This case report details the presentation, diagnosis, and management of optic nerve head drusen (ONHD) in a young male undergoing military recruit training. Understanding the differential diagnosis of ONHD is crucial in primary eye care to ensure accurate diagnosis and appropriate patient management, preventing misdiagnosis with conditions that may require urgent intervention.
A 19-year-old Caucasian male, a recruit at the Marine Corps Recruit Depot in San Diego, presented for an updated spectacle prescription and boot camp glasses. His primary complaint was a noticeable decrease in distance vision with his current spectacles, particularly in low-light conditions. He reported no other visual or ocular symptoms.
His last comprehensive eye examination was six months prior, at which time his best-corrected visual acuity (BCVA) was 20/20 in the right eye (OD) and 20/25 in the left eye (OS). His previous spectacle prescription was -5.25 -0.50 x 010 OD and -6.00 -1.25 x 180 OS. The patient’s ocular and medical history were unremarkable, with no history of ocular trauma, surgery, or infection. His family medical history was also non-contributory. He reported no known drug allergies and was not currently taking any medications.
Diagnostic Data
Upon examination, the patient’s BCVA at distance and near was 20/20 OD and 20/25-3 OS with a refined spectacle prescription of -5.75 -0.75 x 012 OD and -6.25 -1.25 x 178 OS. Pupillary reactions were normal: round, equal, reactive to light, and without a relative afferent pupillary defect (RAPD). Confrontation visual field testing revealed restrictions in the inferior nasal quadrant of the right eye, and in both the superior and inferior nasal quadrants of the left eye. Extraocular muscle movements were full, unrestricted, and painless. Intraocular pressure (IOP) measured 15mm Hg OD and 16mm Hg OS, both within normal limits. All other preliminary findings, including anterior segment examination with slit lamp, were unremarkable, revealing clear lids, conjunctiva, cornea, and lens bilaterally. The irides were hazel in color without noted defects.
Dilated fundus examination revealed optic nerve head (ONH) elevation bilaterally with cup-to-disc ratios of less than 0.1/0.1 in both eyes, suggesting minimal physiological cupping. Both ONHs were well-defined to 360 degrees, appeared pale in coloration, and without hemorrhages. Notably, visible drusen were present in both optic nerves, appearing as bright, reflective, and lumpy calcifications. The macula and peripheral retina were normal in both eyes.
Diagnosis
Based on the initial clinical findings, a preliminary diagnosis of optic nerve head drusen bilaterally was made. Myopia and astigmatism in both eyes were also diagnosed, consistent with the refractive error.
Treatment and Follow-Up
To further investigate the suspected ONHD and rule out other conditions in the differential diagnosis, B-scan ultrasonography, Humphrey Field Analyzer (HFA) 24-2 SITA-Standard visual field test, and digital fundus photography of both eyes were scheduled. The patient was instructed to return to the clinic for a follow-up evaluation after these tests were completed.
Two days later, the patient returned for his follow-up appointment. B-scan ultrasonography confirmed high reflectivity at the ONH in both eyes, consistent with drusen. The Humphrey 24-2 SITA-Standard Test, performed reliably for both eyes using a size III stimulus, demonstrated visual field defects that correlated with the location of the ONHD. During this visit, Ishihara color vision testing was also administered, revealing mild color vision deficiency with scores of 11/15 OD and 10/15 OS.
The final diagnosis was optic nerve head drusen with secondary visual field defects in both eyes.
| Humphrey Visual Field Test Results. The Humphrey 24-2 SITA-Standard test results demonstrate visual field defects consistent with optic nerve head drusen in both eyes (O.D. and O.S. respectively), highlighting the importance of visual field testing in the diagnostic process. |
The patient was thoroughly educated about his condition, with emphasis on the benign nature of ONHD in most cases and the absence of treatment unless hemorrhagic complications arise. He was instructed on self-monitoring his vision weekly in each eye using an Amsler grid and to seek immediate professional care if any visual changes were noted. Furthermore, he was advised to continue routine eye examinations every six to 12 months for monitoring. Unfortunately, due to the diagnosis of ONHD, the patient did not meet the military’s physical standards and was deemed ineligible for service.
Discussion
Optic nerve head drusen (ONHD), also known by various terms including congenitally elevated anomalous discs, pseudopapilledema, pseudo-neuritis, buried disc drusen, and disc hyaline bodies, are typically located in the pre-laminar portion of the optic nerve. Bilateral involvement is common, occurring in approximately 70% of cases. ONHD affects about 1% of the general population, with a higher prevalence in Caucasian individuals.
The exact pathogenesis of ONHD remains incompletely understood. The prevailing theory suggests that a constricted scleral canal opening can lead to impaired axoplasmic flow within the optic nerve. This stasis may result in abnormal axonal metabolism and subsequent mitochondrial calcifications. These calcifications eventually protrude into the extracellular space, manifesting clinically as drusen.
Within the optic nerve, these hyaline bodies are confined to the region anterior to the lamina cribrosa. Their presence can cause compression and compromise of the nerve fibers and vascular supply, potentially leading to visual field defects and, less commonly, disc hemorrhages. Visual field loss is a significant concern, reported in 64% to 87% of patients with ONHD, with progressive defects occurring in up to 22% of these individuals.
Many patients with ONHD are asymptomatic, and the condition is often discovered incidentally during routine eye examinations. However, some patients may present with decreased visual acuity or visual field defects, typically arcuate, sectoral, or altitudinal scotomas. An afferent pupillary defect might be detectable if the condition is severe and asymmetric. Rarely, ONHD can be associated with symptoms such as migraine headaches, seizures, and transient visual disturbances.
Ophthalmoscopically, visible ONHD appear as glistening, globular, or spherical bodies that project forward, obscuring the optic nerve head margins and making them appear irregular and indistinct. While drusen are most commonly observed at the nasal disc margin, they can occur in any part of the optic nerve head. In younger individuals, the disc elevation may be more pronounced, and the drusen are often less calcified, making them less readily visible during ophthalmoscopy. ONHD can mimic pseudopapilledema due to the disc elevation and lack of physiological cupping. As patients age into early adulthood, the optic disc may develop a yellowish hue, and the refractile drusen may become more superficial. The increasing proximity of the drusen to the disc surface and progressive thinning of the nerve fiber layer contribute to their enhanced visibility. When illuminated with red-free light, these refractile bodies exhibit autofluorescence (glow). Ultrasonography is a valuable ancillary test for detecting ONHD, as drusen demonstrate high reflectivity even at low gain settings.
| B-scan Ultrasonography Findings. B-scan ultrasonography of this patient revealed high reflectivity at the optic nerve head in both eyes, a key diagnostic indicator for optic nerve head drusen and a valuable tool in differentiating it from other conditions presenting with optic disc edema. |
Although typically considered a benign condition, ONHD can lead to visual compromise in some individuals. Crucially, several other conditions can mimic ONHD, emphasizing the importance of differential diagnosis in primary eye care. The differential diagnosis of optic nerve head elevation includes:
- Papillitis: Inflammation of the optic nerve head, often associated with pain and acute vision loss.
- Malignant Hypertensive Retinopathy: Optic disc edema secondary to severe hypertension.
- Central Retinal Vein Occlusion (CRVO): Vascular occlusion leading to optic disc swelling and retinal hemorrhages.
- Ischemic Optic Neuropathy (ION): Disruption of blood flow to the optic nerve, causing sudden vision loss and disc edema.
- Optic Disc Vasculitis: Inflammation of the blood vessels of the optic nerve head.
- Infiltration of the Optic Disc: Conditions such as tumors or infections that infiltrate the optic nerve.
- Leber’s Hereditary Optic Neuropathy (LHON): Genetic condition causing bilateral optic neuropathy.
- Orbital Optic Nerve Tumors: Tumors compressing the optic nerve in the orbit.
- Diabetic Papillitis: Optic disc edema in the context of diabetes.
- Graves’ Ophthalmopathy: Optic neuropathy associated with thyroid eye disease.
Effective management of ONHD relies on prompt and accurate diagnosis, primarily through a comprehensive eye examination and appropriate ancillary testing. Ultrasonography is arguably the most critical ancillary test in adults suspected of having ONHD due to its high sensitivity in detecting calcified drusen. However, it may be less reliable in children as drusen are less calcified in younger age groups. A thorough evaluation of optic nerve function is essential, encompassing Snellen visual acuity, contrast sensitivity, color vision testing, and visual field assessment. Photodocumentation of the optic nerve head is recommended to monitor for potential progression over time.
Currently, there is no direct treatment or preventative measure for ONHD unless hemorrhagic complications occur. Hemorrhages associated with ONHD can be located in various retinal layers (retrovitreal, preretinal, intraretinal, or subretinal). Treatment for hemorrhages depends on their location and severity and may include natural resorption, laser photocoagulation, vitrectomy, or scleral buckling.
Patient education is paramount, emphasizing the necessity of regular annual eye exams to monitor for any progression or complications. Patients should be instructed to self-monitor their vision periodically and to promptly report any new visual disturbances. Routine follow-up for typical ONHD cases is generally recommended every six to 12 months to monitor for visual field changes or other potential complications.
References
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- Mustonen E. Pseudopapilledema with and without verified optic disc drusen. A clinical analysis II: visual fields. Acta Ophthalmol (Copenh) 1983 Dec;61(6):1057-66.
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