Lipid, lipase and lipocalin differences between tolerant and intolerant contact lens wearers

Anatomical and physiological considerations in scleral lens wear: Eyelids and tear film

Scleral lenses can affect a range of anterior segment structures including the eyelids and the tears. The eyelids, consisting of the outer skin layer, the middle tarsal plate, and the posterior palpebral conjunctiva, provide physical protection and house the meibomian glands and cilia which have important and unique functions. Tears consist of a mix of aqueous, mucus, and lipidomic components that serve vital functions of lubricity, protection, and nourishment to the ocular surface. Both the eyelids and the tear film interact directly with scleral lenses on the eye and can affect but also be impacted by scleral lens wear. The purpose of this paper is to review the anatomy and physiology of the eyelids and tear film, discuss the effects and impacts of the scleral lenses on these structures, and identify areas that require further research.

Fluorescent aptasensor based on G-quadruplex-assisted structural transformation for the detection of biomarker lipocalin 1

Diabetic retinopathy (DR) is the leading global cause of blindness in the working-age population. Early diagnosis and intervention can effectively reduce the risk for blindness. However, the current diagnostic methods in clinical practice remain constrained by nonquantitative examinations and individual ophthalmologists' experiences. Sensitive, specific and accurate detection of DR-specific biomarkers is an important approach to achieve its early and rapid diagnosis. In this study, a high-affinity aptamer APT12TM that specifically binds to the tear-derived DR biomarker lipocalin 1 was obtained. The aptamer APT12TM can be folded into a stable B-DNA structure, and its strong interaction with LCN 1, including hydrogen bonding and hydrophobic interactions, is an important factor for targeted recognition and high-affinity binding. A G-rich DNA fragment was further assembled at both ends of the aptamer APT12TM, and the B-DNA form was successfully converted into a parallel G-quadruplex. Most importantly, LCN 1 could induce further transformation of the G-quadruplex structure. Therefore, a fluorescent aptasensor based on G-quadruplex-assisted structural transformation was developed through the Thioflavin T mediator. The aptasensor exhibited a broad detection window from 0.25 to 1000 nM LCN 1, with a limit of detection of 0.2 nM. Furthermore, the aptasensor was applied to LCN 1 detection in artificial tear samples and displayed good reproducibility and stability. These results show that the developed aptasensor has significant potential for sensitive, specific and convenient detection of the DR-specific biomarker LCN 1.

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.

Presence of Histatin-1 in Human Tears and Association with Aqueous Deficient Dry Eye Diagnosis: A Preliminary Study

The aims of this study were to determine if histatin-1 (H1) is present in normal human tears and whether tear levels of H1 varied between normal patients and those with aqueous deficient dry eye disease (ADDE). Patient samples were obtained from 11 normal patients and 11 severe ADDE patients. Relevant patient characteristics, including age, sex, and dry eye disease (DED) diagnostic parameters were collected. Multiple qualitative and quantitative methods were used to compare the concentration of H1 between patient groups. Mixed linear modeling was used to compare H1 levels between groups, and diagnostic performance was assessed using the receiver-operator-characteristic (ROC). ADDE patients had significantly lower H1 concentrations (85.9 ± 63.7 ng/ml) than the normal group (891.6 ± 196.5 ng/ml) (p < 0.001), while controlling for age and sex. ROC analysis indicated that H1 concentration is potentially a biomarker for ADDE (area under curve = 0.96). Reclassification of patients by DED parameters including, Ocular Surface Disease Index (OSDI) (≤13, >13) and Schirmer I (without anesthesia) (<10 mm, ≥10 mm) showed significant differences in H1 level (OSDI, p = 0.004) and Schirmer I ((p = 0.010). In conclusion, this is the first preliminary report of the presence of H1 in human tears. H1 concentrations are lower in ADDE patients and H1 may have diagnostic potential in evaluation ADDE patients.

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.

Giant Phospholipid Folds on Air-Water Surface: Structure Details, Formation Pathway, and Possible Recycle Mechanism

In vitro mimics recognized that the propensity of a negatively charged phospholipid, DPPS, monolayers to self-aggregate to three-dimensional (3D) giant folds under overcompression at an air-water interface. Time elapsing microscopical observations confirmed that such giant folds were able to float stably on the air-water interface for weeks or even longer. Ex situ atomic force microscopy (AFM) and transmission electronic microscopy (TEM) characterizations pointed out that such giant folds were composed of compactly stacked lipid layers. Phospholipase A₂ (PLA₂), a principal bactericide in human and animal tear secretion, was chosen to drive the in situ lipid giant folds disassembly on water and supported substrate surfaces, respectively. Our experimental results confirmed the layer-by-layer structures of the giant folds. It is noteworthy that the defect-rich areas of the giant lipid folds were eliminated quickly by PLA₂ while defect-free lipid zones were left untouched, suggesting that PLA₂ may serve as a highly effective and selective regenerator/cleaner of lipid aggregates in the physiological circumstance of certain organs.

Detection of Lipid Mediators of Inflammation in the Human Tear Film

PURPOSE

Lipid mediators of inflammation are a group of signaling molecules produced by various cells under physiological conditions and modulate the inflammatory process during various pathologic conditions. Although eicosanoids and F2-isoprostanes are recognized lipid mediators of inflammation, there is no consensus yet on the extraction and mass spectrometry (MS) method for their analysis in individual human tear samples. Thus, the aim of this study was to develop an optimal method for extraction of lipid mediators of inflammation in the tear film and evaluate MS techniques for their analysis.

METHODS

Basal tears were collected from each eye of 19 subjects using glass microcapillaries. Lipid extraction was performed using either varying concentrations of acidified methanol, a modified Folch method, or solid-phase extraction. Initially, an untargeted analysis of the extracts was performed using SCIEX TripleTOF 5600 mass spectrometer to identify any lipid mediators of inflammation (eicosanoids) and later a targeted analysis was performed using the SCIEX 6500 Qtrap to identify and quantify prostaglandins and isoprostanes. Mass spectra and chromatograms were analyzed using Peakview, XCMS, and Multiquant software.

RESULTS

Prostaglandins and isoprostanes were observed and quantified using the Qtrap mass spectrometer under multiple reaction monitoring (MRM) mode after solid-phase extraction. Extraction with acidified methanol along with the Folch method produced cleaner spectra during MS with the Triple time of flight (TOF) mass spectrometer. Lipid mediators of inflammation were not observed in any of the tear samples using the Triple TOF mass spectrometer.

CONCLUSIONS

Solid-phase extraction may be the method of choice for extraction of prostaglandins and isoprostanes in low volumes of tears. The SCIEX Qtrap 6500 in MRM mode may be suitable to identify and quantify similar lipid mediators of inflammation.

Comparative proteome analysis of the tear samples in patients with low-grade keratoconus

PURPOSE

To elucidate the metabolic processes playing roles in the formation of keratoconus (KC).

METHODS

Tears samples were collected using capillary glass tubes without stimulation and without prior anesthesia from 17 patients and 16 controls. Proteomic analysis by fluorescent 2D gel electrophoresis (DIGE) coupled with MALDI-TOF/TOF was performed. The identified proteins that were differentially regulated were subjected to Ingenuity Pathway Analysis (IPA). Corneal topography analyses with Sirius topography system (Costruzioni Strumenti Oftalmici, Florence, Italy) were performed on all participants. The steepest keratometry index was lower than 50 diopters in all keratoconus patients.

RESULTS

DIGE analysis showed changes in abundance of nine proteins. Six of these proteins, namely serum albumin, Keratin Type II Cytoskeletal 1, IgG gamma chain-1, GAPDH, alpha-1 antitrypsin and ApoA-I, were down-regulated in the KC samples in comparison with the controls. In addition, we detected up-regulation of lysozyme C, keratin type I cytoskeletal 10 and lipocalin. The subsequent IPA predicted that NADH repair pathway is activated in the KC patients. This pathway involves generation of NADHX as a by-product via catalysis by GAPDH. NADHX is an inhibitor of several dehydrogenases and must be removed.

CONCLUSION

The involvement of NADHX repair pathway in KC should be investigated, since preliminary clues obtained in this study point to that direction. In particular, showing the presence of ATP-dependent NAD(P)H-hydrate dehydratase that eliminates NADHX would strengthen our findings and would be a major step toward understanding KC.

Lipid Supplements and Clinical Aspects of Tear Film in Habitual Lens Wearers

PURPOSE

To establish the effect of lipid supplements on the tear lipid layer and their influence on lens wear comfort in habitual lens wearers.

METHODS

Forty habitual soft contact lens wearers were recruited to a double-masked, randomized crossover trial. An emulsion drop containing phosphatidylglycerine (Systane Balance; Alcon) and a saline drop as a placebo or a liposomal spray containing phosphatidylcholine (Tears again; BioRevive) and a saline spray as a placebo were used three times a day for 2 weeks with 48 hours washout between each intervention. Ocular comfort, lipid layer grade, and stability of the tear film using a Tearscope and tear evaporation rate using a modified VapoMeter were assessed after 6 hours of lens wear with lenses in situ.

RESULTS

Neither of the lipid supplements improved lens wear comfort compared to baseline. The noninvasive surface drying time significantly reduced with the placebo spray at day 1 (P = .002) and day 14 (P = .01) whereas the lipid spray had no effect. With the lipid drop and placebo, noninvasive surface drying time was unchanged compared to baseline (P > .05) on day 1, but by day 14, noninvasive surface drying time was reduced with the lipid drop (P = .02) and placebo (P < .001). Symptomatic wearers showed shorter noninvasive surface drying time compared to asymptomatic wearers with the spray treatment on both days (P = .03) but not with the lipid drop (P = .64). The placebo drop significantly changed the lipid layer distribution (P = .03) with a higher percentage of thinner patterns compared to the baseline distribution at day 14. A weak but significant correlation was shown between ocular comfort and noninvasive surface drying time (r = -0.21, P = .003) and tear evaporation rate (r = 0.19, P = .008). Ocular comfort was not associated with lipid layer patterns (r = 0.13, P = .06).

CONCLUSIONS

Ocular comfort during contact lens wear improved with increased tear film stability and a reduced tear evaporation rate. However, the lipid supplements did not improve ocular comfort from baseline.

Disturbing the balance: effect of contact lens use on the ocular proteome and microbiome

Contact lens wear is a popular, convenient and effective method for vision correction. In recent years, contact lens practice has expanded to include new paradigms, including orthokeratology; however, their use is not entirely without risk, as the incidence of infection has consistently been reported to be higher in contact lens wearers. The explanations for this increased susceptibility have largely focused on physical damage, especially to the cornea, due to a combination of hypoxia, mechanical trauma, deposits and solution cytotoxicity, as well as poor compliance with care routines leading to introduction of pathogens into the ocular environment. However, in recent years, with the increasing availability and reduced cost of molecular techniques, the ocular environment has received greater attention with in-depth studies of proteins and other components. Numerous proteins were found to be present in the tears and their functions and interactions indicate that the tears are far more complex than formerly presumed. In addition, the concept of a sterile or limited microbial population on the ocular surface has been challenged by analysis of the microbiome. Ocular microbiome was not considered as one of the key sites for the Human Microbiome Project, as it was thought to be limited compared to other body sites. This was proven to be fallacious, as a wide variety of micro-organisms were identified in the analyses of human tears. Thus, the ocular environment is now recognised to be more complicated and interference with this ecological balance may lead to adverse effects. The use of contact lenses clearly changes the situation at the ocular surface, which may result in consequences which disturb the balance in the healthy eye.

TFOS DEWS II Tear Film Report

The members of the Tear Film Subcommittee reviewed the role of the tear film in dry eye disease (DED). The Subcommittee reviewed biophysical and biochemical aspects of tears and how these change in DED. Clinically, DED is characterized by loss of tear volume, more rapid breakup of the tear film and increased evaporation of tears from the ocular surface. The tear film is composed of many substances including lipids, proteins, mucins and electrolytes. All of these contribute to the integrity of the tear film but exactly how they interact is still an area of active research. Tear film osmolarity increases in DED. Changes to other components such as proteins and mucins can be used as biomarkers for DED. The Subcommittee recommended areas for future research to advance our understanding of the tear film and how this changes with DED. The final report was written after review by all Subcommittee members and the entire TFOS DEWS II membership.

TFOS DEWS II iatrogenic report

Dry eye can be caused by a variety of iatrogenic interventions. The increasing number of patients looking for eye care or cosmetic procedures involving the eyes, together with a better understanding of the pathophysiological mechanisms of dry eye disease (DED), have led to the need for a specific report about iatrogenic dry eye within the TFOS DEWS II. Topical medications can cause DED due to their allergic, toxic and immuno-inflammatory effects on the ocular surface. Preservatives, such as benzalkonium chloride, may further aggravate DED. A variety of systemic drugs can also induce DED secondary to multiple mechanisms. Moreover, the use of contact lens induces or is associated with DED. However, one of the most emblematic situations is DED caused by surgical procedures such as corneal refractive surgery as in laser-assisted in situ keratomileusis (LASIK) and keratoplasty due to mechanisms intrinsic to the procedure (i.e. corneal nerve cutting) or even by the use of postoperative topical drugs. Cataract surgery, lid surgeries, botulinum toxin application and cosmetic procedures are also considered risk factors to iatrogenic DED, which can cause patient dissatisfaction, visual disturbance and poor surgical outcomes. This report also presents future directions to address iatrogenic DED, including the need for more in-depth epidemiological studies about the risk factors, development of less toxic medications and preservatives, as well as new techniques for less invasive eye surgeries. Novel research into detection of early dry eye prior to surgeries, efforts to establish appropriate therapeutics and a greater attempt to regulate and oversee medications, preservatives and procedures should be considered.

Contact Lens-Induced Discomfort and Inflammatory Mediator Changes in Tears

PURPOSE

Studies indicate that contact lens (CL) discontinuation mostly occurs because of dryness and discomfort symptoms. This study aimed to investigate relationships between changes in the concentration of tear inflammatory mediators with subjective comfort ratings with CL wear and no contact lens wear between morning and evening.

METHOD

Forty-five subjects collected tears twice daily in the morning and in the evening with or without lenses. Comfort was rated subjectively on a scale from 1 to 100 (where 100 was extremely comfortable) just before each tear collection. Tear samples were assayed for complement components (C3 and C3a), leukotriene B4 (LTB4), secretory phospholipase A2 (sPLA2), secretory immunoglobulin A (sIgA), and bradykinin using commercially available immuno-based assay kits.

RESULTS

Comfort ratings showed a statistically significant decline from morning to evening both with CL (89.0±10.1 AM vs. 76.7±15.2 PM; P<0.001) and without CL (89.1±10.2 AM vs. 84.2±12.6 PM; P<0.005) wear. The decline was steeper with lens wear (P<0.001). Bradykinin and sPLA2 levels did not change between morning and evening or with CL wear (P>0.05). Leukotriene B4 levels were slightly higher in CL (CL 43.4±12.6 pg/ml vs. No CL 39.4±13.4 pg/mL; P=0.034), whereas the concentration of LTB4, C3, C3a, and sIgA dropped by the end of the day in the presence or absence of lens wear (P<0.001). For most mediators, tear levels were not correlated with comfort ratings in any of the conditions. Leukotriene B4 had a higher concentration in the evening, and when measured as a ratio to sIgA, there was a trend for increased concentration of this mediator during CL wear.

CONCLUSION

Although specific mediators showed changes from morning to evening with and without lens wear, most of these were not correlated with subjective comfort ratings in lens wear. The only mediator that showed an increase in concentration during the day and during lens wear was LTB4, and further studies on this mediator are warranted.

Diagnostic Performance of McMonnies Questionnaire as a Screening Survey for Dry Eye: A Multicenter Analysis

Purpose. To evaluate the diagnostic performance of the McMonnies questionnaire as a screening survey for dry eye in Chinese outpatients. Methods. The questionnaire was self-administered by 27,999 patients with dry eye symptoms. A thorough ophthalmic examination including tear break-up time (TBUT), fluorescein staining, and Schirmer I test was completed to make a clinical diagnosis of dry eye. Reliability, validity, and accuracy of the McMonnies questionnaire were assessed. Results. The McMonnies questionnaire showed poor internal consistency (Cronbach α = 0.37), but excellent validity as the scores correlated with TBUT (Spearman test, r = −0.322, P < 0.001) and Schirmer I test (Spearman's test, r = −0.370, P < 0.001), and significantly differed between the dry eye and control groups (2-sample t-test, t = 69.51, P < 0.001). The area under the receiver-operating characteristics (ROC) curve (AUC) was 0.729, suggesting moderate accuracy in identifying dry eye and non-dry eye patients. However, the AUCs varied significantly in different gender and age subgroups (z test, P < 0.001), as the discriminating ability declined with age. Analysis of the ROC curves also revealed that different cut-off points should be employed for each subgroup to achieve the same level of accuracy. Conclusions. The McMonnies questionnaire demonstrates moderate diagnostic value, and different cut-off points should be selected for various study populations.

Intersubject and Interday Variability in Human Tear and Meibum Lipidomes: A Pilot Study

PURPOSE

Our aim was to quantitate day-to-day changes in the tear and meibum lipid profile of individual subjects in a pilot study of healthy humans.

METHODS

Matched tear and meibum samples were obtained from four subjects on three consecutive days. Quantitative lipid profiles of human basal tears and meibum were compared using multivariate analysis by principal components.

RESULTS

Substantial differences in the lipid profile between subjects were observed, while lipid profiles were steady across the three consecutive days of sampling. Multivariate principal component analysis demonstrated that lysophosphatidylcholine was the largest variant lipid class between subjects in tears, while wax esters comprised the most variation between subjects in meibum secretions.

CONCLUSION

Interday variability is shown to be much smaller than interpatient variability, suggesting that tears and meibum subjects both have unique profiles in humans.

Practical issues concerning tear protein assays in dry eye

Dry eye is a common clinical condition diagnosed by cumulative evidence of symptoms and signs. Many new treatments in dry eye are either expensive, invasive, have potential for side effects, or are not easily accessible. In severe dry eye, the ideal modality of treatment to begin with is often not clear as specific molecular disturbances are not evident from just examination of clinical manifestations. Assessing the effects of ongoing treatment is not straight forward since there is lack of agreement between clinical signs and symptoms. There is a need to have more objective methods of selecting treatment for dry eye and monitoring the effect of treatment. Recently, there are many new technologies applied to the discovery of tear biomarkers, for e.g., mass spectrometry based proteomics techniques and multiplex assays such as the bead-based sandwich indirect immunofluorescent assays. Tear proteins assays have even been made available as point-of-care devices. This review focuses on the evidence for the involvements of tear proteins in dry eye, possible changes in tear concentrations with therapy and the strength of evidence regarding dry eye pathology. Much remains to be done in terms of developing office-based assays and ascertaining their reliability, but current evidence suggests that tear proteins have a role in the clinical practice of dry eye.

A decade of silicone hydrogel development: surface properties, mechanical properties, and ocular compatibility

Since the initial launch of silicone hydrogel lenses, there has been a considerable broadening in the range of available commercial material properties. The very mobile silicon-oxygen bonds convey distinctive surface and mechanical properties on silicone hydrogels, in which advantages of enhanced oxygen permeability, reduced protein deposition, and modest frictional interaction are balanced by increased lipid and elastic response. There are now some 15 silicone hydrogel material variants available to practitioners; arguably, the changes that have taken place have been strongly influenced by feedback based on clinical experience. Water content is one of the most influential properties, and the decade has seen a progressive rise from lotrafilcon-A (24%) to efrofilcon-A (74%). Moduli have decreased over the same period from 1.4 to 0.3 MPa, but not solely as a result of changes in water content. Surface properties do not correlate directly with water content, and ingenious approaches have been used to achieve desirable improvements (e.g., greater lubricity and lower contact angle hysteresis). This is demonstrated by comparing the hysteresis value of the earliest (lotrafilcon-A, >40°) and most recent (delefilcon-A, <10°) coated silicone hydrogels. Although wettability is important, it is not of itself a good predictor of ocular response because this involves a much wider range of physicochemical and biochemical factors. The interference of the lens with ocular dynamics is complex leading separately to tissue-material interactions involving anterior and posterior lens surfaces. The biochemical consequences of these interactions may hold the key to a greater understanding of ocular incompatibility and end of day discomfort.

Changes in tear protein profile in keratoconus disease

PURPOSE

To analyze tear protein profile variations in patients with keratoconus (KC) and to compare them with those of control subjects.

SUBJECTS AND METHODS

Tears from 12 normal subjects and 12 patients with KC were analyzed by two-dimensional gel electrophoresis (2-DE) and liquid chromatography-mass spectrometry (LC-MS). Analysis of the 2-DE gels was performed using Progenesis SameSpots software (Nonlinear Dynamics). Proteins exhibiting high variation in expression levels (P-value <0.05) were identified using matrix-assisted laser desorption/ionization-TOF spectrometry. For LC-MS analysis, a label-free quantification approach was used. Tears were digested with trypsin, subjected to data-independent acquisition (MS(E)) analysis, and identified proteins were relatively quantified using ProteinLynx Global Server software (Waters).

RESULTS

The 2-DE and LC-MS analyses revealed a significant decrease in the levels of members of the cystatin family and an increase in lipocalin-1 in KC patients. A 1.43-fold decrease was observed for cystatin-S by 2-DE, and 1.69- and 1.56-fold for cystatin-SN and cystatin-SA by LC-MS, respectively. The increase in lipocalin-1 was observed by both methods with fold changes of 1.26 in the 2-DE approach and 1.31 according to LC-MS. Significant protein upregulation was also observed for Ig-κ chain C and Ig J chain proteins by 2-DE. Levels of lipophilin-C, lipophilin-A, and phospholipase A2 were decreased in tears from KC patients according to LC-MS. Serum albumin was found to be increased in KC patients according to LC-MS.

CONCLUSION

The results show differences in the tear protein profile of KC and control subjects. These changes are indicative of alterations in tear film stability and in interactions with the corneal surface in KC patients.

Lacritin, a novel human tear glycoprotein, promotes sustained basal tearing and is well tolerated

PURPOSE

Lacritin is a novel human tear glycoprotein that promotes basal tear peroxidase secretion by rat lacrimal acinar cells in vitro. This study investigates whether lacritin is prosecretory when added topically to the ocular surface of normal living rabbits, and if so, what is its efficacy and tolerability versus cyclosporine and artificial tears.

METHODS

Purified recombinant human lacritin (1, 10, 50, or 100 μg/mL), inactive lacritin truncation mutant C-25 (10 μg/mL), cyclosporine (0.05%), or artificial tears were topically administered to eyes of normal New Zealand White rabbits either as a single dose or three times daily for 14 days with monitoring of basal tear production. Basal tearing under proparacaine anesthesia was repeatedly assessed throughout and 1 week after chronic treatment ceased. Eyes were examined weekly by slit-lamp biomicroscopy.

RESULTS

Lacritin acutely increased basal tearing to 30% over vehicle at 240 minutes. Three times daily treatment with 10-100 μg/mL lacritin was well tolerated. Basal tearing became progressively elevated 4, 7, and 14 days later and was 50% over baseline (50 μg/mL lacritin) 1 week after treatment had ceased. Cyclosporine elevated tearing to a similar level on days 4 and 7 but had little or no effect on day 14 and had returned to baseline 1 week after ending treatment. C-25 and artificial tears had no effect.

CONCLUSIONS

Lacritin acutely stimulates basal tear flow that is sustained for at least 240 minutes. Two weeks of lacritin treatment three times daily was well tolerated and progressively elevated the basal tear flow. One week after treatment ended, basal tearing was still 50% over baseline. In contrast, cyclosporine triggered mild to moderate corneal irritation and a temporary elevation in tearing.

Transport of phospholipid in silicone hydrogel contact lenses

Characterization of the transport and release of phospholipids from a silicone hydrogel contact lens is required to assess the possible use of these lenses for phospholipid delivery to increase patient comfort. Contact lenses of silicone hydrogel composition were loaded with varying amounts of radiolabeled 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) from a solution of n-propanol. These lenses were eluted at 35°C into artificial tear fluid (ATF) or ATF containing varying amounts of DMPC. The amount of DMPC loaded into a lens is a linear function of the time of exposure to the DMPC/propanol solution. The initial rate of elution into ATF appears to be diffusion controlled for at least 10 h and is proportional to the amount of DMPC loaded. The elution rate decreases as the DMPC concentration in the ATF increases. The ease of loading and the controllable release of DMPC from silicone hydrogels presents the possibility of using such lenses to counter eye discomfort caused by inherently low levels of phospholipid in tears.

Mass spectrometry-based proteomic analyses in contact lens-related dry eye

PURPOSE

To identify potential protein biomarkers associated with dry eye in contact lens wearers.

METHODS

Upon enrollment, current galyfilcon A contact lens wearers completed a previously described questionnaire used to classify dry eye status. Approximately 5 microL of aqueous tears were carefully sampled from the inferior-lateral tear prism of each eye using glass microcapillaries. A variety of proteomic approaches were used to compare samples including quantification by Bradford analyses, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) (alone in varying percentages and with MultiPlex analyses for posttranslational modifications), nano-liquid chromatography tandem mass spectometry (nano-LC-MS/MS), and differential gel electrophoresis.

RESULTS

Twenty-one subjects were enrolled in the study (age 31.3 +/- 11.6 years). Eleven of the subjects were classified with contact lens-related dry eye, while the remaining 10 were normal contact lens wearers. Across all proteomic approaches, several proteins (including several glycoproteins) were identified as potential biomarkers associated with dry eye disease state. In summary across the approaches used, extracellular proteins identified to be altered included beta-2 microglobulin, proline rich 4, lacritin, and secretoglobin 1D1, which were found to be decreased in the dry eye state. Secretoglobin 2A2, serum albumin, glycoprotein 340, and prolactin-inducible protein were all found to be increased in the dry eye state.

CONCLUSIONS

Dry eye in contact lens wearers is related to several changes in the tear film protein. While functional studies for these candidate proteins are ongoing, initial insights into the functions of these proteins suggest roles in altered tear secretion, in addition to possible increased susceptibility to infection.

sPLA2-IIa is an inflammatory mediator when the ocular surface is compromised

sPLA2-IIa is an enzyme at high concentration in tears that has been known as an innate barrier of the ocular surface against microbial infection. sPLA2-IIa and other enzymes in the same protein family are known to hydrolyze fatty acids resulting in the generation of free arachidonic acid (AA) and lysophospholipids, which are the precursors of pro-inflammatory lipid mediators, such as PGE(2). sPLA2-IIa has been shown to be an inflammatory mediator in non-ocular inflammatory diseases such as rheumatoid arthritis (RA). It was also found to be increased in the tears of the patients with dry eye disease, chronic blepharitis and contact lens intolerance. However, the role of sPLA2-IIa in chronic ocular surface inflammation has yet to be determined. In the current study, we examined the potential role of sPLA2-IIa in inflammation of ocular surface diseases. Our results show that the activity of sPLA2-IIa was significantly increased in tears from dry eye disease patients compared with that from normal subjects. Also, sPLA2-IIa stimulated the production of PGE(2) in ocular surface epithelial cell cultures. The stimulating effect was markedly enhanced when the cells or tissues were pre-compromised with TNF-alpha, IL-1beta or desiccation. Furthermore, sPLA2-IIa stimulated inflammatory cytokine production in the ocular surface epithelial cell cultures in vitro. To our knowledge, this is the first report regarding the role of sPLA2-IIa as an inflammatory mediator in ocular surface inflammation. These findings indicate that sPLA2-IIa may play an important role in chronic ocular surface inflammation, especially when the ocular surface is compromised.