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SA Burns, RH Webb, AE Elsner, S Marcos, S Bara; A scanning laser ophthalmoscope for use with correction for the eye's wave aberrations . Invest. Ophthalmol. Vis. Sci. 2002;43(13):952.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To design and build a new imaging system, based on a confocal scanning laser ophthalmoscope (SLO) for in vivo high resolution imaging of the human fundus. Methods: There has been considerable interest in the application of adaptive optics to improved imaging of the human retina. We designed and constructed a new SLO, with the following properties; 1) a magnified 3 deg field of view on the retina (600x600pixels) using a 5 mm pupil, 2) capability of inserting a custom phase plate produced by photolithography and trial lenses to compensate the optical aberrations of each eye, 3) variable frame rate (from 10 to 30 frames per second), by using a variable speed polygon (Lincoln Laser) and galvanometer for scanning, and variable rate frame grabber, 4) separate pupil imaging system for aligning the eye to the optical axis of the SLO, and thus to the phase plate, 5) real-time monitoring of the pupil and retinal region of interest to allow imaging away from the center of the macula, 6) custom detection eletronics that allow either intensity detection, or via a heterodyne detection arrangement, optical quadrature detection. Results: The system produces images of contrast equal or superior to commercial imaging systems. Upon insertion of the phase correcting plate improved contrast was obtained; vessels at 13 degrees eccentricity increased substantially in contrast (Michaelson contrast increased by 28%). As expected, due to the tightly confocal nature of the imaging system it was very sensitive to defocus, The major limitation of small field systems for continuous viewing is the need for high retinal irradiances. However, we were able to image the eye safely in 633 nm light. The system is also able to use longer (near-IR) wavelengths, where deeper retinal structures should be even more visible. Conclusion: The new system has both advantages and disadvantages for general purpose imaging. Small field of view instruments have the problem that it is difficult to localize where the images are being obtained. The use of a 3 deg scan decreases this problem compared to smaller fields of view, however the use of the polygon fixes the horizontal scan angle. However, it is clear that considerable improvement in retinal image quality in the near periphery can be achieved with fixed compensation of the eye's optical aberrations.
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