Factors associated with intraocular pressure-induced acute visual field depression
J. R. Trible and D. R. Anderson
Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami, Fla, USA.
OBJECTIVE: To determine the factors associated with visual field depression
produced by artificial elevation of intraocular pressure (IOP). METHODS:
The visual threshold was determined at 26 locations in the central visual
field at a spontaneous IOP, at 30 mm Hg, at 40 mm Hg, and at the IOP
immediately following release of the suction cup used to elevate the IOP
artificially in 33 subjects with and without glaucoma. The net decrease in
threshold sensitivity at each IOP level relative to sensitivity obtained at
the spontaneous IOP was calculated (acute visual field depression).
RESULTS: Factors potentially influencing the acute visual field depression
between subjects were determined with stepwise regression. The reciprocal
of ocular perfusion pressure, a clinical measure, was strongly correlated
with acute visual field depression (dependent variable), particularly at 40
mm Hg (at 30 mm Hg, r=0.412, P=.02, n=32; and at 40 mm Hg, r=0.813,
P<.001, n=33). When a second variable, the diagnosis of glaucoma, was
included in the regression at 40 mm Hg, it contributed significantly
(partial r=0.650, P<.001, n=26). The degree of glaucomatous damage
(vertical cup-disc ratio or baseline Humphrey 24-2 visual field mean
deviation) failed to correlate with acute field depression, with or without
correction for ocular perfusion pressure. CONCLUSIONS: The elevation of IOP
produces acute, reversible visual field depression. This depression is
largely dependent on the subject's ocular perfusion pressure. The degree of
depression is greater in those with glaucoma but is not strictly related to
the degree of glaucomatous damage.
