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Old Prof. Palfi (graduated: 1945) talks about how to look at the optic disk. Thanks grandad. :-)
you can download crib-guides for drawing and analyzing the optic disk in two parts here:
https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid...
https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid...
Deals with measuring the nerve fiber layer.
We tend to carefully draw (in colour) the disk and features prior to assessment. This gives us an audit trail.
Any vessels that kink sideways should rise suspicion of neural layer in between.
Thicknesses are conveniently measured by reference to the vessels that cross the disk rim: a veinule averages 140 microns and an arteriole 115 microns. Vertical measurements are important as you are dealing with a 3 dimensional neural layer that sinks vertically. All vessels should be covered by wispy nerve fibers.
A 'cup' is a depression that goes lower than the retinal pigment layer.
A cup that seems smaller when you narrow your slit - is actually a smaller cup but with fainter neural rim.
A cup that doesnot seem smaller with a narrow slit - is that genuine size.
A cup that seems to get larger when you narrow the slit - is actually larger cup!
Most people underestimate the Cd and cup size!
Watch out for the vids on tilted disks we are making at the moment.
Tilted disks come in all shapes and sizes: most are associated with myopia and astigmatism.
They may give a field defect.
Most healthy tilted disks are symmetric about an axis,
Often have PPA beta. They may be very difficult to analyze - but will not change if they are healthy. If not sure - review again in six months.
Healthy tilted disks: all vessels crossing the disk margin will be covered by the neuro layer like a slimy,shiny layer. A red-free filter is ESSENTIAL for fine detail and compliments white light.
The neural rim is illuminated by the lamina - which is chalky, and the rim is coloured by the vascular micro supply. The neurons are like a veil and can be whispy: so look for the neuron rim carefully. You can never get the slit narrow enough to bring out the finest detail! I use a 66ds lens and 25x mag as standard and am always fiddling with the brightness and lit width and length all the time until my drawing is complete. In the glaucomas and optic atrophy - you are looking for neural loss. Disk drusen can mimic disk hemorrhages: both can give field defects-but only one means pathology!
enjoy
Prof. A Palfi
we welcome comments to aid students
Please look at Prof. Adel Shafik's glaucoma disc assessment vid's = they are very helpful for students:
http://www.youtube.com/watch?v=rlui8PZ2wC8&feature=related
He is a very well respected expert in this field and a brilliant educator.
Also please look here for more help:
http://www.optic-disc.org/
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Optic Disc Tips 1 by Volk Bio:assessmentby MsPalfi8,005 views
Well done old chap - very good!
Brownlong 2 months ago