How to examine an optic disc
There are several described methods for examining the optic disc. Using a structured approach is highly recommended.
One method is to use a 3R technique : Ring, Rim and Risk factors.
Firstly identify the scleral Ring. This defines the outer limit of the optic disc and is fundamental in understanding optic disc examination in glaucoma. Without identifying the scleral ring it becomes impossible place the other optic disc structures accurately.
Next the Rim of neuroretinal tissue inside the scleral ring is identified. Look all the way around the scleral ring and note the width and contour of the neuroretinal rim through 360 degrees. The angle of the nerve fibres as they pass over the scleral ring can be anywhere between a very gentle slope down to the lamina cribrosa to vertical, and even beyond vertical in an undermined optic disc edge. Different segments of the neuroretinal rim can also have different colours and translucency due to the different cell types making up the fibres, particularly the papillomacular bundle (for examples of this see here).
Next look around the optic disc circumference once more, this time looking specifically for other optic disc signs signifying Risk factors for the disease or its progression. These are often missed unless carefully looked for.
Optic disc size also needs to be identified. The area of a circle (πr2) changes considerably more than a change in radius, and different sized discs have very different appearances. Look through the collection of normal discs for some examples of these.