Glaucoma is a serious eye condition which can lead to blindness if left untreated. When assessing an optic disc for Glaucoma, there are many subtle characteristics which need to be examined. There are a number of ways to examine the optic disc. In patients presenting with Glaucoma, as a result of increased pressure within the eye and/or loss of blood flow to the optic nerve, the retinal nerve fibers that bundle together within the optic nerve begin to die, this causes the optic cup to become larger when compared to the optic disc. For example, there is the "Three C's" rule - The cup, colour and contour.
The Contour -
The borders of the optic disc should be clear and well-defined. If the OD is not clear and well-defined, it may be swollen and as a result Papilledema is a concern. Papilledema is is OD swelling secondary to raised Intracranial pressure, and can be a sign of a serious medical condition such as a brain tumour or hemorrhage. If Papilledema is present, the patient affected requires immediate medical attention. When severe papilledema is present, small red dots from bleeding and spotty colour changes on the retina may be seen, this is a result of accumulated debris or from damaged retinal cells.
The Colour -
Typically, the colour of the OD looks orange/pink with a pale center. It's orange/pink appearance represents healthy neuro-retinal tissue. If an OD appears pale, there are a number of pathological reasons for this. An example is Optic Atrophy, this condition refers to death of the retinal ganglion cell axons that make up the optic disc which results in a pale optic disc on a fundus image.
The Cup -
The OD has an orange/pink rim with a pale center. The pale center is known as the optic cup. The vertical size of the optic cup can be determined in relation to the OD as a whole and presented as a "cup to disc ratio". A cup to disc ratio of 0.3 (I.E the cup occupies 1/3 of the height of the entire OD) is typically considered a normal optic cup to optic disc ratio. An increased cup to disc ratio may indicate a decrease in the number of healthy neuro-retinal tissue and as a result, glaucomatous change. The optic disc is the location where ganglion cell axons leave the eye to form the optic nerve. A C/D ratio greater than six-tenths is generally considered to be suspicious for Glaucoma.
The most important characteristics of the glaucomatous process are changes that occur in the optic nerve, this is why it is very important to be familiar with the characteristic signs of glaucoma in the optic disc.
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