Ocular manifestations of gravity inversion
T. R. Friberg and R. N. Weinreb
To determine the ocular manifestations of inverting the human body into a
head-down vertical position, we evaluated normal volunteers with
applanation tonometry, fundus photography, fluorescein angiography, and
ophthalmodynamometry. Compared with data obtained in the sitting position,
the intraocular pressure more than doubled on inversion (35.6 +/- 4 v 14.1
+/- 2.8 mm Hg, n = 16), increasing to levels well within the glaucomatous
range. Pressures in the central retinal artery underwent similar increases,
while the caliber of the retinal arterioles decreased substantially.
External ocular findings associated with gravity inversion included orbital
congestion, conjunctival hyperemia, petechiae of the eyelids, excessive
tearing (epiphora), and subconjunctival hemorrhage. We suggest that
patients with retinal vascular abnormalities, macular degeneration, ocular
hypertension, glaucoma, and similar disorders refrain from inversion
altogether. Whether normal individuals will suffer irreversible damage from
inversion is uncertain, but it seems prudent to recommend that prolonged
periods of inverted posturing be avoided.
