Temporal changes in the tear menisci following a blink

In silico evaluation of corneal patch eluting anti-VEGF agents concept

This study introduces a novel approach utilizing a temporary drug-eluting hydrogel corneal patch to prevent neovascularization, alongside a numerical predictive tool for assessing the release and transport kinetics of bevacizumab (BVZ) after the keratoplasty. A key focus was investigating the impact of tear film clearance on the release kinetics and drug transport from the designed corneal patch. The proposed tear drug clearance model incorporates the physiological mechanism of lacrimal flow (tear turnover), distinguishing itself from previous models. Validation against experimental data confirms the model's robustness, despite limitations such as a 2D axisymmetrical framework and omission of blink frequency and saccadic eye movements potential effects. Analysis highlights the significant influence of lacrimal flow on ocular drug transport, with the corneal patch extending BVZ residence time compared to topical administration. This research sets the stage for exploring multi-layer drug-eluting corneal patches as a promising therapeutic strategy in ocular health.

Application of optical coherence tomography and keratograph in the measurements of lower lid margin thickness

PURPOSE

This study aims to investigate the applicability of lower lid margin thickness (LLMT) measurements in adults with and without meibomian gland dysfunction (MGD) by optical coherence tomography (OCT) and keratograph.

METHODS

This is a cross-sectional, observational study. A hundred and eight volunteers aged 20 to 79, including 68 MGD patients and 40 normal subjects, were recruited. Using OCT and keratograph to measure the LLMT from the posterior lash line to anterior edge or outer edge of the tear meniscus was separately performed two times by the same person.

RESULTS

The mean age of normal and MGD subjects was 50.5 ± 14.2 years and 55.8 ± 15.5 years, respectively. The LLMT with OCT and keratograph in MGD patients was significantly greater than that in normal subjects (1.06 ± 0.27 and 1.03 ± 0.25 mm vs. 0.90 ± 0.20 and 0.86 ± 0.16 mm, respectively). In both normal and MGD subjects, the tear meniscus height and LLMT with OCT were both greater than that with keratograph (P < 0.05), and intraclass correlation coefficient (ICC) demonstrated a good agreement in the LLMT measurements between two devices (ICC = 0.83 and 0.79, respectively). Additionally, the LLMT in MGD patients was appeared to be positively correlated with meiboscore (rs = 0.37, P = 0.002).

CONCLUSIONS

The OCT and keratograph were two reliable tools in the LLMT measurements, which may have potential applications for diagnosis and evaluation of MGD. Furthermore, we found that the LLMT measured by OCT was greater than that measured by keratograph.

Dynamic Aspects of Pre-Soft Contact Lens Tear Film and Their Relation to Dry Eye: Basic Science and Clinical Relevance

Soft contact lens (SCL) perturbs the intimate connection between the pre-lens tear film (PLTF) and the ocular surface in various ways, i.e., (i) decrease in tear meniscus radius and aqueous tear thickness, (ii) attenuation of tear film lipid layer spread, (iii) limited wettability of SCL surface, (iv) increased friction with eyelid wiper, etc. This often results in SCL-related dry eye (SCLRDE) manifested as PLTF instability and contact lens discomfort (CLD). In this review, the individual contributions of factors (i-iv) to PLTF breakup patterns (BUP) and CLD are considered via the tear film-oriented diagnosis framework adopted by the Asia Dry Eye Society from a clinical and basic science perspective. It is shown that SCLRDE (due to aqueous deficiency, increased evaporation, or decreased wettability) and BUP of PLTF classify within the same types as the ones observed for the precorneal tear film. The analysis of PLTF dynamics reveals that the inclusion of SCL enhances the manifestation of BUP associated with (i) decreased thickness of PLTF aqueous layer and (ii) limited SCL wettability as shown by the rapid expansion of BUP area. PLTF thinness and instability result in increased blink-related friction and lid wiper epitheliopathy as major contributor to CLD.

An Emerging Method to Assess Tear Film Spread and Dynamics as Possible Tear Film Homeostasis Markers

Purpose: This study aims to assess the performance of an analysis method to measure in vivo the movement speed of tear film particles post-blink as a measure of tear film spreading.Materials and methods: Ocular surface parameters and the recording of tear film particles' spreading post-blink were assessed in eighty-one healthy volunteers (43.7 ± 27.0 years) using Keratograph 5 M. The developed software automatically decomposed the video into frames to manually track particles' position for 1.75 seconds after a blink. The following tear film-dynamic metrics were automatically calculated: mean, median, maximum, and minimum particles' speed at different times after blinking and time for particle speed to decrease to <1.20 mm/second. Repeatability of each tear film-dynamic metric and its correlations with ocular surface signs and symptoms were analyzed. Binomial logistic regression was performed to assess the predictability of new metrics to ocular parameters.Results: Repeatability tended to be lower just after blinking (variability of 12.24%), whereas the metrics from 0.5 s onwards had acceptable repeatability (variability below 10%). Tear film-dynamic metrics correlated positively with Non-Invasive Break-Up Time (NIKBUT) while negatively with meibomian gland drop-out. Binomial logistic regression analysis revealed that tear film-dynamic metrics were able to predict NIKBUT. Nevertheless, no statistically significant association was found with gland drop-out. This means that higher particle speed is related to larger NIKBUT. The metric "time for particle speed to decrease to <1.20 mm/second" can be considered the best metric to assess the quality of the tear film, since it was more strongly correlated with NIKBUT (r = 0.42, p = .004), it was more strongly associated in the binomial logistic regression analysis with NIKBUT and showed good repeatability (variability = 5.49%).Conclusions: Tear film-dynamic metrics are emerging homeostasis parameters for assessing indirectly the tear film quality in natural conditions with acceptable repeatability.

The influence of a lipid reservoir on the tear film formation

We present a mathematical model to study the influence of a lipid reservoir, seen experimentally, at the lid margin on the formation and relaxation of the tear film during a partial blink. Applying the lubrication limit, we derive two coupled non-linear partial differential equations characterizing the evolution of the aqueous tear fluid and the covering insoluble lipid concentration. Departing from prior works, we explore a new set of boundary conditions (BCs) enforcing hypothesized lipid concentration dynamics at the lid margins. Using both numerical and analytical approaches, we find that the lipid-focused BCs strongly impact tear film formation and thinning rates. Specifically, during the upstroke of the eyelid, we find specifying the lipid concentration at the lid margin accelerates thinning. Parameter regimes that cause tear film formation success or failure are identified. More importantly, this work expands our understanding of the consequences of lipid dynamics near the lid margins for tear film formation.

The Tear Function in Electronic Cigarette Smokers

SIGNIFICANCE

Prominent ocular surface dryness and poor tear film quality among electronic cigarette (e-cigarette) smokers (or vapers) indicate potential harm to the eyes from vaping. These findings may serve as precautionary signs for e-cigarette users and exposed bystanders.

PURPOSE

Little is known about the effect of e-cigarettes on the eyes except for reported eye irritation among individuals who were exposed to e-cigarette vapors and e-liquids. This study aims to investigate the effect of vaping on ocular surface health of long-term vapers.

METHODS

Twenty-one vapers and 21 healthy nonsmokers who are all male underwent measurements of the Ocular Surface Disease Index, noninvasive tear breakup time, fluorescein breakup time, ocular surface staining, tear meniscus height, and the Schirmer test. The effect of voltage used during vaping was also evaluated against the measurements.

RESULTS

Vapers experienced moderate-to-severe eye dryness (25.0 [interquartile range, 14.6 to 43.7]) as indicated by the Ocular Surface Disease Index. Significant reductions of noninvasive tear breakup time (3.13 ± 0.97 vs. 6.57 ± 2.31 seconds; P < .0001), fluorescein breakup time (2.68 [interquartile range, 2.33 to 3.18] vs. 4.12 [3.56 to 5.07] seconds; P < .0001), and tear meniscus height (203.0 [193.0 to 225.5] vs. 235.0 [210.0 to 253.50] μm; P = .002) were noted in vapers, but the Schirmer test showed higher results (14.5 [12.0 to 17.0] vs. 8.0 [7.0 to 11.0] mm; P = .001) compared with nonsmokers. Increase in vaping voltage aggravated the dry eye symptoms and tear instability (P < .05). Higher Schirmer test result was also noted as voltage increases.

CONCLUSIONS

Vapers showed moderate-to-severe symptomatic dry eye and poorer tear film quality compared with nonsmokers. High vaping voltage may have aggravated the dry eye syndrome because of hazardous by-products from pyrolysis of the e-liquid constituents. Investigation of the ocular surface health at cellular and molecular levels is warranted to gain a deeper understanding on the effect of e-cigarette to the eyes.

Tracking the Reflective Light Particles Spreading on the Cornea: An Emerging Assessment for Tear Film Homeostasis

Purpose

To implement an emerging noninvasive approach for assessing the dynamic tear film (TF) homeostasis.

Methods

The video records of dynamic TF from 12 healthy orthokeratology lens wearers were obtained by a clinically available TF analyzer and decomposed as image sequences. The trajectories of TF particles were analyzed by two tracking models, the full-span model (FSM) and the fixed-duration model (FDM). FSM tracked a particle for a complete opening blink cycle, while FDM tracked 1 second of the same cycle. A power-law fitting operation \begin{document}\newcommand{\bialpha}{\boldsymbol{\alpha}}\newcommand{\bibeta}{\boldsymbol{\beta}}\newcommand{\bigamma}{\boldsymbol{\gamma}}\newcommand{\bidelta}{\boldsymbol{\delta}}\newcommand{\bivarepsilon}{\boldsymbol{\varepsilon}}\newcommand{\bizeta}{\boldsymbol{\zeta}}\newcommand{\bieta}{\boldsymbol{\eta}}\newcommand{\bitheta}{\boldsymbol{\theta}}\newcommand{\biiota}{\boldsymbol{\iota}}\newcommand{\bikappa}{\boldsymbol{\kappa}}\newcommand{\bilambda}{\boldsymbol{\lambda}}\newcommand{\bimu}{\boldsymbol{\mu}}\newcommand{\binu}{\boldsymbol{\nu}}\newcommand{\bixi}{\boldsymbol{\xi}}\newcommand{\biomicron}{\boldsymbol{\micron}}\newcommand{\bipi}{\boldsymbol{\pi}}\newcommand{\birho}{\boldsymbol{\rho}}\newcommand{\bisigma}{\boldsymbol{\sigma}}\newcommand{\bitau}{\boldsymbol{\tau}}\newcommand{\biupsilon}{\boldsymbol{\upsilon}}\newcommand{\biphi}{\boldsymbol{\phi}}\newcommand{\bichi}{\boldsymbol{\chi}}\newcommand{\bipsi}{\boldsymbol{\psi}}\newcommand{\biomega}{\boldsymbol{\omega}}{\rm{MMS}}\left( t \right) = {\rm{\alpha }} \times {t^{ - {\rm{\beta }}}}\end{document} was used to extract homeostasis markers based on the tracking model for each subject.

Results

Comparing two tracking models (N = 6), only one subject had statistical difference in averaged momentary moving speed (MMS; P = 0.0488), while none had significant difference in averaged momentary moving direction (MMD). However, both models showed good correlations in average MMS (ρ = 0.94, P = 0.0048) and MMD (ρ = 1.00, P < 0.0001) and all extracted homeostasis markers [α, β, MMS(0.1), and MMS(2.0)]. Assessing interblink reliability in these markers under FDM tracking (N = 12), only one subject in the MMS (0.1) and another subject in the MMS (2.0) were outside 95% limits of agreement, respectively.

Conclusions

FDM is a good alternative to FSM and has tracking properties of higher efficiency and easier implementation. The homeostasis markers under FDM tracking showed a good interblink consistence; therefore this approach will be a promising method for analyzing dynamic TF homeostasis in future practice.

Translational Relevance

FDM analytical architecture can practice the past experimental platform on a TF analyzer to obtain homeostasis markers of TF.

Computed flow and fluorescence over the ocular surface

Fluorescein is perhaps the most commonly used substance to visualize tear film thickness and dynamics; better understanding of this process aids understanding of dry eye syndrome which afflicts millions of people. We study a mathematical model for tear film flow, evaporation, solutal transport and fluorescence over the exposed ocular surface during the interblink. Transport of the fluorescein ion by fluid flow in the tear film affects the intensity of fluorescence via changes in concentration and tear film thickness. Evaporation causes increased osmolarity and potential irritation over the ocular surface; it also alters fluorescein concentration and thus fluorescence. Using thinning rates from in vivo measurements together with thin film equations for flow and transport of multiple solutes, we compute dynamic results for tear film quantities of interest. We compare our computed fluorescent intensity distributions with in vivo observations. A number of experimental features are recovered by the model.

Schirmer tear test I in dogs: results comparing placement in the ventral vs. dorsal conjunctival fornix

OBJECTIVE

To compare Schirmer tear test I (STT I) values obtained from placement of tear strips in the ventral and dorsal conjunctival fornices in dogs.

PROCEDURE

Schirmer tear test I was performed on each eye of 16 clinically normal dogs (32 eyes) in a crossover study. Initial tear strip placement site was randomized for each eye. Alternative placement site measurements were obtained after 1 week.

RESULTS

The mean (± standard deviation, SD) STT I for dorsal and ventral conjunctival fornices was 20.44 (±4.46) mm/min and 23.56 (±3.98) mm/min, respectively. STT I values obtained from the ventral conjunctival fornix were significantly greater than those obtained from the dorsal conjunctival fornix (P = 0.004).

CONCLUSIONS

Schirmer tear test I values were significantly greater with tear strips placed in the ventral conjunctival fornix.

"Coffee Ring Effect" in Ophthalmology: "Anionic Dye Deposition" Hypothesis Explaining Normal Lid Margin Staining

The process of formation of Marx line is studied in this article. Various theories have been proposed previously, in order to explain the mechanisms which lead to the development of Marx line. These theories are based on the characteristics of stained area and do not pay attention to the behavior of dye solution itself on the surface. The aim of this study is to investigate the latter behavior and introduce a new theory based on it, in order to explain the process of the Marx line formation.This study also introduces "Coffee Ring Effect" and its possible applications in explaining some ophthalmological phenomena.The effect of dye solution's behavior on the beneath surface is adopted in order to propose a novel theory. This new hypothesis is called "Anionic Dye Deposition" which was based on "Coffee Ring Effect" phenomenon. For evaluation of this theory, Evaporation pattern of Rose Bengal and fluorescein were analyzed on different surfaces. Furthermore, the effect of tear meniscus alteration on lid margin staining is studied.During the evaporation process of dye solutions, it was observed that almost all of the solute was deposited at the edge of the drop on hydrophilic surfaces. Furthermore, in the study of lid margin staining, it is observed that tear meniscus alteration during gaze affects staining pattern. This observation invalidates former hypotheses which only focus on stained surface characteristics.According to the observations in this study, it is proposed that Marx line staining occurs as a result of "anionic dye deposition" due to evaporation.

An investigation of non-invasive tear break up time and tear meniscus height of keratoconic versus non-keratoconic individuals

Keratoconus is a debilitating condition where the cornea develops a conical shape rather than the characteristic round shape due to various physiological and structural changes taking place within the layers of the cornea. As a result of the pathogenesis of keratoconus, there are numerous changes that may occur within the tears of these patients. Research has shown changes in the tear metabolome, the presence of degradation products as well as loss of goblet cells into the tears. Could the changes occurring within the tear structure of these patients affect the results of various tear quantity and quality tests? Non-invasive tear break up time (NTBUT) is a diagnostic test used to determine the quality of the tear film and has been used extensively when diagnosing dry eye disease. This test is utilised in order to determine the time taken for the tear film to begin breaking apart, signalling thinning of the tears. Shorter break up times are therefore indicative of instability or changes occurring within the tear film which could be diagnostic of dry eye disease. Tear meniscus height (TMH) measurements have also been utilised in clinical practice, where these measurements provide an indication of the volume of tears contained within the upper and lower menisci. Lower tear volumes have been shown to be present in cases of dry eye disease where either tear production or tear drainage may be affected. Changes in the quality and quantity of the tear film in subjects with dry eye disease have been thoroughly investigated; however, the same cannot be said for subjects with keratoconus. Could the same findings be possible in subjects with keratoconus? Is it possible that the changes occurring within the tears of keratoconic subjects could lead to abnormal NTBUT and TMH measurements when compared to those of control subjects? Could the results of the NTBUT and TMH tests be related to one another? This study compares the NTBUT and TMH measurements of both keratoconic and control subjects by making use of a single type of instrumentation, namely the Oculus Keratograph 4 (OK4). The results of this study reveal that the values obtained for each of the two subject groups are not shown to be statistically significantly different and that there is no significant correlation between the NTBUT and TMH measurements when comparing keratoconic and control subjects.

Comparison of Tear Meniscus Height Measurements Obtained With the Keratograph and Fourier Domain Optical Coherence Tomography in Dry Eye

PURPOSE

To study the repeatability and reproducibility of tear meniscus height (TMH) measurements obtained with a keratograph and Fourier domain optical coherence tomography (FD-OCT) and to assess their agreement in patients with dry eye.

METHODS

Sixty-four eyes with dry eye were analyzed by the Schirmer test, tear breakup time test, and fluorescein corneal staining. The TMH was measured 3 times using both devices by 2 different examiners. The repeatability and reproducibility of measurements were assessed by within-subject standard deviation (Sw), repeatability (2.77 Sw), coefficient of variation (CoV), and intraclass correlation coefficient.

RESULTS

The TMH measured with the keratograph and FD-OCT was 0.232 ± 0.074 mm and 0.308 ± 0.129 mm, respectively (P < 0.01). A close correlation was found between the TMH measured with the keratograph and FD-OCT (r = 0.343). There was a negative correlation between the mean TMH and differences in the TMH measured with the keratograph and FD-OCT (r = 0.359). Both measurements correlated with the Schirmer test score, tear breakup time, and corneal staining score with P < 0.01. Intraexaminer CoV, 2.77 Sw, and intraclass correlation coefficient of the TMH were <6.5%, <0.059 mm, and >0.986, respectively, and interexaminer CoV and 2.77 Sw were 5.58% and 0.039 mm, respectively.

CONCLUSIONS

Although the TMH measured with the keratograph tended to be lower than that measured with FD-OCT, the TMH measured with the keratograph closely correlated with the TMH measured with FD-OCT and conventional tests and had good repeatability and reliability.

Comparison of a new portable digital meniscometer and optical coherence tomography in tear meniscus radius measurement

PURPOSE

Non-invasive measurement of tear meniscus radius (TMR) is useful in the assessment of tear volume for dry eye diagnosis. This study investigates the agreement between a new, portable, slit-lamp mounted, digital meniscometer (PDM) and optical coherence tomography (OCT) in the measurement of human TMR.

METHODS

Images of the tear meniscus at the centre of the lower lid of 30 normal subjects (8M, 22F; mean age 27.5 SD ± 9.6 years) were taken using the PDM and the OCT. On the PDM and OCT images, TMR was measured using imagej 1.46b software. The meniscus on the OCT images was subdivided vertically into three equal sections and the radius calculated for each: bottom (BTMR), centre (CTMR) and top (TTMR). The relationship between PDM and OCT measurements was analysed using Spearman's rank coefficient, and differences between PDM and OCT subsection measurements were evaluated using Bland-Altman plots.

RESULTS

Tear meniscus radius measured with the PDM (0.25 ± 0.06 mm) and OCT (0.29 ± 0.09 mm) was significantly correlated (r = 0.675; p < 0.001). The mean differences between TMR using the PDM and the subsections from OCT showed that TMR measured with PDM was greater for BTMR (0.07 mm; CI 0.05-0.10; p < 0.001), similar for CTMR (-0.01 mm; CI -0.04 to 0.02; p = 0.636) and steeper for TTMR (-0.07 mm; CI -0.10 to -0.04; p < 0.001).

CONCLUSIONS

Portable digital meniscometer and OCT measurements of the TMR are significantly correlated, suggesting that the new PDM is a useful surrogate for OCT in this respect. The PDM appears to measure the radius of the central section of the tear meniscus.

Voluntary blinking and use of 0.25% dye on fluorescein dye disappearance test

OBJECTIVE

To evaluate the effect of voluntary blinking and use of diluted fluorescein dye on fluorescein dye disappearance test (FDDT) in terms of diagnostic ability and test time.

DESIGN

Prospective, nonrandomized case series.

PARTICIPANTS

Thirty-nine patients who visited Hadong Seoul Eye Clinic between April 2009 and September 2009.

METHODS

All participants underwent FDDT and a lacrimal syringing test, and were divided into 2 groups according to the lacrimal syringing test results. FDDT was performed using 3 protocols: conventional FDDT (2% FDDT), FDDT with voluntary blinking (2% FDDTb), and FDDT with voluntary blinking using diluted fluorescein (0.25% FDDTb). The results were assessed by comparing initial tear meniscus height and those at 5 (2% FDDT) or 3 minutes (2% FDDTb, 0.25% FDDTb) after dye instillation. Results were considered "normal" when the tear meniscus decreased to less than 50% of its initial height, and "delayed" when it decreased to≥50%. In cases with a normal result, a half-period of dye disappearance was also recorded.

RESULTS

Regarding diagnostic ability, the 0.25% FDDTb test had highest sensitivity and specificity among 3 protocols (100% and 80%, respectively). The half-period of dye disappearance was 3.17±1.72 minutes for 2% FDDT, 1.82±0.64 minutes for 2% FDDTb, and 1.04±0.69 minutes for 0.25% FDDTb, and showed significant difference among 3 tests (P = 0.001).

CONCLUSIONS

The FDDT with voluntary blinking using 0.25% fluorescein had comparable diagnostic ability with the conventional FDDT, and allowed the test time to be significantly reduced.

Evaluation of dry eye

Dry eye is a common yet complex condition. Intrinsic and extrinsic factors can cause dysfunction of the lids, lacrimal glands, meibomian glands, ocular surface cells, or neural network. These problems would ultimately be expressed at the tear film-ocular surface interface. The manifestations of these problems are experienced as symptoms such as grittiness, discomfort, burning sensation, hyperemia, and secondary epiphora in some cases. Accurate investigation of dry eye is crucial to correct management of the condition. Techniques can be classed according to their investigation of tear production, tear stability, and surface damage (including histological tests). The application, validity, reliability, compatibility, protocols, and indications for these are important. The use of a diagnostic algorithm may lead to more accurate diagnosis and management. The lack of correlation between signs and symptoms seems to favor tear film osmolarity, an objective biomarker, as the best current clue to correct diagnosis.

The challenge of dry eye diagnosis

The currently available methods for the diagnosis of dry eye are still far from being perfect for a variety of reasons. This review attempts to highlight the advantages and disadvantages of both traditional tests (such as Schirmer’s test, break-up time and ocular surface staining) and innovative noninvasive procedures, including tear meniscus height measurement, corneal topography, functional visual acuity, tear interferometry, tear evaporimetry and tear osmolarity assessment.

Spontaneous eyeblink activity

Spontaneous blinking is essential for maintaining a healthy ocular surface and clarity of vision. The spontaneous blink rate (SBR) is believed to reflect a complex interaction between peripheral influences mediated by the eye surface and the central dopaminergic activity. The SBR is thus extremely variable and dependent on a variety of psychological and medical conditions. Many different methods have been employed to measure the SBR and the upper eyelid kinematics during a blink movement. Each has its own merits and drawbacks, and the choice of a specific method should be tailored to the specific needs of the investigation. Although the sequence of muscle events that leads to a blink has been fully described, knowledge about the neural control of spontaneous blinking activity is not complete. The tear film is dynamically modified between blinks, and abnormalities of the blink rate have an obvious influence on the ocular surface.

Comparison of Tearscope-plus versus slit lamp measurements of inferior tear meniscus height in normal individuals

PURPOSE

To measure the lower tear meniscus height (LTMH) with image by Tearscope and using slit-lamp biomicroscopy with or without fluorescein staining.

METHODS

The lower tear meniscus height was measured in 31 eyes of 31 healthy volunteers (mean age 31.29 years; SD 4.83) with Tearscope and slit lamp with and without fluorescein staining. The mean values of LTMH were measured with different methods and the repeatability of the measurements was statistically analyzed. Measurement of fluorescein tear film break up time (FBUT) and Schirmer test were also performed.

RESULTS

The mean value of LTMH was 0.21 mm (SD 0.07) with Tearscope, 0.20 mm (SD 0.06) with slit lamp without fluorescein staining, and 0.23 mm (SD 0.07) with fluorescein staining. There was no significant difference among the mean values of LTMH with these 3 different measurement methods. Based on the random effect analysis of variance (p=0.05), the measurements were more repeatable with Tearscope-plus than with the other 2 methods. No correlation was found between the LTMH and the results of Schirmer test or FBUT.

CONCLUSIONS

The LTMH could be reliably measured with slit-lamp biomicroscopy without staining, but the measurements were more repeatable with Tearscope.

Influence of the blink interval on tear meniscus height in soft contact lens and nonlens wearers

PURPOSE

Tear meniscus height (TMH) is an indirect measurement of tear film volume. This study investigated the temporal changes in the TMH during the blink interval in the morning (8-9 am) and at the end of the day (5-6 pm) in both soft contact lens (CL) and nonlens wearers (NLW).

METHODS

Fifty participants (25 CL; 25 NLW) were evaluated for their subjective symptoms, TMH, noninvasive break up time, and bulbar hyperemia at the am and pm visits on the same day. The TMH was measured at set intervals between 2 and 15 sec during the blink interval, using an optical coherence tomographer.

RESULTS

The NLW group revealed no changes in a variety of symptoms during the day, whereas the CL group reported an increase in dryness (P=0.03) and grittiness (P=0.02) over the day. For both groups, the TMH and calculated tear meniscus volume revealed lower values immediately after the blink and increased progressively afterwards, mainly due to reflex tearing. The am tear meniscus volume values tended to be higher than the pm values for both groups, but this was not significant (NLW P=0.13; CL P=0.82). Noninvasive break up time deteriorated during the day for both groups but was only significant for the CL group (P=0.002), whereas bulbar hyperemia revealed no statistically significant change for either group.

CONCLUSIONS

Reflex tearing may play a substantial role in the TMH differences observed over the blink interval. Standardization of the time when a TMH measurement is performed will be valuable in comparing tear film clinical studies.

Nanoscale phase dynamics of the normal tear film

The tear film is a dynamic multilayered structure. The interactions and the interfacial dynamics between the layers that occur during a blink cycle must be such that they allow for maintenance of a stable tear film. Attempts to understand these dynamics have been limited by the techniques and biomarkers used. Quantum dots (qdots) offer a new potential to monitor the dynamics of the tear film layers in vivo without the drawbacks of previously used methodologies. Indium phosphide-gallium qdots were used to differentially assess the dynamics of the lipid and aqueous layers of the tear film in real time. In the aqueous, qdots dispersed to form a stable local region that was swept away into the upper and lower menisci during a blink. They did not redisperse onto the ocular surface but were progressively removed from the menisci through the puncta. Some of these qdots adhered to the mucin layer on the ocular surface in a meshlike pattern and remained there for five to six blinks before they were removed. The organic qdots dispersed quickly but patchily over the whole outer surface of the tear film. They also strongly marked both eyelid margins and slowly dispersed onto the skin and eyelashes and not through the puncta. Some were trapped in the menisci as blobs that rolled along the meniscus. These data support the view of a distinct three-layered tear film: an inner mucin layer attached to the epithelial cells, a fluid aqueous layer, and an outer viscoelastic lipid layer.

Reduced tear meniscus dynamics in dry eye patients with aqueous tear deficiency

PURPOSE

To measure the tear meniscus dynamics in aqueous tear deficiency dry eye patients using optical coherence tomography.

DESIGN

Clinical research study of a laboratory technique.

METHODS

Twenty-five aqueous tear deficiency dry eye patients and 30 healthy subjects were recruited. Upper and lower tear menisci of 1 randomly selected eye of each participant were imaged during normal and delayed blinking using optical coherence tomography. Measured parameters included upper tear meniscus height and volume, lower tear meniscus height and volume, the blink outcome defined as the meniscus volume change during blink action, and open eye outcome defined as the meniscus volume change during the open eye period.

RESULTS

During normal blinking, both tear meniscus height and volume before blink in dry eye patients were significantly smaller than those in healthy subjects, except for the upper tear meniscus volume. During normal blinking, the blink outcome and open eye outcome of lower tear meniscus were significantly smaller in dry eye patients compared with healthy subjects. During delayed blinking, the upper and lower tear menisci heights and volumes significantly increased in both groups. However, dry eye patients had smaller increases than healthy subjects. During delayed blinking, the open eye outcomes of upper and lower tear menisci were smaller in dry eye patients than healthy subjects.

CONCLUSIONS

Dry eye patients seem to have reduced tear meniscus dynamics during normal blinking and smaller increases of meniscus volume during delayed blinking. Analysis of tear meniscus dynamics may provide more insight in the altered tear system in dry eye patients.

Effect of blinking on tear volume after instillation of midviscosity artificial tears

PURPOSE

To determine by optical coherence tomography (OCT) the effect of blinking on ocular surface tear volume after instillation of artificial tears.

DESIGN

Experimental study.

METHODS

Normal human eyes (n = 21) were imaged to obtain dimensions of the tear film and menisci during blinking. The imaging was carried out immediately and five minutes after the instillation of 35 microl midviscosity artificial tears (1.0% carboxymethylcellulose; Refresh Liquigel; Allergan, Irvine, California, USA). The exposed ocular surface area and the lid lengths were used to calculate the volumes.

RESULTS

Immediately after the instillation, total tear volume was increased (P < .001) compared with five minutes after the instillation, with the major increases in the lower tear meniscus volume and tear film volume. After the instillation, blinking caused tear loss in total tear volume because of the decrease of the lower tear meniscus volume (P < .05). In contrast, blinking increased the tear film volume (P < .05). At the end of the eye-opening period, tear film volume decreased and lower tear meniscus volume increased significantly (P < .05), with no significant changes in total tear volume (P > .05). During the blink cycle immediately after the instillation, net loss was evident in tear film volume, lower tear meniscus volume, and total tear volume (P < .05).

CONCLUSIONS

Blinking plays a crucial role in distribution and removal of instilled tears. When the tear system is overloaded, the increase in blink output helps restore balance.

Correlations among upper and lower tear menisci, noninvasive tear break-up time, and the Schirmer test

PURPOSE

To determine the relationships among tear meniscus parameters, noninvasive tear break-up time (NITBUT), and the Schirmer test.

DESIGN

Experimental study.

METHODS

Thirty-six subjects were tested on one randomly selected eye. Real-time corneal optical coherence tomography (OCT) was used to image the upper and lower tear menisci during normal and delayed blinking followed by measurement of NITBUT and the Schirmer test. Digital images of the eye were taken for measuring the lid lengths to estimate tear volume in the menisci.

RESULTS

Compared with normal blinking, significant increases of tear menisci occurred during delayed blinking (post hoc, P < .01). NITBUT was weakly but significantly correlated with the height (r = 0.36; P = .03) and area (r = 0.37; P = .03) of the lower tear meniscus during normal blinks. NITBUT was also correlated with the lower tear meniscus volume (r = 0.45; P < .05) and total tear meniscus volume (r = 0.43; P < .05) during normal blinking. The Schirmer test was not significantly related to any parameters of the tear menisci, volumes, or NITBUT; however, it was negatively correlated with the age of the subjects (r = -0.47; P = .004). The age was negatively correlated with the upper tear meniscus (r ranged from 0.36 to 0.37 for the radius, height, and area, P < .05) measured during delayed blinking.

CONCLUSIONS

NITBUT appears correlated with the lower tear meniscus during normal blinking, and the Schirmer test appears not correlated with the noninvasively measured tear meniscus.

Variability of the Analysis of the Tear Meniscus Height by Optical Coherence Tomography

PURPOSE

Tear meniscus height (TMH) is an established parameter indicative of tear film volume and has recently been determined using an optical coherence tomographer (OCT). The purpose of this study was to evaluate the inter and intra observer variability in TMH assessment using OCT.

METHODS

Ten subjects (6 M, 4 F; aged 32.5 +/- 6.4 years) had 10 consecutive scans taken of their inferior central tear meniscus (5 scans originating at 90 degrees and 5 origination at 270 degrees) using the OCT2 (Humphrey-Zeiss). Images were analyzed by two observers using custom software on three separate occasions. Following a training session among observers, the images were reevaluated to assess differences in variability. Data were analyzed for differences within and across examiners, for the effect of examiner training and between scan directions.

RESULTS

The mean TMH and tear volume collapsed across subjects were between 0.24 and 0.25 mm and 25 to 27 nL/mm, respectively. No difference was noted within observers. An interobserver mean volume difference (p = 0.044) was present but was eliminated post training (p = 0.167). Variability was less with scans originating at 90 degrees.

CONCLUSIONS

The values of the TMH and tear volume are similar to those reported in the literature. Due to the interobserver differences observed, a training session between examiners may prove to be valuable, especially in a large or multicenter study.