Optic Disc Drusen

From EyeWiki



Optic Disc Drusen
Classification and external resources
ICD-10 H47.3
DiseasesDB 31338


Disease Entity

  • Consist of refractive, hyaline-like calcified nodules located within the optic nerve head
  • Prevalence 0.4-3.7%
  • Males = Females
  • Whites > Blacks
  • >85% bilateral, but asymmetric
  • Familial – Autosomal dominant inheritance


Etiology

Disc drusen are composed of small proteinaceous material that become calcified with advancing age. These deposits can be considered small tumors that develop within the optic nerve head, and may lead to an elevated disc (and therefore pseudopapilledema).  They are bilateral in approximately 70% of cases.  They also may lead to a loss of visual field or, in rare cases, central acuity.

Pathophysiology

Pathogenesis is thought to be due to slowed axoplasmic flow, thus forming calcific excrescences

Diagnosis

Diagnosis is made by clinical examination of the optic nerve head in addition to ancillary imaging studies (see below).  Pseudopapilledema vs. true papilledema must be distinguished. 

History

Patients are usually asymptomatic.  Rarely, they can have transient visual obscurations (approximately 9% of patients).  Visual field loss may also be seen gradually.  If the patient is symptomatic with symptoms of increased intracranial pressure (ICP), the clinician must rule out papilledema. 

Physical examination

If the optic disc drusen are superficial, this can aid in diagnosis during the dilated fundus exam.  The optic nerve usually has a "lumpy-bumpy" appearance. 

Signs

  • Elevated optic disc, with small contour
  • Indistinct and irregular disc margins
  • Anomalous vascular branching pattern (tortousity, optociliary shunt vessels)
  • Drusen seen as round, white/yellow refractile bodies on the surface of the nerve or buried beneath it
  • Buried drusen show elevated disc with scalloped margin with a very small or abscent physiologic cup. 
  • Nasal margin is most common site of drusen
  • Spontaneous venous pulsations often seen
  • Afferent pupillary defect if there is asymmetric nerve involvement
Fundus image of optic disc drusen with "lumpy-bumpy" appearance

Symptoms

  • Asymptomatic (most commonly)
  • Transient visual obscurations

Clinical diagnosis

  • Fundus exam, with signs described above
  • B-Scan (see below)
  • FA / Autofluorescence


Must distinguish True Papilledema from Pseudopapilledema:

Assess the following:

  1. Is the optic disc hyperemic?
    • In true disc edema, there is congestion of the disc microvasculature, with reddish hue of the disc. 
  2. Are there microvascular abnormalities on the surface of the disc?
    • True edema is associated with dilation and telangiectasia of the surface disc capillaries and may be demonstrate flame hemorrhages on or adjacent to the disc.
  3. At what depth in the retina does the blurring of the disc margin originate?
    • In true disc edema, there is obscuration of both the retinal vessels and the disc margin, since the edema is at the level of the disc and peripapillary nerve fiber layer. In contrast, most cases of pseudopapilladema, the blurring usually results from abnormalities that are located deep to the retinal blood vessels, thus, the vessels are clearly visible as they cross the disc margin. Myelinated nerve fibers are an exception to this rule.
  4. Optical Coherence Tomography:
    • Is able to detect early NFL thinning in cases of optic nerve head drusen, and is predictive of visual field loss

Diagnostic procedures

Ancillary testing:

B scan ultrasound optic disc drusen
  1. B scan ultrasound: optic nerve head with ODD is elevated and highly reflective; even on on decreasing the sensitivity of the display, calcified drusen maintains high signal intensity, whereas with papilladema, the signal intensity decreases along with the remainder of the ocular signal
  2. FA: Drusen close enough to disc surface will demonstrate autoflourescence. Early frames will demonstrate focal blockage of fluorescence.  There may also be nodular late staining without leakage from disc surface capillaries. Papilladema in contrast shows early diffuse hyperflourescence, with late leakage overlying and adjacent to the disc.
  3. CT scan: Superior to MRI for detection of drusen: Calcium produces bright signal at junction of the posterior globe and optic nerve on a CT scan.

Differential diagnosis

  • Papilledema
  • Pseudopapilledema
  • Pseudotumor Cerebri
  • Tilted disc
  • Myelinated NFL
  • Crowded disc associated with hyperopia

Management

Pseudopapilledema is not treated, as this is a normal physiologic variant.  The visual prognosis for optic disc drusen is generally good, and patients are observed.  There is currently no effective treatment for patients that have gradual loss of visual fields (some studies have suggested IOP lowering medications). 

Surgery

There is currently no surgical treatment for optic disc drusen.  Laser therapy has been used to stop progression of peripapillary subretinal neovascularization that is threating the macula. 

Complications

Rarely, the following vascular complications may occur, presumably due to a mass effect:

  • Flame disc hemorrhages
  • NAION
  • CRAO
  • Peripapillary neovascular membranes

Additional Resources


References

  1. Davis et al. Optic disc drusen. Seminars in Ophthalmology, 2003, Vol. 18, No. 4, pp. 222–242
  2. Gossman MV.  Pseudopapilledema.  eMedicine.  http://emedicine.medscape.com/article/1217393-overview
  3. Kanski JJ.  Clinical Ophthalmology, 6th edition.