EARLY DRY EYE

A thermography device capable of delivering highly reproducible measurements of the dynamic ocular surface temperature (OST) could play an important role in helping to detect early dry eye disease or other ocular pathologies, according to a number of researchers. 'Our initial findings indicate that the TG-1000 Ocular Surface Thermographer (OST, Tomey Corp.) may serve as an appropriate device to detect early dry eye disease or corneal pathology. However, to establish its clinical use, the impact of tear film properties or corneal parameters has to be taken into consideration,' Sarah Moussa told delegates attending the 2nd EuCornea Congress. Dr Moussa, Saarland University Medical Centre, Germany, noted that attempts to measure OST began in earnest in 1950 when Stoll and Hardy developed a contact technique for measuring OST with the use of topical anaesthesia, which resulted in low accuracy and poor resolution. A breakthrough of sorts, however, came in 1960 when Mapstone introduced infrared thermometry, a non-contact technique which allowed repeated measurements to be made.

Dr Moussa's prospective, longitudinal, single-centre study set out to determine the zonal differences of corneal surface temperature in adults following blinking. OST was measured at three different time points in the day and was measured every second for 10 seconds immediately after blinking. The researchers measured and compared the OST at the corneal centre and at three peripheral quadrants at 3 o' clock (temporal), 6 o' clock (inferior) and 9 o' clock (nasal) at the corneal limbus. During the 10 seconds following eye opening and between the various time points, the observed corneal OST parameters did not change significantly. A significant difference was found, however, between temperatures in the nasal quadrant and the centre of the cornea when the eye was refrained from blinking for 10 seconds at each individual time point. In addition the temperature was found to be warmer nasally than temporally in the time interval between six and 10 seconds after blinking, she said. In a separate presentation, Matthias Klamann MD also lauded the potential benefits of using the TG-1000 to measure OST. 'Temperature is one of the fundamental characteristics of tissue metabolism and is certainly of major interest to investigate ocular physiology. This non-contact device offers new options for a better understanding of both ocular surface physiology and pathology. It demonstrates excellent intra-observer reproducibility, so it may be used for dry eye screening, ocular surface inflammation and other potentially useful applications such as for filtering bleb function,' he said.

Dr Klamann, Department of Ophthalmology, University Hospital of Berlin, Germany, noted that the TG-1000 incorporates a touch panel, an infrared sensor and colour images, with an infrared wavelength of between 8 um and 14 um, a frame rate of 4 frames-per-second, and a temperature accuracy to within +- 0.1 Celsius in a target range of 30 to 40 degrees Celsius. In Dr Klamann's study the device was tested on 60 eyes of 30 healthy patients. The results showed that ocular surface temperature measurements were highly reproducible with a mean ocular surface temperature for this patient population of 34.02 Celsius. Dr Klamann concluded that non-contact thermography provides valuable visual and qualitative documentation of temperature changes in the vascular tissues, and will play an increasingly important role in the field of ophthalmology in the future.