An analysis of tear break up time, tear meniscus height and area, the grade of keratoconus and dry eye symptoms in keratoconic and non-keratoconic individuals

Abstract: Keratoconus, being one of the most common corneal disorders has various structural and functional implications. A keratoconic cornea may exhibit a variety of structural changes occurring within each individual layer, affecting the collagen structure and therefore the transparency of the cornea. Research has revealed the presence of symptoms being experienced by these patients, symptoms affecting vision as well as the comfort of the ocular system. These symptoms may be likened to those being experienced by patients who suffer from dry eye syndrome. Dry eye symptoms often occur as a result of changes within the structural and functional components of the tear system and therefore may occur in cases of keratoconus. One of the structural alterations which has been demonstrated in previous research may be changes occurring within the tear meniscus. The tear meniscus has been shown to be a valid and reliable indicator of tear volume and has therefore been used as a diagnostic factor for dry eye. The presence of dry eye symptoms in keratoconic individuals has been documented in previous research, however, the tear meniscus dimensions have not been extensively investigated. Could it be possible that these symptoms may be related to changes within the structure of the tears, namely tear meniscus dimensions specifically? The aim of this study was to determine whether significant differences in symptoms and tear meniscus dimensions exist between keratoconic subjects and those of control subjects. If so, could a correlation be established between the symptoms being experienced and the alterations in the tear meniscus structure? This study involves the Ocular Surface Disease Index (OSDI) questionnaire, which is a subjective measure of dry eye symptoms, giving an indication of the severity of symptoms being experienced. Two diverse types of instrumentation are utilized in order to measure the dimensions of the tear meniscus. These instruments being the Keratograph 4 and the iVue Optical Coherence Tomographer (OCT). Through the use of the Keratograph 4, non-invasive tear break up time (NTBUT) measurements and corneal topography readings were additionally measured. The study comprised of 50 subjects, being separated into 25 keratoconic and 25 control subjects which could be used for comparison. The results of the study could be summarized as follows: Keratoconic subjects are shown to experience symptoms of a greater severity compared to control subjects as given by the OSDI scores...M.Phil. (Optometry