Optic disc drusen
Optic disc drusen (ODD) are globules of protein and calcium that accumulate and harden in the eye's optic disc. Optic nerve drusen usually do not cause symptoms and are never diagnosed unless the optic nerve is examined, but they can cause peripheral vision loss over time.
Definition & Facts
The optic nerve is the connection that carries visual information from the eye to the brain. Optic nerve drusen are abnormal buildups of protein and calcium salts that accumulate in the optic nerve. Drusen are fairly common and occur in about 1-2% of people and many are never diagnosed because they usually do not cause symptoms.
In some cases, these drusen can cause slowly progressing, minimal peripheral vision loss. Very rarely, there is an abrupt loss of part of a patient's peripheral vision or choroidal neovascularization occurs which is when a collection of abnormal blood vessels grow under the retina close to the optic nerve. If these vessels bleed, they can suddenly reduce central vision.
Symptoms & Complaints
Hard drusen are not a symptom of underlying eye disorders, but a large number of soft optic disc drusen can be an early sign of dry age-related macular degeneration. Macular degeneration can cause a range of tell-tale symptoms, including hazy or blurred vision, difficulty adjusting vision from bright light to low light, and a blank or fuzzy spot in the patient's central vision.
In children who have optic disc drusen, the drusen are typically undetectable even through ophthalmoscopy (also known as fundoscopy), although the axons over the disc eventually atrophy and the drusen become easier to detect with age. This can come with some visual field loss toward the end of adolescence or the beginning of adulthood.
Choroidal neovascularization is a potential but rare complication of OOD. These new blood vessels can develop and disrupt vision or cause bleeding under the retina and scarring of the retina. These new blood vessels grow beneath the retina and may penetrate the retina. CNV can leak blood and fluid that damages photoreceptor cells in the eyes and the vessels may disrupt vision.
Most people who have optic disc drusen retain normal central vision, but 70% of patients lose at least some peripheral vision over time. The amount of peripheral vision loss varies from mild to severe. People with OOD may be at a higher risk of developing conditions like central retinal vein occlusion (CRVO) and branch retinal vein occlusion (BRVO).
Optic disc drusen are found in about 1% of adults, but they are found in around 3.4% of people who have a family history of ODD. In up to 75% of cases, the drusen are bilateral, or occurring in both eyes. It's believed that optic disc drusen are inherited, likely due to an genetic inheritance pattern that may be associated with inherited dysplasia or enlargement of the optic disc.
Men and women are affected by drusen at equal rates, but caucasians have been found to be more likely than others to develop them. Some eye conditions have also been associated with drusen, including angioid streaks, Usher syndrome, Noonan syndrome, retinitis pigmentosa, and Alagille syndrome, although the links are still not well understood.
Diagnosis & Tests
Most cases of optic disc drusen are never diagnosed and there is no need for diagnosis as they do not usually cause symptoms. The physician will inquire about the patient's family history of ODD, which is particularly relevant for diagnosing forms of the condition that are inherited. In most cases, drusen are diagnosed during a routine full or dilated eye examination.
Sometimes the margins of the optic nerve can appear blurred by drusen which may make it seem that the nerve is swollen, a condition called papilledema. This is a very serious condition that indicates pressure in the brain is very high (intracranial hypertension). While these conditions can appear similar during an eye exam, ocular ultrasound and other tests can differentiate between the two for an accurate diagnosis. One important reason for an accurate diagnosis of drusen is to prevent unnecessary testing and treatment for pailledema.
Treatment & Therapy
Optic disc drusen are very rarely treated as they do not cause symptoms in most cases and are not dangerous. There is also no standard or proven treatment option for optic disc drusen, although careful monitoring of the patient's visual field is important to detect any progression of peripheral vision loss.
In very rare cases, such as with choroidal neovascularization, laser surgery or another type of therapy may be recommended. Thermal laser treatment is a commonly used treatment for choroidal neovascularization and optic disc drusen with symptoms.
Laser treatment is done on an outpatient basis in a doctor's office and it uses a high-energy, focused laser beam to produce a small burn in the area of the retina that is treated. This destroys abnormal blood vessels and stops further bleeding and growth.
Anti-VEGF (vascular endothelial growth factor) drugs may also block abnormal blood vessel growth in the eye and slow vision loss. Finally, photodynamic therapy (PDT) may be recommended. This treatment uses a combination of light-activated medication called a photosensitizer and a cool laser to target the abnormal blood vessel growth. Performed on an outpatient basis, PDT may require multiple sessions to be effective.
Prevention & Prophylaxis