Purpose
To determine variations in human ONH structures associated with age and race (African descent or AD; European descent or ED) with OCT images using either Bruch’s membrane opening (BMO) or peripapillary scleral opening (PSO) as reference planes.
Methods
This study included 166 OCT ONH volumes from normal healthy subjects (64 AD subjects, 102 ED subjects). Adaptive compensation was applied to all volumes to enhance the visibility of ONH tissue structures (Girard, Mari, et al., IOVS 2013). Anatomic structures were delineated in 12 of the 48 radial B-scans in each OCT volume using Devers Eye Institute Multiview custom software to develop 3D reconstructions. A best-fitting plane was computed using principal component analysis to define BMO and PSO, which were used as anatomic measurement reference planes. Using a uniform sampling grid we computed the mean and max distances from the BMO and PSO reference planes to the anterior lamina cribrosa (LC) surface (distance defined as the LC depth or LCD) and to the internal limiting membrane (ILM) (distance defined as the cup depth or CD). Mixed effects models were used to measure structural variations associated with race, age, axial length and age/race interactions. The BMO and PSO reference plane results were then compared.
Results
Consistent results (Table 1) were found using either BMO or PSO as reference planes. Specifically, variation in LCD and CD were both independently associated with age and race. Significant reduction in LCD was observed with advancing age in ED eyes. Subjects of AD had significantly greater deepening of LCD and CD compared to the ED group. There was a significant interaction between race and age in LCD and CD; with increasing age in AD subjects, LCD and CD increased. Significant reduction in max CD was seen with advancing age in ED eyes. Axial length was not a significant variable in any measurement and was not included in the final model.
Conclusions
Consistent measurements of deep ONH tissue structures were produced using as separate reference planes, BMO position and PSO position. There were no significant differences in LCD and CD measurements using the two reference planes. Determining a stable reference plane is critical in the quantification of ONH parameters.
Keywords: 550 imaging/image analysis: clinical •
629 optic nerve •
473 computational modeling