Differentiation between optic disc drusen and optic disc oedema using fundus photography

Area of Science:

• Ophthalmology
• Medical Imaging
• Diagnostic Signs

Background:

• Differentiating optic disc drusen (ODD) from optic disc oedema (ODE) is crucial for accurate patient management.
• Blurred disc margins can present a diagnostic challenge, necessitating reliable clinical signs.

Purpose of the Study:

• To describe and validate a novel funduscopic sign, the 'halo sign,' for distinguishing between ODD and ODE.
• To assess the diagnostic accuracy and reliability of the halo sign.

Main Methods:

• Retrospective analysis of 73 eyes with blurred disc margins evaluated by spectral-domain optical coherence tomography (SD-OCT).
• Fundus photographs were analyzed for the presence of a halo sign, defined as a smooth contour strip between the nasal disc margin and juxtapapillary retina.
• SD-OCT was used for definitive diagnosis of ODD and ODE, with specific criteria for each.

Main Results:

• The halo sign was present in 100% of eyes with ODD (45/45) and absent in all eyes with ODE alone (0/45).
• The halo sign demonstrated perfect agreement (Cohen's kappa = 1.000) for predicting ODD and high agreement (Cohen's kappa = 0.971) for predicting the absence of ODE.
• SD-OCT confirmed that halos represent retinal elevations overlying ODD, and the sign showed excellent interobserver reliability (ICC = 0.944).

Conclusions:

• The presence of a halo sign on funduscopic examination is a strong indicator of optic disc drusen (ODD) in patients presenting with blurred disc margins.
• This easily identifiable sign aids in differentiating ODD from optic disc oedema (ODE), improving diagnostic accuracy.