Understanding the Importance of IOP Variables
in Glaucoma: A Systematic Review
Marla B. Sultan, MD, MBA,
Steven L. Mansberger, MD,
and Paul P. Lee, MD, JD
New York Eye & Ear Inﬁrmary, New York, New York;
Pﬁzer Inc, New York, New York;
Devers Eye Institute, Legacy
Health System, Portland, Oregon; and
Glaucoma Service, Duke University Eye Center, Durham, North Carolina, USA
Abstract. Glaucoma is one of the leading causes of visual impairment and blindness. Lowering
intraocular pressure (IOP) is the only proven means to slow or halt disease progression among those at
higher risk of developing glaucoma and those with early to moderate or more advanced glaucoma.
Recent publications have highlighted the potential for increased rates or likelihood of worsening
glaucoma among those with larger IOP swings within deﬁned time periods. The purpose of this
systematic, comprehensive review and analysis of the literature was to assess the state of knowledge in
the area of IOP changes over time and the potential impact of such changes on treatment. Current
literature indicates that a random IOP measurement is a poor surrogate for IOP levels throughout the
day and across visits. We address several key questions: 1) What is the best way to measure IOP? 2)
Should multiple IOP measurements be performed in a day in the ofﬁce (short-term IOP ﬂuctuation)?
3) Is measurement at night required? 4) Should clinicians begin to assess long-term IOP ﬂuctuation in
patients under stable treatment (across days or visits)? and 5) Should therapy choices be inﬂuenced by
properties of different treatment options relative to short- or long-term IOP ﬂuctuation? (Surv
Ophthalmol 54:643--662, 2009. Ó 2009 Elsevier Inc. All rights reserved.)
Key words. adrenergic beta antagonists
carbonic anhydrase inhibitors
ophthalmologic diagnostic techniques
Glaucoma is one of the leading causes of visual
impairment and blindness in the United States
Lowering intraocular pressure
(IOP) is the only proven means to slow or halt disease
progression in studies of those at high risk of de-
veloping glaucoma (Ocular Hypertension Treatment
those with early to moderate
glaucoma (Collaborative Initial Glaucoma Treatment
and Early Manifest Glaucoma Trial
and those with more advancedglaucoma
(Collaborative Initial Normal-Tension Glaucoma
and Advanced Glaucoma Intervention Study
Across all randomized, controlled trials,
lowering IOP by at least 18% (mean) from baseline
resulted in at least a 40% reduction in rates of
worsening of glaucoma over 5 years.
studies conﬁrm that a pathophysiological basis for
glaucoma is elevated IOP. Studies of the biomechanical
properties of the cornea have improved our under-
standing of the effect of IOP on the optic nerve and
sclera, although this understanding has not led, as yet,
to a systematic effect on therapy.
The potential for
increased rates or likelihood of worsening glaucoma
among those with larger IOP swings within deﬁned
time periods has received increasing attention.
Ó 2009 by Elsevier Inc.
All rights reserved.
0039-6257/09/$--see front matter
SURVEY OF OPHTHALMOLOGY