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Retinal photocoagulation techniques are widely used to treat various retinal diseases such as retinal detachment, diabetic retinopathy and ischemic retinal vein occlusion. The degree of coagulation, which plays important role for optimal surgical outcomes, depends on the tissue temperature achieved and the exposure time. The temperature distribution is affected by indeterminate characteristics, such as the pigmentation of the retinal tissue and the radiative transfer by its structure, in addition to the laser radiation condition. Therefore, an accurate measurement of the tissue temperature offers crucial information that could prevent excessive burning and collateral damage.
There have been many researches on temperature monitoring methods using various sensors or imaging systems such as fiber optic sensor, ultrasound imaging, MRI, photoacoustic imaging, and optical coherence tomography (OCT). Among them, the OCT is a promising technique for retina imaging because it is a non-invasive system providing depth resolved images with microscale resolution. One of the OCT technique, speckle variance optical coherence tomography (svOCT), is known to detect moving molecules or coagulation in tissues sensitively by calculating changes of speckle pattern with time.
In this paper, we proposed temperature monitoring of retinal tissues by svOCT imaging during photocoagulation since photocoagulation of retinal tissues is closely related to its temperature distribution. An ex-vivo bovine retina was continuously radiated by 10 mW green laser after removal of cornea, lens, and vitreous humor. SvOCT images of the retina was acquired every 1 minutes and analyzed with temperature data measured by thermometer. The results showed that speckle variance signal increases as temperature increases. Based on our result, we expect that svOCT will be an effective method for temperature monitoring to improve and automate laser treatments in ophthalmology.
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