Purpose:
To quantify the range of physiologic, inter-eye difference (PID) in ONH neural and connective tissue architecture in 6 normal NHPs.
Methods:
Trephinated ONHs (6 mm diameter) from both eyes of 6 normal NHPs perfusion fixed at IOP 10 mmHg OU were 3D reconstructed (IOVS 2004; 45:4388) with 1.5µm voxel resolution. Within each ONH reconstruction, 14 landmarks were delineated within 40 serial, radial, digital, sagittal section images (every 4.5°) as described in 3 recent IOVS reports (Downs, et al IOVS,2007;48:3195;Yang et al, IOVS, 2007;48:4597;48:5068).For each ONH, overall and regional neural canal offset and depth, lamina cribrosa and peripapillary position and thickness, and laminar and prelaminar cupping were calculated. Quantitative PID maps for each parameter (absolute difference between OD and OS in each NHP) were generated and used to construct regional mean and 95% confidence interval (CI) maximums for each parameter. These summary difference results were compared with the magnitude of the treatment effects reported for 3 early experimental glaucoma (EEG) NHPs from our 2007 IOVS reports.
Results:
Overall mean value, mean PID, PID range and 95%CI maximums of the PID are reported in the attached table. Overall mean PIDs are small (<15 µm) with ranges from 1~ 28 µm and 95%CI maximums for the mean of the PIDs from 5 to 23 µm. In general, regional 95%CI maximums were greater than the overall mean PID for each parameter. However, 85% of the regional differences within the 3 EEG eye difference maps from our 3 previous EEG,NHPs exceed the regional PID 95% CI maximums established by the 6 normal NHPs reported here.
Conclusions:
This study provides the first quantification of PID for three levels of 3D histomorphometric ONH and peripapillary scleral quantification. These data preliminarily suggest that normal NHP PID is small enough to allow early detection of glaucomatous damage in the NHP model of experimental glaucoma.
Keywords: optic nerve • lamina cribrosa • sclera