While papilledema is disc edema secondary to increased intracranial pressure, pseudopapilledema is apparent optic disc swelling that simulates some features of papilledema but is secondary to an underlying, usually benign, process.
Most patients with pseudopapilledema lack visual symptoms, not unlike patients with true papilledema. In pseudopapilledema, no obscuration of the peripapillary vessels by the nerve fiber layer edema occurs. Pseudopapilledema may be unilateral or bilateral, but almost all cases of papilledema are bilateral. An extensive workup is usually unnecessary, and an experienced general ophthalmologist or neuro-ophthalmologist can correctly diagnose pseudopapilledema via an ophthalmoscopic examination.
There are a multitude of causes of true disc swelling and other disorders that may mimic disc swelling, some of which represent a morphologic variant of normal.
The optic nerve may be elevated, simply because the optic nerve enters the eye at an extremely oblique angle (tilted disc), giving a portion a more elevated aspect (usually nasally).
The optic cup may be smaller than usual in a hyperopic eye. This causes crowding of the axons, which become heaped-up and elevated as they leave the eye.
The nerve fiber layer, which is normally translucent, may be partially myelinated. This can lead to the appearance of a large cup with blurring of the disc margins.
A subtler (but common) cause of pseudopapilledema is buried disc drusen. This article focuses primarily on optic disc drusen. Disc drusen are composed of small conglomerates of mucopolysaccharides and proteinaceous material that become calcified with advancing age. These small tumors develop within the substance of the nerve tissue (bilateral in 70% of cases) and can lead to an elevated disc; they also may lead to a loss of visual field or, in rare cases, central acuity.  They may be inherited as an autosomal trait with irregular penetrance. Disc drusen may be associated with retinitis pigmentosa and pseudoxanthoma elasticum.
Rarely, pseudopapilledema may be caused by remnants of the congenital hyaloid system and localized gliosis. An experienced observer can almost always distinguish these entities.
Primary and metastatic optic nerve tumors can result in a swollen disc but ordinarily only when intraorbital disease is present and is seldom unaccompanied by other signs and symptoms of orbital disease, such as proptosis and motility disturbance.
A host of inflammatory, infiltrative, and infectious conditions can cause true disc edema, which may be confused with true papilledema due to elevated intracranial pressure. In these cases, the swelling is usually unilateral (with the major exception of hypertensive crisis). Examples of infectious causes include syphilis, Lyme disease, and cat-scratch disease. Examples of inflammatory disorders that cause true disc edema include anterior ischemic optic neuropathy, optic neuritis, diabetes, sarcoidosis, and leukemic infiltration. These conditions should be seen as causes of papillitis, which is a distinct entity apart from pseudopapilledema.
This condition affects 2-5% of the population. It is clinically apparent in only about 0.35% of individuals.
Optic disc drusen may be associated with progressive visual field loss, more rarely loss of central acuity, and, in very rare cases, blindness. However, congenital causes are not associated with any progressive visual loss.
Disc drusen are more common in whites and are believed to be less common in African Americans.
No sexual predilection exists.
The condition occurs at any age, although disc drusen tend to enlarge with time and become more prominent with advancing age.