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L. Chen, D. A. Chernyak; Elimination of Cornea Reflections Using Polarized Illumination. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4196.
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© ARVO (1962-2015); The Authors (2016-present)
The treatment accuracy of LASIK refractive surgery relies on precise iris registration and precise eye image detection. Images captured from eye tracking cameras are affected by various corneal reflections from the infrared LED illumination. These reflections can be the combination of specular reflection from the cornea’s smooth anterior surface, and diffuse reflections caused by the textured corneal surface after the flap is lifted. These cornea reflections can distort pupil image detection for positional tracking, and also reduce the number of iris registration match points for torsional tracking. This paper used polarized illumination to remove the specular reflections and diffuse reflections in surgical eyes.
LASIK refractive surgery devices were modified with the polarized illumination. There were 3 IR LED banks for the eye illumination. Each LED bank used an array of 2x3 LEDs with 870nm wavelength. A polarizer with rotating stage was added in front of each IR LED bank. There were three eye tracking cameras used for positional and torsional angle detection in the refractive surgery device. A polarizer with rotation stage was also mounted in front of each tracking camera. Pupil images were captured from the tracking cameras without and with polarized illumination added to the refractive surgery device. Artificial eyes and normal eyes were used to align the orientation of each polarizer.
Pupil images from the tracking cameras in a modified LASIK refractive surgery device showed that the specular reflections are eliminated significantly from artificial eyes and normal eyes under the polarized IR illumination. Diffuse reflections were also greatly reduced from an artificial eye with rough surface to simulate the flapped cornea surface. Pupil images captured from the tracking cameras during the treatment of LASIK refractive surgery showed that both specular reflections and diffuse reflections were eliminated efficiently from all 12 surgical eyes.
Surgical eyes showed significant reduction of cornea reflections during LASIK refractive surgery under the polarized IR illumination. Polarized IR illumination produces clear iris structure for torsional tracking, as well as provides clear pupil image for positional tracking.
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