High-Resolution Ocular Surface Imaging: Real-Time Visualization of Tear Film Dysfunction.

PURPOSE: Recent advancements in infrared sensing technology have made it possible to visualize tear film dynamics in real time, enabling evaluation of tear film quality during blinking. A retrospective clinical evaluation was conducted to explore this by grading videos of the tear film and comparing grading data with dry eye diagnostic results using the OCULUS keratograph (K5M). METHODS: Videos were used to grade patients' tear film perturbations as compared with healthy control subjects. The grading was then correlated with the ocular surface disease index (OSDI) scores, tear film breakup time (TFBUT), tear meniscus height (TMH), corneal staining, redness, and meibography data. RESULTS: Infrared imaging of the ocular surface revealed instantaneous and recurring dynamic characteristics of the tear film, allowing for the differentiation between normal and abnormal tear films. Abnormal features included a complete absence of a spreading tear film, hindered spreading of the tear film after blinking, areas of tear film instability, or a combination of the latter 2. Some of these features show a resemblance to the tear film appearance after fluorescein staining. The grading of these features correlated with TFBUT and, to a lesser extent, with TMH but did not show significant correlation with any other diagnostic data from the K5M. Furthermore, the speed of tear film spreading after blinking showed a positive correlation with TMH. CONCLUSIONS: Direct visualization of the tear film across the entire palpebral aperture using infrared sensing offers a noninvasive, reproducible, and rapid method for assessing the health and quality of the tear film.

Effects on the Human Tear Film of Applying Skin Lipids to the Ocular Surface.

PURPOSE: The effect of skin lipids on the formation and stability of the human tear film was investigated. METHODS: Skin swab substances (SSSs) were applied to the eyes of volunteers and studied using fluorescein or with TearView, which records infrared emissivity showing tear film integrity in real time. Results were compared with similar experiments using castor oil, freshly collected meibum, or acetic acid, which simulated the low pH of the skin. RESULTS: Fluorescein and TearView results were comparable. TearView showed the natural unaltered tear film over the whole eye, instant changes to the tear film, and meibomian gland activity. Minimal amounts of SSS destroyed the integrity of the film and caused pain. Corneal epithelial damage could be detected. TearView showed that SSS stimulated meibomian gland secretion if applied directly to the posterior eyelid margin. Excess meibum had no effect on the tear film spread or integrity. Castor oil formed floating lenses on the tear film which were spread by a blink but then condensed back toward themselves. There was no pain or surface damage with these oils. CONCLUSIONS: SSS contamination of the ocular surface disrupts the tear film, causes stinging, and fluorescein staining of the corneal epithelial cells after a blink. SSS stimulates meibomian gland activity. It is possible that various ocular conditions associated with dry eye, such as blepharitis and ocular rosacea, may compromise a meibomian lipid barrier of the eye lid margin. Skin lipids would then have access to the ocular surface and cause dry eye symptoms.

A pilot study on corneal Langerhans cells in keratoconus.

PURPOSE: To report the density and morphology of cells that are analogous to corneal Langerhans cells and their associations in keratoconus. MATERIALS AND METHODS: This prospective cross-sectional study included a convenience sample of keratoconus subjects aged between 18-65 years. Corneal topography, assessment of ocular symptoms, tear variables, corneal sensitivity, in-vivo confocal microscopy were performed. The number of Langerhans cells were manually counted and averaged across three central corneal images. Cell morphology was graded on a 0-3 scale, where grade 3 indicates cells with long visible dendrites. Associations of Langerhans cells with other variables were evaluated using Spearman's correlation. RESULTS: Twenty-one keratoconus subjects with a mean age of 43±11 years were included. Eighty-one percent of them were males, 48% had mild keratoconus and 52% were contact lens wearers. Langerhans cells were present in the central cornea in 91% of subjects. Median cell density was 15 cells/mm2(IQR: 3-21). Cell morphology of grades 2 or 3 (with short or long dendrites) was seen in 71% of subjects. There was a significant association between Langerhans cell frequency and density with male gender (rho and p-values: -0.669, 0.001 and -0.441,0.045) and between Langerhans cell density and nerve fibre tortuosity (0.479,0.028). No significant association observed with age, contact lens wear or ocular symptoms. CONCLUSION: Langerhans cells were present in a significant number of subjects suggesting the possibility of inflammation in keratoconus. Based on the association of Langerhans cells with nerve parameters, we propose inflammation as the underlying cause for corneal nerve changes in keratoconus.

Pilot Study of Corneal Sensitivity and Its Association in Keratoconus.

PURPOSE: To evaluate corneal sensitivity and its association with other clinical parameters in keratoconus. METHODS: Twenty-four subjects with keratoconus aged between 18 and 65 years were recruited in this cross-sectional study. Ocular symptoms, corneal topography, tear variables such as tear osmolarity, volume and lower tear meniscus height, ocular surface staining, central sensitivity threshold (CST), and corneal subepithelial nerve mapping were obtained. Association between central CST and other clinical variables was examined using the Spearman correlation coefficient. Partial correlation was performed to control for effects of confounding factors. RESULTS: Data from the most severe eye of each subject were included in analyses. Based on the maximum simulated keratometry (Kmax) reading, subjects were graded as having mild (N = 11; K max ≤ 52 D) or severe (N = 13; K max > 52 D) keratoconus. Central corneal sensitivity was lower (ie, increased CST) in the severe keratoconus group compared with that in the mild keratoconus group (median, interquartile range: 1.09; 0.60-19.66 vs. 0.51; 0.39-1.51 g/mm, P = 0.035). In bivariate correlations, reduced corneal sensitivity in keratoconus was associated with age (ρ = 0.42, P = 0.040), disease duration (ρ = 0.49, P = 0.015) and severity (ρ = 0.44; P = 0.032), lower central nerve fiber density (ρ = -0.68, P = 0.014), contact lens wear (ρ = 0.44; P = 0.025), and contact lens tolerance (ρ = 0.46; P = 0.033). After adjusting for contact lens wear, reduced corneal sensitivity was negatively associated with ocular symptoms (ρ = -0.426, P = 0.048) and pain sensitivity (ρ = -0.423, P = 0.045) and positively associated with corneal staining (ρ = 0.52, P = 0.011). CONCLUSIONS: Altered corneal sensitivity in keratoconus affected ocular symptoms and ocular surface health, which may have significant impact on the success of management options for keratoconus.

Therapeutic treatment of keratoconus: a survey of local optometric practice criteria.

BACKGROUND: Defining the threshold for therapeutic and surgical intervention in patients with keratoconus presents a considerable challenge given the lack of clear, evidence-based data. Little is known about the patterns of practice and referral criteria of optometrists within Australia. METHODS: All members of the NSW branch of Optometrist Association Australia were invited to complete an online survey in January 2013. This survey was designed to elicit practice information regarding the evaluation and therapeutic treatment of patients with keratoconus in the optometric setting. RESULTS: Responses were received from 71 optometrists, of whom 65.2 per cent had 15 years or greater experience as an optometrist. Many (35.4 per cent) responded that they prescribed soft contact lenses daily. This percentage dropped to 9.2 per cent for rigid gas-permeable lenses (RGP), although 47.7 per cent said they would prescribe RGP lenses at least once per month. The main barriers to prescribing were experience with fitting RGP lenses, time and low market demand. In terms of patient referral to an ophthalmologist, the results were variable, with 34.4 per cent stating that they would refer on progression of corneal signs, 23.4 per cent suggesting no set time and 7.8 per cent would refer on initial diagnosis. Many optometrists (62.9 per cent) would refer a patient for possible surgery, when visual acuity dropped to between 6/9 and 6/12. The size or location of the practice was not associated with the number of newly diagnosed cases of keratoconus. Optometrists with greater experience were more likely to prescribe RGP lenses and co-manage patients with ophthalmologists. Ownership of a corneal topographic unit suggested an increased likelihood of prescribing RGP lenses but did not appear to alter referral patterns. CONCLUSION: Optometrists have an integral role in the diagnosis and management of patients with keratoconus. Our survey provides a basic snapshot of current, local practice. Additionally, ophthalmology should continue to work with optometry to develop guidelines for referral and co-management to optimise future outcomes for our patients.

Correlation of central corneal thickness measurements using Topcon TRK-1P, Zeiss Visante AS-OCT and DGH Pachmate 55 handheld ultrasonic pachymeter.

BACKGROUND: Corneal pachymetry is an important aspect of modern eye care. This study aims to compare the measurement of central corneal thickness (CCT) using automated optical pachymetry, anterior segment optical coherence tomography (AS-OCT) and ultrasound. METHODS: Fifty volunteers participated in this study. Central corneal thickness was measured using the Topcon TRK-1P (Topcon, Tokyo, Japan) automated optical pachymeter, the Visante AS-OCT (Carl Ziess Meditec, Dublin, CA, USA) and the Pachmate 55 handheld ultrasonic pachymeter (DGH, Exton, PA, USA). Pearson correlation coefficients were calculated to compare automated optical pachymetry and AS-OCT with ultrasound. Bland-Altman plots were generated and limits of agreement (LOA) calculated. RESULTS: Fifty eyes were measured for comparison. The mean and standard deviation of the CCT measured by optical pachymetry was 523.7 ± 42.3 µm (range: 412 to 594), 536.0 ± 36.9 µm (range: 425 to 607) for AS-OCT and 553.4 ± 40.7 µm (range: 431 to 630) for ultrasound. Comparison of optical pachymetry and AS-OCT with ultrasound, generated Pearson correlation coefficients of 0.96 and 0.98, respectively. Measurements using optical pachymetry and AS-OCT were consistently lower than when measuring with ultrasound. Bland-Altman plots revealed mean differences of 29.7 µm between optical pachymetry and ultrasound (LOA -5.4 to -54.1) and of 17.4 µm (LOA +0.9 to -35.7) between AS-OCT and ultrasound. CONCLUSION: Due to AS-OCT and automated optical pachymetry consistently measuring lower than ultrasound, it should be noted that these devices are not interchangeable in clinical practice.