Optical coherence tomography study of peripapillary retinal nerve fiber layer and choroidal thickness in eyes with tilted optic disc

Abstract

Purpose: The tilted optic disc is associated with peripapillary choroidal and retinal nerve fiber layer (RNFL) changes as well as visual field defects, often leading to diagnostic difficulties due to similarities with glaucomatous discs. We studied the peripapillary RNFL of the tilted optic disc by comparing values obtained with spectral-domain (SD) and time-domain (TD) optical coherence tomography (OCT) in order to identify characteristic RNFL patterns verified by both OCT devices, and also to determine whether SD-OCT offers any diagnostic advantage over TD-OCT.

Methods: Prospective case-control study of 16 individuals with tilted optic discs (27 eyes) and an age-matched control group (10 individuals, 20 eyes). Each case was subjected to ophthalmological examination and automated perimetry. Tilt orientation was classified based on observation of optic disc photographs, and angle of disc torsion was calculated with image processing software. RNFL measurements were obtained with TD-OCT and SD-OCT. Peripapillary choroid thickness was measured with SD-OCT. The findings were related with optic disc morphology and automated perimetry results.

Results: Stratus OCT results showed significantly lower superior RNFL (P<0.001) on the tilted group, whereas Spectralis indicated significantly lower superotemporal (P<0.001), superonasal (P=0.001), temporal (P=0.01), and global (P=0.01) RNFL on the tilted disc group. A significant correspondence was found between elevated disc rim and location of RNFL defect on the Spectralis (P=0.004). On the tilted group, peripapillary choroidal thickness was significantly thicker adjacent to the elevated rim (P<0.001). No correspondence was found between tilt orientation, peripapillary RNFL, or choroidal thickness and location of perimetric defects.

Conclusions: Our results provide a clinical characterization of the main tilted disc morphologies and are valuable for correctly differentiating a tilted disc from a myopic glaucomatous disc. RNFL assessment by Spectralis OCT seems to be more susceptible to altered disc morphologies. The peripapillary RNFL changes found on titled disc cases could not predict the location of visual field defects.