The case of the blurred disc margins

A 16-year-old female was scheduled for her periodic ophthalmic evaluation to update her spectacle lens prescription. At the visit, she reported a history of migraines, but the remainder of her personal and family medical history was non-contributory. She took no medications and had a history of low hyperopic refractive correction.

Exam findings

On examination, her visual acuity was corrected to 20/20 and 20/25 in the right and left eyes. The anterior segments of each eye were unremarkable with applanation tonometry pressures measured at 16 mm Hg.

Dilated fundus evaluation revealed the presence of blurred disc margins.

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With access to B-scan ultrasonography, we performed a scan of each eye at standard as well as reduced gain. 

Optical coherence tomography (OCT) was also performed.The upper left showed a reflectance image of the optic nerve head. The lower left was a representative cross-section through the disc. Note that the elevation is confined within the scleral ring, consistent with optic nerve head drusen (ONHD).

Topographic representation of the disc reflected the elevation seen in the cross-sectional presentation. Note that the scale bar to the right indicates that hotter colors are consistent with greater elevation.

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Any encounter of an elevated optic disc raises the question of whether the patient is presenting with true or pseudo-papilledema. The data in this case are all consistent with a diagnosis of optic disc drusen. These findings spare the patient a neuro-ophthalmic workup.

Further analysis included a visual field evaluation. 

Both eyes had good reliability with only a few sporadic depressions in the right eye but a pattern consistent with retinal nerve fiber damage secondary to the ONHD.

The patient has been asked to return annually to monitor changes in the visual field. 

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Recent discussions

A recent study examined the use of spectral domain optical coherence tomography (SD-OCT) as the gold standard in distinguishing optic disc drusen (ODD), optic nerve head drusen (ONHD), or from optic disc edema (ODE).¹ The authors also identified the halo sign for making the distinction using fundus photography.

In all cases of ODD, the halo sign was present, indicating the confinement of the elevation within the scleral ring/disc margin. For those without access to SD-OCT, the identification of the halo sign at fundus examination and on photography may serve as a valuable diagnostic tool to prevent unnecessary work-ups.²

In cases of mild/early papilledema, others have reported that OCT perhaps does not offer a final adjudication.³ With advances in OCT technology, the utility as a differentiator may become more widespread. Alternative imaging may prove valuable, but not widely available.⁴ The utility of OCT for establishing a diagnosis of optic disc drusen had been suggested several years ago as a benchmark.⁵

Related: Top 5 reasons to request a retinal consult

References

1. Lee KM, Woo SJ, Hwang JM. Differentiation between optic disc drusen and optic disc oedema using fundus photography. Acta Ophthalmol. 2017 Jan 13. doi: 10.1111/aos.13338.

2. Costello F. Optical Coherence Tomography in Neuro-ophthalmology. Neurol Clin. 2017 Feb;35(1):153-163.

3. Kulkarni KM, Pasol J, Rosa PR, Lam BL. Differentiating mild papilledema and buried optic nerve head drusen using spectral domain optical coherence tomography. Ophthalmology. 2014 Apr;121(4):959-63.

4. Shah A, Szirth B, Sheng , Xia T, Khouri AS. Optic disc drusen in a child: diagnosis using noninvasive imaging tools. Optom Vis Sci. 2013 Oct;90(10):e269-73.

5. Katz BJ, Crum AV, Digre KB, Warner JE. Optic disc edema and optic nerve head drusen. J Neuroophthalmol. 2013 Jun;33(2):204-5. 

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