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Zhaohua Yu, Karl Schulmeister, Nooshin TalebiZadeh, Martin Kronschlager, Per G Soderberg; Ocular heat diffusion after threshold in vivo exposure to 1090 nm infrared radiation. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1213.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the heat flow in the ocular media after in vivo exposure to 1090 nm radiation at the radiant exposure dose intended for cataract induction
Altogether 20 six-weeks-old albino Sprague-Dawley rats were anesthetized and the pupils were bilaterally dilated prior to experimental exposure. The animals were randomly divided into two groups of 10. All animals were unilaterally exposed to 6.2 W coherent infrared radiation at 1090 nm with a spot size of 2 mm within the dilated pupil for 8 seconds (1.6 kJ/cm2). The beam was divergent on the cornea generating a close to collimated beam between the lens and the retina to minimize retinal heating. In one group, temperature was recorded with three thermocouple probes placed at the limbus, in the vitreous just behind lens, and on the outer sclera next to the optic nerve, respectively. In the other group, one thermocouple probe was placed at the limbus and another probe on the outer sclera next to the optic nerve. Temperature was recorded from the end of the exposure till temperature descended back to normal.
After the exposure, the temperature decreased exponentially as a function of time asymptotically approaching a minimum. In the three-probes group, the temperature rise at the end of the exposure, expressed as a 95 % confidence interval for the mean was 11 ± 3 °C at the limbus, 16 ± 6 °C in the vitreous behind lens and 16 ± 7 °C on the sclera next to the optic nerve. Heat diffusivity, estimated as the rate constant was, estimated as a 95 % confidence interval for the mean, 3 ± 0.4 × 10-2 s-1 at the limbus, 5 ± 1 × 10-2 s-1 in the vitreous behind lens, and 7 ± 2 × 10-2 s-1on the sclera next to the optic nerve (d.f. = 9). In the two-probes group, the temperature elevation at the end of the exposure was 9 ± 1 °C at the limbus and 26 ± 10 °C on the sclera next to the optic nerve. The heat diffusivity, estimated as a 95 % confidence interval for the mean, was 3 ± 0.4 × 10-2 s-1 at the limbus and 11 ± 3 × 10-2 s-1 on the sclera next to the optic nerve (d.f.= 9).
An irradiance of 197 W/cm-2 of 1090 nm for 8 s (1.6 kJ/cm-2), in the corneal plane close to collimated between the lens and the retina, induces a temperature increase of about 10 °C at the limbus and about 25 °C close to the retina. It takes about 30 s at the limbus and about 10 s close to the retina for temperature to fall down 67% of the induced temperature rise.
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