A 19-year-old Caucasian male, undergoing recruit training at the Marine Corps Recruit Depot in San Diego, presented for an updated spectacle prescription and to obtain boot camp glasses. He reported a decline in his distance vision with his current glasses, particularly at night. No other visual complaints were noted.
The patient’s previous eye examination occurred six months prior. At that time, his best-corrected visual acuity was 20/20 in the right eye (O.D.) and 20/25 in the left eye (O.S.), with a spectacle prescription of -5.25 -0.50 x 010 O.D. and -6.00 -1.25 x 180 O.S. His ocular and medical history were unremarkable, with no history of ocular trauma, surgery, or infection. His family medical history was also unremarkable. He reported no known drug allergies and was not currently taking any medications.
Diagnostic Findings and Initial Assessment
Upon examination, the patient’s best-corrected visual acuity at distance and near was measured at 20/20 O.D. and 20/25-3 O.S. with a refined spectacle prescription of -5.75 -0.75 x 012 and -6.25 -1.25 x 178, respectively. Pupillary responses 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 and painless. Intraocular pressure (IOP) measured 15mm Hg O.D. and 16mm Hg O.S. All other preliminary findings were within normal limits.
Slit lamp biomicroscopy showed clear eyelids, conjunctiva, cornea, and lens in both eyes. The irides were hazel in color and without any observed 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. The ONH margins were distinct to 360 degrees, but 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.
Funduscopic view illustrating the typical glistening appearance of optic nerve head drusen, crucial for initial differential diagnosis in primary eye care.
Differential Diagnosis in Primary Eye Care
In primary eye care, the presentation of optic nerve head elevation necessitates a comprehensive differential diagnosis. While our initial findings pointed towards optic nerve head drusen (ONHD), it is crucial to consider other conditions that can mimic this presentation. This process is essential to ensure accurate diagnosis and appropriate patient management, aligning with the principles outlined in resources such as “Differential Diagnosis in Primary Eye Care” by Bezan and colleagues, although a direct “Differential Diagnosis In Primary Eye Care Bezan Pdf” was not explicitly utilized in this case, the principles of systematic differential diagnosis are paramount.
Conditions in the differential diagnosis of ONH elevation include:
- Papillitis: Inflammation of the optic nerve head, often associated with pain and vision loss, which was not evident in this asymptomatic patient.
- Pseudopapilledema: Apparent optic disc edema without true swelling, which ONHD can often resemble.
- Malignant Hypertensive Retinopathy: Optic disc swelling due to severe hypertension, typically accompanied by other retinal signs of hypertensive damage. Patient history did not suggest hypertension.
- Central Retinal Vein Occlusion (CRVO): Usually presents with sudden vision loss, retinal hemorrhages, and optic disc edema. The patient’s presentation was not consistent with CRVO.
- Ischemic Optic Neuropathy (ION): Can cause optic disc edema and visual field defects, often with sudden onset vision loss. Again, the patient’s history was not typical for ION.
- Optic Disc Vasculitis: Inflammation of blood vessels of the optic disc, a less common cause of optic disc edema.
- Infiltration of the Optic Disc: Infiltrative processes such as tumors or leukemia can cause disc elevation, though usually with other systemic signs.
- Leber’s Hereditary Optic Neuropathy (LHON): A genetic condition causing optic nerve dysfunction, typically with more acute and severe vision loss.
- Orbital Optic Nerve Tumors: Tumors compressing the optic nerve can cause disc edema, but often with proptosis or other orbital signs.
- Diabetic Papillitis: Optic disc edema in diabetic patients, though typically associated with other diabetic retinopathy findings.
- Graves’ Ophthalmopathy: Optic neuropathy associated with thyroid eye disease, often with other signs of Graves’ disease.
Considering this broad differential, ancillary testing is crucial to refine the diagnosis.
Confirmatory Diagnostic Testing and Refinement of Diagnosis
To further investigate the preliminary diagnosis of ONHD and to differentiate it from other conditions in the differential, we ordered B-scan ultrasonography, Humphrey 24-2 SITA-Standard visual field test, and digital photography of both optic nerves.
The patient returned two days later for a follow-up evaluation after completing these tests. B-scan ultrasonography revealed high reflectivity at the ONH in both eyes, a characteristic finding in optic nerve head drusen due to their calcified nature.
B-scan ultrasonography demonstrating the hyper-reflective nature of optic nerve head drusen, a key diagnostic indicator in differentiating ONHD from other causes of optic disc elevation.
The Humphrey 24-2 SITA-Standard visual field test, performed with a size III stimulus, was reliable for both eyes and demonstrated visual field defects consistent with the expected location of ONHD. These defects corresponded to the areas of nerve fiber layer compromise due to the drusen. At this visit, we also administered a color vision test using Ishihara color plates, which revealed mild color vision deficiencies with scores of 11/15 O.D. and 10/15 O.S.
Based on these findings, we refined the diagnosis to optic nerve head drusen with secondary visual field defects in both eyes. The visual field defects corroborated the structural findings of ONHD and helped to rule out other conditions that might present with different patterns of visual field loss.
Management, Patient Education, and Prognosis
We thoroughly explained the nature of ONHD to the patient, emphasizing that it is a benign condition in most cases, although it can lead to visual field defects and, rarely, other complications. We informed him that there is no direct treatment for ONHD itself unless hemorrhagic complications occur. Management primarily involves monitoring for progression and managing any associated complications.
We provided the patient with an Amsler grid and instructed him on how to self-monitor his vision weekly in each eye, advising him to seek immediate professional care if he noticed any new visual distortions or defects. We also scheduled routine follow-up care every six to 12 months to monitor for any progression of visual field loss or other changes.
Unfortunately, due to the visual field defects associated with his ONHD, the patient did not meet the military physical standards for service and was deemed ineligible to continue his military career. This highlights a significant real-world consequence of ONHD in certain professions and emphasizes the importance of early and accurate diagnosis in primary eye care settings.
Discussion: Optic Nerve Head Drusen and Primary Eye Care
Optic nerve head drusen (ONHD) are hyaline bodies located in the prelaminar portion of the optic nerve, often bilaterally (approximately 70% of cases). They are estimated to occur in about 1% of the general population, with a higher prevalence in Caucasian individuals. Historically referred to by various names, including congenitally elevated anomalous discs, pseudopapilledema, pseudo-neuritis, buried disc drusen, and disc hyaline bodies, the term ONHD is now the preferred nomenclature.
The exact pathogenesis of ONHD is still under investigation, but current theories suggest that a constricted scleral canal opening may lead to axoplasmic flow stasis within the optic nerve. This stasis can result in abnormal axonal metabolism and mitochondrial calcifications, which eventually erupt into the extracellular space as visible drusen.
Within the optic nerve, these hyaline bodies are confined anterior to the lamina cribrosa, potentially causing compression and compromise of nerve fibers and the vascular supply. This can lead to the development of visual field defects and, less frequently, disc hemorrhages. Visual field loss is a common complication, reported in 64% to 87% of individuals with ONHD, and in a subset (up to 22%), these defects can be progressive.
While many individuals with ONHD remain asymptomatic, clinical findings are often discovered during routine eye examinations, underscoring the importance of comprehensive primary eye care. When symptomatic, patients may present with decreased visual acuity and visual field defects, typically arcuate, sectoral, or altitudinal scotomas. An afferent pupillary defect might be present in cases that are both significant and asymmetric. Rarely, ONHD has been associated with migraine headaches, seizures, and transient visual disturbances.
Visible ONHD are characterized as glistening, globular, or spherical-shaped bodies that protrude anteriorly, causing irregular and indistinct ONH margins. They most commonly appear on the nasal disc margin but can be found in any part of the nerve head. In younger individuals, the disc elevation may be more pronounced, and the drusen less calcified, making them less easily visible ophthalmoscopically. ONHD can mimic pseudopapilledema, lacking physiologic cupping. As individuals age, the disc may become more yellowed, and the calcified drusen become more surface-visible due to nerve fiber layer thinning. When illuminated with red-free light, these refractile bodies exhibit autofluorescence. Ultrasonography remains a critical ancillary test for detecting ONHD, particularly in adults, due to the high reflectivity of drusen.
The management of ONHD in primary eye care focuses on accurate diagnosis through careful clinical examination and ancillary testing, particularly ultrasonography. While generally considered a benign condition, the potential for visual field loss and the need to differentiate ONHD from other more serious conditions necessitate diligent monitoring and patient education. Prompt and accurate differential diagnosis, as emphasized in resources like Bezan’s “Differential Diagnosis in Primary Eye Care,” is paramount for optimal patient care and outcomes. Regular follow-up examinations are essential to monitor for any progression and to provide appropriate counseling and support to patients affected by this condition.
References
- Sowka JW, Gurwood AS, Kabat AG. OpticNerve Head Drusen. Handbook of Ocular Disease Management. Rev Optom Online, www.revoptom.com/handbook/SECT50a.htm.
- Nishimoto J. Anomalies of Optic Disc Contour and Position. In: Bezan D, LaRussa F, Nishimoto J, et al. Differential Diagnosis in Primary Care. Boston: Butterworth-Heinemann, 1999:388-9.
- Haynes RJ, Manivannan A, Walker S, et al. Imaging of optic nerve head drusen with the scanning laser ophthalmoscope. Br J Ophthalmol 1997 Aug;81(8):654-7.
- Chang A, Flaherty M. Disc Drusen: A headache for child and clinician. Aust N Z J Ophthalmol. 1996 Nov;24(4):381-4.
- 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.
- Roh S, Noecker RJ, Schuman JS, et al. Effect of optic nerve head drusen on nerve fiber layer thickness. Ophthalmology 1998 May;105(5):878-85.
