Contactless Heat Measurement System for Retinal Coagulation

Abstract

Introduction: Current heat measurement systems for retinal coagulation are insufficient to demonstrate the safety of intraocular diathermy instruments. Therefore, this paper aims to design and test a novel coagulation heat measurement system that attempts to infer direct retinal tissue temperature using contactless thermal measurements. Methods: In four experiment conditions, the direct temperature on the lower surface of the tissue is measured from below with a thermography camera measuring the temperature through a semi-transparent window that holds the tissue, and contactless measurements are made with a multi-sensor containing vertically aligned micro sensors located in the fluid medium above the sample. Results: The lowest mean temperature increase at both the thermography measurements (1.52°C) and sensor measurements (0.08°C), is found in the condition of 2.2 J (2.2 W and 1”). At thermography, the highest mean increase (8.67°C) resulted from the condition of 4 J (4 W and 1”) and positive. At the sensor, the highest mean increase (0.25°C) is found in the condition of 4 J (2 W and 2”). Discussion: The use of 2.2 J appears too low for proper sensor measurement. For the two conditions of 4 J there is a contradictory indication of the influence of application time in thermography measurements versus sensor measurements, as the sensor is expected to be more sensitive to changes in the application time than the thermal camera. Conclusion: Since no similar trends have been observed between the thermography and multi-sensor measurements, the contactless sensor cannot infer the direct tissue temperature.