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Selective laser trabeculoplasty for the treatment of glaucoma

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Selective laser trabeculoplasty for the treatment of glaucoma

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Content SELECTIVE LASER TRABECULOPLASTY FOR THE TREATMENT OF
Copyright 2006
GLAUCOMA
by
Brandon C. Traudt
A Thesis Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERNA CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE
(APPLIED BIOSTASTISTICS/EPIDEMIOLOGY)
May 2006
Brandon C. Traudt
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UMI Number: 1437843
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Table of Contents
List of Tables and Figures iii
Abstract iv
Introduction 1
Methods 3
Figure 1: Survival curve showing the proportion of eyes that
underwent successful select laser trabeculoplasty surgery 5
Results 5
Discussion 9
References 11
Bibliography 13
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List of Tables
Table 1: Baseline and Ocular Characteristics o f Case Series
Table 2: IOP and Change in IOP Post-Laser Treatment
Table 3: Medications and Change in Medications Post-Laser
Treatment
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Abstract
The primary aim of this study was to evaluate the efficacy of selective laser
trabeculoplasty as treatment for open-angle glaucoma after failed trabeculectomy.
This prospective, non-randomized, interventional clinical trial included 26 eyes of 21
consecutive glaucoma patients who had a previous failed trabeculectomy with
medically uncontrolled intraocular pressure. Selective laser trabeculoplasty was
performed. Success was defined as an intraocular pressure lowering of 3 or more
mmHg. There was a statistically significant decrease in mean intraocular pressure
when comparing pre-operative intraocular pressure and intraocular pressure at one
month to 12 months. The mean decrease in number of medications was not
statistically significant except at one month. These data indicate that selective laser
trabeculoplasty is moderately effective in lowering intraocular pressure after failed
trabeculectomy. In most patients, the procedure resulted in a clinically and
statistically significant intraocular pressure decrease of 3 or more mmHg.
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Introduction
Glaucoma is an eye disease that is characterized by ocular tissue damage and
vision loss caused by elevated intraocular pressure and is the leading cause of
blindness in the United States. This damage may be temporary or permanent.
Elevated intraocular pressure without tissue damage may result from ocular
hypertension, which may or may not lead to a diagnosis of glaucoma (1). Elevated
intraocular pressure is a problem for 4% to 7% of those older than 40 (2, 3).
Glaucoma may be a result of co-existing conditions, or may be the primary
condition.
Glaucoma is typically classified as either open-angle or closed-angle
glaucoma. Open-angle glaucoma is caused by problems within the drainage system
within the eye itself while closed-angle glaucoma is caused by poor access to the
drainage system (1). Open-angle glaucoma affects nearly 2% of the adult population
in the United States (4). In virtually all cases, open-angle glaucoma is bilateral,
though the lag-time between diagnoses may be months or years. Specifically, for
open-angle glaucoma cases, the elevated pressure within the eye damages the optic
nerve. In open-angle glaucoma, the angle between the iris and the cornea is open,
however problems in the drainage system do not allow for proper drainage of
aqueous humor, the fluid within the eye that allows the eye to function normally (1).
When the pressure is too high, the optic nerve is damaged and vision is impaired (1).
Glaucoma is not a curable disease; however there are several ways in which it
can be managed. This routinely involves attempts to control ocular hypertension by
1
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lowering intraocular pressure. A decrease in intraocular pressure may be sought in
order to delay or avoid the onset of glaucoma in the ocular hypertensive, or to delay
or avoid vision loss in those already diagnosed with glaucoma. Typically, this
process ranges from the minimally to the highly invasive. A medicine-only approach
is generally considered as the first option; as it is the least invasive (5). This is
usually followed by laser surgery, and then regular surgery. There are several types,
or classes, of medication, and the magnitude of the resultant decrease in intraocular
pressure ranges from 20% - 35% (5). Laser surgery is next in the scale of
invasiveness. Laser surgery is relatively non-invasive and unlike medicinal treatment
does not suffer from non-compliance issues. The average decrease in intraocular
pressure varies as widely as that with medicine, 20% to 30%, but the effects may
wear off after an extended period of time— as soon as five years (6). Laser
trabeculoplasty mainly consists o f two types: argon laser trabeculoplasty and
selective laser trabeculoplasty. The remainder of this report will be concerned with
selective laser trabeculoplasty.
Laser surgery itself is not a new procedure. Argon laser trabeculoplasty was
evaluated as a potential treatment for glaucoma in 1979 and proved to be able to
lower intraocular pressure (7). However, argon laser trabeculoplasty has the
disadvantage of potentially causing structural damage, scarring and other problems.
Compared with argon laser trabeculoplasty, selective laser trabeculoplasty emits less
energy. Since selective laser trabeculoplasty results in less overall damage, it is safer
2
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and may be repeated over time (8). Safety and efficacy have been demonstrated in
several clinical trials (9, 10, 11, 12).
The objective of this paper is to evaluate, in a case series of glaucoma
patients, the ability of selective laser trabeculoplasty to lower intraocular pressure,
and if that decreased intraocular pressure is maintained at month one, three, six, nine,
and 12 months thereafter.
Methods
Twenty-one glaucoma patients (26 eyes) were recruited from the clinical
practice from a referral glaucoma department at the Doheny Eye Institute at the
University of Southern California (USC). Patient enrollment was staggered over a
period of approximately 2 years. The cohort consisted of patients who had a previous
failed trabeculectomy and medically uncontrolled intraocular pressure and were
unable or unwilling to undergo further incisional surgery. Informed consent was
received prior to surgery and the USC Institutional Review Board (IRB) for research
on human subjects approved the study.
The laser procedure was performed with a Latina laser gonioscopy lens
coupled with methylcellulose 1%. A drop of topical proparacaine was instilled for
anesthesia. The helium-neon aiming beam was focused on the trabecular meshwork.
The entire available trabecular meshwork was treated with 70-110 adjacent spots,
using a standard spot size of 400 microns and pulse duration of 3 nanoseconds.
Energy was initially set at 0.9 mJoules and titrated up or down based upon the
observed tissue effect (when the power is sufficient to form small cavitation bubbles
3
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anterior to the trabecular meshwork, the power was decreased by 0.1 mJoule). One
drop of brimonidine 0.2% was applied topically after the procedure to reduce the risk
of IOP spike. Post-operative medication consisted of a topical non-steroidal anti
inflammatory drug used twice to three times daily for up to 7 days as needed for
post-operative pain. All IOP measurements were made by Goldmann applanation
tonometry by observers masked to the treatment. The IOP was measured at 1 hour
after the procedure. If it was elevated 10 mmHg or more, the patient was placed on
acetazolamide 250 mg QID or methazolamide 25 to 50 mg BID by mouth and seen
the following day. IOP was measured at 1, 3, 6, 9 and 12 months following laser in
all patients.
The main outcome measures of this study were intraocular pressure before
and after laser surgery and the number o f glaucoma medications taken before surgery
and after surgery. As these data are dependent, that is, there is a correspondence
between each data point (intraocular pressure), a simple paired t-test was used to
compare changes in pre-operative and post-operative intraocular pressure. A paired t-
test was performed comparing: 1.) pre-operative intraocular pressure and intraocular
pressure at three months, six months, nine months, and 12 months; and 2.) mean
number of medications taken pre- and post-operatively. Success of the procedure in
terms of a decrease in intraocular pressure was defined as a drop in pressure of 3mm
Hg or more from baseline or as a continued maintenance of the target intraocular
pressure with a reduced number of medications. This success is demonstrated as a
Kaplan Meier survival curve with cumulative success (failure is the defining
4
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endpoint) plotted as a function o f time for time points from one to twelve months at
three month intervals (Figure I).
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Figure 1. Survival curve showing the proportion of eyes that underwent successftil
select laser trabeculoplasty surgery. The Y-axis represents the proportion of eyes
that reduced IOP by at least 3 mm HG.
Results
There were 15 females (57.7%) and 11 males (42.3%) (Table 1). The
procedure was performed on the right eye (OD) in nine patients, performed on the
left eye (OS) in seven patients, and on both eyes for five patients, for a total of 26
eyes (Table 1). Some subjects were lost to follow-up after nine months.
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Table 1. Baseline and Ocular Characteristics of Case Series (n=21 patients, 26
eyes)
Characteristic
Gender
Male* 8(38.1% )
Female 13 (61.9%)
Age** 78.3 (7.3)
62-88
IOP (mm Hg) 19.3 (4.7)
11-34
Eye
Right 9 (42.8%)
Left 7 (33.3%)
Both 5 (23.8%)
Lens Status
Pseudophakic 21 (80.8%)
Phakic 5 (19.2%)
Number of
medications
2.04 (0.66)
* Frequency (%)
** Mean (SD), range
Approximately 80% of the eyes were pseudophakic (intraocular lens
implant), the rest being phakic (a natural lens) (Table 1). The mean age was almost
79 (Table 2). The mean intraocular pressure pre-laser was about 19. Mean
intraocular pressure at one month was about 17.4 mm Hg and decreased to
approximately 15 .1 mm Hg at 12 months (Table 2). The mean decrease in mean
intraocular pressure over 12 months ranged from approximately 1.9 mm Hg to 4.0
mm Hg. Intraocular pressure measurements and prescribed medicines were not
available for all patients at all time points (Tables 2 and 3).
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Table 2: IOP and Change in IOP Post-Laser Treatment
Time post-laser IOPa Change in
IOPb
P-value 3mm
Decrease
in IOPc
1 month (n=26) 17.4(5.8)
9 -3 3
1.92 (9.8%)
0 .3 9 -4 .2 4
0.09 16(61.5%)
3 months (n=26) 15.9(4.5)
1 0 -3 2
3.42(17.6% )
1.57-5.28
<0.001 19 (73.1%)
6 months (n=23) 16.2 (3.3)
1 0 -2 2
3.30 (16.0%)
1.1 7 -5 .4 4
0.004 17 (73.9%)
9 months (n=19) 16.0(4.3)
6 -2 3
4.05 (17.1%)
0 .7 9 -7 .3 2
0.018 15 (78.9%)
12 months (n=17) 15.1 (2.7)
7 -1 9
3.59 (20.5%)
1.25-5.93
0.005 14 (82.3%)
a. Mean (SD), Range
b. Mean (%), 95% confidence interval
c. Also includes those that achieved the target IOP while reducing the number of
medications.
Table 3. Medications and Change in Medications Post-Laser Treatment
Time post-laser Mean number
of medications*
Change in
number of
medications**
P-value
1 month (n=26) 2.04 (0.66) 0.31 (15.2%)
0 .0 6 -0 .5 6
0.02
3 months (n=26) 1.73 (0.91) 0.27 (13.2%)
0 .1 2 -0 .6 6
0.17
6 months (n=25) 1.76 (0.97) 0.24(13.7%)
0 .1 6 -0 .6 4
0.23
9 months (n=23) 1.65 (1.07) 0.35 (19.1%)
0.08 - 0.77
0.10
12 months (n=21) 1.67(1.06) 0.38(18.1%)
0 .0 8 -0 .8 5
0.10
* Mean (SD)
** Mean (%), 95% confidence interval
These data show that there is a statistically significant decrease in mean
intraocular pressure when comparing pre-operative intraocular pressure and
7
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intraocular pressure at one month, three months, six months, nine months, and 12
months. For example, there was a statistically significant decrease in mean
intraocular pressure (3.6 mm Hg) at 12 months (Cl: 1.2 - 5.9, p < 0.05) (Table 2).
Pre-laser, the mean number of medications was approximately 2 (Table 3)
The decrease in mean number of medications was approximately 1.6 for month(s)
one to 12, however the difference was statistically significant only at one month (Cl:
0.14-0.64, p < 0.05).
At 12 months, more than 50% of eyes maintained their target intraocular
pressure, or had lower intraocular pressure with or without medication (Figure 1).
Out of the 26 eyes, 13 maintained their visual acuity at six months when
compared to their pre-operative vision as measured by visual acuity. There were four
eyes that had an increase or decrease of only one line, there were five eyes that had
improved vision of two lines or more, and there were four eyes that had a decrease in
vision of two or more lines (data not shown). For example, a patient who had 20/30
pre-operative vision would have increased their vision by two lines if their vision
was 20/20 at six months (after surgery).
Similar patterns were seen when the data were re-analyzed excluding the eye
with the initial lower intraocular pressure of patients that underwent treatment for
both eyes. The results were generally consistent with those results that included both
eyes of the patients (data not shown).
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Discussion
While the small sample prohibits definitive conclusions, this small study
shows that select laser trabeculoplasty is, in the short term, effective in reducing
intraocular pressure in open-angle glaucoma patients. The mean IOP lowering was
3.6 mmHg at 12 months following laser. According to the definition of success
presented here of IOP lowering of 3 or more mmHg, approximately 50% of patients
were successful. While this moderate decrease in intraocular pressure is not as
significant as seen in a previous trial of selective laser trabeculoplasty (10), the
current study includes those patients with a history of failed trabeculectomy. This
likely will decrease the success rate as those patients with failed trabeculectomy
likely have a more aggressive glaucoma with high intraocular pressure that is
difficult to control. Furthermore, patients with intraocular pressure that is difficult to
control have potentially undergone previous procedures that reduce the likelihood of
success with selective laser trabeculoplasty. In addition to a moderate reduction in
intraocular pressure, there is evidence here that selective laser trabeculoplasty may
lead to a reduction in the number of medications a patient will need to take.
Prospective, non-randomized, interventional clinical trials, such as this, are
inherently self-limiting, in that there is not a separate control group and there is no
randomization. However, it is unlikely that the decrease in intraocular pressure
observed in these patients would have occurred absent selective laser
trabeculoplasty. Because these were a select group o f patients, these results may not
be generalizable to other open-angle glaucoma patients.
9
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Further studies with a greater number of patients and with longer follow-up
are necessary in order to better evaluate selective laser trabeculoplasty as means to
control high intraocular pressure in open-angle glaucoma patients and reduce the
number of medications the patient needs to take.
10
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References
1. YanoffM. Fine BS. Ocular Pathology: A Text and Atlas, 2n d ed. Philadelphia, PA:
Harper and Row, Publishers, Inc., 1982: 743-784.
2. Lebowitz HM, Krueger DE, Maunder LR, et al.. The Framingham Eye Study
monograph: An ophthalmological epidemiological survey of cataract, glaucoma,
diabetic retinopathy, macular degeneration, and visual acuity in a general population
of 2631 adults, 1973 - 1975. Surv Ophthalmol 1980, 24(suppl):335-610.
3. Sommer A, Tielsch JM, Katz J, et al.: Relationship between intraocular pressure
and primary open-angle glaucoma among white and black Americans: The Baltimore
Eye Survey. Arch Ophthamol 1991, 109:1090-1095.
4. The Eye Diseases Prevalence Research Group. Prevalence of open-angle
glaucoma among adults in the United States. Arch Ophthalmol 2004, 122:532-538.
5. Schwartz K, Budenz D. Current management of glaucoma. Curr Opin Ophthalmol
2004; 15:119-126.
6. Holz HA, Lim MC. Glaucoma lasers: a review of the newer techniques. Curr Opin
Ophthalmol 2005; 16:89-93.
7. Wise JB, Witter SL. Argon laser therapy for open-angle glaucoma: A pilot study.
Arch Ophthalmol 1979, 97:319-322.
8. Kramer TR, Noecker RJ. Comparison of the morphologic changes after selective
laser trabeculoplasty and argon laser trabeculoplasty in human eye bank eyes.
Ophthalmology 2001; 108:773-779.
9. Damji KF, Shah KC, Rock WJ, et al. Selective laser trabeculoplasty vs. argon
laser trabeculoplasty: A prospective randomized clinical trial. Br J Ophthalmol
1999;83:718-722.
10. Latina MA, Sibayan SA, Shin DH, et al. Q-switched 532-nm Nd.YAG laser
trabeculoplasty (selective laser trabeculoplasty): A multi-center, pilot, clinical study.
Ophthalmology 1998;105:2082-2090.
11. Juzych MC, Chopra V, Banitt MR, et al. Comparison of long-term outcomes of
selective laser trabeculoplasty versus argon laser trabeculoplasty in open-angle
glaucoma. Ophthalmology 2004; 111:1853-1859.
11
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
12. Francis BA, Ianchulev T, Schofield JK, et al. Selective laser trabeculoplasty as a
replacement for medical therapy in open-angle glaucoma. Am J Ophthalmol. 2005
Sep; 140(3): 524-5.
12
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Bibliography
Damji KF, Shah KC, Rock WJ, et al. Selective laser trabeculoplasty vs. argon laser
trabeculoplasty: A prospective randomized clinical trial. Br J Ophthalmol
1999;83:718-722.
Francis BA, Ianchulev T, Schofield JK, et al. Selective laser trabeculoplasty as a
replacement for medical therapy in open-angle glaucoma. Am J Ophthalmol. 2005
Sep;140(3):524-5.
Holz HA, Lim MC. Glaucoma lasers: a review o f the newer techniques. Curr Opin
Ophthalmol 2005; 16:89-93.
Juzych MC, Chopra V, Banitt MR, et al. Comparison of long-term outcomes of
selective laser trabeculoplasty versus argon laser trabeculoplasty in open-angle
glaucoma. Ophthalmology 2004; 111:1853-1859.
Kramer TR, Noecker RJ. Comparison of the morphologic changes after selective
laser trabeculoplasty and argon laser trabeculoplasty in human eye bank eyes.
Ophthalmology 2001; 108:773-779.
Latina MA, Sibayan SA, Shin DH, et al. Q-switched 532-nm Nd:YAG laser
trabeculoplasty (selective laser trabeculoplasty). A multi-center, pilot, clinical study.
Ophthalmology 1998;105:2082-2090.
Lebowitz HM, Krueger DE, Maunder LR, et al.: The Framingham Eye Study
monograph: An ophthalmological epidemiological survey of cataract, glaucoma,
diabetic retinopathy, macular degeneration, and visual acuity in a general population
o f2631 adults, 1973 - 1975. Surv Ophthalmol 1980, 24(suppl):335-610.
Schwartz K, Budenz D. Current management o f glaucoma. Curr Opin Ophthalmol
2004; 15:119-126.
Sommer A Tielsch JM, Katz J, et al.: Relationship between intraocular pressure and
primary open-angle glaucoma among white and black Americans. The Baltimore
Eye Survey. Arch Ophthamol 1991, 109:1090-1095.
The Eye Diseases Prevalence Research Group. Prevalence o f open-angle glaucoma
among adults in the United States. Arch Ophthalmol 2004, 122:532-538.
Yanoff M, Fine BS. Ocular Pathology: A Text and Atlas, 2n d ed. Philadelphia, PA.
Harper and Row, Publishers, Inc., 1982: 743-784.
13
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

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Asset Metadata

Creator Traudt, Brandon C. (author)

Core Title Selective laser trabeculoplasty for the treatment of glaucoma

Degree Master of Science

Degree Program Applied Biostatistics and Epidemiology

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag health Sciences, ophthalmology,OAI-PMH Harvest

Language English

Contributor Digitized by ProQuest (provenance)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c16-53656

Unique identifier UC11338146

Identifier 1437843.pdf (filename),usctheses-c16-53656 (legacy record id)

Legacy Identifier 1437843.pdf

Dmrecord 53656

Document Type Thesis

Rights Traudt, Brandon C.

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Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus, Los Angeles, California 90089, USA