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Optic disc drusenSaturday 6 April 2013 00:01 CEST
Optic nerve drusen is a sneaky condition: it can develop for years without symptoms, sometimes is hard to diagnose and can cause a major vision complications.
First, the condition is known under several different terms: optic disc drusen (ODD), optic nerve head drusen (ONHD), pseudopapilledema, pseudoneuritis, anomalous discs, and disc hyaline bodies, or buried disc drusen.
So, patients sometimes have a hard time knowing the right condition, especially if they change the doctor and he changes the description of the condition. We'll use the most common term optic disc drusen.
Optic disc drusen is a condition when small deposits of protein build up in the optic disc. Those proteins tend to calcify and that calcification cause vision problems, from minor to major ones. While it is true that that condition affects about one percent of the people, the problem is that symptoms are very rare which makes it difficult to diagnose. In a small number of cases it can lead to a complete vision loss.
Regarding patient's age, optic disc drusen are almost never visible at birth and are very rare in children. That condition develops slowly through years and, as a rule of thumb, it appears at 12 years of age when the calcification becomes visible.
A big problem with optic nerve drusen is its progressive nature. Although a small number of patients will lose sight, ODD will cause other very serious problems. Blind spots, bad image in the main line of vision, flickering, greying out of vision, and visual field abnormalities can make daily activities very hard and sometimes impossible. Over time, some 70% of patients lose peripheral vision but that loss varies from patient to patient.
The bad news is that optic nerve drusen may be present without symptoms which mean that it goes unnoticed while it grows. It is often detected at a regular eye examination and patient may have a slight vision problem but not so big to see his doctor.
When a problem occur, such as a blind spot in the vision field, that means that the condition has become a major problem but even then it's sometimes hard to confirm drusen. To do that, the doctor will use visual fields test, an ultrasound and CT scan, and with all that data he is able to diagnose the problem.
How to diagnose ODD? First, the doctor must be sure that it really is optic disc drusen and not disc enema which needs treatment immediately. Ultrasound is useful in diagnosis because the calcified hyaline bodies have the high reflectivity and they are clearly visible on B-scan ultrasonography. A battery of tests is also performed, such as contrast sensitivity test, colour vision testing, and threshold visual fields.
We are not sure what the cause is for ODD. Sometimes it is family-related but genes are not directly related to it. It usually develops in both eyes but we don't know why and we don't know why it can, in rare cases, develop in just one eye.
As of now, there is no way to prevent optic disc drusen and we can only follow the development. The patient is examined regularly, drops may help in some cases, they decrease the pressure on the optic disc, and sometimes medicine in a form of an injection is necessary. In more serious cases, although a very rare ones, laser therapy may also help.
C. A. V. Nogueira, MD