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The predictive ability of clinical tests for dry eye in contact lens wear

Pult, Heiko 2008. The predictive ability of clinical tests for dry eye in contact lens wear. PhD Thesis, Cardiff University.

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Thirty to fifty percent of contact lens wearers discontinue contact lens wear. Therefore it is essential for the clinician to have a predictive method that can forecast the development of dryness symptoms in contact lens wear. Contact lens wear induces tear film instability leading to increased tear film evaporation and its associated hyperosmolarity. This in turn causes ocular surface inflammation resulting in the release of cytokines, impacting tear mucin production, which further destabilises the tear film. Since this mechanism can only be fully evaluated by an intensive laboratory-based approach, the clinician must rely on assessing those factors easily accessible within the practice situation: tear film stability and mucin loss/epithelial damage. These two factors are inter-related, and investigating one also provides information about the other. For this PhD, these two components of the mechanism have been investigated. This PhD has found that: (1) Bulbar and limbal redness are inter-related using the CCLRU grading scales, a limbal redness grade above 2.5 or a bulbar redness grade above 3.0 may be considered abnormal. (2) Symptomatic, experienced soft contact lens wearers exhibit significantly more lid wiper epitheliopathy (LWE) and lid parallel conjunctival folds (LIPCOF) but not corneal staining, bulbar hyperaemia or decreased Pre-lens break up time (PLBUT). LWE and LIPCOF are significantly correlated, suggesting that both are related to mechanical forces during blinking caused by a deficiency of the mucin layer. (3) LIPCOF and LWE are also positively correlated with symptoms amongst non-contact lens wearers. Using these two tests as a surrogate, the clinician has, for the first time, a useful indication of the mucin layer in contact lens patients. Returning then to the fundamental question—"Can the development of dryness symptoms in soft contact lens wearers be predicted?" This PhD has found that the clinician can use a combination of currently available tests to meet this question. The optimum combination of tests was found to be LIPCOF Sum plus NIBUT plus OSDI, termed the P-Test. The P-Test shows outstanding potential as a discriminator and predictor of contact lens induced dry eye.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Optometry and Vision Sciences
Subjects: R Medicine > RE Ophthalmology
ISBN: 9781303213342
Date of First Compliant Deposit: 30 March 2016
Last Modified: 04 Jun 2017 05:55

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