Optical Coherence Tomography of Ocular Structures in Epiphora and Dry Eye Syndrome (OCT)
Optical Coherence Tomography of Ocular Structures in Epiphora and Dry Eye Syndrome (OCT)
The primary aim of the study is to investigate whether optical coherence tomography (OCT) may be a useful tool for investigating the in-vivo histology of ocular structures in patients with tear film pathology. In epiphora the investigators will image the proximal lacrimal system. In dry eye syndrome the investigators will image the lacrimal gland and also the buccal mucosa.
The secondary aim of the study is to investigate the appearance of the normal cornea and conjunctiva under OCT imaging.
Optical Coherence Tomography (OCT) is a safe and non-invasive method of high resolution cross-sectional imaging of tissue microstructures using infra-red radiation. It was first described by Huang et al in 1991.
The principle of OCT imaging is similar to ultrasound; infra-red light is shone at a tissue of interest and the reflectivity of each layer within the tissue gives rise to a signal that enables a cross-sectional picture of the tissue to be constructed. In contrast to ultrasound however, it is not possible to use the timing of reflected pulses of light to infer the distance of the reflecting surface. This is because of the extremely high velocity of light (3x10^8 ms^-1), which would require the detector to have a temporal resolution of a few tens of femtoseconds in order to provide a spatial resolution of 10 microns within the tissue under observation. therefore, interferometry is applied to the infra-red light source in order to determine the distance that reflected light has travelled.
OCT currently has a wide range of applications including imaging the retina, the anterior chamber of the eye and the endothelium of the coronary arteries (when used intravascularly). It has also been used in preclinical cancer research to image tumours. IT has a resolution of 1-20µm and can penetrate approximately 1-2mm into tissue.
Dry Eye Syndrome:
Sjögren's is a common cause of dry eye syndrome. Currently a biopsy of the lacrimal gland is required to establish the diagnosis. In this study the investigators explore whether it is possible to distinguish the lacrimal gland in Sjögren's patients from the normal lacrimal gland using OCT imaging. The investigators will also image the buccal mucosa of suspected Sjögren's patients and compare the results to previously published images of the normal mucosa.
Epiphora:
Punctal anatomy is clinically relevant in the management of epiphora because punctal stenosis is one of the many causes of this condition. However, there are currently no routinely used imaging modalities or objective quantitative assessment systems for the proximal lacrimal system.
OCT seems to be ideally suited to imaging the punctum due to its high resolution and non-invasive nature. The investigators have recently completed a study demonstrating the feasibility of OCT imaging of the proximal lacrimal system in a cohort of subjects with normal ocular anatomy and no symptoms of epiphora. In this study the investigators will examine the practical clinical applications of OCT imaging pre and post-operatively in patients undergoing punctoplasty or conjunctivoplasty to treat epiphora.
Asymptomatic Patients:
The investigators aim to establish the normal OCT appearance of the conjunctiva and cornea; and also aim to establish the normal appearance of the lacrimal gland and the buccal mucosa.
Inclusion Criteria:
Exclusion Criteria: