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Yuan Liu, Keith O'Hara, YINGJIAN WANG, Nathan Shemonski, Jochen Straub, Charles Campbell; Characterizing retinal radiant exposure of line illumination. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5870. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Line illumination allows parallel detection along the line direction and therefore faster imaging speed as compared to point illumination. The parallelization speed advantage and higher power allowed for imaging the eye have been gaining research interest in ophthalmologic imaging. Understanding the retinal radiant exposure distribution of line illumination is crucial for eye safety and for optimizing its imaging performance. Here, we propose a method to characterize the 2D line illumination profile at the retina and to compute the retinal radiant exposure for safety compliance.
A prototype line illuminating ophthalmologic imaging system (ZEISS, Dublin, CA) comprises a 785-nm laser as the light source, a cylindrical lens to form the line illumination, and relaying optical elements to guide the light to the retina. The beam profiles at the subject’s pupil plane and at the back focus of a 17-mm lens placed at pupil plane are photographed with a camera. The first measurement provides the spatial frequency content perpendicular to the line at retina, which is used to compute the tightest possible 1D focused beam profile. The second measurement provides the 1D spatial distribution of energy along the line orientation. The 2D beam profile at the retina corresponding to the most hazardous focusing condition can be inferred by combining the two mutually perpendicular 1D profiles from the two measurements. With the optical energy measured at pupil plane using a power meter, the retinal radiant exposure can be fully characterized by distributing the energy across the 2D beam profile at high spatial resolution. The results from the system are compared with the ANSI.Z80-36:2016 standard to examine its eye safety.
The line illumination profiles photographed at the proposed planes and the computed 2D beam profile at retina are shown in Fig.1. The energy measured with a power meter is distributed across the beam profile to obtain the distribution of retinal radiant exposure. The peak value 0.2723 J/cm2 is below the limit set forth by the ANSI standard.
The proposed method provides a systematic approach to characterize beam profile and radiant exposure of a line illuminating ophthalmologic imaging system, and can be applied to examine the safety compliance of such a system.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Fig. 1. Computing the 2D beam profile at retina from the measurements at pupil plane and at back focus of a 17-mm lens.
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