Dynamic ocular thermography

The ability to measure ocular surface temperature (OST) with thermal imaging offers potential insight into ocular physiology that has been acknowledged in the literature. The TH7102MX thermo-camera (NEC San-ei, Japan) continuously records dynamic information about OST without sacrificing spatial resolution. Using purpose-designed image analysis software, it was possible to select and quantify the principal components of absolute temperature values and the magnitude plus rate of temperature change that followed blinking. The techniques was examined for repeatability, reproducibility and the effects of extrinsic factors: a suitable experimental protocol was thus developed. The precise source of the measured thermal radiation has previously been subject toe dispute: in this thesis, the results of a study examining the relationships between physical parameters of the anterior eye and OST, confirmed a principal role for the tear film in OST. The dynamic changes in OST were studied in a large group of young subjects: quantifying the post-blink changes in temperature with time also established a role for tear flow dynamics in OST. Using dynamic thermography, the effects of hydrogel contact lens wear on OST were investigated: a model eye for in vivo work, and both neophyte and adapted contact lens wearers for in vivo studies. Significantly greater OST was observed in contact lens wearers, particularly with silicone hydrogel lenses compared to etafilcon A, and tended to be greatest when lenses had been worn continuously. This finding is important to understanding the ocular response to contact lens wear. In a group of normal subjects, dynamic thermography appeared to measure the ocular response to the application of artificial tear drops: this may prove to be a significant research and clinical tool

Development of a new grading scale for tear ferning

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.clae.2013.09.011" © 2014. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Purpose: This paper reports on the development of a new tear ferning (TF) subjective grading scale, and compares it with the Rolando scale. Method: TF patterns obtained from tear film samples collected from normal and dry eye subjects in previous studies were collated into a large image library. From this library, 60 images were selected to represent the full range of possible TF patterns, and a further sub-set of 15 images was chosen for analysis. Twenty-five optometrists were asked to rank the images in increasing order between extreme anchors on a scale of TF patterns. Interim statistical analysis of this ranking found 7 homogeneous sub-sets, where the image rankings overlapped for a group of images. A representative image (typically the mean) from each group was then adopted as the grade standard. Using this new 7-point grading scale, 25 optometrists were asked to grade the entire 60 image library at two sessions: once using the 4-point Rolando scale and once using the new 7-point scale, applying 0.25 grade unit interpolation. Results: Statistical analysis found that for the larger image set, the Rolando scale produced 3 homogeneous sub-sets, and the 7-point scale produced 5 homogeneous sub-sets. With this refinement, a new 5-point TF scale (Grades 0–4) was obtained. Conclusions: The Rolando grading scale lacks discrimination between its Type I and II grades, reducing its reliability. The new 5-point grading scale is able to differentiate between TF patterns, and may provide additional support for the use of TF for both researcher and clinician

Influence of Conjunctival Folds on Calculated Tear Meniscus Volume Along the Lower Eyelid

The final publication is available at Elsevier via 10.1016/j.jtos.2016.04.001. © 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Purpose: In calculating tear meniscus volume (TMV), tear meniscus height (TMH), radius (TMR) and cross-sectional area (TMA) are usually measured at the center of the lower lid margin, but lid-parallel conjunctival folds (LIPCOFs) are known to influence the tear meniscus regularity. The aim of this study was to analyze the influence of LIPCOFs on TMA measured by optical coherence tomography (OCT) and consequently, the calculated tear meniscus volume (TMV). Methods: Using OCT (Cirrus-HD; Carl Zeiss Meditec, Jena, Germany), the TMH, TMR and TMA in 42 subjects (13M, 29F; mean age 27.3 SD±8.4 years) were measured directly below the pupil center, plus at temporal and nasal locations perpendicularly below the limbus, where LIPCOFs were also evaluated and graded. TMV for the different locations was calculated. Correlations between LIPCOFs and the tear meniscus parameters were analyzed using the Spearman Rank-Order coefficients. Differences between tear meniscus parameters at the different locations were evaluated by the paired t-test. Results: Central TMV (5.30±1.42 x10−2μl/mm) was significantly positively correlated to LIPCOF sum (grade 2.4±1.2) (r=0.422; P<.05). The calculated temporal TMV was greater by 0.53x10−2μl/mm compared to the central TMV (P=.037), while there was no significant difference in tear volume between the other locations.Conclusions: Using OCT it was possible to investigate the influence of LIPCOFs on TMH, TMR, and for the first time on TMA, at central and paracentral positions along the lower lid margin. The presence of LICPOF results in an irregularity of tear meniscus with a difference in the amount of predicted tear volume while measuring TMH or TMR at the different locations

Investigating the subjective cooling effect of eyelid cleansing gel on eyelid and ocular surface temperature

PurposeTo investigate if the application of Blephagel, an eyelid cleansing gel, causes subjective and/or objective cooling effects by measuring ocular symptomology and temperature. MethodsTwenty-five healthy subjects underwent baseline non-invasive temperature measurements on the closed upper eyelid (centrally, nasally, and temporally) and ocular surface temperature (OST) on both eyes using an infrared camera. A standard application of Blephagel was then applied to the closed upper eyelid and eyelashes with a sterile cotton-wool to one eye selected at random. Temperature measures were then repeated on both eyes after 30–60, 120–150, and 180–210 s. At each interval, subjects rated the comfort and any cooling sensation of each eye on a 0–10 scale. ResultsAfter application of the gel, there was a significant difference in temperature at all locations on the eyelid between the test and control eyes over time (F = 9.322, p < 0.001). Post hoc analysis revealed this was significant from 30 to 60 s interval (36.3 ± 1.1 °C versus 37.2 ± 0.7 °C; p < 0.001) and the 120–150 s interval (36.8 ± 0.8 °C versus 37.2 ± 0.6 °C; p < 0.001). There was no significant variation between the OST locations over time (F = 3.350, p = 0.07). With respect to symptoms, there was a significant increase in cooling sensation in the test eye compared to the control eye over time (F = 10.438, p < 0.001), that remained throughout the experiment. ConclusionsBlephagel produces a reduction in temperature of the eyelids that is accompanied with a subjective cooling sensation

Improved Demodex diagnosis in the clinical setting using a novel in situ technique

Purpose: To compare existing and novel diagnostic techniques for confirming ocular Demodex infestation and to recommend the most reliable method for routine use by eye care practitioners, based on yield and clinical applicability. Methods: Fifteen participants with a prior Demodex blepharitis diagnosis or featuring typical cylindrical dandruff (CD) collarettes, and seven healthy controls were enrolled. Demodex presence was assessed using five techniques, applied consecutively, on a minimum of two different eyelashes on each eyelid of every participant, for each test, in situ: 1. using fine-point forceps and 25-40x biomicroscopy magnification, by eyelash rotation as proposed by Mastrota (ROT); 2. by removing cylindrical dandruff and exposing the eyelash insertion point at the lid margin (CDR); and 3. by laterally tensioning the eyelash (LET) following CDR. The typical appearance of cigar-shaped mite tails protruding from each assessed eyelash follicle was observed, and mite tails counted and averaged per participant for each assessment technique. 4. Lash epilation, and mite presence evaluated using bright-field microscopy at 10-40x magnification (EPI). 5. Finally, eyelash follicles were imaged using in vivo confocal microscopy (IVCM) and the images visually inspected for mite presence. Results: In the Demodex group, the highest numbers of mites/eyelash were identified by LET (3.8 ± 1.4), versus CDR (2.4 ± 1.6) and ROT (1.1 ± 1.2), alone (all p < 0.002). An average of 1.0 ± 0.8 mites/lash was identified by EPI. IVCM failed to offer unequivocal evidence of Demodex presence even in confimed cases. Conclusions: A novel technique for the clinical diagnosis and grading of Demodex in situ is described. By removing cylindrical dandruff and applying static, lateral tension to the eyelash without epilation, large numbers of mites are visible at the exposed eyelash follicle. The proposed method is convenient and clinically applicable, requiring only forceps and 25-40x biomicroscope magnification, and allowing rapid, efficient evaluation of large numbers of eyelashes

Does air gas aesthesiometry generate a true mechanical stimulus for corneal sensitivity measurement?

Background: Belmonte Ocular Pain Meter (OPM) air jet aesthesiometry overcomes some of the limitations of the Cochet-Bonnet aesthesiometer. However, for true mechanical corneal sensitivity measurement, the airflow stimulus temperature of the aesthesiometer must equal ocular surface temperature (OST), to avoid additional response from temperature-sensitive nerves. The aim of this study was to determine: (A) the stimulus temperature inducing no or least change in OST; and (B) to evaluate if OST remains unchanged with different stimulus durations and airflow rates. Methods: A total of 14 subjects (mean age 25.14 2.18 years; seven women) participated in this clinical cohort study: (A) OST was recorded using an infrared camera (FLIR A310) during the presentation of airflow stimuli, at five temperatures, ambient temperature (AT) +5C, +10C, +15C, +20C and +30C, using the OPM aesthesiometer (duration three seconds; over a four millimetre distance; airflow rate 60 ml/min); and (B) OST measurements were repeated with two stimulus temperatures (AT +10C and +15C) while varying stimulus durations (three seconds and five seconds) and airflow rates (30, 60, 80 and 100 ml/min). Inclusion criteria were age <40 years, no contact lens wear, absence of ocular disease including dry eye, and no use of artificial tears. Repeated measures (analysis of variance) and appropriate post-hoc t-tests were applied. Results: (A) Stimulus temperatures of AT +10C and +15C induced the least changes in OST (−0.20 0.13C and 0.08 0.05C). (B) OST changes were statistically significant with both stimulus temperatures and increased with increasing airflow rates (p < 0.001), and were more marked with stimulus temperature AT +10C. Conclusion: A true mechanical threshold for corneal sensitivity cannot be established with the air stimulus of the Belmonte OPM because its air jet stimulus with mechanical setting is likely to have a thermal component. Appropriate stimulus selection for an air jet aesthesiometer must incorporate stimulus temperature control that can vary with stimulus duration and airflow rate

Relationship between corneal sensation, blinking, and tear film quality

Purpose: To examine the possible role of corneal sensitivity and tear film quality in triggering a blink by investigating the relationship between blink rate, central corneal sensitivity threshold (CST), ocular surface temperature (OST), tear meniscus height (TMH), tear film quality (noninvasive tear break-up time [NIBUT]), and tear film lipid pattern under normal conditions. Methods: Forty-two volunteers (average age, 27.76 ± 5.36 years; 11 males) with good ocular health (Ocular Surface Disease Index, <15.0) were recruited for this cross-sectional cohort study. Blink rate, CST (noncontact corneal air gas aesthesiometry, NCCA), minimum and maximum OST in the central and inferior cornea between blinks (thermal infrared camera), TMH, NIBUT, and lipid pattern of the tear film (Keeler Tearscope Plus) were recorded on the right eye only. Results: Median blink rate was 11 blinks/min (interquartile range [IR], 6.95 to 17.05), CST was 0.35 mbars (IR, 0.30 to 0.40), minimum OST in the central cornea was 35.15°C (IR, 34.58 to 35.50), and NIBUT was 34.55 s (IR, 12.45 to 53.80). Moderate but statistically significant correlations were observed between CST and NIBUT (r = 0.535, p < 0.001), CST and blink rate (r = -0.398, p < 0.001), lipid pattern and OST (r = 0.556, p < 0.001), and between CST and OST (r = 0.371, p = 0.008). The correlations between blink rate and NIBUT (r = -0.696, p < 0.001) and between OST and NIBUT (r = 0.639, p < 0.001; Spearman test) achieved higher significance; this was highlighted by the linear regression model where NIBUT and minimum central and inferior OST were identified as significant predictor variables. Conclusions: There is strong evidence for significant interactions between corneal sensitivity, NIBUT, OST, and blink frequency, emphasizing that ocular surface conditions represent a possible important trigger for the initiation of a blink. However, the mechanisms involved in the initiation of a blink are complex, with local ocular sensory input as only one trigger, along with other external influences and internal factors under cortical control

Effect of a liposomal spray on the pre-ocular tear film

Purpose: With the potential to address evaporative dry eye, a novel spray has been developed in which phospholipid liposomes are delivered to the tear film via the surface of the closed eyelid. This study evaluated the short-term effects of liposomal spray application on the lipid and stability characteristics of the pre-ocular tear film in normal eyes. Methods: Twenty-two subjects (12M, 10F) aged 35.1 ± 7.1 years participated in this prospective, randomised, double-masked investigation in which the liposomal spray was applied to one eye, and an equal volume of saline spray (control) applied to the contralateral eye. Lipid layer grade (LLG), non-invasive tear film stability (NIBUT) and tear meniscus height (TMH) were evaluated at baseline, and at 30, 60, 90 and 135 minutes post-application. Subjective reports of comfort were also compared. Results: Treated and control eyes were not significantly different at baseline (p>0.05). Post-application, LLG increased significantly, at 30 and 60 minutes, only in the treated eyes (p=0.005). NIBUT also increased significantly in the treated eyes only (p0.05). Comfort improved relative to baseline in 46% of treated and 18% of control eyes, respectively, at 30 minutes post-application. Of those expressing a preference in comfort between the eyes, 68% preferred the liposomal spray. Conclusions: Consistent with subjective reports of improved comfort, statistically and clinically significant improvements in lipid layer thickness and tear film stability are observed in normal eyes for at least an hour after a single application of a phospholipid liposomal spray

Ocular impression-taking - which material is best?

Objectives: To assess the efficacy and effect on clinical signs of a polyvinylsiloxane (Tresident; Shütz Dental Group GmbH, Germany) compared with an irreversible hydrocolloid (Orthoprint; Zhermack SpA, Badia Polesine, Italy) for ocular impression-taking. Methods: Twenty subjects were recruited (13 female and 7 male), with mean age 31.1±4.6 years (SD) (range 25.8–39.7). Subjects attended for 2 sessions, each of 1-hr duration, on 2 separate days. Each session was scheduled at the same time on each day. At each visit, the subject underwent an ocular impression procedure, using either Tresident or Orthoprint, in random order and to one eye only. Investigator 2 was blind to this assignment. Two experienced practitioners conducted the study, investigator 1 performed the ocular impression procedures and investigator 2 observed and assessed the clinical signs: logMAR visual acuity, ocular surface staining, tear break-up time (TBUT), and ocular hyperemia. Results: Visual acuity was unaffected by either material; TBUT was marginally disrupted by both materials, but was not clinically significant according to published criteria; ocular redness increased with both materials; and corneal staining was significantly greater after Orthoprint impression. Less redness and clinically insignificant staining after impression-taking, with fewer clinical complications, was found after use of Tresident. Conclusions: Tresident offers a quicker, more effective, and clinically viable method of obtaining ocular impression topography compared with the traditional Orthoprint, and Orthoprint causes significantly more superficial punctuate staining of the corneal epithelium than Tresident