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Title: The role of the meniscus in the tear film
Author: Bandlitz, Stefan
ISNI:       0000 0004 5354 9902
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2015
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In the diagnosis of dry eye, an evaluation of tear fluid volume is an important parameter. The tear menisci hold approximately 75-90% of the overall tear fluid volume and serve as reservoirs, supplying tears to the pre-corneal tear film. The measurement of the anterior curvature radius of the tear meniscus (TMR) is an indicator of tear film volume and when it is performed non-invasively has been found to have good dry eye diagnostic accuracies. Optical coherence tomography and meniscometry are existing techniques that can measure TMR non-invasively. These techniques have not found wide application among clinicians, either because they are not commercially available or they are too expensive. This PhD describes a series of experiments that investigated the development, evaluation and application of a new instrument for non-invasive tear meniscus measurement. From the results of these studies, it can be concluded: A Portable Digital Meniscometer (PDM) was developed. This consists of an application tool for the iPod-touch, a slit-lamp holder for the iPod-touch and an image analysis software for TMR calculation. A simple iPod-touch or an iPhone mounted on a commercially available digital slit-lamp can be used to project a grid of black and white lines on the tear meniscus. Using the principal of reflective meniscometry, the radius of the lower tear meniscus can be non-invasively measured. This newly developed instrument is a simple, mobile and useful device for measuring tear meniscus radius, and therefore tear volume, and is suitable for use by clinicians. The newly developed PDM was evaluated in vitro and in vivo. It produced accurate and reliable measurements and provided similar values for the tear meniscus radius, in human studies, to the existing video-meniscometer. PDM and OCT measurements of the TMR were significantly correlated. Since with the PDM no image calibration is needed, it seems to be a quick and non-invasive technique for evaluation of tear fluid quantity. The PDM appears to measure the radius of the central section of the tear meniscus The PDM was able to non-invasively measure alterations in TMR and TMH along the lower lid. The flatter TMR and higher TMH at the nasal and temporal locations may be caused by the LIPCOF degree of the underlying conjunctiva. To avoid any interference by LIPCOF, it is recommended that TMR and TMH be measured along the lower lid margin below the pupil centre. Furthermore, the PDM was able to usefully detect changes in TMR following the instillation of artificial tears. The difference in residence time is likely to reflect the different viscosity and Newtonian properties of these drops. An overload with a large drop may result in initial increased blink rate. Blink rate at baseline is significantly related to dry eye symptoms.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: RE Ophthalmology