Ocular Thermographic Assessment of Internal Carotid Artery Stenosis

Overview

Project status: In progress

Research leader

• Professor Nathan Efron

Research team

QUT

• Dr Nicola Pritchard

Organisational unit

Lead unit Faculty of Health Other units

• Institute of Health and Biomedical Innovation
• School of Optometry and Vision Science

Research area

Vision Improvement

Details

Figure 1: Hand held ocular thermographic camera for measurement of the temperature of the surface of the eye (Image courtesy of FLIR Systems)

Figure 2: Ocular thermogram showing the temperature profile of the normal eye

ICAS is a major risk factor for ischemic stroke. Once ICAS is detected, therapeutic and surgical measures are available to lessen the risk of stroke. Stroke is a significant health problem: each year there are about 40,000 - 48,000 stroke events among Australians. Although it is effective in diagnosing ICAS, CDUS is relatively expensive in terms of equipment and the operator dependence of this technique demands the employment of highly trained operators. Clearly, the development of new, effective and inexpensive methodologies to screen for ICAS could have a significant impact on the detection of carotid artery disease and the prevention of stroke.

As the vascular supply to the eye is the dominant feature in the determination of its temperature, it might be supposed that a total or partial occlusion of the internal carotid artery system would cause a reduction in temperature on the affected side, notwithstanding compensatory collateral blood flow via the circle of Willis. OT can accurately measure eye temperature and in that way has the potential to serve as a simple screening tool for the identification of haemodynamically significant ICAS.

The intended outcome of this work will be to define the sensitivity and specificity of OT as a screening test for haemodynamically significant ICAS when compared with the assessment of ICAS using CDUS and MRA. This work will also reveal the effect of collateral circulation in the circle of Willis upon eye temperature in patients with unilateral ICAS. A clear demonstration of the associations between ocular temperature, patterns of compensatory flow in the circle of Willis, and the extent of ICAS, could pave the way for a better understanding of ICAS and the causation of stroke, and validate OT as a simple, operator-independent, inexpensive, rapid and non-invasive adjunct to CDUS in the clinical evaluation and diagnosis of ICAS.

Publications and output

1. Morgan PB, Soh MP, Efron N, Tullo AB. Potential applications of ocular thermography. Optom Vis Sci 1993; 70: 568-576.
2. Morgan PB, Smyth JV, Tullo AB, Efron N. Ocular temperature in carotid artery stenosis. Optom Vis Sci 1999; 76: 850-854.