OP: Advanced Ocular Imaging - Week 7 Flashcards
What is the key component used in adaptive optics?
A deformable mirror.
How does the deformable mirror deform?
Behind the mirror there are ‘actuators’ that push and pull on the surface of the mirror membrane. You can bend the shape of the mirror by driving these actuators backwards and forwards in small amounts
How can we use a deformable mirror to change wavefronts?
When light hits a reflecting surface, it will reflect the spatial characteristics of that surface. So if we know the wavefront beforehand, we can shape our mirror to cancel out any aberrations and produce a flat wavefront – therefore correct aberrations
What percentage of the light entering the eye comes out again?
0.05%
How does micro-oximetry work?
By imaging 1 different wavelengths simultaneously: one that is absorbed more by oxygenated Haemoglobin, and the other by de-oxygenated Hb.
– allows you to find areas of oxygenated blood.
Can you perform micro-oximetry on capillaries?
No, capillaries are too small, therefore there will be too many interference effects. (you can do it for venules however, which are slightly bigger)
Why is not much light returned by photoreceptors at start after cone bleaching?
because the photoreceptors are filled with photopigment
List one advantage and one disadvantage of Scanning Laser Optics (SLO and AO-SLO) compared to flood adaptive optics
Adv: Better contrast
Disadv: Harder to see - can get distortions (b/c when the eye moves, image quality is disrupted)
How do scanning laser ophthalmoscopes (SLO) differ from scanning laser microscopes (SLM)?
In an SLO, the optics of the eye serve as the objective lens and the fundus is always the sample
What component of SLO allows us to place a pinhole, and where would we place it?
The fact that the returning light is rendered stationary after de-scanning allows us to place a confocal aperture prior to the PMT detector
What happens to light scattered past the plane of focus when a confocal pinhole is in place?
Most of it gets absorbed by the confocal pinhole
What is the purpose of a confocal pinhole in SLO? Is there any downside?
Serves to enormously improve the contrast of light scattered from your plane of interest
(downside is that you can only do this one point at a time, therefore slow)
What does OCT achieve?
Allows us to get info about the cross-sectional structure of the eye
How big is the FOV in OCT?
Wide FOV
How fast is OCT?
Slow
