MAJOR REVIEW
Understanding the Importance of IOP Variables
in Glaucoma: A Systematic Review
Marla B. Sultan, MD, MBA,
1,2
Steven L. Mansberger, MD,
3
and Paul P. Lee, MD, JD
4
1
New York Eye & Ear Infirmary, New York, New York;
2
Pfizer Inc, New York, New York;
3
Devers Eye Institute, Legacy
Health System, Portland, Oregon; and
4
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
glaucoma
intraocular pressure
ocular tonometry
ophthalmologic diagnostic techniques
prostaglandin analogs
I. Introduction
Glaucoma is one of the leading causes of visual
impairment and blindness in the United States
21,32
and worldwide.
101
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
Study [OHTS]),
48
those with early to moderate
glaucoma (Collaborative Initial Glaucoma Treatment
Study
67
and Early Manifest Glaucoma Trial
[EMGT])
42,66
and those with more advancedglaucoma
(Collaborative Initial Normal-Tension Glaucoma
Study
19,20
and Advanced Glaucoma Intervention Study
[AGIS]).
2
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.
20,42,66,67
These
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.
17,109
The potential for
increased rates or likelihood of worsening glaucoma
among those with larger IOP swings within defined
time periods has received increasing attention.
643
Ó 2009 by Elsevier Inc.
All rights reserved.
0039-6257/09/$--see front matter
doi:10.1016/j.survophthal.2009.05.001
SURVEY OF OPHTHALMOLOGY
VOLUME 54
NUMBER 6
NOVEMBER–DECEMBER 2009