School of Medicine

Translational Vision Research in the Department of Ophthalmology

Tear and Ocular Surface - Dr Jennifer Craig

deprod Various therapies are commercially available for treating Dye Eye.

Subjectively, dry eye can rank amongst some of the most painful and debilitating chronic eye conditions. Objectively, an untreated dry eye can eventually result in a loss of corneal transparency. A thorough examination of a dry eye is crucial, therefore, to allow the underlying cause to be identified and ensure that the most appropriate therapy is administered.The term "dry eye" encompasses a variety of conditions of differing aetiology, which all result in similar symptoms, including abnormalities of the ocular surface, tear film and eyelids. The preocular tear film is remarkably complex, comprising a multitude of components within a carefully ordered structure. A deficiency in the quality or quantity of any one of the components can prevent the tear film from performing its important functions, resulting in ocular surface damage and dry eye symptoms. Assessment of the tear film is therefore important, not only for idiopathic dry eye, but also for dry eye related to systemic disease or that which can be induced by contact lens wear.

evapsetup The evaporimeter measures the rate of tear film evaporation.
ts The Tearscope Plus.
mlcam The Microlens Camera.
prt Phenol Red threads stimulate tear production.

Within a practice setting, clinically-available instruments can be used to assess the components which may be responsible for causing the dry eye. Surface abnormalities can be examined in detail by slit-lamp biomicroscopy, with or without staining agents, and by assessing corneal topography. Several clinical methods of examining the tear film exist, with tests, which are minimally or non-invasive, being far superior to tests which induce reflex tearing. To this end, various techniques have been developed to allow visualisation of the tear film, in situ, and without significant disturbance. One such instrument is the Tearscope Plus(tm) (Keeler Ltd., UK) which is utilises interferometric principles to view the suface lipid layer of the tears. These video images can be captured by the Microlens camera (Keeler Ltd., UK) for subsequent analysis. Various inserts which project grid patterns onto the tear film are available for the Tearscope Plus(tm) to allow tear film stability to be measured, non-invasively.

begat BEGAT for measuring high (top) and low contrast visual acuity, including the effects of glare.

Newer, commercially available products such as the DET (Akorn Inc, USA) also allow the measurement of the tear film break-up time. For measuring tear flow, Phenol Red Threads (Zone-Quick, Menicon Co. Ltd., Japan) provide a lesser stimulus to reflex tearing than the traditional Schirmer test. Additionally, the department has acquired an evaporimeter (Servomed, Sweden) in recent months, which is being adapted for measuring tear film evaporation rates. Tear film evaporation increases in cases of dry eye where the lipid layer is abnormal. Variations in high contrast and low contrast visual acuity, including the effects of glare, can be assessed with the newly available BEGAT (Tawa Medical Holdings Ltd., New Zealand).

These techniques available in the department for assessing the tear film and ocular surface are used in studies observing the tear film in health, disease, contact lens wear, and in response to various therapies.