March 2012
Volume 53, Issue 14
Free
ARVO Annual Meeting Abstract  |   March 2012
Low-cost Confocal Retinal Imaging With A Digital Light Projector Source
Author Affiliations & Notes
  • Matthew S. Muller
    Aeon Imaging, LLC, Bloomington, Indiana
  • Ann E. Elsner
    Optometry, Indiana University, Bloomington, Indiana
  • Dean A. Van Nasdale
    Optometry, Indiana University, Bloomington, Indiana
  • Footnotes
    Commercial Relationships  Matthew S. Muller, Aeon Imaging, LLC (I, R), US Patent Application 13/302,814 (P); Ann E. Elsner, Aeon Imaging, LLC (F, I, S); Dean A. Van Nasdale, None
  • Footnotes
    Support  NIH Grant EY020017
Investigative Ophthalmology & Visual Science March 2012, Vol.53, 3099. doi:
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      Matthew S. Muller, Ann E. Elsner, Dean A. Van Nasdale; Low-cost Confocal Retinal Imaging With A Digital Light Projector Source. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3099.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: : To provide confocal and dark field imaging with a novel retinal camera, the DLP-Cam. To perform low cost, portable, non-mydriatic imaging with visible wavelength illumination for rapid diagnosis and screening.

Methods: : The DLP-Cam is a confocal ophthalmoscope that uses a compact digital light projector (DLP) to rapidly illuminate the retina with a series of projected lines, removing the need for a scanner such as a galvanometer. The projected line position at the retina is matched to that of the rolling shutter of a CMOS sensor used for detection, which allows the rejection of unwanted scattered light from out of plane scatterers. Dark field imaging is performed by acquiring a series of image frames with varied spatial-temporal offsets between the projected lines and the rolling shutter. The DLP-Cam has a small pupil entrance / exit diameter of 2.25 mm, a 23.5 deg field of view, a working distance of 19 mm, and a digital resolution of 7 µm on the retina. Nonmydriatic retinal imaging is performed at 20 frames per second with an average illumination power of 50 µW and at a selectable wavelength of 516 or 631 nm. A single focusing knob permits simple correction over a wide range of refractive errors (+/-10 diopters). Custom internal fixation patterns are provided by the DLP via software at a resolution of 0.14 deg on the retina. We performed nonmydriatic imaging of the retinas of 11 subjects aged 42 ± 14 yr, including 3 Asians and 8 Caucasians, 4 of whom were female. 4 of the subjects also had the pupil of one eye dilated. 60 image frame buffers were acquired of the optic nerve head of each eye in confocal and dark field imaging modes at both 516 and 631 nm. Dark field images were acquired while varying the timing of the projected lines with respect to the sensor, via software. Confocal image sets acquired using 516 and 631 nm were registered and averaged. The confocal retinal images of 2 subjects were compared to those taken previously with the GDx scanning laser ophthalmoscope. Dark field images were registered and compared to dark field images previously acquired at 850 nm with the laser scanning digital camera (LSDC).

Results: : Confocal images acquired using 516 nm illumination showed excellent vessel contrast and visibility of lamina cribrosa. Third-order vessel branches were seen in both DLP-Cam and GDx images. As expected, the 631 nm illumination provided images with greater light return from the retina, which assisted pupil alignment in undilated subjects. As seen in prior LSDC studies, the dark field images enhanced the visibility of atrophic boundaries around the optic nerve head of myopic subjects.

Conclusions: : The DLP-Cam provides a new approach for low-cost and flexible retinal imaging.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • image processing 
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