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Lijun Jia, William O. Cepurna, Elaine C. Johnson, John C. Morrison; Patterns of Intraocular Pressure Elevation after Aqueous Humor Outflow Obstruction in Rats. Invest. Ophthalmol. Vis. Sci. 2000;41(6):1380-1385.
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purpose. To determine the diurnal intraocular pressure (IOP) response of Brown
Norway rat eyes after sclerosis of the aqueous humor outflow pathways
and its relationship to optic nerve damage.
methods. Hypertonic saline was injected into a single episcleral vein in 17
animals and awake IOP measured in both the light and dark phases of the
circadian cycle for 34 days. Mean IOP for light and dark phases during
the experimental period were compared with the respective pressures of
the uninjected fellow eyes. Optic nerve cross sections from each nerve
were graded for injury by five independent masked observers.
results. For fellow eyes, mean light- and dark-phase IOP was 21 ± 1 and
31 ± 1 mm Hg, respectively. For four experimental eyes, mean IOPs
for both phases were not altered. Six eyes demonstrated significant
mean IOP elevations only during the dark phase. Of these, five showed
persistent, large circadian oscillations, and four had partial optic
nerve lesions. The remaining seven eyes experienced significant IOP
elevations during both phases, and all had extensive optic nerve
conclusions. Episcleral vein injection of hypertonic saline is more likely to
increase IOP during the dark phase than the light. This is consistent
with aqueous outflow obstruction superimposed on a circadian rhythm of
aqueous humor production. Because these periodic IOP elevations
produced optic nerve lesions, both light- and dark-phase IOP
determinations are necessary for accurate correlation of IOP history to
optic nerve damage in animals housed in a light–dark
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