Purpose:
The purpose of this study is to test the hypothesis that ONH and pp-scleral connective tissue deformation is clinically detectable within Spectralis 3D OCT ONH Bscan images of 4 NHP following acute and chronic IOP elevation.
Methods:
Both the Normal (N) and EEG eyes of 2 EEG NHP received Spectralis (Heidelberg Engineering) OCT imaging of the optic nerve head (ONH) 2 or less days prior to sacrifice (4 weeks after onset of chronic IOP elevation) Each OCT volume was 15x15 deg, centered on the ONH and consisted of 145 horizontal B Scans (each the average of 9 sweeps to reduce noise), with 756 A Scans per B Scan. Both ONH of 2 additional bilaterally normal NHPs were 3D OCT imaged after IOP was manometrically lowered to 10 mm Hg, then 60 minutes following IOP elevations to 30 and 45 mm Hg. Matched horizontal B Scans (through the central disc as well as the superior and inferior disc margins as defined by Bruch’s membrane opening (BMO) from the N and EG eye of each EEG animal, and the IOP 10 and 45 - 60 minute images of the right eye of each bilaterally normal NHP, were viewed together at identical magnification for comparison.
Results:
Profound posterior bowing of the peripapillary BM (presumably following the underlying sclera) and lamina were qualitatively present within both EEG (compared to their contralateral normal) eyes. While minimal to moderate posterior bowing of the peripapillary BM was present in the IOP 45 images of both normal eyes (compared to their IOP 10 images), posterior bowing of the lamina was only present in 1 of the 2 eyes (expansion of orange and green outlined areas in figure).
Conclusions:
Early glaucomatous alterations in laminar and pp-scleral connective tissue architectures are clinically detectable by 3D OCT ONH imaging in the NHP eye. Acute, IOP elevation-induced alterations in these same architectures are evident in 2 of 2 NHP eyes and may provide essential data for refinement and validation of individual-eye ONH and pp-scleral finite element models.
Keywords: optic disc • optic nerve • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)