Ability and reproducibility of Fourier-domain optical coherence tomography to detect retinal nerve fiber layer atrophy in Parkinson's disease

Purpose: To evaluate and compare the ability of 3 protocols of Fourier-domain optical coherence tomography (OCT) to detect retinal thinning and retinal nerve fiber layer (RNFL) atrophy in patients with Parkinson's disease (PD) compared with healthy subjects. To test the intrasession reproducibility of RNFL thickness measurements in patients with PD and healthy subjects using the Cirrus (Carl Zeiss Meditec Inc., Dublin, CA) and Spectralis (Heidelberg Engineering, Inc., Heidelberg, Germany) OCT devices.

Design: Observational, cross-sectional study.

Participants: Patients with PD (n = 75) and age-matched healthy subjects (n = 75) were enrolled.

Methods: All subjects underwent three 360-degree circular scans centered on the optic disc by the same experienced examiner using the Cirrus OCT instrument, the classic glaucoma application, and the new Nsite Axonal Analytics of the Spectralis OCT instrument.

Main outcome measures: Differences between the eyes of healthy subjects and the eyes of patients with PD were compared using the 3 protocols. The relationship between measurements provided by each OCT protocol was evaluated. Repeatability was studied by intraclass correlation coefficients and coefficients of variation.

Results: Retinal nerve fiber layer atrophy was detected in eyes of patients with PD (P = 0.025, P=0.042, and P < 0.001) with the 3 protocols used, but the Nsite Axonal Analytics of the Spectralis OCT device was the most sensitive for detecting subclinical defects. In eyes of patients with PD, RNFL thickness measurements determined by the OCT devices were correlated, but they were significantly different between the Cirrus and Spectralis devices (P = 0.038). Reproducibility was good with all 3 protocols but better using the Glaucoma application of the Spectralis OCT device.

Conclusions: Fourier-domain OCT can be considered a valid and reproducible device for detecting subclinical RNFL atrophy in patients with PD, especially the Nsite Axonal Analytics of the Spectralis device. Retinal nerve fiber layer thickness measurements differed significantly between the Cirrus and Spectralis devices despite a high correlation of the measurements between the 2 instruments.