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Influences of stimulus characteristics and ocular surface conditions on non-invasive corneal sensitivity measurement

Nosch, Daniela 2015. Influences of stimulus characteristics and ocular surface conditions on non-invasive corneal sensitivity measurement. PhD Thesis, Cardiff University.
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Purpose: To i) investigate the stimulus characteristics of the Belmonte OPM pneumatic aesthesiometer in vitro and in vivo; ii) explore the relationship between corneal sensitivity threshold (CST), spontaneous eye blink rate (SEBR), ocular surface temperature (OST) and tear film quality, using the non-contact aesthesiometer (NCCA), and iii) investigate the relationship between heating and cooling of the ocular surface on CST (with the NCCA). Methods: Stimulus flow rate (airflow meter), air stimulus volume (air capture) and force (weight scales) were recorded in vitro. Stimulus temperature was measured in vitro (using thermocouples) and in vivo (via a thermal infrared camera). SEBR, CST, OST, NIBUT and lipid pattern of the tear film were recorded. CST (using NCCA), OST and tear film quality were obtained at baseline, and after increasing and decreasing OST, using heated goggles or cooling gel mask, respectively, until OST baseline level was reached again. OST was recorded during stimulus presentation at CST, immediately after heating and cooling of the ocular surface. Conclusions: Stimulus characteristics measured in vitro showed little variability and may therefore be considered as reliable. Stimulus temperature recorded in vivo showed that a change in stimulus flow rate produced a small, but statistically significant effect on OST. Consequently, this air stimulus may not be exclusively ‘mechanical’, and may provoke an additional response from temperature sensitive C fibres. A moderate correlation between corneal sensitivity and blink frequency was established, and a strong correlation between tear film quality, SEBR and OST was obtained, emphasising that ocular surface condition represents one important trigger for the initiation of a blink. After both an increase and a decrease of OST, a greater localised OST decrease was required at CST, indicating that heating or cooling of the ocular surface may affect the nervous activity / sensitivity of cold thermoreceptors in the superficial cornea.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Optometry and Vision Sciences
Subjects: R Medicine > RE Ophthalmology
Uncontrolled Keywords: ocular surface sensitivity, air gas aesthesiometry, blinking, tear film, ocular surface temperature, iris pigmentation
Date of First Compliant Deposit: 30 March 2016
Last Modified: 19 Mar 2016 23:57

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