2 weeks, change in CLDEQ-8 scores by improvement status was as follows: Much Improved: -16.7 ± 10.0, Unchanged: -2.3 ± 5.0, to Much Worse +8.5 ± 5.8 (ANOVA, F = 16.5, p < 0.001). The CLDEQ-8 score significantly reflected baseline status and change in overall opinion after refitting with two types of silicone hydrogels. The CLDEQ-8 score is a valid outcome measure in SCL clinical trials to reflect opinion of SCLs.

Development of Methicillin-Resistant Staphylococcus aureus Keratitis in a Dry Eye Patient With a Therapeutic Contact Lens

The aim was to report a case of methicillin-resistant Staphylococcus aureus (MRSA) keratitis possibly associated with the use of a silicone hydrogel soft contact lens in a patient with dry eye. This is a case report. A 61-year-old woman who wore a silicone hydrogel lens as therapy for filamentary keratitis with severe dry eye presented with pain and redness in her left eye. She developed severe keratitis with ulceration and hypopyon. The MRSA grew in the culture, and intensive systemic and topical antibiotics resolved the corneal keratitis. The MRSA may cause infectious keratitis associated with silicone hydrogel contact lens therapy.

Protein deposition on contact lenses: The past, the present, and the future

Proteins are a key component in body fluids and adhere to most biomaterials within seconds of their exposure. The tear film consists of more than 400 different proteins, ranging in size from 10 to 2360 kDa, with a net charge of pH 1-11. Protein deposition rates on poly-2-hydroxyethyl methacrylate (pHEMA) and silicone hydrogel soft contact lenses have been determined using a number of ex vivo and in vitro experiments. Ionic, high water pHEMA-based lenses attract the highest amount of tear film protein (1300 μg/lens), due to an electrostatic attraction between the material and positively charged lysozyme. All other types of pHEMA-based lenses deposit typically less than 100 μg/lens. Silicone hydrogel lenses attract less protein than pHEMA-based materials, with <10 μg/lens for non-ionic and up to 34 μg/lens for ionic materials. Despite the low protein rates on silicone hydrogel lenses, the percentage of denatured protein is typically higher than that seen on pHEMA-based lenses. Newer approaches incorporating phosphorylcholine, polyethers or hyaluronic acid into potential contact lens materials result in reduced protein deposition rates compared to current lens materials.

Adhesive Capabilities of Staphylococcus Aureus and Pseudomonas Aeruginosa Isolated from Tears of HIV/AIDS Patients to Soft Contact Lenses

Fifty conjunctival swab samples collected from ELISA confirmed HIV/AIDS seropositive patients who were referred to the HIV/AIDS laboratories of the University of Benin Teaching Hospital and Central Hospital both based in Benin City, Nigeria were aseptically cultured on appropriate media by standard methods. The resulting isolates/strains, after identification by standard methods, were tested for their ability to adhere to two hydrophobic non-ionic daily wear silicone hydrogel soft contact lenses (i.e. lotrafilcon B, WC 33% and polymacon, WC 38%) as well as to two hydrophilic ionic conventional extended wear silicone hydrogel soft contact lenses (i.e. methafilcon A, WC 55% and omafilcon A, WC 60%) by the adhesiveness/slime production modified vortex/Robin device method. Evidence of adhesiveness/slime production was indicated by presence of a visible stained film lining the surface of the contact lens which was measured and recorded as strong or weak according to the density of the adhered bacterial film. Fourteen (28.0%) Staphylococcus aureus strains and 10 (20.0%) Pseudomonas aeruginosa strains were obtained among other organisms. Staphylococcus aureus strains adhered in decreasing order to lotrafilcon B (55.4 ± 4.7), polymacon (46.4 ± 8.4), methfilcon A (46.4 ± 8.4) and omafilcon A (25.0 ± 6.4) with no significant difference in adhesive strengths of individual strains (P > 0.05). Pseudomonas aeruginosa strains also recorded decreasing adhesive strengths to lotrafilcon B (37.5 ± 8.2), polymacon (28.6 ± 6.3), methafilcon A (26.8 ± 5.5) and omafilcon A (23.2 ± 5.5) also with no significant difference in adhesive strengths of individual strains (P > 0.05). Attachment strengths of Staph. aureus strains to all four contact lenses were higher than those of Pseudomonas aeruginosa strains. Both organisms adhered most to hydrophobic lotrafilcon B and least to hydrophilic omafilcon A. This invitro adhesion studies revealed that daily wear silicone hydrogel low water content, non-ionic contact lenses are more prone to bacterial adhesion than the conventional extended wear hydrogel high water content, ionic contact lenses and hence, there is more risk of microbial adhesion to the former compared to the latter. Other implications are highlighted.

The influence of soft contact lenses on the intraocular pressure measurement

To evaluate the influence of silicone hydrogel contact lenses on the intraocular pressure (IOP) measurement using Goldmann applanation tonometry (GAT), non-contact tonometry (NCT), and Pascal dynamic contour tonometry (DCT). We included in the study 40 eyes of 40 patients who did not have any ocular or systemic diseases or contraindications to contact lens use. We measured and recorded the IOP values of each patient using NCT without and with contact lenses (groups 1 and 2, respectively), using DCT without and with contact lenses (groups 3 and 4, respectively), and using GAT without contact lenses (group 5). The mean IOP value of group 1 was 14.55 ± 2.95 mm Hg and 13.92 ± 2.58 mm Hg in group 2. We detected no statistically significant difference between group 1 and group 2 (P=0.053). The mean IOP values for group 3 and group 4 were 16.26 ± 2.33 mm Hg and 15.19 ± 2.40 mm Hg, respectively. We detected a statistically significant difference between groups 3 and 4 (P=0.005). Group 5's mean IOP value was 12.97 ± 2.65 mm Hg. IOP values measured with DCT were statistically significantly higher compared with IOP values measured with NCT and GAT (P<0.0001 and P<0.0001, respectively). Additionally, IOP values measured with NCT were statistically significantly higher compared with IOP values measured with GAT (P<0.0001). According to the results of our study, silicone hydrogel soft contact lens use does not significantly affect IOP values measured with NCT, but it affects IOP values measured with DCT.

Effect of Controlled Adverse Chamber Environment Exposure on Tear Functions in Silicon Hydrogel and Hydrogel Soft Contact Lens Wearers

To prospectively evaluate the effect of controlled adverse chamber environment (CACE) exposure on tear function, including tear osmolarity, in subjects wearing narafilcon A versus those wearing etafilcon A soft contact lens (SCL). Thirty-one healthy subjects with no history of contact lens wear (13 women, 18 men; average age, 30.5 ± 6.5 years) were randomly divided into age- and sex-matched groups (15 subjects wearing narafilcon A SCL; 16 subjects wearing etafilcon A SCL) and entered a CACE for 20 minutes. All subjects underwent tear osmolarity, tear evaporation rate, strip meniscometry, tear film breakup time, fluorescein vital staining, and functional visual acuity measurement before and after exposure to the controlled adverse chamber. The mean blink rate increased with significant deteriorations in the mean symptom VAS scores, mean tear osmolarity, tear evaporation rate, strip meniscometry score, and tear stability with CACE exposure along with a decrease in visual maintenance ratio in functional visual acuity testing in etafilcon A wearers. The mean symptom VAS scores, mean tear evaporation rate, tear stability, blink rates, and visual maintenance ratios did not change significantly in narafilcon A wearers after CACE exposure. This study suggested marked tear instability, higher tear osmolarity, and increased tear evaporation with marked dry eye and visual symptomatology in nonadapted hydrogel SCL wearers, suggesting that silicone hydrogel SCLs may be suitable for persons who live and work in cool, low-humidity, and windy environments, as tested in this study.

Contact Lenses Wettability In Vitro: Effect of Surface-Active Ingredients

To investigate the release of surface-active agents (surfactants) from unworn soft contact lenses (SCLs) and their influence on the lens surface wettability in vitro. Surface tension (ST) of blister pack solutions was measured by pendant-drop technique. STs at the air-aqueous interface and contact angles (CAs) of four conventional and seven silicone hydrogel SCLs were evaluated in a dynamic-cycling regime using a modified captive-bubble tensiometer-goniometer. Measurements were performed immediately after removal from blister packs, and after soaking in a glass vial filled with a surfactant-free solution, which was replaced daily for 1 week. Lens surface wettability was expressed as adhesion energy according to Young equation. STs of all blister pack solutions were lower than the reference ST of pure water (72.5 mN/m), indicating the presence of surfactants. When lenses were depleted of surfactants by soaking, the STs for all studied lenses and advancing CAs of selected lenses increased (p < 0.001). Receding CAs of all studied lenses were 12 degrees +/- 5 degrees and were not affected by the presence of surfactants. For most of the conventional lenses, the surface wettability was largely dependent on surfactants, and reduced significantly after surfactant depletion. In contrast, most silicone hydrogel lenses exhibited stable and self-sustained surface wettability in vitro. The manufacturer-added surfactants affected wetting properties of all studied SCLs, although to different degrees.