Abstract
In humans, the longitudinal characterisation of early optic nerve head (ONH) damage in ocular hypertension (OHT) is difficult as patients with glaucoma usually have structural ONH damage at the time of diagnosis. Previous studies assessed glaucomatous ONH cupping by measuring the anterior lamina cribrosa depth (LCD) and minimal rim width (MRW) using optical coherence tomography (OCT). In this study, we induced OHT by repeated intracameral microbead injections in 16 cynomolgus primates (10 unilateral; 6 bilateral) and assessed the structural changes of the ONH longitudinally to observe early changes. Elevated intraocular pressure (IOP) in OHT eyes was maintained for 7 months and serial OCT measurements were performed during this period. The mean IOP was significantly elevated in OHT eyes when compared to baseline and compared to the control eyes. Thinner MRW and deeper LCD values from baseline were observed in OHT eyes with the greatest changes seen between month 1 and month 2 of OHT. Both the mean and maximum IOP values were significant predictors of MRW and LCD changes, although the maximum IOP was a slightly better predictor. We believe that this model could be useful to study IOP-induced early ONH structural damage which is important for understanding glaucoma pathogenesis.
Highlights
In humans, the longitudinal characterisation of early optic nerve head (ONH) damage in ocular hypertension (OHT) is difficult as patients with glaucoma usually have structural ONH damage at the time of diagnosis
In primary open angle glaucoma (POAG), chronic intraocular pressure (IOP) elevation or ocular hypertension (OHT) induces neural and connective tissue deformation and/or remodelling within the ONH that can lead to permanent structural d amage[3,4,5,6]
The ONH changes induced by experimental glaucoma (EG) can be monitored by assessing the lamina cribrosa depth (LCD) and minimum rim width (MRW) using spectral-domain (SD) optical coherence tomography (OCT) in the laser-induced primate OHT model
Summary
The longitudinal characterisation of early optic nerve head (ONH) damage in ocular hypertension (OHT) is difficult as patients with glaucoma usually have structural ONH damage at the time of diagnosis. The ONH changes induced by EG can be monitored by assessing the lamina cribrosa depth (LCD) and minimum rim width (MRW) using spectral-domain (SD) optical coherence tomography (OCT) in the laser-induced primate OHT model. The MRW (the width of the neuroretinal rim at the ONH) correlates well with the RNFL thickness[4,5,20,21,22,23] Both thinning of the MRW and deepening of the LCD occurs earlier than RNFL thinning in the laser-induced primate OHT model; as such, these parameters have been used to detect early structural ONH changes[20,21,23]
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