Randomized crossover trial of silicone hydrogel contact lenses

PurposeThe aim of the current study is to assess, using new technologies, the interaction of four monthly silicone hydrogel contact lenses on the ocular surface and the comfort over 15 days of use.MethodsProspective cross-over, randomized and double-masked study including four materials (lotrafilcon-B, samfilcon-A , comfilcon-A and filcom-V3). Clinical examination was performed in the following order: tear meniscus height, first break-up of the tear film, the average time of all tear film breakup incidents, bulbar redness, limbal redness (Keratograph 5M ,Oculus, Germany); central corneal thickness (Pentacam, Oculus, Germany), thermography values (FLIR A325; FLIR Systems Inc., USA), and slit-lamp evaluations, including ocular surface staining. Finally, subjective comfort was obtained from Contact Lens Dry Eye Questionnaire-8.ResultsThe impact of contact lens wear on the ocular surface didn’t show statistically significant changes over time except for corneal and conjunctival staining grades on day 15 compared to day 1 for the comfilcon A group (P = .003 and P = .01, respectively). Contact lens stability and impact on the ocular surface during contact lens wear didn’t show statistically significant changes over time except in the case of the comfilcon A material with respect to the irritation item (P = .01).ConclusionsThese results suggest that the impact of monthly silicone hydrogel contact lens materials on the ocular surface after and during contact lens wear, contact lens stability over time, and subjective comfort did not reveal any significant changes over 15 days of use for any of the materials.     

Stabilization of comfort and visual quality after the insertion of soft contact lenses

PurposeTo evaluate comfort, visual function, and in vivo wettability after the insertion of hydrogel and silicone hydrogel contact lenses for a better understanding of how long practitioners should wait for the initial evaluation of soft contact lenses.MethodsA short-term prospective, contralateral, randomized, and participant-masked study was carried out. Twenty healthy participants (25.4 ± 2.6 years) were evaluated after the insertion of two different soft contact lenses at different times (1, 5, 10, 20, 30 min). Ocufilcon D (hydrogel) and Somofilcon A (silicone hydrogel) contact lenses were randomly assigned to both eyes of the same participant. Comfort, visual function under photopic conditions in terms of high-contrast visual acuity, low-contrast visual acuity, contrast sensitivity, and in vivo wettability were measured.ResultsThere was an increase in comfort (p < 0.001), high-contrast visual acuity (p < 0.05), and contrast sensitivity (p < 0.001, only with silicone hydrogel) directly related to time after contact lens insertion. Besides, in vivo wettability suffered a statistically significant deterioration directly related to time with both contact lenses (p < 0.05). Except for comfort and contrast sensitivity, all the parameters stabilized their values 10 min after the insertion of both soft contact lenses. Additionally, in vivo wettability and visual acuity differences were found between hydrogel and silicone hydrogel contact lenses (p < 0.05).ConclusionsIt would be possible to properly evaluate high-contrast visual acuity, low-contrast visual acuity, and in vivo wettability 10 min after the insertion of both soft contact lenses.     

The influence of lens care systems on eyelid tissue changes during silicone hydrogel contact lens wear

Purpose

To compare the effects of a hydrogen peroxide (H₂O₂)-based lens care solution and a polyhexamethylene biguanide (PHMB) multi-purpose solution on the eyelids when used with silicone hydrogel (SiHy) contact lenses.

The accuracy of Goldmann applanation tonometry over silicone hydrogel contact lenses in patients with glaucoma

PurposeTo investigate the accuracy of measuring intraocular pressure over a silicone hydrogel contact lens using Goldmann applanation tonometry in eyes with glaucoma.MethodsThis was a prospective, randomized study and enrolled 28 patients (28 right eyes) with primary open angle glaucoma. Intraocular pressure was taken with and without a silicone hydrogel contact lens (−0.50 D), in situ (using Goldmann applanation tonometry), in a randomized order of measurements. Statistical analysis was performed using paired t-test and Bland–Altman plot.ResultsThe mean difference (± standard deviation) found between intraocular pressure measurement without (mean 16.7 ± 3.2 mmHg) and with (mean 17.3 ± 3.0 mmHg) contact lens was found to be −0.57 ± 2.3 mmHg (95% confidence interval, −1.5 to 0.3). No significant statistical difference was found between the two groups with paired t-test (p = 0.19). The Bland Altman plot showed some evidence of increasing variability of differences between two measures of intraocular pressure, with increasing intraocular pressure. The 95% limits of agreement of the Bland Altman plot were unacceptably large (−5 mmHg to 3.9 mmHg).ConclusionAgreement between Goldmann applanation tonometry with and without contact lenses seems to be poor in patients with glaucoma, especially for high intraocular pressure.     

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.     

Masked comparison of two silicone hydrogel bandage contact lenses after photorefractive keratectomy

PurposeTo compare the efficiency and safety of two bandage contact lenses after photorefractive keratectomy (PRK).MethodsIn this double-blind study, 45 patients (90 eyes) received PRK in both eyes and wore bandage contact lenses (BCLs), PureVision (Bausch & Lomb, Rochester, NY, USA) in one eye and PureVision2 (Bausch & Lomb, Rochester, NY, USA) in the other eye, randomly assigned. The medication regimen after surgery was the same for both eyes. The epithelial defect's size, conjunctival hyperemia and lens centration were graded objectively using slit-lamp biomicroscopy on days 1, 3 and 5 after surgery. Also ocular symptoms of discomfort including tearing, photophobia, foreign body sensation and visual fluctuations were assessed subjectively at each visit.ResultsThe mean epithelial defect size on the first day after operation was similar in eyes fitted with PureVision (30.08 ± 5.30 mm²) and PureVision2 (30.25 ± 5.72 mm²) lenses. (p = 0.79) Contact lens deposits and bulbar hyperaemia on days 1 and 3 after PRK were similar between the two eyes, but were significantly greater on day 5 for PureVision2 lenses. (p = 0.02; p = 0.04 respectively) There was no difference in contact lens decentration, and discomfort symptoms including pain, tearing, foreign body sensation, photophobia and visual fluctuations between the eyes fitted with PureVision and PureVision2. (p > 0.05)ConclusionsPureVision and PureVision2 contact lenses are equivalent as bandage lenses in important aspects such as corneal re-epithelialization and subjective comfort., although PureVision2 led to a higher incidence of contact lens deposits and conjunctival hyperemia early post-PRK.     

Compatibility of phospholipid liposomal spray with silicone hydrogel contact lens wear

Purpose

To assess the effects of two weeks of regular phospholipid liposomal spray application on lipid layer grade, tear film stability, subjective comfort, visual acuity, and lipid deposition in silicone hydrogel contact lens wearers.

Applanation tonometry in silicone hydrogel contact lens wearers

INTRODUCTION: Previous studies have investigated intraocular pressure (IOP) measurements through conventional soft (hydrogel) therapeutic contact lenses, and have found that an accurate IOP can be recorded in normal eyes, and in eyes with abnormal anterior segments. The IOP measurement through soft contact lenses may be affected by the water content and centre thickness of the lens. Silicone hydrogel contact lenses are now being used as therapeutic contact lenses due to their high oxygen permeability. The purpose of this study is to investigate if IOP can be accurately measured in a subject wearing a silicone hydrogel contact lens. METHODS: In a cohort study, the IOP was measured with a Goldmann applanation tonometer without a contact lens and then repeated with a hydrogel contact lens in situ. RESULTS: The IOP of 20 eyes of 10 volunteers with no ocular pathology was measured. The mean difference (+/-S.D.) found between IOP measurement with (mean 15.55+/-1.70 mmHg) and without (mean 16.05+/-1.90 mmHg) contact lens was found to be -0.5+/-0.89 mmHg. Statistical analysis was performed which revealed a correlation coefficient of 0.89. No significant statistical difference was found between the two groups with paired t-test (p=0.19). CONCLUSION: Accurate measurement of IOP by applanation tonometry can be achieved through a silicone hydrogel contact lens.     

Trends in the use of silicone hydrogel contact lenses for daily wear

Although the first silicone hydrogel contact lenses introduced onto the world contact lens market in 1999 held approval for both daily wear and extended wear use, the latter modality was promoted much more heavily by the manufacturers. The first silicone hydrogel lenses specifically promoted for daily wear were introduced in 2003. Data that we have gathered from annual contact lens fitting surveys demonstrate an immediate increase in market share whereby this lens type now represents more than one-third of soft lens fits in the United Kingdom. The success of this lens category is attributed to the health and safety benefits of silicone hydrogel materials and the positive impact of lens manufacturers by way of the effective marketing and distribution of these products.     

Rebound tonometry measurements over extended-wear bandage contact lenses

BackgroundThe aim of this study was to assess the validity of rebound tonometry measurements obtained over eyes wearing extended-wear bandage contact lenses with the highest oxygen transmissibility (Dk/t) value of 175 @ -3.00 D.MethodsA total of 151 normal eyes were included in this prospective pretest-posttest study. A rebound tonometer (iCare PRO) was used to collect intraocular pressure readings from “naked” eyes (eyes without contact lenses) and the same eyes wearing extended-wear lotrafilcon A bandage contact lenses (Alcon Air Optix Night & Day Aqua Contact Lenses). The mean pre- and post-application values were pooled and compared using the paired t-test.ResultsThe application of extended-wear lotrafilcon A contact lenses over normal eyes did not cause a statistically significant change in the intraocular pressure measurements obtained using an iCare PRO tonometer (13.74 ± 2.15 mm Hg vs. 13.77 ± 2.26 mm Hg, p-value = 0.6506).ConclusionBased on this study conducted on normal eyes, the removal of extended-wear bandage contact lenses is not necessary when taking intraocular pressure measurements using the iCare PRO rebound tonometer.     

Contact lens induced papillary conjunctivitis with silicone hydrogel lenses

Purpose

To describe the refitting of a soft lens wearer into a silicone hydrogel lens due to neovascularization. This change, in turn, caused contact lens induced papillary conjunctivitis (CLPC) and a further refitting was necessary.

Methods

The patient was refit into a high Dk surface treated silicone hydrogel with a high modulus value. A second refitting was undertaken into a lower Dk silicone hydrogel contact lens with a lower modulus value which had no surface treatment but incorporated an internal wetting agent.

Results

A high Dk/t lens was used to resolve existing neovascularization and chronic hyperaemia. Subsequently, CLPC response occurred, possibly due to a combination of factors, resulting in irritation of the palpebral conjunctiva. This resulted in temporary lens discontinuation. A second silicone hydrogel lens was fit, along with the use of a non-preserved care system, which led to improvement and eventual resolution of the condition.

Conclusion

High Dk silicone hydrogel lenses have shown excellent efficacy in resolving hypoxic complications such as neovascularization and hyperaemia. However, attention needs to be paid to their potential effect on the upper tarsal plate. More than one silicone hydrogel lens may be needed to help resolve these issues.     

Factors influencing the prescribing of hydrogel contact lenses

Despite the current market popularity of silicone hydrogel contact lenses, conventional hydrogel lenses still represent a significant proportion of the overall contact lens market. Data gathered from annual UK contact lens fitting surveys over the past 13 years indicate that 64% of hydrogel lenses prescribed during this period were of low/medium water content (≤60% water). Whereas, in the past, practitioners would choose the water content of a hydrogel lens to meet specific clinical needs, this choice appears today to be largely governed by product availability.     

Predicted tear layer oxygen tensions under two designs of silicone hydrogel toric lenses

Introduction

The goal of this study was to apply a theoretical analysis of the relationship between contact lens oxygen transmissibility and tear layer oxygen tension to silicone hydrogel toric lenses and thereby model the success of such lenses in decreasing corneal hypoxia.

Method

Lens thickness was measured at different points along the vertical meridian of one prism-ballasted, one dynamic-stabilized silicone hydrogel toric lens design, and one control “traditional” hydrogel toric lens design. Using lens thickness measurements and the nominal oxygen permeability values of these three lens designs, the subsequent oxygen tension in the tear layer trapped between the contact lens and the anterior cornea (P2) were calculated for both open- and closed-eye conditions using a single corneal chamber model with a personal computer program.

Results

We found that cylindrical powers, regardless of lens materials, did not have a statistically significant effect on lens thickness (F = 0.30, p = 0.5834) to the limitation of our measurements, while contact lens type, spherical power, location on lens, and axis of cylindrical power were all found to do so. When multi-factor ANOVA was applied to the lens thickness and P2 data, contact lens location had a statistically significant effect on P2 values for both prism-ballasted (F = 640.16, p < 0.0001) and dynamic-stabilized toric lenses (F = 352.85, p < 0.0001). When the same statistical methodology was used to compare the relative performance of all three lenses on P2 during daily wear, the average P2 values for the three different lens brands were all statistically significantly different, while under closed-eye conditions the average P2 values for both silicone hydrogel toric lenses were no longer statistically significantly different (F = 1.00, p = 0.3178).

Conclusion

Assuming that the critical P2 was 100 mmHg, we predicted that silicone hydrogel toric soft lenses would provide reasonable anterior corneal oxygenation, certainly much enhanced over the environment predicted under traditional hydrogel designs, especially during daily (e.g. open eye) wear. Substantial corneal hypoxia continued to be predicted during extended wear of all lenses, but especially so with the use of traditional hydrogels.     

Lipid deposition on contact lenses in symptomatic and asymptomatic contact lens wearers

PurposeLipid deposition on contact lenses (CL) has traditionally been believed to reduce comfort during CL wear. The purpose of this study was to quantify lipid deposition on CL in a group of symptomatic and asymptomatic adapted CL wearers.MethodsThis was a single-masked, randomized clinical trial. Only confirmed symptomatic (comfortable lens wear time (CWT) < 8 h and a noticeable reduction in comfort over the course of the day) and asymptomatic (CWT > 10 h and minimal reduction in comfort over the course of the day) participants were recruited to participate in the study. Participants wore senofilcon A lenses in combination with a polyquaternium-based care solution (OPTI-FREE Replenish). Worn CL samples were collected on Day 14. Deposited lipid amounts from the lenses (including cholesteryl ester, cholesterol and triolein) were quantified using a liquid chromatography-mass spectrometry technique.ResultsLipid deposition was significantly higher in CL extracts of asymptomatic wearers compared to the symptomatic wearers for all lipid types quantified, including cholesteryl ester (2.1 ± 0.6 vs 1.6 ± 0.5 log μg/lens), cholesterol (1.5 ± 0.3 vs 1.1 ± 0.3 log μg/lens) and triolein (0.3 ± 0.2 vs 0.1 ± 0.1 log μg/lens) (all p < 0.002). The amount of cholesteryl ester deposited was greatest (p = 0.0001), followed by cholesterol, then triolein, for both the asymptomatic and symptomatic groups (both p = 0.0001).ConclusionThis study demonstrated that the asymptomatic group deposited a significantly greater amount of lipid on their CL. Although lipid levels measured are considered low to trigger any observable clinical deposition, they may influence other clinical outcomes, particularly comfort.     

A silicone hydrogel contact lens after 7 years of continuous wear

PurposeTo report an unusual case with a bandage silicone hydrogel lens that was applied over cyanoacrylate glue application for corneal perforation.DesignRetrospective, interventional case report.MethodsA 67-year-old woman with a history of corneal trauma experienced spontaneous corneal perforation in her left eye. Upon arrival, her anterior chamber was flat and Seidel test was positive. After initial treatment with cyanoacrylate adhesive and a bandage silicone hydrogel contact lens, there was no leakage and the anterior chamber was formed at the follow-up period. She was started topical antibiotics.ResultsAfter 7 years, she came back with the complaint of permanent redness in her left eye with the same silicone hydrogel lens in her eye.ConclusionsCorneal healing may occur under cyanoacrylate adhesive glue with therapeutic contact lenses and with proper antibiotic application. Silicone hydrogel contact lenses exhibit good efficacy and safety when utilized as a continuous wear therapeutic lens with antibiotics.     

Effect of material and care system combination on subclinical inflammation of the ocular surface in soft contact lens wear

PurposeTo investigate the ocular subclinical inflammatory response in two soft contact lens materials when used in combination with two different care systems (‘solutions’).MethodsFifteen established soft contact lens wearers wore each of two lenses: Acuvue® 2 (CH) and Acuvue® Oasys® (SiH) or no lenses in random sequence for one week. Two care systems were used: a peroxide system: Oxysept 1 Step® (P) for the right lens and Opti-Free® Replenish® (MPS) for the left lens. After one week of lens/no lens wear, in vivo confocal microscopy (IVCM) of corneal and conjunctival regions was carried out. Density of presumed dendritic cells (DC) and ‘white spots’ (WS) were quantified. Impression cytology of the bulbar and upper eyelid margin conjunctivae was carried out and samples were analysed for CD45+, CD3+ and CD11c+ cells.ResultsThe SiH + MPS combination showed a greater inflammatory response compared to SiH + P in seven out of 12 parameters investigated (p < 0.05). The remaining five were not statistically different between the two solutions. The converse was found for the CH lens, with four of the 12 parameters showing a greater response with the P solution compared to the MPS (p < 0.05).ConclusionThis study suggests that the SiH lens investigated demonstrated an upregulated response when used with a MPS compared to a P solution whereas the converse is true for the CH lens which showed a reduced response when used with a MPS compared to a P solution. This finding aids in the understanding of the biological underpinnings of manifest corneal inflammatory events during contact lens wear.     

The relationship between compliance with lens replacement and contact lens-related problems in silicone hydrogel wearers

Purpose

To evaluate the relationship between compliance with replacement frequency (RF) and contact lens (CL)-related problems in silicone hydrogel (SiHy) wearers.

Methods

501 SiHy wearers from seven optometry offices completed surveys regarding their lens wear and any CL related problems which they may have experienced in the preceding 12 months. File review was subsequently conducted at their optometry offices to confirm the information provided.

Results

49% of respondents were wearing 2-week replacement (2WR) and 51% 1-month replacement (1MR) SiHy lenses. 67% wore their lenses for longer than the manufacturers’ recommended RF (MRRF) and 60% for longer than their optometrist's recommended RF (ORRF). The mean RF was 2.6× the MRRF for 2WR and 1.5× for 1MR wearers (p < 0.001) with median values of 31 and 37 days, respectively. Twenty-three percent reported signs or symptoms consistent with potential complications relating to CL wear. This rate was significantly higher for wearers who were non-compliant with the ORRF than compliant wearers (26% versus 18%, p = 0.028). It was also higher for those multipurpose solution users who reported never/almost never rubbing and rinsing their lenses when compared with those who did this every night (29% versus 17%, p = 0.007).

Conclusions

Two thirds of the SiHy wearers did not comply with the MRRF and 2WR wearers stretched the replacement interval of their lenses to a greater degree than 1MR wearers. Failing to replace lenses when recommended and failing to rub and rinse lenses were associated with a higher rate of patient-reported CL problems.     

Patterns of prescribing extended wear contact lenses

Patterns of prescribing extended wear contact lenses in the UK were determined by mining through data gathered from annual contact lens fitting surveys conducted over the past 12 years. The increased rate of extended wear prescribing this century - which in 2007 had reached 7% and 19% of all soft lens new fits and refits, respectively - probably reflects the superior clinical performance of silicone hydrogel lenses for this purpose.     

Effects of lysosomal deposition on the friction coefficient of hydrogel contact lenses

When a contact lens is in contact with the eyelid and the cornea, tear proteins start to be accumulated on the lens and may subsequently undergo conformational changes. Protein adsorption or conformational changes on the lens may lead to discomfort, red eye, or even inflammatory reactions. Although measuring the friction coefficient of contact lens has been linked to comfort degree in vivo, there is not much research about the effects of tear protein deposition on the friction coefficient of the contact lens. Therefore, we investigated the friction coefficient of three distinct materials of contact lenses in two different lysosomal concentrations. We also studied lysozyme deposition on the lens without the influence of friction. The results demonstrated that although the amount of lysozyme deposition was high on all the materials we tested, it was not corresponded to higher friction coefficient. In addition, we investigated the effect of the contact lens care solution we developed on friction coefficient and lysozyme deposition of three different materials of contact lenses. The results showed that the care solution could reduce the increased friction coefficient caused by high lysosomal concentration. Therefore, we proposed a potential mechanism of why lysosomal deposition may result in high friction coefficient for certain types of hydrogel contact lenses.     

The impact of lens care solutions on corneal epithelial changes during daily silicone hydrogel contact lens wear as measured by in vivo confocal microscopy

Purpose

To assess corneal epithelial microstructure via confocal microscopy and determine if cellular changes are associated with lens care solutions during daily wear of silicone hydrogel contact lenses.