Publications

Showing 25 results out of 74 in total.

Bai,Y., Ngo,W., Khanal,S., Nichols,K. K., Nichols,J. J. Human precorneal tear film and lipid layer dynamics in meibomian gland dysfunction Ocular Surface 2021;Online ahead of print [ Show Abstract ]

Purpose: To evaluate the precorneal tear film (PCTF) and lipid layer (TFLL) thicknesses and thinning rates in meibomian gland dysfunction (MGD) using a combined ultra-high-resolution optical coherence tomography (OCT) and thickness dependent fringe (TDF) interferometry system.

Methods: Based on the Tear Film and Ocular Surface Society (TFOS) International Workshop on Meibomian Gland Dysfunction diagnostic algorithm, the Ocular Surface Disease Index (OSDI) and meibum grade score (MGS) were used to classify subjects into four groups: Normal (OSDI<13 and MGS<10), MGD (OSDI≥13 and MGS≥10), Asymptomatic MGD (OSDI<13 and MGS≥10), and Mixed (OSDI≥13 and MGS<10). The OCT/TDF system was used to capture PCTF and TFLL thicknesses and thinning rates. Kruskal-Wallis was used to compare median PCTF and TFLL thicknesses and thinning rates.

Results: There were 190 subjects categorized into four groups: Normal (n = 63), MGD (n = 51), Asymptomatic MGD (n = 29), and Mixed (n = 47). The PCTF was significantly thinner in the Mixed group (3.3 [1.2]) than in the Normal (p < 0.001), MGD (p < 0.001) and Asymptomatic MGD (p = 0.009) groups. Relative to the Normal (4.5 [4.5] μm/min) and Mixed (5.0 [2.0] μm/min) groups, the rate of PCTF thinning was faster in the MGD (8.1 [3.0] μm/min, both p < 0.001) and Asymptomatic MGD (6.9 [3.1] μm/min, p = 0.009 and p = 0.04, respectively) groups. The correlation between PCTF thinning rate and TFLL thickness was ρ = −0.46, p < 0.001.

Conclusions: Symptomatic and asymptomatic MGD shows rapid PCTF thinning rates (evaporation), while the PCTF thickness was reduced in mixed disease. Thicker lipid layers were associated with slower PCTF thinning.

Chan,V. W. Y., Phan,C-M., Ngo,W., Jones,L. Lysozyme Deposition on Contact Lenses in an In Vitro Blink-Simulation Eye Model Versus a Static Vial Deposition Model Eye & Contact Lens 2021;47(7):388-393 [ Show Abstract ]

Purpose:
To evaluate active lysozyme deposition on daily disposable (DD) contact lenses (CL) using a novel in vitro blink model.

Methods:
Three conventional hydrogel DD CL materials (etafilcon A, omafilcon A, nelfilcon A) and three silicone hydrogel DD CL materials (delefilcon A, senofilcon A, somofilcon A) were tested. The device blink rate was set to 6 blinks/min with a tear flow rate of 1 μL/min using an artificial tear solution (ATS) containing lysozyme and other typical tear film components. After incubation at 2, 4, or 8 hr, lenses were removed, and lysozyme activity was measured. A separate experiment was conducted with lenses incubated in a static vial containing 480 μL of ATS.

Results:
Etafilcon A deposited significantly higher amounts of active lysozyme (402±102 μg/lens) than other lens materials after 8 hr (P<0.0001). Etafilcon A had a higher amount of active lysozyme using the blink model compared with the static vial (P=0.0435), whereas somofilcon A (P=0.0076) and senofilcon A (P=0.0019) had a higher amount of lysozyme activity in the vial compared with the blink model.

Conclusion:
The blink model can be tuned to provide quantitative data that closely mimics ex vivo studies and can be used to model deposition of lysozyme on CL materials.

Chan,V. W. Y., Phan,C-M., Walther,H., Ngo,W., Jones,L. Effects of Temperature and Blinking on Contact Lens Dehydration of Contemporary Soft Lens Materials Using an In Vitro Blink Model Translational Vision Science & Technology 2021;10(8):Article 11 [ Show Abstract ]

Purpose: The purpose of this studywas to evaluate the effects of temperature and blinking on contact lens (CL) dehydration using an in vitro blink model.

Methods: Three silicone hydrogel (delefilcon A, senofilcon A, and comfilcon A) and two conventional hydrogel (etafilcon A and omafilcon A) CL materials were evaluated at 1
and 16 hours. The water content (WC) of the CLs was measured using a gravimetric method. Lenses were incubated on a blink model, internally heated to achieve a clinically relevant surface temperature of 35°C. An artificial tear solution (ATS) was delivered to the blink model at 4.5 μL/min with a blink rate of 6 blinks/min. A comparison set of lenses were incubated in a vial containing either 2 mL of ATS or phosphate-buffered saline (PBS) at 35°C.

Results: Increasing temperature to 35°C resulted in a decrease in WC for all tested CLs over time (P ≤ 0.0052). For most CLs, there was no significant difference in WC over time between ATS or PBS in the vial (P > 0.05). With the vial system, WC decreased and plateaued over time. However, on the blink model, for most CLs, the WC significantly decreased after 1 hour but returned toward initial WC levels after 16 hours (P > 0.05).

Conclusions: The reduction in WC of CLs on the eye is likely due to both an increase in temperature and dehydration from air exposure and blinking.

Translational Relevance: This study showed that the novel, heated, in vitro blink model could be used to provide clinical insights into CL dehydration on the eye.

Chang,J. M. L., Seo,J., Kwan,M. M. Y., Oh,S., McCanna,D. J., Subbaraman,L., Jones,L. Determining the Toxicity of UV Radiation and Chemicals on Primary and Immortalized Human Corneal Epithelial Cells Journal of Visualized Experiments 2021;173(July):Article # e62675 [ Show Abstract ]

This article describes the methods of measuring the toxicity of ultraviolet (UV) radiation and ocular toxins on primary (pHCEC) and immortalized (iHCEC) human corneal epithelial cell cultures. Cells were exposed to UV radiation and toxic doses of benzalkonium chloride (BAK), hydrogen peroxide (H2O2), and sodium dodecyl sulfate (SDS). Metabolic activity was measured using a metabolic assay. The release of inflammatory cytokines was measured using a multi-plex interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor-alpha (TNF-α) assay, and cells were evaluated for viability using fluorescent dyes.

The damaging effects of UV on cell metabolic activity and cytokine release occurred at 5 min of UV exposure for iHCEC and 20 min for pHCEC. Similar percent drops in metabolic activity of the iHCEC and pHCEC occurred after exposure to BAK, H2O2, or SDS, and the most significant changes in cytokine release occurred for IL-6 and IL-8. Microscopy of fluorescently stained iHCEC and pHCEC BAK-exposed cells showed cell death at 0.005% BAK exposure, although the degree of ethidium staining was greater in the iHCECs than pHCECs. Utilizing multiple methods of assessing toxic effects using microscopy, assessments of metabolic activity, and cytokine production, the toxicity of UV radiation and chemical toxins could be determined for both primary and immortalized cell lines.

Craig,J.P., Muntz,A., Wang,M.T.M., Luensmann,D., Tan,J., Travé-Huarte,S., Xue,A.L., Jones,L.W., Willcox,M.D.P., Wolffsohn,J.S. Developing evidence-based guidance for the treatment of dry eye disease with artificial tear supplements: A six-month multicentre, double-masked randomised controlled trial Ocular Surface 2021;20(April):62-69 [ Show Abstract ]

Purpose
To assess the six-month therapeutic profiles of lipid and non-lipid-based artificial tear supplements in managing dry eye disease (DED).

Methods
Ninety-nine participants fulfilling the TFOS DEWS II diagnostic criteria for DED (64% females; mean ± SD age, 44 ± 16 years) were enrolled in a prospective, multicentre, double-masked, parallel group, randomised controlled trial. Participants instilled lipid-based nanoemulsion drops or non-lipid-based aqueous drops for six months, at least four times daily. Symptomology, tear film and ocular surface characteristics were assessed at Days 0, 30, 60, 90, 120, 150 and 180.

Results
Sustained reductions in OSDI, DEQ-5, and SANDE symptom scores from baseline were observed from Day 30 onwards in both groups (all p < 0.05) and decreased superior lid wiper epitheliopathy grades from Day 60 onwards (all p ≤ 0.01). Improvements in non-invasive tear film breakup time, and sodium fluorescein and lissamine green staining scores followed from Day 120 onwards in both groups (all p < 0.05). Tear lipid layer grades increased from Day 90 onwards only with the lipid-based drops, and with significantly greater improvement in those with suboptimal lipid layer thickness at baseline (grade ≤3; p = 0.02). By Day 180, 19% of participants no longer fulfilled the diagnostic criteria for DED.

Conclusions
Over a six-month treatment period, improvements in dry eye symptomology preceded tear film and ocular surface changes with regular use of both lipid and non-lipid-based artificial tear supplements. Both formulations addressed most mild-to-moderate forms of aqueous deficient and evaporative DED, while evaporative cases benefitted preferentially from lipid-based supplementation. This represents a first step towards mapping DED therapeutic strategies according to disease subtype and severity.

Craig J, Jones L, Papas E, Sawyer WG. Comfort in Practice - Powered by Alcon BCLA Virtual Clinical Conference & Exhibition, June 13, 2021

Downie,L. E., Bandlitz,S., Bergmanson,J. P. G., Craig,J. P., Dutta,D., Maldonado-Codina,C., Ngo,W., Sowjanya Siddireddy,J., Wolffsohn,J. S. CLEAR - Anatomy and physiology of the anterior eye Contact Lens Anterior Eye 2021;44(2):132-156 [ Show Abstract ]

A key element of contact lens practice involves clinical evaluation of anterior eye health, including the cornea and limbus, conjunctiva and sclera, eyelids and eyelashes, lacrimal system and tear film. This report reviews the fundamental anatomy and physiology of these structures, including the vascular supply, venous drainage, lymphatic drainage, sensory innervation, physiology and function. This is the foundation for considering the potential interactions with, and effects of, contact lens wear on the anterior eye. This information is not consistently published as academic research and this report provides a synthesis from all available sources. With respect to terminology, the report aims to promote the consistent use of nomenclature in the field, and generally adopts anatomical terms recommended by the Federative Committee for Anatomical Terminology. Techniques for the examination of the ocular surface are also discussed.

Efron,N., Jones,L. W., Morgan,P. B., Nichols,J. A On the art and science of rigid contact lens fitting Clinical and Experimental Optometry 2021;104(6):684-690 [ Show Abstract ]

Examination of the literature can help answer the age-old question of the extent to which rigid contact lenses can be considered an art versus a science.

Efron,N., Jones,L. W., Morgan,P. B., Nichols,J. A. Bibliometric analysis of the literature relating to scleral contact lenses Contact Lens Anterior Eye 2021;44(4):Article number 101447 [ Show Abstract ]

Adolf Eugene Fick, a German ophthalmologist working in Zurich, published the first journal paper on contact lenses in 1888. In this paper, he described the process of fabricating and fitting afocal scleral contact lenses first on rabbits, then on himself and finally on a small group of volunteer patients with keratoconus.

Efron,N., Morgan,P. B., Jones,L. W., Morgan,G. A., Nichols,J. J. Global optometrist top 200 research ranking Clinical and Experimental Optometry 2021;104(4):471-485 [ Show Abstract ]

Clinical relevance: Clinical optometric practice is underpinned by a rigorous research base, the
primary evidence for which is publications in refereed scientific journals. Leading optometrists who
publish this work should be identified and celebrated.
Background: This work aims to derive publication metrics of the leading optometric researchers
worldwide.
Methods: An extensive global search was conducted to discover leading optometric researchers; 480
names were identified. A custom-designed bibliographic search tool was developed to interrogate
the Scopus database (Elsevier) and extract publication metrics using the unique Scopus Author
Identifier number for each optometrist. On 13 January 2021, the full list was reduced to 200
optometrists (the ‘Top 200’) ranked by h-index – the ‘Global Optometrist Top 200 Research
Ranking’. The output from the custom tool automatically updates every 24 hours and is available at
www.optomrankings.com.
Results: The Top 200 have h-indices ranging from 20 to 67 and have published between 28 and 440
papers. Sixty one (30.5%) are women. Konrad Pesudovs has the highest h-index (67) and citations
(51,193). The most prolific author is Robert Hess (442 papers). David Piñero is publishing at the
fastest rate (17.6 papers per year). The Top 200 work in 13 nations, of whom 172 (86.0%) work in
four nations: USA – 76 (38.0%), Australia – 43 (21.5%), UK – 41 (20.5%) and Canada – 16 (8.0%). Of
the 72 institutions represented, the University of California, Berkeley, USA is home to the most Top
200 optometrists (17) and has the highest combined h-index of Top 200 optometrists (132).
Conclusions: The optometric profession is supported by a robust research base, prosecuted by
a large international cohort of optometric researchers who publish extensively on a broad range of
ophthalmic issues and whose work is highly cited. The 200 most impactful optometrists in the world
are identified

Efron,N., Morgan,P. B., Jones,L. W., Nichols,J. A Bibliometric analysis of the refractive error field Clinical and Experimental Optometry 2021;104(5):641-643 [ Show Abstract ]

Research into the epidemiology, aetiology, and optics of ametropia is a fundamental cornerstone of the correction and management of refractive errors by eye care practitioners. At present, much of this work is driven by the clinical concern that myopia is a common cause of vision loss, with uncorrected myopia the leading cause of vision impairment globally. Holden et al. predict that by 2050, about 50% of the population of the world will be myopic.
The aetiology of myopia continues to be hotly debated, centring around the relative impact of nature (genetics) versus nurture (environment). Research aimed at optimising optical (spectacles and contact lenses) and surgical (laser refractive techniques) modes of correcting refractive error continues unabated, and novel approaches for arresting the progression of myopia, using ophthalmic lenses, contact lenses (including orthokeratology), pharmacological approaches, or lifestyle modification, are also under active investigation. As is the case in all fields of investigation, the foundation of these various lines of refractive error research is rooted in the ophthalmic literature. Modern bibliographic search tools enable targeted interrogation of this vast literature to facilitate identification of the research foundations that underpin our understanding of refractive error. This Viewpoint uses
these bibliographic search tools and employs a subjectspecific measure of impact to identify key papers, authors, institutions, countries, and journals in the field of refractive error research.

Efron,N., Morgan,P. B., Jones,L. W., Nichols,J. J. 21st century citation analysis of the field of contact lenses Clinical and Experimental Optometry 2021;104(5):634-638 [ Show Abstract ]

Clinical relevance: The scientific foundations for clinical contact lens practice are rooted in the ophthalmic literature. This analysis of contact lens papers celebrates contemporary research achievements in the contact lens field.

Background: This work aims to assemble contact lens-related publication metrics so as to identify the most impactful papers published so far this century, as well the top countries, authors, institutions and journals.

Methods: A search was undertaken of the titles of papers on the Scopus database to identify contact lens-related articles published this century. The ten most highly cited papers were determined from the total list of 4,164 papers found. Rank-order lists by count were assembled for the ‘top 25ʹ in each of four categories: authors, institutions, countries and journals. A 20-year subject-specific contact lens h-index (hCL-20-index) was derived for each author, institution, country and journal to serve as a measure of impact in the field. The top 10 constituents (of the top 25) of each category were ranked by hCL-20-index and tabulated for consideration.

Results: The most highly cited paper this century is entitled ‘Soft contact lens polymers: An evolution’, by Nicholson and Vogt. Lyndon Jones is the most impactful author, with a hCL-20-index of 32. The University of New South Wales (Australia) produces the most impactful contact lens-related papers, and the United States is the most highly-ranked country. Optometry and Vision Science is the most impactful journal in the contact lens field.

Conclusions: Contact lens materials and lens-associated keratitis are topics of high interest in the contemporary contact lens literature, with an emerging interest in orthokeratology for myopia control and glucose monitoring. Impactful 21st century authors, institutions, countries and journals are identified. Optometry is revealed as the leading profession in relation to the publication of impactful contact lens-related papers.

Guthrie S, Luensmann D, Woods J, Vega J, Orsborn G. Comfort and vision correlations in daily disposable multifocal lenses BCLA Virtual Clinical Conference & Exhibition, 2021 [ Show Abstract ][ PDF ]

Purpose: To evaluate the subjective responses to two daily disposable multifocal contact lenses (MFCLs), stenfilcon A (stenA-MF) and delefilcon A (delA-MF), and to see if there is a correlation between preferences based on vision and comfort.

Method: Habitual MFCL wearers participated in a prospective, randomized, subject-masked, bilateral crossover study at five sites. Subjects wore the study MFCLs for 2-weeks each and then responded to preference questions comparing the study lenses for comfort and vision for near, intermediate, distance, digital device use and overall at all distances. A 5-point Likert scale (Strong/slight preference for each lens or no preference) was used.

Results: For the 58 eligible subjects (50F:8M; mean 54.4±7.3 years), preferences were as follows (#stenA-MF:#delA-MF, p-value): subjects favoured stenA-MF for overall comfort (26:9, p=0.03), intermediate vision (25:8, p=0.03), overall vision (34:10, p=0.04) and vision for digital device use (27:10, p=0.03). Preferences were equivocal for near vision (29:14, p=0.06) and distance vision (13:19, p=0.51). Correlation analysis found that the lens preference based on overall comfort was significantly correlated (all p<0.05) with lens preference based on vision at near (rs=0.61), intermediate (rs=0.48), overall (rs=0.65) and for digital device use (rs=0.66). Lens preference based on overall vision was also correlated with lens preference based on vision at near (rs=0.85), intermediate (rs=0.71), and for digital device use (rs=0.87). Lens preference based on vision with digital device use correlated with lens preference based on vision at near (rs=0.85), and intermediate distance (rs=0.69).

Conclusions: Subjects preferred stenA-MF for a range of comfort and distance measures. Preferences for overall comfort and overall vision were both significantly correlated to the same three preferences of near, intermediate and digital device vision, illustrating how comfort and vision are intricately related when evaluating MFCLs and supporting how poor vision could potentially impact comfort.

Heynen,M., Ng,A., Martell,E., Subbaraman,L. N., Jones,L. Activity of Deposited Lysozyme on Contemporary Soft Contact Lenses Exposed to Differing Lens Care Systems Clinical Ophthalmology 2021;15(April):1727-1733 [ Show Abstract ]

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).

Huynh,C. B., Ngo,W. Quantifying the Effect of Spectacle Frame Dimensions on Wind-Induced Ocular Plane Evaporation Using an in Vitro Model Eye & Contact Lens 2021;47(347):351 [ Show Abstract ]

Purpose: To quantify the effect of spectacle frame dimensions on wind-induced ocular plane evaporation.

Methods: A drop of 0.5 μL water was pipetted onto an eye of a mannequin head. The face was fitted with a spectacle frame. A fan positioned 10 cm away directed air (185 CFM) toward the face and the time required for the drop to evaporate was recorded. This procedure was repeated with 31 different frames to obtain evaporation times for various eye sizes, vertical heights, vertex distances, temperature, and humidity. This was also repeated 30 times without spectacle wear to obtain evaporation times for various temperature and humidity conditions.

Results: Spectacle wear increased evaporation times compared with nonspectacle wear, in both high (>35%) and low humidity (<30%) conditions (both P<0.01). Humidity was correlated with evaporation time, regardless of spectacle and nonspectacle wear (both P<0.01). Evaporation time did not correlate with spectacle eye size, vertical height, or vertex distance (all P≥0.21).

Conclusion: This study showed that spectacle wear guarded against wind-induced evaporation at the ocular plane compared with nonspectacle wear. However, once spectacles were worn, eye size, vertical height, and vertex distance were not correlated with evaporation times. Humidity drove evaporation independent of spectacle wear.

Jones,L., Hui,A., Phan,C-M., Read,M. L., Azar,D., Buch,J., Ciolino,J. B., Naroo,S. A., Pall,B., Romond,K., Saknaridurg,P., Schnider,C. M., Terry,L., Willcox,M. CLEAR - Contact lens technologies of the future Contact Lens Anterior Eye 2021;44(2):398-430 [ Show Abstract ]

Contact lenses in the future will likely have functions other than correction of refractive error. Lenses designed to control the development of myopia are already commercially available. Contact lenses as drug delivery devices and powered through advancements in nanotechnology will open up further opportunities for unique uses of contact lenses.

This review examines the use, or potential use, of contact lenses aside from their role to correct refractive error. Contact lenses can be used to detect systemic and ocular surface diseases, treat and manage various ocular conditions and as devices that can correct presbyopia, control the development of myopia or be used for augmented vision. There is also discussion of new developments in contact lens packaging and storage cases.

The use of contact lenses as devices to detect systemic disease has mostly focussed on detecting changes to glucose levels in tears for monitoring diabetic control. Glucose can be detected using changes in colour, fluorescence or generation of electric signals by embedded sensors such as boronic acid, concanavalin A or glucose oxidase. Contact lenses that have gained regulatory approval can measure changes in intraocular pressure to monitor glaucoma by measuring small changes in corneal shape. Challenges include integrating sensors into contact lenses and detecting the signals generated. Various techniques are used to optimise uptake and release of the drugs to the ocular surface to treat diseases such as dry eye, glaucoma, infection and allergy. Contact lenses that either mechanically or electronically change their shape are being investigated for the management of presbyopia. Contact lenses that slow the development of myopia are based upon incorporating concentric rings of plus power, peripheral optical zone(s) with add power or non-monotonic variations in power. Various forms of these lenses have shown a reduction in myopia in clinical trials and are available in various markets.

Jones L. Contact lens comfort: Materials and methodologies to reduce drop outs Optician Contact Lens Week webinar, February 10, 2021

Jones L. Dry eye & contact lenses: COVID-19 did not help! Online Optom Learning Series, Webinar (India), March 6, 2021

Jones L. CLEAR: Future applications of contact lenses BCLA Virtual Clinical Conference & Exhibition, June 13, 2021

Jones L. Material and solution impacts on contact lens discomfort and dropout OVN (Netherlands Association of Optometrists) webinar, March 15, 2021

Jones L. CLEAR report summary: Contact Lens Wettability, Cleaning, Disinfection and Interactions with Tears https://contactlensupdate.com/2021/06/15/contact-lens-wettability-cleaning-disinfection-and-interactions-with-tears/ 2021

Jones L, Stahl U, Guthrie S, Yang M, Moezzi A, Thom M. Contact Lens Compendium: Contact Lenses & Solutions Available in America. Vol 2 2021.

Jones L, Stahl U, Guthrie S, Yang M, Moezzi A, Thom M. Contact Lens Compendium: Contact Lenses and Solutions Available in Canada. Vol 47 2021.

Khanal,S., Ngo,W., Nichols,K. K., Wilson,L., Barnes,S., Nichols,J. J. Human meibum and tear film derived (O-acyl)-omega-hydroxy fatty acids in meibomian gland dysfunction Ocular Surface 2021;21(July):118-128 [ Show Abstract ]

Purpose: The molecular basis of the tear film and lipid layer alterations in meibomian gland dysfunction (MGD) is unknown. This study aimed to identify and compare (O-acyl)-omega-hydroxy fatty acids (OAHFAs) derived from human meibum and tears in MGD. Methods: Of 195 eligible subjects (18–84 years, 62.6% female), 183 and 174 provided samples for tears and meibum, respectively. Subjects were classified into four groups: Normal, Asymptomatic MGD, MGD, and Mixed. Samples from the right eye of each subject were infused into the SCIEX 5600 TripleTOF mass spectrometer in negative ion mode. Lipid intensities identified with Analyst1.7 TF and SCIEX LipidView1.3 were normalized by an internal standard and total ion current, then statistically compared in MetaboAnalyst 4.0. Results: In meibum and tears, 76 and 78 unique OAHFAs were identified, respectively. The five most frequent and abundant OAHFAs were 18:2/16:2, 18:1/32:1, 18:1/30:1, 18:2/32:1, and 18:1/34:1. Two OAHFAs, 18:2/20:2 and 18:2/20:1, were identified only in tears. Initial univariate analysis revealed three differently regulated OAHFAs in meibum and eight in tears. Partial Least Square Discriminant Analysis showed 18:1/32:1, 18:2/16:2, 18:1/34:1 and 18:0/32:1 in tears, and 18:2/16:2, 18:1/32:1 and 18:2/32:2 in meibum, had variable importance in projection scores >1.5 and contributed the most to the separation of groups. In both meibum and tears, all OAHFAS except 18:2/16:2 were reduced in MGD compared to the normal group. Conclusion: MGD is accompanied by differential expression of specific OAHFAs in meibum and tears. These results suggest OAHFAs play a role in the altered biochemical profile of the tear film lipid layer in humans with MGD.

Kondela,T., Dushanov,@., Vorobyeva,M., Mamatkulov,K., Drolle,E., Soloviov,D., Hrubovcak,P., Kholmurodov,K., Arzumanyan,G., Leonenko,Z., Kucerka,N Investigating the competitive effects of cholesterol and melatonin in model lipid membranes Biochimica et Biophysica Acta - Biomembranes 2021;1863(9):183651 [ Show Abstract ]

We have studied the impact of cholesterol and/or melatonin on the static and dynamical properties of bilayers made of DPPC or DOPC utilizing neutron scattering techniques, Raman spectroscopy and molecular dynamics simulations. While differing in the amplitude of the effect due to cholesterol or melatonin when comparing their interactions with the two lipids, their addition ensued recognizable changes to both types of bilayers. As expected, based on the two-component systems of lipid/cholesterol or lipid/melatonin studied previously, we show the impact of cholesterol and melatonin being opposite and competitive in the case of three-component systems of lipid/cholesterol/melatonin. The effect of cholesterol appears to prevail over that of melatonin in the case of structural properties of DPPC-based bilayers, which can be explained by its interactions targeting primarily the saturated lipid chains. The dynamics of hydrocarbon chains represented by the ratio of trans/gauche conformers reveals the competitive effect of cholesterol and melatonin being somewhat more balanced. The additive yet opposing effects of cholesterol and melatonin have been observed also in the case of structural properties of DOPC-based bilayers. We report that cholesterol induced an increase in bilayer thickness, while melatonin induced a decrease in bilayer thickness in the three-component systems of DOPC/cholesterol/melatonin. Commensurately, by evaluating the projected area of DOPC, we demonstrate a lipid area decrease with an increasing concentration of cholesterol, and a lipid area increase with an increasing concentration of melatonin. The demonstrated condensing effect of cholesterol and the fluidizing effect of melatonin appear in an additive manner upon their mutual presence.