Intraocular pressure, retinal vascular, and visual acuity changes during 48 hours of 10 degrees head-down tilt.
Aviat Space Environ Med
; 61(9): 810-3, 1990 Sep.
Article
em En
| MEDLINE
| ID: mdl-2241746
ABSTRACT
Intraocular pressures, retinal vascular diameters, and visual acuities of nine men (ages 19-29), were repeatedly measured while the subjects were tilted 10 degrees head-down for 48 h and while they were seated before (baseline), and after the tilt. An immediate increase in intraocular pressure, measured by pneumatonometer (4.7 +/- 0.6 mm Hg, p less than 0.001) was recorded when subjects assumed the head-down position, and diurnal variations in intraocular pressures were observed for the 48 h. The initial and final head-down intraocular pressures were not significantly different (18.9 +/- 1.2 mm Hg vs. 17.9 +/- 1.4 mm Hg, respectively). However, when subjects resumed the sitting position, intraocular pressures fell below the initial sitting values (14.2 +/- 0.9 pre vs. 11.2 +/- 0.5 post, p less than 0.04). Computer image analysis of the retinal vasculature detected a 6% and 2% reduction in the caliber of arteries and veins, respectively, as compared with sitting baseline values. No changes in visual acuity were documented during the 48 h of head-down tilt. Our data suggest that the choroidal blood reservoir increases in volume over 48 h at continuous head-down position with a compensatory decrease in aqueous volume. These findings may explain intraocular pressure changes noted in astronauts during previous space missions and in studies associated with change in body position.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Postura
/
Vasos Retinianos
/
Acuidade Visual
/
Pressão Intraocular
Limite:
Adult
/
Humans
/
Male
Idioma:
En
Revista:
Aviat Space Environ Med
Ano de publicação:
1990
Tipo de documento:
Article