Pt: 36 yo Caucasian male
Chief Complaint: blurry vision at distance (OU)
History of Present Illness: 36 yo male presents to the clinic with blurry vision at distance. Patient reports losing his glasses at a recent visit to the hospital. Pt notices that occassionally his vision will blur more than usual or momentarily disappear.
Ocular History: No past ocular surgery or trauma.
Medical History: Patient was recently hospitalized for car accident.
Medications: None
Allergies: Rifampin
Family History: No significant family history.
Social History: Patient is currently unemployed, but enjoys photography as a hobby. He does not smoke or drink.
Ocular Examination:
- BCVA: OD -- 20/20; OS -- 20/20-1
- Motility: SAFE OU
- Intraocular pressure: 14 mm Hg OU
- Pupils: Equally reactive, -RAPD
- Anterior Segment: Normal OU
- Dilated Fundus Exam (DFE):
- OD: disc had "lumpy, bumpy" appearance, obscuring the margins of the disc; C/D appeared small: 0.15 H/V
- OS: disc had one waxy, pearl-like circular lesion in inferior margin at 7 o'clock; C/D appeared small: 0.15 H/V
- Normal macula, vessels and periphery OU
- Humphrey Visual Fields (C-76): Superior defects OU
Figure 1A: Numerous round, yellow elevations visible in optic nerve head, OD
Figure 1B: One waxy, pearl-like lesion in inferior margin of optic disc, OS
Discussion:
Optic disc drusen are composed of calcific material that accumulate anterior to the lamina cribosa in the optic nerve head. Although there is no known cause for these accumulations, some believe these depositions are caused by axonal degeneration of the optic nerve or axoplasmic transport stasis due to congenitally crowded optic nerve heads. Clinically, they are present in 0.3% of population and are often bilateral. They are more common among Caucasians and are believed to be inherited autosomal dominant with incomplete penetrance.
There are two types of ONHD: buried and exposed (as in this patient). Buried drusen may be difficult to detect and often mimic papilloedema. Signs suggesting disc drusen are elevated disc with scalloped margin without a physiologic cup, hyperaemia is absent and surface vessels are not obscured, despite disc elevation, and anomalous vascular patterns such as early branching. Drusen generally emerge during the early teenage years and appear as waxy, pearl-like irregularities that transilluminate with slit lamp beam.
Diagnosis:
Patients with ONHD are usually asymptomatic; therefore, there is a high rate of incidental discovery. The first symptoms are peripheral vision abnormalities or transient visual obscurations, such as flickering or 'graying out.' Patients do not generally have problems with central vision because central visual acuity is generally spared.
Complications:
Complications are rare but include juxtapapillary CNV, disc neovascularization, central retinal arterial and venous occlusion: progressive but limited loss of visual field with a nerve fiber bundle pattern may occur.
Imaging:
Imaging may be necessary for the definitive diagnosis of disc drusen, particularly when buried. Several imaging techniques to diagnose drusen are: fluorescein angiography, ultrasound (most readily available and reliable method), CT scan.
Treatment:
No definitive treatment currently exists for optic disc drusen. Patients diagnosed with ONHD should be monitored with annual visual field exams, optic nerve fiber analysis and repeated intraocular pressure measurements. If visual field loss occurs, consider using medications to lower intraocular pressure.
Epidemiology:
- 0.3% of population
- Mainly Caucasians
Signs:
- 75-85% bilateral
- Yellowish depositions with raised optic nerve head
- May resemble papilloedema
Symptoms:
- Usually asymptomatic
- Visual Field Defects
- Transient visual obscurations (up to 8.6%)
Treatment:
- No definitive therapy available
- Intraocular pressure with medication
- Laser photocoagulation to choroidal neovascularization (if central VA threatened)
References:
Optic Nerve Drusen Visual Field Loss. University of Iowa, Health Care. http://webeye.ophth.uiowa.edu/eyeforum/cases/72-Optic-Nerve-Drusen-Visual-Field-Loss.htm
Clinical Ophthalmology: A Systematic Approach. Kanski, Jack J. Sixth Edition. Butterworth Heinemann Elsevier. 2008.
