Sensitivity and specificity of time-domain and spectral-domain optical coherence tomography in differentiating optic nerve head drusen and optic disc oedema.

Purpose: To evaluate the efficacy of time-domain optical coherence tomography (TD-OCT) and spectral-domain optical coherence tomography (SD-OCT) in differentiating between optic nerve head drusen (ONHD) and optic disc oedema (ODE).

Methods: We studied 66 patients with ONHD, 31 patients with ODE, and 70 controls using TD-OCT and SD-OCT. We analysed two aspects of the tomographic findings: (i) quantitative, through measurement of the retinal nerve fibre layer (RNFL) and papillary elevation; and (ii) qualitative, through assessment of the hyporeflective space, morphology of the internal contour, focal papillary mass and RNFL increases in seven contiguous clock hours. We evaluated the sensitivity, specificity, intra-class correlation coefficient (ICC), and inter-observer agreement (κ).

Results: The quantitative analysis of the RNFL revealed an average thickness of the RNFL <124μm with TD-OCT (sensitivity=91%; specificity=94%) and <116μm with SD-OCT (sensitivity=91%; specificity=97%). The thickness of the nasal quadrant was <108μm with TD-OCT (sensitivity=89%; specificity=87%) and with SD-OCT was <92μm (sensitivity=88%; specificity=94%), however without significant differences between the nasal, superior and inferior quadrants' and average thickness. The measurement of papillary elevation was 0.85mm with TD-OCT (sensitivity=96%; specificity=84% [ICC=0.96]) and was <0.80 mm with SD-OCT (sensitivity=86%; specificity=87% [ICC=0.94]). The abrupt termination of the hyporeflective space measured with TD-OCT had sensitivity=79% and specificity=90% (κ=0.60) and with SD-OCT had sensitivity=88% and specificity=89% (κ=0.75); the irregularity of the internal contour with TD-OCT had sensitivity=80% and specificity=90% (κ=0.70) and with SD-OCT had sensitivity=88% and specificity=90% (κ=0.75); and the absence of seven contiguous clock hours had values of sensitivity=97% and specificity=77% with TD-OCT and had sensitivity=98% and specificity=77% with SD-OCT.

Conclusions: Optical coherence tomography allowed for differentiation between ONHD and ODE, yielding similar results with TD-OCT and SD-OCT. The new quantitative parameters of papillary elevation and RNFL measurements showed greater sensitivity and specificity than the qualitative criteria.