omi term 2 confocal lens Flashcards
what is confocal principle
a single point of specimen can be illuminated by a point light source while simultaneously being imaged by a camera in the same plane
wha does confocal principle rely on
relies on out of focus that is rejected by the system
waht does it result in
high res image with small fov due to single point of illumination and detection
how to expand fov
to expand field of view instrument needs to instantaneously illuminate and image region of specimen
this is done by scanning tissue with lots of spots of light which are reconstructed to create usable fov with high res and mag
how does confocal principle work
light source laser is shone through oinhole aperature and through dichroic mirror (beam splitter) this then focused through lens onto specimen (part of eye)
refelected rays reflected off dicroic mirror to detector through another pinhole aperature. this means only information from focal plane(where light focussed) is detected.
confocal laser scanning tomography
utilise confocal principle to take images of human tissues at diff depths
this is done by changing how focus comes in and allows 3d view of focus
tomography is slice images which build up cross sections images and is useful for imaging tissue in depth
waht is the brightest point
the brightest point is the most accurate depth for that particular point
how to you find profile maximum
profile maximum is brightest point
- series of optical section images are scanned through retina
- each pixel series has varying brightness
- determination of postion of profile maximum gives height of each pixel
- computer systems build up image based on data obtained either 3d or 2d
typical depth is 0.5-4mm in 0.5 mm steps
A-confocal laser scanning tomography used for glaucoma
used for checking health of optic nerve head
introcular pressure increases which puts pressure on the optic nerve head and this damges nerve fibres and causes abnormal cupping. 3d imaging can evidence this easily and be compared over time
how can images be analysed in confocal laser scanning tomography
32 2d images are scanned in sequence from anterior to posterior
can be viewed as a movie to analyse excessive eye movements
images combine to make one 3d topogrophic image which can be analysed using reflectance information
what is moorfields regression analysis
it compares rim area of imaged optic nerve head to a normal database
it then makes prection of normality of the disc as a whole and in individual sectors
confocal microscopy
useful for checking health of cornea
patients with diabetes can exhibit cellular change
due to rection in desnity of based epithelial cells and thicker nerves in stroma
