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Spotlight on Optics

Spotlight on Optics


  • June 2011

Optics InfoBase > Spotlight on Optics > Reflective afocal broadband adaptive optics scanning ophthalmoscope

Reflective afocal broadband adaptive optics scanning ophthalmoscope

Published in Biomedical Optics Express, Vol. 2 Issue 6, pp.1757-1768 (2011)
by Alfredo Dubra and Yusufu Sulai

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Spotlight summary: In this paper, Dubra and Sulai present an adaptive optics (AO) scanning ophthalmoscope design that implements nonplanar folding of the telescopes to reduce pupil and image plane astigmatism. This relatively simple alteration of optical design dramatically improves AO performance and therefore has the potential to influence design of any future AO retinal imaging system.
Besides introducing and implementing this optical design, the authors demonstrate very impressive images of the mosaic of the smallest foveal cone photoreceptors at a resolution not reported previously. These foveal cone photoreceptors were acquired simultaneously at 680 and 796 nm wavelengths. Additionally, the authors elaborate on the benefits of implementing logarithmic rather than linear intensity scales for displaying the cone photoreceptor mosaic.
Compared with previously reported AO-based scanning ophthalmoscopes that place reflective elements in one plane, folding of each reflective afocal telescope allowed reduction of the wavefront error and beam wandering due to optical scanning. It also provided diffraction-limited performance over a 3-diopter vergence supporting simultaneous diffraction-limited imaging of any combination of retinal layers in the 450–850-nm wavelength range.
The broadband nature of this AO scanning ophthalmoscope and its potential still remain to be explored as the authors present images acquired at two wavelengths only. One can imagine, however, as is pointed out by the authors, that several retinal imaging modalities, including optical coherence tomography, multispectral and hyperspectral imaging, as well as single-photon and multiphoton fluorescence could clearly benefit from implementation of this design. Thus the full potential of this novel design will be unfolded as it will be used by groups working on retinal imaging systems implementing these modalities.
In summary, the nonplanar arrangement of reflecting afocal telescopes should become a new standard for AO scanning ophthalmoscopes as well as other cellular resolution retinal imaging modalities that will result in improved image quality of retinal cellular structures.

--Robert J. Zawadzki

ToC Category: Ophthalmology Applications
OCIS Codes: (170.4460) Medical optics and biotechnology : Ophthalmic optics and devices
(170.4470) Medical optics and biotechnology : Ophthalmology
(080.4035) Geometric optics : Mirror system design
(110.1080) Imaging systems : Active or adaptive optics

Posted on June 08, 2011

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