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Retinal Imaging Protocols for Constructing High Resolution
Mosaics of In Vivo Photoreceptor Cells
Blanca E. MarinezCabrillo CollegeAptos, California
Thomas Hebert, Austin Roorda, College of Optometry, University of
Houston, Houston, Tx.
Why is retinal imaging important?
Retinal imaging, the process of obtaining detailed images of the retina, it is important for:
• Early diagnosis of retinal diseases.
• Monitoring the progression of retinal diseases.
• Studying the distribution of photoreceptors throughout the retina.
AOSLO Image 1.5x1.4 deg
Courtesy: Austin Roorda
How is retinal imaging possible?
Adaptive Optics Scanning Laser Ophthalmoscope (AOSLO)
wavefrontwavefrontsensingsensing
light light deliverydelivery
wavefrontwavefrontcompensationcompensation
lightlightdetectiondetection
rasterrasterscanningscanning eyeeye
Courtesy: Austin Roorda
M O S A I C S
To Construct a mosaic…
Why is the protocol important?
High correlation between images is important when matching them.
THE B I G PICTURE…
M O S A I C S
To Construct a mosaic…
Why is the protocol important?
High correlation between images is important when matching them.
THE B I G PICTURE…
M O S A I C S
To Construct a mosaic…
Why is the protocol important?
High correlation between images is important when matching them.
THE B I G PICTURE…
M O S A I C S
To Construct a mosaic…
Why is the protocol important?
High correlation between images is important when matching them.
THE B I G PICTURE…
M O S A I C S
To Construct a mosaic…
Why is the protocol important?
High correlation between images is important when matching them.
(Images from different protocols)
The protocol affects the clarity of the images, the ability of the subject to fixate well, the region of the retina being imaged and the problems when creating the mosaic.
THE B I G PICTURE…
AOSLO Image 1.5x1.4 deg
Courtesy: Austin Roorda
This shows a mosaic of approximately 9x9 degrees co-aligned with the same region of the fundus photograph.
Targets allow you to map the region of the retina that you want to image and to keep track of where your images should match when constructing the mosaic.
P r o t o c o lIt’s what you look at…
how you look at it...
And how we collect the data.
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P r o t o c o lIt’s what you look at…
how you look at it...
And how we collect the data.
The subject can fixate at one point of the target, gaze across given points or line on the target, or follow a moving point of light like a laser.
Video of a subject gazing across a line on a target.
P r o t o c o lIt’s what you look at…
how you look at it...
And how we collect the data.
The subject can fixate at one point of the target, gaze across given points or line on the target, or follow a moving point of light like a laser.
Video of a subject fixating at one point of the target.
P r o t o c o l It’s what you look at…
how you look at it...
And how we collect the data.
• The length of your videos.You may vary:
•The number of images you register and sum for each location.
• The number of videos you take.
Protocol A
Target
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Twenty-five videos, twenty seconds each.
Protocol A
•Drastic difference in intensity of photoreceptors in the two images.
•Low correlation between images.
•Edges are more prominent.
Courtesy: Ramesh Sundaram
KV
Protocol B
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Target
Ten continuous videos where the subject gazes across given points.
Protocol B
RS
• Noticeable change in images from different videos.
•Good foveal region due to the amount of videos taken at the fovea.
•When constructing the mosaic there was a high correlation between images of the same video but not between corresponding images of different videos.
Protocol C
Target
One continuous video where the subject gazes across lines 1-11.
Protocol C
RS
•The mosaic shows uniform brightness.
•Edges are not prominent.
•High correlation between images.
•The subject had difficulties gazing across the lines.
•Fixation on the central region was minimal therefore we didn’t get a good image of the foveal region.
Protocol D
Target
One continuous video where the subject followed a laser point move along lines 1-11.
Protocol D
RS•The mosaic shows uniform brightness.
•Edges are not prominent
•High correlation between images.
•Subject could fixate well following the laser across the lines.
• Fixation on the central region was minimal therefore we didn’t get a good image of the foveal region.
C o n c l u s i o n
Subjectively, the best results were given by Protocol D. This protocol allows the subject to fixate well and it minimizes the effect of change in reflectivity of photoreceptors due to time difference in which the images were captured. It also allows us to match common features of neighboring frames more accurately. This creates a mosaic that is uniform in brightness, that has less visible edges, and easy to construct.
Acknowledgments
• Center for Adaptive Optics• National Science Foundation #AST-987683• Dr. Tom Hebert• Dr. Austin Roorda• Dr. Fernando Romero• Ramesh Sundaram• Dr. Krishnakumar Venkateswaran • Siddharth Poonja• The Roorda Lab
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