Contact Lens Deposits, Adverse Responses, and Clinical Ocular Surface Parameters

Analysis of Deposition and Diffusion of Cholesterol in Silicone Hydrogel Contact Lenses Using Confocal Microscopy

In this study, we investigated lipid deposition and diffusion in silicone hydrogel (Si-Hy) contact lenses using confocal microscopy. Different Si-Hy lenses were analyzed to understand the interaction patterns of cholesterol with various lens materials. The results highlight significant differences in the deposition and diffusion of lipids through the lenses, revealing that some materials, such as comfilcon A, allow lipids to diffuse more freely compared to others, such as samfilcon A, which provides a greater barrier. The study also observed different morphology and movement of lipid agglomerates across the lenses and above it surfaces. These findings contribute to the understanding of lipid-lens interaction, which is important for the development of lenses with improved comfort and functionality. The research highlights the importance of considering lipid interactions in the design and selection of Si-Hy contact lenses to enhance wearer comfort and lens performance.

Assessing neophyte response to daily disposable silicone hydrogel contact lenses: A randomised clinical trial investigation over one month

OBJECTIVE

This randomised clinical trial assessed the impact on symptoms, tear film dynamics and ocular surface integrity of daily disposable silicone-hydrogel contact lenses (CLs) over a month, paying special attention to lid wiper epitheliopathy (LWE) and its implications for CL discomfort.

METHODS

Neophyte CL wearers (n = 44, 21.09 ± 5.00 years old) were randomly assigned to either the experimental (n = 24) or control group (n = 20). Participants assigned to the experimental group were required to wear daily disposable CLs for 1 month for at least 8 h/day and 6 days/week. All participants were healthy subjects (no history of ocular surgery or active ocular disease) with spherical refractive errors between -8.00 and +5.00 D and cylindrical power <0.75 D. At the baseline and 1-month sessions, the Dry Eye Questionnaire 5 (DEQ-5) was completed, together with the measurement of tear film osmolarity with the TearLab osmometer, tear meniscus height (TMH) and lipid layer pattern (LLP) using a slit-lamp with Tearscope Plus attached, fluorescein break-up time (FBUT), maximum blink interval (MBI), corneal staining with fluorescein under cobalt blue light and LWE with lissamine green under slit lamp and halogen white light.

RESULTS

At the baseline session, LWE showed a negative correlation with DEQ-5 (r = -0.37, p = 0.02). Significant differences in FBUT and LWE (p = 0.04) and a positive correlation between LWE and DEQ-5 (r = 0.49, p = 0.007) were observed at 1 month. Intrasession analysis at 1 month showed significant differences between the experimental and control groups in DEQ-5, FBUT and LWE (all p ≤ 0.02). Intersession analysis in the experimental group showed variations in DEQ-5, FBUT and LWE (all p ≤ 0.02) but no significant variation in the control group (all p ≥ 0.11).

CONCLUSION

The presence of LWE was significantly correlated with higher symptom values in the DEQ-5. Also, participants in the experimental group presented higher values of LWE after 1 month of CL wear, in comparison with the control group.

Contact Lens Wear Induces Alterations of Lactoferrin Functionality in Human Tears

The tear film is a complex matrix composed of several molecular classes, from small metal ions to macromolecules. Contact lens (CL) wear can affect the protein homeostasis of the tear film, by accumulating deposits on the CL surface and/or altering their structural and functional properties. This work investigates the effect of CL wear on lactoferrin (Lf), one of the most abundant tear proteins, known as an unspecific biomarker of inflammation. Tears from eight volunteers were collected and analyzed after alternated periods of CL wear and without CL. The experimental approach is to probe Lf into unprocessed human tears by the peculiar fluorescence emission originating from complex formation of Lf with terbium (Tb³⁺) at the iron-binding sites. The experimental data indicate that CL wear does not significantly affect the total amount of Lf. On the other hand, Lf affinity for Tb³⁺ is reduced upon CL wear, suggesting relevant changes in Lf structure and possible alterations of protein functionality. Future studies based on this approach will help define CL features (material, lens-care solution, wearing time, etc.) with minimal effects on tear protein activity, in order to obtain more biocompatible and comfortable devices.

Advanced morphological analysis of siloxane-hydrogel contact lenses

The purpose of this work is to provide a better understanding of three-dimensional (3-D) surface texture of siloxane-hydrogel contact lenses (CLs) using atomic force microscopy (AFM) and stereometric analysis. The 3-D surface texture characterization of unworn/worn siloxane-hydrogel CLs made of Filcon V (I FDA group) was performed with stereometric analysis. The atomic force microscopy (AFM) measurements of surface roughness and micromorphology of CLs were made using a Nanoscope V MultiMode (Bruker) in intermittent-contact mode, in air, on square areas of 5 × 5 μm. Stereometric study of 3-D surface texture was made according with ISO 25178-2:2012 for CL_rins (taken from the blister and rinsed with deionized water); CL_ss (preserved for 12 hr in saline solution and rinsed with deionized water); CL_worn-smooth (worn for 8 hr and presenting the smooth type morphology), and CL_worn-sharp (worn for 8 hr and presenting the sharp-type morphology). The 3-D surface texture of siloxane-hydrogel CLs was found to have specific morphological characteristics. Statistical parameters revealed local geometrical and morphological spatial structures at nanometer scale attributed to the specific interactions at the CLs surface. Before wear, the surface micromorphology of Filcon V CLs is regular with uniformly distributed microasperities and relatively small heights (Sq = 0.6 nm). After 12 hr in saline, it is found that the micromorphology changes relatively easily, but retaining the main morphological characteristics (Sq = 1.2 nm). After 8 hr of wear, there are two typical micromorphologies: smooth type, characterized by gutter structures and isolated microasperities (Sq = 2.5 nm), while the sharp type has an appearance with compactly arranged microasperities of hill type flanked by compactly arranged microregions of valley type (Sq = 2.2 nm). Surface statistical parameters allow manufacturers in developing the next generation of CLs with improved surface texture while improving biocompatibility and minimizing the impact of the material on corneal physiology. Furthermore, the micro-elastohydrodynamic lubrication due to surface texture at a nanometer scale between the back surface of the CL with the corneal surface and the front surface of the CL with the under-surface of the eyelid can be deeper and more nuanced to understand in light of modern tribological theories.

Fast versus gradual adaptation of soft monthly contact lenses in neophyte wearers

AIM

To determine if a gradual adaptation period is necessary for neophytes when fitted with modern hydrogel or silicone hydrogel reusable disposable contact lenses.

METHOD

Across four sites, 74 neophytes (18-28 years) were randomly assigned to a reusable lens cleaned nightly with Opti-Free® Puremoist® multi-purpose contact lens solution: Proclear® (hydrogel) or Biofinity® (silicone hydrogel) and an adaptation schedule: fast (10 h wear from the first day) or gradual (4 h on the first day, increasing their wear time by 2 h on each subsequent day until they had reached 10 h). Masked investigators graded ocular surface physiology and non-invasive tear breakup time (NIBUT) and a range of comfort, vision and lens handling subjective ratings (0-100 visual analogue scales) were recorded at the baseline visit and after 10 h of lens wear, 4-6 days and 12-14 days after lens fitting. Subjective scores were also repeated after 7 days.

RESULTS

There was no difference (p > 0.05) in ocular surface physiology or NIBUT between fast and gradual adaptation groups at any time point in either lens type with the exception of increased corneal staining (p = 0.019) in the silicone hydrogel fast adaptation group after 4-6 days, but was similar by 12-14 days. Subjective scores were also similar across the visits and lens types with the exception of 'lens awareness' (p = 0.019) which was less in the gradual versus the fast adaptation silicone hydrogel lens group at 12-14 days.

CONCLUSION

There seems to be no clinical benefit for recommending a gradual adaptation period in new wearers fitted with modern soft reusable disposable contact lenses. The findings of this work add to a growing body of evidence suggesting that such advice is unnecessary in regular soft contact lens wear, which has important ramifications for the initial clinical management of these patients.

Activity of Deposited Lysozyme on Contemporary Soft Contact Lenses Exposed to Differing Lens Care Systems

Purpose

The amount of protein deposition on soft contact lenses and to what extent the proteins are denatured may have an impact on comfortable wearing times of contact lenses. The purpose of this study was to evaluate the effects of two lens care systems on total protein and the quantity and activity of lysozyme deposited on worn senofilcon A, silicone hydrogel contact lenses.

Participants and Methods

Thirty symptomatic soft contact lens wearers were enrolled into a 4-week prospective, randomized, bilateral eye, daily-wear, crossover, double-masked study. Participants were fitted with biweekly senofilcon A lenses and were assigned either a polyquaternium-1 and myristamidopropyl dimethylamine-containing system (OPTI-FREE RepleniSH) or a peroxide-based system (CLEAR CARE). After each wear period, proteins were extracted from the lenses and analyzed for total protein, total lysozyme quantity and activity.

Results

The use of either the peroxide-based system or the polyquaternium-1 and myristamidopropyl dimethylamine-containing system resulted in no difference (P>0.05) to the amount of total protein deposited on the lenses (6.7 ± 2.8 micrograms/lens versus 7.3 ± 2.8 micrograms/lens, respectively) or to the amount of denatured lysozyme deposits (0.8 ± 0.7 versus 0.9 ± 0.7 micrograms/lens), respectively. The total amount of lysozyme deposited on the lenses was significantly lower when using the peroxide-based system (1.3 ± 0.9 micrograms/lens) compared to the polyquaternium-1 and myristamidopropyl dimethylamine-containing system (1.7 ± 1.0 micrograms/lens) (P=0.02).

Conclusion

The inactivation of lysozyme deposited on senofilcon A lenses when disinfected with the peroxide-based or the polyquaternium-1 and myristamidopropyl dimethylamine-containing systems were neither statistically nor clinically significant and the overall amounts of denatured lysozyme recovered from the lenses were low (<1 microgram/lens).

Deposition of Fluorescently Tagged Lysozyme on Contact Lenses in a Physiological Blink Model

PURPOSE

To visualize the deposition of fluorescein isothiocyanate (FITC) lysozyme on daily disposable contact lenses (CLs) using a novel blink model.

METHODS

Three daily disposable conventional hydrogel CLs (etafilcon A, omafilcon A, and nelfilcon A) and three silicone hydrogel CLs (delefilcon A, senofilcon A, and somofilcon A) were evaluated in the study. The CLs were mounted onto a novel blink model and exposed to an artificial tear solution containing FITC lysozyme for 2 and 10 hr. The flow rate and blink speed were set to 1 μL/min and 6 blinks/min, respectively. After the incubation period, a 5-mm-diameter disc was punched out from the center of the lens and mounted on a microscope slide. The slides were imaged using the Zeiss 510 Meta confocal laser scanning microscope, which scanned the lens from the front to the back surface at 5-μm increments.

RESULTS

There was an increase in deposition of FITC lysozyme for all lens types with increasing incubation time (P<0.05), with the exception of somofilcon A, which did not show statistical significance between 2 and 10 hr (P>0.05). The conventional hydrogel CLs deposited higher amounts of FITC lysozyme than the silicone hydrogel CLs (P<0.001), with etafilcon A depositing the highest at all time points (P<0.05). Interestingly, at the 2-hr incubation time, most CLs showed a higher amount of deposition at the front surface than the back surface of the lens. In particular, etafilcon A showed preferred deposition at the front surface at all time points.

CONCLUSION

The results suggest that there is differential deposition at the front surface of the CL, which is exposed to the prelens tear film, compared with the back surface of the CL, which is exposed to the postlens tear film. Therefore, it may be beneficial to design CL materials with differing surface properties for the front and back surfaces of the CL to enhance interactions with the tear film and ocular surface.

Application of systane complete for the treatment of contact lens discomfort

PURPOSE

To understand the safety of treating contact lens (CL) discomfort with a new artificial tear when it is directly applied to a CL-wearing eye.

METHODS

This was a two-week, two-visit, double-masked study that randomized participants with CL discomfort to use Systane Complete (artificial tear), Sensitive Eyes (rewetting drop), or no treatment. Drops were applied before, twice during, and after CL use each day. Corneal staining served as the primary safety metric. Conjunctival staining, tear break-up time, Schirmer's test, CL comfort (Contact Lens Dry Eye Questionnaire-8 [CLDEQ-8]), and dry eye symptoms (Standardized Patient Evaluation of Eye Dryness [SPEED]) were also evaluated.

RESULTS

This study recruited 73 participants with a mean age of 30.3 ± 11.5 years; 18 % of the participants were male. There were no significant changes in ocular surface signs from baseline or between the artificial tear and rewetting drop groups after two weeks (p ≥ 0.05). Participants in the artificial tear and rewetting drop groups had significant improvements in CLDEQ-8 scores after two weeks of treatment compared with baseline (p < 0.0001), though scores for this test were not significantly different between these groups after two weeks (p = 0.94). CLDEQ-8 scores were significantly better in the artificial tear and rewetting drop groups compared with no treatment after two weeks (p < 0.0001).

CONCLUSIONS

Both drops were found to be safe for use with CLs while also significantly improving ocular symptoms compared to no treatment after two weeks of use.

Does placebo effect exist in contact lens discomfort management?

PURPOSE

To study the effect of daily disposable contact lens (DDCL) refitting in monthly contact lens (CL) wearers suffering from contact lens discomfort (CLD), and to assess if there is a placebo effect associated with this CLD intervention.

METHODS

Symptomatic CL wearers, according to the Contact Lens Dry Eye Questionnaire 8 (CLDEQ-8 ≥ 12 points), were divided into two groups. The study group was provided with DDCLs (delefilcon A) and the control group with a masked pair of their habitual monthly CLs (placebo effect) and were assessed after one month. Then, the control group was provided with the same DDCLs and evaluated one month later. The symptoms were recorded with the CLDEQ-8 and global rating of change scale (GRCS). Non-invasive tear break-up time (NITBUT), conjunctival hyperaemia, fluorescein staining, and lid wiper epitheliopathy (LWE) were evaluated. Changes between visits, groups, and the effect of each intervention were analysed.

RESULTS

Thirty-one participants (mean age: 23.2 ± 5.3 years) were recruited. The study group (n = 14) showed an improvement of -39.6 ± 25.8 % (p < 0.001) in CLDEQ-8 and 31.3 ± 14.6 points in GRCS (p < 0.001) after one month of DDCL use, while no changes in clinical tests were found. In the control group (n = 17), symptoms improved significantly after wearing the masked monthly CL (CLDEQ-8: -26.1 ± 31.0 %, p = 0.03; GRCS: 14.9 ± 17.0, p = 0.002), however a worsening in bulbar (26.5 ± 40.0 %; p = 0.02) and limbal hyperaemia (21.6 ± 34.7 %, p = 0.02) and an improvement of -19.1 ± 37.0 % (p = 0.049) in LWE was found. When the control group was fitted with the DDCL, improvements in GRCS (20.5 ± 25.5, p = 0.02), NITBUT (37.9 ± 42.3 %, p = 0.002), and conjunctival staining (-47.1 ± 59.9 %, p = 0.005) were noted.

CONCLUSIONS

Refitting symptomatic monthly CL wearers with Delefilcon A DDCL is effective in reducing symptoms related to CLD. However, clinicians and researchers must be aware of the existence of a placebo effect when assessing the effectiveness of any CL refitting.

In vitro Evaluation of the Location of Cholesteryl Ester Deposits on Monthly Replacement Silicone Hydrogel Contact Lens Materials

Purpose

The deposition profile of cholesteryl ester on the surface and throughout the matrix of silicone hydrogel contact lens (CL) materials was determined under conditions that mimic a daily wear regimen.

Methods

In this in vitro study, four SiHy CL materials (senofilcon C, lotrafilcon B, comfilcon A and samfilcon A) were incubated in an artificial tear solution (ATS) for up to 30 days. CL incubation was alternated between the ATS (16 hours) and a multipurpose care regimen (8 hours). The ATS included fluorescently tagged cholesteryl ester (5-cholesten-3ß-ol 6-[(7-nitro-2-1,3-benzoxadiazol-4-yl)amino]caproate; CE-NBD) and confocal laser scanning microscopy visualized the distribution of the lipid through the CLs.

Results

The distribution of CE-NBD was homogenous from the anterior to posterior surface in senofilcon C and comfilcon A, at all time points. For lotrafilcon B and samfilcon A, CE-NBD localization was heterogeneous, with greater amounts on the surfaces on Day 1 and Day 14 compared to the lens matrix; however, differences in concentration between the surface and bulk diminished by Day 30.

Conclusion

The distribution of the non-polar lipid CE-NBD varied with lens material chemistry. While some lens materials deposited the lipid primarily on the surface after 16 hours of exposure, all materials exhibited a homogenous distribution after one month.

Use of digital displays and ocular surface alterations: A review

Digital display use has been accepted to be implicated as a contributing factor for dry eye disease (DED). Abnormal blinking during computer operation, including a reduced blink rate and an incomplete eyelid closure, increased palpebral fissure as consequence of high visualization angles, and meibomian gland dysfunction associated to long-term display use, are behind the increased prevalence of dry eye signs and symptoms found in digital display users. Previous research reveals significant reductions in tear volume and stability, alterations in tear film composition, including increased osmolarity, inflammatory cytokines, oxidative stress markers and reduced mucin secretion, eyelid abnormalities and ocular surface damage, encompassing corneal and conjunctival staining and bulbar redness, as a direct consequence of digital display use. In this regard, individual differences in the way that the various digital displays are typically set up and used may account for differences in their effects on induced dryness signs and symptoms. Furthermore, factors such as the use of contact lenses or inappropriate working environments, usually accompanying the use of displays, may significantly increase the prevalence and the severity of induced dry eye. Other factors, such as old age and female gender are also relevant in the appearance of associated alterations. Finally, clinicians should adopt a treatment strategy based on a multidirectional approach, with various treatments being applied in conjunction.

Lipid Analysis on Block Copolymer-containing Packaging Solution and Lens Care Regimens: A Randomized Clinical Trial

SIGNIFICANCE

Lotrafilcon B lenses packaged in and cared for with block copolymer-containing (polyoxyethylene-polyoxybutylene; EOBO) lens care solutions resulted in lower cholesterol extraction than each of the habitual silicone hydrogel lens/multipurpose solution (MPS) regimens tested.

PURPOSE

This study aimed to compare the extracted cholesterol of lotrafilcon B lenses packaged in and cared for with EOBO-containing lens care solutions with the extracted cholesterol of habitual silicone hydrogel lenses cared for with MPS not containing EOBO.

METHODS

In this prospective, randomized, observer-masked parallel study, habitual wearers of senofilcon C, senofilcon A, comfilcon A, and samfilcon A contact lenses using a non-EOBO MPS were randomized 1:1 to lotrafilcon B lenses packaged in and cared for with EOBO-containing solutions or to their habitual lenses and MPS. Subjects randomized to lotrafilcon B were further randomized to one of two EOBO-containing lens care solutions, OPTI-FREE PUREMOIST or CLEAR CARE PLUS with HydraGlyde (Alcon Laboratories, Inc., Fort Worth, TX). A subset of right eye lenses was collected after wear, and total cholesterol was extracted and measured using a fluorometric enzymatic assay.

RESULTS

Of 143 lenses analyzed, 95 were from subjects randomized to their habitual lenses/MPS and 48 to lotrafilcon B + EOBO lenses plus CLEAR CARE PLUS with HydraGlyde or OPTI-FREE PUREMOIST. The mean amounts of cholesterol extracted from lotrafilcon B + EOBO lenses cared for with CLEAR CARE PLUS with HydraGlyde (0.28 ± 0.18 μg/lens) and OPTI-FREE PUREMOIST (0.28 ± 0.48 μg/lens) were significantly lower than those extracted from senofilcon C (4.18 ± 3.25 μg/lens), senofilcon A (2.19 ± 2.69 μg/lens), comfilcon A (2.17 ± 1.47 μg/lens), and samfilcon A (2.07 ± 1.48 μg/lens) lenses used with MPS (P < .0001 each).

CONCLUSIONS

Cholesterol sorption was significantly lower in wearers of lotrafilcon B lenses cared for with polyoxyethylene-polyoxybutylene-containing lens care solutions than in users of habitual silicone hydrogel lenses cared for with non-polyoxyethylene-polyoxybutylene MPS.

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

PURPOSE

Lipid 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.

METHODS

This 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.

RESULTS

Lipid 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).

CONCLUSION

This 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.

Kinetic Deposition of Polar and Non-polar Lipids on Silicone Hydrogel Contact Lenses

Purpose: This study investigated kinetic lipid uptake to four silicone hydrogel (SiHy) lenses over a period of four weeks, using an in-vitro radiolabel method. Methods: Four contemporary monthly replacement SiHy lenses (lotrafilcon B, senofilcon C, comfilcon A, samfilcon A) were incubated in three different solutions: 1) An artificial tear solution (ATS) containing ¹⁴C-labeled phosphatidylcholine (PC), 2) an ATS containing ¹⁴C-cholesteryl oleate (CO) and 3) an ATS containing four ¹⁴C-radiolabeled lipids (PC, phosphatidylethanolamine, CO, and cholesterol (total lipid)). After 16 hours, lipids were extracted twice from the lenses with chloroform:methanol and the radioactive counts determined the lipid quantities to simulate 1 day of wear. OPTI-FREE PureMoist (Alcon) was used to clean and disinfect the remaining lenses daily and the lipid quantities were further determined after 2 weeks and 4 weeks. Results: The amount of total lipid increased for all lenses over time (p < .01). After four weeks, total lipid accumulated was 20.26 ± 0.15 µg/lens for senofilcon C, which was significantly higher (p < .01) than all other lens materials (samfilcon A - 17.84 ± 0.21; comfilcon A - 16.65 ± 0.12; lotrafilcon B - 7.41 ± 0.56 µg/lens). CO was highest on lotrafilcon B (1.26 ± 0.13 µg/lens) and senofilcon C attracted the most PC (3.95 ± 0.12 µg/lens) compared to the other materials. Conclusion: The amount of both polar and non-polar lipid deposition on monthly replacement SiHy lenses increased over 4 weeks, with significant differences being seen between lens materials.

Tear film, contact lenses and tear biomarkers

This article summarises research undertaken since 1993 in the Willcox laboratory at the University of New South Wales, Sydney on the tear film, its interactions with contact lenses, and the use of tears as a source of biomarkers for ocular and non-ocular diseases. The proteome, lipidome and glycome of tears all contribute to important aspects of the tear film, including its structure, its ability to defend the ocular surface against microbes and to help heal ocular surface injuries. The tear film interacts with contact lenses in vivo and interactions between tears and lenses can affect the biocompatibility of lenses, and may be important in mediating discomfort responses during lens wear. Suggestions are made for follow-up research.

Short-Term Deposition of PM2.5 Particles on Contact Lens Surfaces: Effect on Oxygen Permeability and Refractive Index

PURPOSES

To identify the deposition of fine (≤2.5 μm diameter) particulate matter (PM) particles (PM_2.5) on contact lens surfaces and to investigate the effects of such deposition on the oxygen permeability (OP) and refractive index (RI) of contact lenses.

METHODS

A total of 36 contact lenses, including rigid gas permeable (RGP) lens and soft contact lens (SCL), were investigated. RGP lens (n=12) and SCL (n=12) (experimental group) were incubated in a PM_2.5 solution for 24 h, after which PM_2.5-treated RGP lens (n=6) and SCL (n=6) were further washed for 1 h in phosphate-buffered saline (PBS). All lenses were examined by field emission scanning electron microscopy. OP and RI of all lenses were measured.

RESULTS

Average-sized PM_2.5 particles deposited on RGP contact lens and SCL surfaces after immersion in the PM_2.5 solution were 3.192 ± 1.637 and 2.158 ± 1.187/100 μm², respectively. On RGP lens surfaces, we observed both large (≥2.5 µm diameter) and small (PM_2.5) particles. PM_2.5 particles were deposited in diffuse patterns, primarily along the honeycomb structural border of SCL, while no PM_2.5 particles were found in the honeycomb hole of SCL surfaces. Washing in PBS removed the larger PM particles from RGP lens surfaces, but left copious amounts of PM_2.5 particles. In contrast, nearly all PM particles were removed from SCL surfaces after PBS washing. OP values of RGP lens and SCL appeared to be unchanged by PM_2.5 deposition. RI values increased in both RGP lens and SCL groups after PM_2.5 deposition. However, these increases were not statistically significant, suggesting that PM_2.5 deposition itself does not cause fluctuations in contact lens RI.

CONCLUSIONS

Deposition of PM_2.5 particles on contact lens surfaces varies according to lens material. PM_2.5 particles deposited on SCL, but only large particles on RGP surfaces were able to be removed by washing in PBS and did not appear to alter OP and RI of either lens type.

Meibomian Gland Dysfunction and Contact Lens Discomfort

Meibomian glands are located in the eyelids and secrete meibum, which gives rise to the lipid layer of the tear film. Changes to these glands can lead to the development of meibomian gland dysfunction (MGD), which is associated with various ocular symptoms such as fatigue, dryness, burning sensation, and heavy sensation. The diagnosis of MGD thus relies on evaluation of ocular symptoms, meibum condition, and lid margin abnormalities. The recent development of noninvasive meibography and tear interferometry has provided important insight into meibomian gland structure and function, respectively. Wearers of contact lenses complain of ocular symptoms that are thought to be attributable to a variety of causes, such as a diminished aqueous or mucin layer of the tear film, changes in tear protein concentration, and altered meibomian gland structure or function. Many studies have examined the relation between contact lens wear and meibomian gland changes. Such studies have found that lens wear is associated with adverse changes in meibomian gland morphology and in the condition of the lid margin and meibum, suggesting that contact lenses negatively affect meibomian glands. Meibomian gland dysfunction-like changes in meibomian glands induced by contact lens wear may thus be responsible for at least some of the ocular symptoms in lens wearers.

Short-term clinical comparison of two dual-disinfection multipurpose disinfecting solutions

OBJECTIVE

To compare the short-term clinical performance of two dual-disinfectant multipurpose disinfecting solutions (MPDS) when used in conjunction with two silicone hydrogel contact lenses.

METHODS

Participants wore galyfilcon A and balafilcon A lenses, randomly allocated one type to each eye. Multipurpose disinfecting solutions were double-masked and allocated using a randomized crossover design. Lenses were presoaked overnight in the allocated MPDS, containing either polyquaternium-1/alexidine dihydrochloride (PQ-alexidine) or polyquaternium-1/myristamidopropyl dimethylamine (PQ-MAPDA). Lenses were worn daily for 4 days and disinfected with the same MPDS in which they had been soaked. Clinical assessments occurred immediately after insertion, 2 hours after insertion, and after 2 hours of wear on day 4. Subjective ratings were collected at each assessment and after 6 hours of wear on days 1 to 3. Linear mixed models were used for statistical analysis.

RESULTS

Solution-induced corneal staining (SICS) incidence was significantly different between MPDS lens combinations (P=0.01) with PQ-MAPDA-balafilcon A showing the highest incidence (27.8%). The incidence of SICS was significantly higher when balafilcon A lenses were worn compared with galyfilcon A (19.4% vs. 2.8%; P=0.04). There was no significant difference in SICS incidence between MPDS (PQ-alexidine=5.6%, PQ-MAPDA=16.7%; P=0.08). Polyquaternium-1/alexidine dihydrochloride was associated with significantly fewer symptoms of burning/stinging (9.7±0.6 vs. 9.1±2.2; P=0.03) and self-assessed redness (9.8±0.5 vs. 9.2±1.9; P=0.03) on initial lens insertion. There were no significant differences between MPDS for comfort ratings (P>0.05).

CONCLUSION

These short-term clinical results provide an initial indication that PQ-alexidine is associated with fewer symptoms on insertion but no significant difference in ocular comfort compared with PQ-MAPDA. Longer studies are required to provide further evidence.

Biocompatibility in the development of silicone-hydrogel lenses

In response to patient demands for extended contact lens wearing times, the contact lens industry has developed novel silicone-hydrogel (SiHy) lens materials that combine the enhanced oxygen permeability of silicone polymers with the water-based comfort of conventional hydrogels. In the past 12 years since the successful launch of these SiHy lenses, much has been learned about their ability to provide the biocompatibility necessary to sustain ocular health and comfort. A review of the unique physiologic requirements for a successful extended wear lens and how the first and current SiHy lenses address them is provided.

Predisposing factors for solution-induced corneal staining

PURPOSE

To evaluate predisposing factors in subjects susceptible to solution-induced corneal staining (SICS).

METHODS

Four hundred forty-six existing soft contact lens wearers were randomly fitted with one of two study lenses (lotrafilcon B, CIBA Vision, or omafilcon A, CooperVision) and used a hydrogen peroxide care system (Clear Care, CIBAVision) for a 1-month period. Each subject was then challenged with the same lenses presoaked in a multipurpose solution (ReNu MultiPlus, Bausch & Lomb) and assessed after approximately 2 h to be categorized as either "stainers" or "non-stainers" based on whether they showed a classic SICS pattern (diffuse punctate corneal staining in three or more peripheral quadrants).

RESULTS

Overall, 36% (155 of 425) of eligible subjects were classified as stainers and included a higher proportion of omafilcon wearers: 44% (91 of 205) vs. 29% (64 of 220). After using the peroxide system, the stainers were more likely to show poorer wetting (odds ratio [OR] = 1.76, p = 0.02) compared with the non-stainers. Lens wetting showed a significant negative correlation with film deposits (r = -0.63, p < 0.0001, n = 425). Furthermore, on slit lamp examination, the stainers were more likely to show higher levels of upper- and lower-palpebral hyperemia (OR = 2.18, p = 0.02; OR = 1.93, p = 0.04), tarsal roughness (OR = 1.71, p = 0.01), corneal staining (OR = 17.1, p < 0.0001), and conjunctival staining (OR = 1.94, p = 0.004). Although not exposed to preservatives, twice as many eyes in the stainers group had some level of corneal staining: 51% vs. 25%. There were no significant differences between the stainers and non-stainers with respect to age, sex, refraction, or keratometry (p > 0.05).

CONCLUSIONS

This study highlighted some notable trends in patients susceptible to SICS. The findings point toward poor tear quality as a predisposing factor for SICS.

Preservation of human tear protein structure and function by a novel contact lens multipurpose solution containing protein-stabilizing agents

OBJECTIVES

Tear film proteins have antimicrobial and other functions that may be lost after denaturation during contact lens wear. A new multipurpose solution has recently become available (Biotrue, Bausch + Lomb Inc., Rochester, NY), which contains protein-stabilizing agents including hyaluronic acid, poloxamine, and sulfobetaine 10, the latter used previously as a laboratory tool to renature proteins. We examine whether this new multipurpose solution formulation can prevent the denaturation of human lactoferrin and lysozyme at physiologic levels in response to a powerful denaturing challenge.

METHODS

Human lactoferrin and lysozyme were treated with sodium dodecyl sulfate (SDS) either with or without an investigational version of the new multipurpose solution (without its two disinfectant agents) (investigational multipurpose solution [iMPS]). The structure was assessed by native-polyacrylamide gel electrophoresis (PAGE), differential scanning calorimetry (DSC), and fluorometry; additionally, antimicrobial activity against Pseudomonas aeruginosa and Staphylococcus aureus was measured.

RESULTS

The iMPS prevented an SDS-induced shift in the native-PAGE banding position of lactoferrin. The SDS treatment substantially altered the lactoferrin DSC and fluorescence spectra, indicating that the protein had denatured. This change did not occur in the presence of iMPS. Lactoferrin and lysozyme showed antibacterial and bacteriolytic activity, which was abolished after SDS treatment; this loss of activity did not occur for proteins treated with iMPS.

CONCLUSIONS

These data clearly show that the iMPS prevents the denaturation of physiologic levels of human lactoferrin and lysozyme by the strongly denaturing surfactant SDS and that stabilized proteins retain their function. We conclude that this solution has the capacity to stabilize the structure and function of tear proteins.