Optic Cup Shape and Depth
Overview
The normal shape of the optic disc is slightly vertically oval, whereas the shape of the optic cup (the excavation in the optic disc) is horizontally oval.1 Therefore, the normal neuroretinal rim is broadest in the inferior and superior disc regions.
Pearls
Optic cup shape:
Normal eyes: the horizontal diameter of the optic cup is about 8% greater than the vertical diameter in over 93% of normal eyes.1
The horizontal optic cup-disc ratio (CDR) is greater than the vertical CDR in most normal eyes (i.e., the quotient of the horizontal to vertical CDR is usually higher than 1.0).
In early to moderate stages of glaucoma, the vertical CDR increases faster than the horizontal CDR, leading to a decrease in the quotient of horizontal to vertical CDR to values lower than 1.0.
Optic cup depth:
Normal eyes: cup depth is somewhat proportional to the cup area (i.e., the larger the optic cup, the deeper the cup).
Glaucoma eyes:
Cup depth deepens, depending on the type of glaucoma and level of intraocular pressure (IOP).
The optic cup depth is usually greatest in glaucomatous eyes with elevated intraocular pressures.
The maximum cup depth, as well as the cup area, cup volume, and CDR area is greater in glaucomatous eyes than nonglaucomatous eyes in large- and average-size optic nerves.2,3
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
