Abstract
Purpose :
To measure acute lamina cribrosa (LC) deformations induced by elevated intraocular pressure (IOP) when healthy and at onset of experimental glaucoma (EG).
Methods :
The optic nerve heads (ONHs) of four eyes of four rhesus macaque monkeys were imaged using optical coherence tomography (OCT, Spectralis) in three imaging sessions before (baselines 1 and 2) and at the onset of laser-induced EG. Onset was defined as confirmed peripapillary RNFL loss from OCT. In each session, the ONHs were scanned after IOP was set for 10 minutes to 10 mmHg and to 40 mmHg. Digital volume correlation (DVC) analysis was then used to determine the LC changes between scans. LC changes represent either acute (between IOP levels) or chronic deformations (between sessions at the same IOP, Fig. 1).
Results :
LC deformations between baseline 1 and baseline 2 at low IOP (10 mmHg) were the smallest (compression 2-3%) in all four eyes, indicating good repeatability (Fig. 2, Step 4). During baseline, acute IOP-induced LC deformations were substantially larger (8-12%) and consistent in all four eyes at both tests (Fig. 2, Steps 1 and 2), indicating stable LC compliance. Compared with the acute IOP effects at baseline, the acute IOP effects at onset (Fig. 2, Step 3) were larger in three monkeys (up to 17%) and smaller in one monkey (5%). Interestingly, chronic changes induced by onset of EG (Fig. 2, Step 5, 8-15%) were larger than the acute IOP-induced LC deformations at baseline.
Conclusions :
Acute and chronic IOP-induced LC changes can be reliably measured using OCT and DVC. At EG onset, three of four monkeys exhibited substantial changes in the LC and increased LC compliance, suggesting that the damage and remodeling processes are already advanced.
This is a 2021 ARVO Annual Meeting abstract.