OPTIC DISC DRUSEN
The optic nerve is the transmission cable that connects the retina of the eye to the brain. Anatomically, the optic nerve consists of over one million retinal cells called ganglion cell axons. The face of the optic nerve that is seen during examination of the central retina is called the optic disc. This face of the optic nerve or disc is void of the seeing elements of the retina, specifically the rod and cone cells, and as a result, the optic nerve is naturally a non-seeing part of the retina. A primary artery and vein enter into the eye through the middle of the optic nerve and branch out like branches on a tree to supply nutrition to the surface of the retina.
Optic disc drusen is generally a familial condition observed in both sexes, at any age and most commonly in Caucasions. It occurs in approximately 1% of the population and a much higher incidence in individuals with a documented family history of the condition. Disc drusen are considered to be globules of chemicals called microproteins and acid mucopolysaccharides that progressively calcify in the optic disc. In most cases, they are considered to be congenital remnants of degenerated ganglion cells that comprise the optic nerve. Optic disc drusen may or may not be associated with varied degrees of vision loss and can present a risk of blindness. Typically, no symptoms are observed by patients and the finding is discovered only by routine ocular examination. It is common for patients with this condition to demonstrate a field of vision loss that may progress slowly over time.
Diagnosis is comprised of careful examination of the central retina and the optic nerve, computer-assisted visual field examination, visual acuity comparison over time, color vision testing and intra-ocular pressure measurements. When caution exists, B-scan ultrasound testing and computer-assisted tomography are commonly recommended. Even with ultrasound technology, optic disc drusen are more difficult to observe in children, slowly becoming more visible by mid-teens. It is important to consider optic nerve drusen in the differential diagnosis of other optic nerve conditions such as papilledema and optic nerve swelling.
Although this condition is generally considered a benign condition, it can lead to modest visual compromise. Unfortunately, there is no widely accepted treatment for patients with vision or field loss resulting from optic disc drusen. Some treatments involve the use of intra-ocular pressure lowering eye drops to theoretically relieve mechanical pressure on the ganglion fibers of the optic nerve. Caution is the rule with this condition since the risk of optic nerve damage is generally progressive and insidious. Once diagnosed, it has been documented that 75% of patients will eventually develop some peripheral visual field loss.