Eyes (Ocular System)
The eye consists of three layers: the outer fibrous layer (cornea and sclera), middle uveal layer (choroid, ciliary body, iris), and inner retina. Intraocular pressure (IOP) is normally 10-21 mmHg, maintained by aqueous humor production and drainage.
Normal Function
Light detection via photoreceptor cells (rods and cones) in the retina; signal processing and transmission to visual cortex via optic nerve. Accommodation (near/far focus) via ciliary muscle and lens.
Lunar Adaptations
On Arrival (First Weeks)
Some residents report visual blurring in first days — likely vestibular-related (nystagmus affects visual acuity). Intraocular pressure may change slightly with fluid redistribution.
6-Month Resident
SANS (Spaceflight-Associated Neuro-Ocular Syndrome) findings may become apparent: optic disc edema, choroidal folds, hyperopic shift (far-sighted change). OCT shows retinal nerve fiber layer thickening in some residents. Regular monitoring is essential.
Long-Term Resident (2+ Years)
Approximately 20-35% of long-term residents develop clinically significant SANS findings. Hyperopic shift may become permanent in some. Visual field testing shows subtle changes in affected residents. The mechanism involves chronic intracranial pressure elevation transmitted to the optic nerve sheath. Radiation also directly damages retinal cells over time, contributing to degenerative changes.