Dry eye assessment using ocular thermography – a review

The International Dry Eye workshop (DEWS) defined dry eye as a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance, and tear film instability with potential damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and may also be accompanied with inflammation of the ocular surface (Foulks 2007; Lemp et al. 2007). Up to 25% of patients presenting to optometric practices have some level of dry eye symptoms. Causes of dry eye include meibomian gland dysfunction, atrophy or fibrosis of the lacrimal tissue (as in keratoconjunctivitis sicca) and medication use (eg. beta-blockers, antihistamines and antidepressants). Nearly half of contact lens wearers report symptoms of dryness (Nichols et al. 2000).Symptoms by case history, fluorescein staining and fluorescein tear break-up time are standard for the assessment of dry eye. Common practice among optometrists and ophthalmologists is to use symptoms and at least one other test in the clinical diagnosis of dry eye (Nichols et al. 2000). Tear volume tests, tear quality assessment and lipid evaluation are necessary in the classification of dry eye into the tear-deficient or evaporation subtypes.Assessment and diagnosis of dry eye is still a challenging task in many cases, after more than 100 years of research (Giacomo et al. 2008). Researchers have attempted to evaluate the efficacy of currently available dry eye assessments but has proved problematic due to poor test reliability (Vanley et al. 1977; Cho et al. 1992; Cho 1993; Cho and Brown 1993). There is some evidence in the literature showing that ocular thermography has the potential in assessing the anterior eye surface particularly the tear film. It is non invasive and could provide instantaneous results. This paper will review the consistency of currently available dry eye assessment and discussing the ability of ocular thermography as a device to screen dry eyes.