What is a bad cup to disc ratio?
The average cup to disc ratio is about 0.4, and ratios of 0.7 or greater happen only 2.5% of the time, so cups this big raise our suspicion that glaucoma might already have started (Figure 13). Figure 13: Optic nerve exam. (Left) Drawings of how the doctor estimates glaucoma damage from optic nerve head examination.
Does cup to disc ratio improve?
Clinical improvement in visual fields was correlated with the degree of improvement of cup:disc ratio (P = 0.025). Conclusion: Most patients showing a 40% lowering of IOP after glaucoma surgery show improved optic nerve morphology as measured by the HRT.
What is considered a large optic disc?
Investigators there found the average disc diameter to be 1.5 mm; they classified discs from 1.0 to 1.3 mm as small, from 1.4 to 1.7 mm as medium, and from 1.8 to 2.0 mm as large.
What is Disc at risk?
Classically, the patient has a “disc at risk,” which can often be appreciated by a small cup-to-disk ratio in the unaffected eye. It is believed that this “crowding” of the optic disc makes the optic nerve more vulnerable to ischemic events in high-risk individuals.
What is the cup of the optic disc?
The optic cup is the white, cup-like area in the center of the optic disc. The ratio of the size of the optic cup to the optic disc (cup-to-disc ratio, or C/D) is one measure used in the diagnosis of glaucoma. Different C/Ds can be measured horizontally or vertically in the same patient.
Why does the cup disc ratio increase in glaucoma?
In people with glaucoma damage, because of increased pressure in the eye and/or loss of blood flow to the optic nerve, these nerve fibers begin to die. This causes the cup to become larger in comparison to the optic disc, since the support structure is not there.
What is the healthiest cup-to-disc ratio?
The normal cup-to-disc ratio is less than 0.5. A large cup-to-disc ratio may imply glaucoma or other pathology. However, cupping by itself is not indicative of glaucoma.
What causes large optic disc?
What is a crowded disc?
Crowded Disc also known as CFD is the result of a normal number of retinal axons passing through a small posterior scleral foramen. The resulting appearance is that of a densely packed or crowded optic nerve head as the axons exit the globe.