Abstract
Purpose :
Computational modeling has been used to better understand how intraocular pressure (IOP), intracranial pressure (ICP), and choroidal swelling influence deformation of the human optic nerve head (ONH). Here, we expand on these models to investigate how pathophysiological levels of choroidal swelling occurring during spaceflight (Laurie+, IOVS 2018) compare to the effects of other pathological conditions, e.g. glaucoma (elevated IOP) and idiopathic intracranial hypertension (elevated ICP).
Methods :
We used our established computational model of the posterior eye (Feola+, IOVS, 2018), which included the choroid and Bruch’s membrane to examine choroidal changes over a cardiac cycle. Our baseline condition represented an individual in the upright position: IOP=15 mmHg, ICP=0 mmHg, mean arterial pressure=57 mmHg, and no choroidal swelling (0 uL). We then applied supra-physiologic or “pathologic”, loading conditions including choroidal swelling (50 uL of swelling), elevated IOP (30 mmHg), and elevated ICP (20 mmHg), and then calculated the peak first and third principal strains in the prelaminar neural tissue (PLNT), lamina cribrosa (LC), and retrolaminar neural tissue (RLNT) relative to our baseline condition.
Results :
Variation in material properties resulted in a wide range of predicted strains under supra-physiological loading (Figure). In the PLNT, increasing choroidal swelling affected the magnitude and range of peak strains. Within the lamina cribrosa, elevated IOP caused the highest peak compressive strains. Elevated ICP resulted in the largest strains in the RLNT.
Conclusions :
Computational modeling indicates that pathologic choroidal swelling places biomechanical strain on tissues of the ONH that are similar or larger than the peak strains associated with elevated IOP and ICP. Changes in the choroid likely play a larger role in ophthalmic pathologies, such as spaceflight-associated neuro-ophthalmic syndrome (SANS) than previously recognized.
This is a 2021 ARVO Annual Meeting abstract.