Optics: Posterior Segment Imaging Flashcards
In vivo retinal imaging is used for:
-view cellular structures in living retina
-surgical procedures
-early detection
-follow up procedures
What causes challenges in retinal imaging?
-diffraction
-aberrations
-light scattering
-light safety
-eye motion artifacts
What is the resolution of the fundus camera limited by?
The optics of the human eye NOT the camera itself
3 major retinal imaging tools:
- Fundus camera
- Scanning laser ophthalmoscope (SLO)
- Optical coherence tomography (OCT)
Conventional imaging tools improve the _____________ but not the __________________
Axial resolution, transverse resolution
What two things does an adaptive optics system consist of?
-a wavefront sensor to detect the shape of the wavefront generated by eyes optics
-a correcting element that dynamically compensates for the aberrations in the wavefront
Why does the star twinkle?
Due to turbulence causing the light to refract
What did we learn from viewing the photoreceptors?
-the amount of the different photoreceptors present in the retina (red, green, blue)
If you use red light (650nm bleach), which photoreceptors are seen?
The green are seen
If you use blue light (470nm bleach), which photoreceptors are seen?
Red and green
Proportion of S cones in different eyes range between
3.9-6.6. Photoreceptors
L and M cones are _________ arranged
Randomly
What does knowing the organization of the 3 cone types provide?
A way to determine developmental mechanisms responsible for the variation and the consequences of that on color vision
The reflectance of individual cones is a dynamic property of the ________
Mosaic
What is the cause of the variation in the photoreceptors?
Due to the disc shedding —> can happen at an abnormal rate
Sensitivity of the cone photoreceptors ________ the intensity of the imaging with __________ ___________ of the illumination beam in the pupil
Decrease, increasing eccentricity
The ability to image cones at a high resolution with AO opened a cruicial window to examine what?
Both normal and abnormal processes in the retina
When the L cones are missing, what happens?
The L-cones are missing and are replaced by M cones
What happens if a person is missing M cones?
There is a patchy loss of M cones throughout —> L and S cones intact and still has good VA
What is achromatopsia?
When there is a complete loss of cone function and color perception
Two parts of the adaptive optics optical system:
- Wavefront sensor or aberrometer
- Adaptive corrector or deformable mirror
Uses for AO scanning Laser ophthalmoscope (SLO)
- Retinal vasculature
- Blood flow tracking
- Capillary map
- Arterioles
- Axial sectioning
- Diabetic retinopathy follow ups
- Ganglion cells
- RPE
AO provides diagnostic “__________” for diabetes, HTN, etc
Biomarkers
AO combined with _________ allows imaging of fine structures of the retinal capillary bed
FA
Quantitative measurements of vascular parameters allows for…
Monitoring of disease progression
Adaptive optics allow for _______ detection and _________ diagnostics of retinal diseases
Earlier, improved
How is the retinal image conveyed to the brain?
Through an array of 17 or more parallel ganglion cell pathways in the primate
Blindness results from what?
The death of ganglion cells
New ways to image ganglion cells at a microscopic spatial scale may lead to what?
Earlier diagnosis and delivery of therapy
Where is the RPE situated?
Immediately behind the photoreceptors and plays several critical roles in maintaining their function
Where is RPE cell damage seen?
Many retinal degenerative diseases: AMD, retinitis pigmentosa, and stargardts disease
AO reflectance imaging makes it possible to view RPE in living eyes where photoreceptors are intact by…
Using the auto-fluorescence properties of lipofuscin in the RPE
Bright regions correlate to areas with what?
Accumulation of lipofuscin within the RPE cells
Dark regions correlate to what?
Nuclei of the RPE cells
Applications AO-OCT
-AMD
-glaucoma
-Diabetic retinopathy
-stem cell treat,ent of degenerative disorders of the retina
