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E Maguen, T Papaioannou, WS Grundfest; Spatiotemporal Temperature Profiling of Corneal Surface During Laser Thermal Keratoplasty (LTK) . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4117.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Accurate prediction of LTK treatments requires refined thermal corneal models which necessitate precise input parameters. The overall objective of this study was to provide detailed information on the spatiotemporal temperature profile of the corneal surface, during in-vitro thermal keratoplasty. Methods: LTK was performed in-vitro on freshly harvested porcine eyes (N=16) with the Sunrise Technologies corneal shaping system (Model SUN 1000). Spatiotemporal thermal imaging of the irradiated corneas were obtained with a short wave Inframetrics thermal camera (Model PM290). Images were obtained at 8-bits resolution, with ∼100 microns spatial and ∼17 msec temporal resolution respectively. Treatment pattern consisted of eight spots at 6 mm zone, while lasing was conducted at settings of either 100-mJ and 15 pulses (N=8), or 260-mJ and 7 pulses (N=8). Time and spatial variation of the corneal surface temperatures were calculated at locations of importance to LTK. Results: At the laser spot, temperature profiles consisted of transients coinciding approximately with the laser pulses. Maximum transient temperatures observed were 98.0±4.6 0C for the high and 56.3±2.6 0C for the low energy respectively. These temperature transients were superimposed on an envelope of lower-slowly varying temperatures. The maximum temperatures observed for this temperature envelope, were 51.8±3.4 0C for the high and 35.4±3.4 0C for the low energy respectively. The evolution of either the maximum temperature transients or the lower temperature envelope, followed exponential growth of the form: T = A * exp(B*t). Maximum temperatures at locations 0.5 mm and 1 mm away from the laser spot, reached 25.7 0C and 23.3 0C for the low energy, and 34 0C and 25.6 0C for the high energy settings respectively. Temperatures decay constants were approximately 2 to 3 sec, while the spatial temperature profile at the laser spot extended to approximately 2-mm at 2.5-sec post irradiation. Conclusions: The data obtained may help to refine corneal thermal modeling during LTK, and thus improve predictability of current or future-modified-treatments.
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