Analysis of the glaucomatous optic nerve head using 1050nm OCT

Abstract

Purpose: To assess optic nerve head (ONH) parameters in open angle glaucoma.

Methods: A laboratory-based 1050nm spectral domain optical coherence tomography device (SD-OCT) was used to acquire 3D ONH datasets in glaucomatous and healthy subjects. OCT tomograms (20° scan, 512x512 a-scans) centred on the optic nerve head (ONH) were acquired, with visual field deficit determined using a Humphrey visual field analyser. ONH parameters (including Bruch’s membrane opening (BMO), optic cup, prelamina and lamina cribrosa (LC) thickness and volume, and anterior and posterior LC surfaces) were manually delineated and quantified using ImageJ and Amira image analysis software. The cohort was ordered according to mean deviation (MD). Statistical analysis were performed using SPSS.

Results: Prelamina volume decreased significantly with increasing field loss (p<0.05). A significant correlation was also identified between increasing cup volume and prelamina thinning (p<0.05). LC thickness was reduced in the glaucoma group compared to the control group (p<0.05), more significantly in the superior and inferior regions (p<0.01). BMO area demonstrated significant correlation with axial length (p<0.05) and mean spherical refraction (p<0.001). The ratio of vertical:horizontal BMO diameter was higher in the glaucoma group than control (p>0.05). When eyes with axial length >24.50mm were excluded from analysis to limit the influence of axial myopia on disc parameters the same differences were found. In addition, increased BMO area showed significant correlation with increased central LC thickness (p<0.05), and an increase in cup volume was found to correlate with decreasing prelamina thickness (p<0.05).

Conclusions: Significant differences were found in prelamina and LC thickness and volume in glaucomatous ONHs when compared to healthy ONHs. Although visual field loss has traditionally been used to monitor the progression of glaucoma, here we present data on ONH parameters that have the potential to characterise early stages of disease. In the future these could be used to help identify those at risk of further glaucomatous progression.

Keywords: 629 optic nerve • 550 imaging/image analysis: clinical • 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)