Spectral Domain Optical Coherence Tomography (SDOCT) detects lamina cribrosa hypercompliance in Non-human Primate (NHP) early experimental glaucoma (EEG)

Abstract

 

Purpose:

 

To compare acute SDOCT IOP 10/30 optic nerve head (ONH) parameter change (SDOCT compliance) within the normal (N) and EEG eyes of NHPs at the onset of unilateral EEG.

 

Methods:

 

In both eyes of 9 rhesus NHPs (5-22 y.o.) SDOCT and Confocal Scanning Laser Tomography (CSLT) (both Heidelberg Engineering) ONH imaging was performed 30 minutes after manometric IOP lowering to 10 mm Hg and again 30 minutes after elevation to 30 mm prior to and every two weeks following the onset of unilateral laser-induced chronic IOP elevation. EEG was defined as the onset of CSLT surface change confirmed on two occasions. Within the 40 radial B-scans of the 30º SD-OCT volumes from the second EEG confirmation session, masked operators delineated the retinal and ONH landmarks necessary to quantify: anterior lamina cribrosa surface depth (ALCSD) relative to a Bruch’s Membrane Opening (BMO) reference plane (ALCSD-BMO, see Figure), ALCSD relative to a peripheral BM reference plane (ALCSD-BM), neuroretinal rim width and BMO depth relative to the same peripheral BM reference plane (BMODepth). Random effects models assessed the relative effects of acute IOP elevation, N vs EEG eye status and the interactions between the two on each parameter.

 

Results:

 

ALCSD-BMO change due to acute IOP elevation was significantly greater in the EEG (50±40 μm (mean±s.d.)) compared to normal (10±16 μm) eyes (p=0.0009). ALCSD-BM change due to IOP was greater in EEG (80±66 μm) compared to normal (40±27 μm) eyes (p=0.07). Significant compliance was observed for all eyes between IOP 10 and 30 for BMO depth (p<0.0001) and rim width (p<0.0001) , but no significant difference in compliance was observed between N and EEG eyes for these two parameters.

 

Conclusions:

 

In a pooled analysis, NHP EEG eyes cross-sectionally exhibit significantly more SDOCT lamina cribrosa compliance than their contralateral normal eyes as measured by ALCSD-BMO. This finding appears to be eye-specific and may be a manifestation of EEG-induced alterations in lamina cribrosa and peripapillary scleral structural stiffness.  

 

Keywords: optic nerve • lamina cribrosa • imaging/image analysis: non-clinical