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View Full Version : Volk Lens Optom use optic disk,naevi,macula video



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07-24-2012, 09:19 PM
Keep the room very dark and control the patient gaze to a target.
When learning the technique - don't dilate. Its difficult - but will teach you to hold the Volk very still - thats the big secret on good technique! With mydriasis all your new skill will fall into place and it will be a breeze.

You can sometimes get a stereo view if you pull yr eyes away from the slitlamp eye pieces slightly.

For macula viewing.
! get the patient to press head into the slitlamp.
Couple the light and viewing system and set them at 90 degrees. Magnification 16 minimum and slit 1mm narrow medium brightness.
They look into the slit lamp light and you move the slit lamp back and forwards until the macula is seen in the middle of the picture.
Open the slit slightly and have a good look! You may need to tilt the volk to remove reflections.
The tip is to use small lights!
We tend to carefully draw (in colour) the disk and features prior to assessment. This gives us an audit trail.

Dealing with measuring the nerve fiber layer.
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 doesn't 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.

The neural rim is illuminated by the lamina - whcih is chalky, and the rim is coloured by the vascular micro supply. The neurons are like a veil and can be wispy: 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!

a crib aiding drawing of the optic disk in a standard way (help from the prof. - thanks) can be downloaded here in two parts-feel free
https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid...
https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid...

enjoy
SM
we welcome comments to aid students

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