Original Article
Efficacy and Safety of Argon Laser Trabeculoplasty in
Lowering Intraocular Pressure as Adjunctive Treatment to Primary Open Angle
Glaucoma
Uzma Fasih, Erum Shahid, Arshad Sheikh
Pak
J Ophthalmol 2019, Vol. 35, No. 1
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See end of article for authors affiliations …..……………………….. Correspondence to: Uzma Fasih FCPS, Associate Professor Eye
department, Karachi Medical and Dental College Abbasi Shaheed Hospital Email: yousufuzma@hotmail.com |
Purpose: To assess efficacy and safety of argon laser
trabeculoplasty (ALT) to lower intra ocular pressure (IOP) as adjunctive
treatment in primary open angle glaucoma (POAG) patients. Study Design: Descriptive Cross Sectional. Place and Duration of Study: Ophthalmology Department, Abbassi Shaheed Hospital
from May 2016 to August, 2017. Materials and Methods: Primary open glaucoma patients were selected from eye
OPD. Patients with Inflammatory, angle closure, traumatic glaucoma were
excluded. Pre laser and Post laser IOP was measured at 1st week
then at 1, 3 and 6 months. Data was collected and analyzed on SPSS version
20. There were 114 patients. Sample
size was calculated by Rao Soft Sample size calculator. Results: There were 69 (61%) male patients. Mean age of patients
was 60.53 ± 10.71 years. Mean pre laser Intraocular pressure was 23.98 ±
10.01 mm Hg. Mean post laser IOP at one month was 15.6 ± 3.25 and at 6 months
was 14.8 ± 3.28 mm Hg. Overall mean reduction of IOP was 9.18 mm Hg from
baseline, with p value less than < 0.005. Pre laser 3 medications were
used by 20 (18%) and 2 medications by 49 (43%). At 6 months follow-up 4 (3.5%)
patients were on 3 medications and 31 (37%) were on 2 medications. It has a p
value < 0.005. Drug free patients at 6 months follow-up were 37 (33%).
Mild iritis was seen in 7 (6.14%) patients. Conclusion: Argon Laser Trabeculoplasty is effective and safe
method to control IOP in POAG when used as an adjunct to medical therapy. It
also decreases number of drugs used by patients. Key Words: Argon laser trabeculoplasty, intraocular pressure,
primary open angle glaucoma. |
Glaucoma is the leading cause of irreversible blindness world
over. It is estimated that 64 million people suffer from this diease around the
world1. It is characterized by optic nerve damage, cupping of the
optic disc and typical visual field defects. Rise in intra ocular pressure is a
major risk factor. Reduction of intraocular pressure (IOP) may be helpful in
reducing the optic nerve damage2. It is the third leading cause of
irreversible blindness over the age of 40 years in Pakistan3.
Primary open angle glaucoma (POAG) commonly presents in
our clinics where the cause of raised intraocular pressure is functional
impairment of trabecular meshwork (TM). Medical treatment is the first line of
treatment. Surgical treatment is generally offered when patient does not
respond to medical treatment. Wise and Witter are credited for describing first
successful protocol, which is widely known as Laser Trabeculoplasty (LTP) in
19794.
The utilized energy source for modern LTP is
continuous-wave argon laser, operated in the blue-green wavelength spectrum
(454-529 nm)5. The exact mechanism of the procedure is not known,
but it is believed that the laser energy applied to the trabecular meshwork
initiates structural and/or physiologic changes that facilitate aqueous outflow6.
Wise and Witter stated that thermal energy produced by
pigment absorption of laser light causes fibrosis of collagen in trabecular
lamellae. Subsequent shortening of treated meshwork might enlarge existing
spaces between two treatment sites and expands Schlemm’s canal by pulling
meshwork centrally which facilitates the aqueous drainage from the trabecular
meshwork4,7.
Microscopic and immune histochemical analysis of the
trabecular meshwork after ALT has shown local photocoagulation of treated
trabecular tissue, while cells adjacent to treated areas have shown increased
phagocytic activity.
Moreover studies have reported changes in the
extracellular matrix after LTP related to an induction of matrix
metalloproteinases. These enzymes normally break down extracellular matrix to
maintain normal turnover of trabecular meshwork. Thus there is cellular
activation of trabecular mesh work with increased trabecular cell replication
and increased number of cells involved in maintaining the outflow from
trabecular meshwork8.
Laser trabeculoplasty (LTP) is a well known therapeutic
method for the management of glaucoma since the last 30 years, which became
popular during the past 10 years. LTP is an effective therapeutic option, as it
can supplement topical medical treatment. One laser session can reduce the
Intraocular pressure (IOP) for many years, thus reducing the adverse effects of
poor compliance associated with medical treatment. More over LTP is in general
a well tolerated and usually a low-risk procedure, as compared with glaucoma
surgery5.
Majority of patients coming to government hospitals
belong to poor socioeconomic class with poor compliance. This procedure will be
safe and cost effective in lowering intraocular pressure. It will also decrease
number of topical anti glaucoma medication which are a financial burden for
them. Little work has been published on this topic in local journals. We
conducted this study to asses efficacy and safety of argon laser
trabeculoplasty to lower intra ocular pressure as adjunctive treatment in
patients with primary open angle glaucoma.
MATERIALS AND METHODS
The study was carried out at ophthalmology department
Abbasi Shaheed Hospital and Karachi Medical & Dental College from May 2016
to August 2017. It was a descriptive cross sectional study. It was started
after approval from Ethical Review Committee of the hospital. Informed consent
was taken. Patients were registered through non probability consecutive
sampling technique. Sample size was calculated using Rao Soft Sample Size Calculator taking confidence interval 90%,
Margin of error 5%, population size 10,000 and prevalence P for reduction in
intraocular pressure 12.1 mm Hg from the
reference study.9 Calculated sample size was 114.
Patients 45 years of age or above, diagnosed with Primary
open angle glaucoma with failed medical treatment were included in the study.
Patients with angle closure glaucoma, inflammatory glaucoma, traumatic
glaucoma, aphakic and pseudophakic glaucoma
and those having history of previous trabeculectomy and cataract surgery
were excluded from the study.
Written informed consent was taken from them. Detail
history was taken. Ocular examination was conducted including visual acuity,
slit lamp examination, intraocular pressure, gonioscopy and fundoscopy.
Diagnosis of Primary open glaucoma was established after ocular examination,
optical coherence tomography and visual fields.
These patients underwent laser trabeculoplasty under
topical anaesthesia. Pressure lowering agents Brimonidine and Pilocarpine were
instilled 1 hour before surgery. A Goldmann 3-mirror goniolens was placed on
the eye with 1% methylcellulose. The helium-neon aiming beam was focused at the
junction of pigmented and non pigmented trabecular meshwork with a spot size of
50 microns and duration of 0.1 seconds, keeping the starting energy level at
200 watts and increased according to the level of TM pigmentation. Blanching of
the TM or bubble formation was taken as the end result. Approximately 50 adjacent
laser spots were applied over inferior 180° of the TM, 25 spots in each
quadrant.
Post laser IOP was measured at one hour, one day, one
week, and one, three, and six months. These responses were recorded on
predesigned performa. During the post laser follow-up period, patients were
treated with mild steroid (flouromethalone) 4 times a day which was withdrawn
after I week, topical nonsteroidal anti-inflammatory drug (nepafenac) 3 times a
day which was continued for 1 month and topical antiglaucoma medications as
required. Progression of glaucoma was monitored by visual fields and OCT
(Optical coherence tomography) throughout the study.
Data was collected and analyzed on SPSS version 20. Means
were computed for numerical variables like age, pre-laser intraocular pressure
and post laser intraocular pressure with standard deviations. Frequencies of
gender, eye, systemic diseases, visual acuity, prelaser and post laser
medications were calculated. A paired t test was used for assessing changes in
IOP at different follow up visits. Reduction in number of topical medications
pre laser and post laser treatment was assessed with help of pair t test. P
value of less than 0.05 was taken as statistically significant.
RESULTS
A total of 114 patients were included in our study. Out
of these male patients were (69) 61%. Mean age of the patients was 60.53 ± 10.71
SD years ranging from 45 to 82 years. Right eye was treated in 54 (47%)
patients and left eye was treated in 60 (53%) patients. All other demographic
features of patients are given in Table 1. Mean pre laser IOP was 23.98 ± 10.01
SD mm Hg. Mean IOP at day one post laser was 15.7 ± 3.68 SD mm Hg. Mean IOP at
one month post laser follow up was 15.6 ± 3.25 SD mm Hg. Mean IOP at 3 and 6
months post laser follow up visit was 14.8 ± 2.61 SD mm Hg and 14.8 ± 3.28 SD mm
Hg respectively. There was an overall mean reduction of 9.18 mm Hg from
baseline which was statistically significant (Table 2). Pre laser patients on 3
medications were 20 (18%) and those on 2 medications were 49 (43%) while at 3
months follow 4 (3.5%) patients were on 3 medications and 39 (34%) were on 2 medications. At 6 months follow-up 4 (3.5%) patients were
on 3 medications and 31 (37%) patients were on 2 medications (Table 3). This
reduction in medications was statistically significant with p value < 0.005.
Drug free patients at 6 months follow up were 37 (33%) (Table 1). No
significant post laser complications were seen except mild iritis in 7 (6.14%)
patients and transient rise in IOP in 2 (1.75%) patients which were managed
with topical steroids and pressure lowering agents.
Pair T test
was conducted to evaluate the effect of Argon laser trabeculoplasty on intra
ocular pressure. There was a significant difference in mean pre laser IOP
(23.98 ± 10.01 mm Hg SD) and 1 month post laser IOP (15.5 ± 3.2 mm Hg SD) with 95%
CI ranging from 6.66 to 10.1 with p value of less than 0.005. Three
Table 1: Demographic Characteristics.
Variables |
Frequencies |
Percentages |
Mean Age in years Minimum maximum |
60.53 ± 10.71SD 45 82 |
|
Gender Male |
69 |
61% |
Right eye Left eye |
54 60 |
47% 53% |
Duration of glaucoma (mean) years |
6 ± 3.6 years |
|
Visual acuity 6/6 -6/9 6/12- 6/18 6/24- 6/60 Less than 6/60 |
21 18 41 34 |
18.4% 16% 36% 30% |
Systemic disease HTN DM |
15 7 |
13% 6% |
Both eyes |
78 |
68.4% |
Drug free at 6 months post laser |
37 |
33% |
Table 2: Post Alt Reduction in IOP.
No. |
IOP |
Mean IOP
± SD mmhg |
Comparison |
P value |
1. |
Pre laser |
23.98 ± 10.01 |
|
|
2. |
1 day |
15.7 ± 3.68 |
1 & 2 |
<. 000 |
3. |
1 month |
15.6 ± 3.25 |
1 & 3 |
<. 000 |
4. |
3 months |
14.8 ± 2.61 |
1 & 4 |
<. 000 |
5. |
6 months |
14.8 ± 3.28 |
1 & 5 |
<. 000 |
Table 3: Post Alt Reduction in Medications.
|
Frequency |
% |
Pre laser medication 1 medication 2 medications 3 medications 4 medications |
25 49 20 20 |
22% 43% 18% 18% |
Post laser 3 month 1 medication 2 medications 3 medications 4 medications |
45 39 4 0 |
40% 34% 3.5% |
Post laser 6 month 1 medications 2 medications 3 medications 4 medications |
38 35 4 0 |
33% 31% 3.5% |
Table 4: Pair-T Test.
No. |
No of Medications |
P value |
1. |
Prelaser medications & at 3 month |
<. 000 |
2. |
Prelaser medication & at 6 month |
<. 000 |
month post laser mean IOP was 14.8 ± 2.61SD mm Hg with
95% CI ranging from 7.4 to 10.8 and P value of less than .005. Six month post
laser mean IOP was 14.8 ± 3.2 mm Hg SD with 95% CI ranging from 7.4 to 10.9 and
p value of less than .005. So the difference between pre laser mean IOP and
post laser mean IOP at 1, 3 and 6 months was highly significant.
Pair T test was conducted to see the reduction in
prelaser and post laser medication. Mean difference in prelaser medication was
2.307 with 95% confidence interval from 2.12 to 2.49. While 6 months post laser
medication mean difference was 1.053 with 95% confidence interval ranging from
0.89 to 1.22. with p value less than 0.005 which was highly significant.
DISCUSSION
In the developing world treatment options for glaucoma
are becoming more complicated as all treatment modalities and health care
facilities are not available in all environments. In addition cost of medicines
and hurdles in their distribution make medical treatment of glaucoma very
difficult and sometimes impossible in most of the developing countries.
Prostaglandin analogs are said to be the first line of treatment currently10.
Topical B blockers, alpha adrenergic agonists and Carbonic anhydrase inhibitors
may be used as additional therapies when required but there may be a
significant inter patient variability in their response.11,12.
ALT has been known to be an effective method for
reduction of IOP in POAG patients. Use of this modality as an adjunctive to the
medical treatment cannot be overlooked. ALT does not cure glaucoma but provides
a long term reduction in IOP when used as an adjunctive treatment to medical
treatment of glaucoma. In addition ALT cannot be relied upon as primary
treatment option in patients who have poor compliance as there may be long
periods of uncontrolled IOP. So ALT could be a better adjunctive treatment for
glaucoma rather than primary treatment10.
We conducted this study to document the efficacy of this
procedure as an adjunctive therapy to medical treatment in patients of POAG. We
found in our study that there was a mean reduction of 9.18 mm Hg in post laser
IOP as compared to base line and 6 month follow up period there was a
significant reduction in number of topical medications. A randomized clinical
trial known as Glaucoma Laser Trial GLT was carried out in America to assess safety
and efficacy of LTP for controlling IOP in POAG patients .They reported a mean
reduction of 9 mm Hg in IOP among the laser treated eyes as compared to 7 mm Hg
reduction in IOP among those who were treated with medical treatment. The study
also reported that ALT could be regarded as an equally effective therapy as
medical treatment for POAG patients. Our study also reported similar reduction
in IOP12.
Shawartz and Coworkers also reported a drop of 9.7 mm Hg
in mean IOP at 2 months follow-up, 7.3 mm Hg at 2 years and 4.9 mm Hg at 5
years follow up after Argon Laser Trabeculoplasty in cases of POAG13.
Speath and Et al concluded in their study that LTP deferred the need of
surgical treatment in about one third of the patients of POAG14.
Sharma and Gupta reported 76% success rate of ALT in POAG
in their study.9 One of the local study by Mehar and et al reported
12.1 mmHg reduction in mean IOP at 6 months follow up in their case series of
35 eyes15.
Detry-Morel et al also reported a mean reduction of 4.9 mmhg
in IOP and significant reduction in number of drugs required at final visit
along with minimal anterior chamber inflammation16. Grinich
et al reported 7.8 mmmHg reduction in IOP at 3 years follow-up17.
Achadi Et al reported 40.3% success rate of ALT at 5 years follow up18.
Agarwal and et al reported reduction of 7.2 mm Hg in mean
IOP at 6 month follow up after LTP which is quite similar to 9.18 mm Hg post
laser reduction of IOP in our study. Post Laser complications in their study
like transient rise of IOP was found to be 51.3% patients, Iritis in 5%
patients, formation of peripheral anterior synechia in 2.5% patients and rarely
hyphaema19.
The frequency of complications was fewer in our study
like mild iritis was seen in 7 (6.14%) patients, transient rise in IOP in 2 (1.75%)
patients and no hyphaema. The reason for few complications could be that
patients were kept on topical nonsteroidal antinfammatory drugs in addition to
steroids and topical brimonidine.
In our study pre laser patients on 3 medications were 20
(18%), those on 2 medications were 49 (43%) and on one medication were 25 (22%).
At 6 months follow up 4 (3.5%) patients were on 3 medications and 35 (31%)
patients were on 2 medications and 38(33%) on one medication. This reduction in
medications was statistically significant p value < 0.005. Drug free
patients at 6 months follow up were 37 (33%) while 4 (3.7%) patients had to be
supplemented with trabeculectomy due to uncontrolled IOP at 6 months follow up.
In study by Agarwal 10.2% patients underwent trabeculectomy at 6 momths follow
up. Agarwal and et al reported 10% drug free patients, 15% on one medication
and 20% on 2 medications at 5 year follow up. The differences from our study
could be due to their prolonged follow up period19.
Adequate safety and efficacy profiles of laser
trabeculoplasty have been reported .Due to the reliable safety and
efficacy of laser trabeculoplasty this procedure can be used at any time during
the treatment of POAG as primary or adjunctive therapy and also decreases the
need of any medical treatment before going for any surgical intervention20.
It can also be tried before cataract surgery of glaucoma
patients to achieve a better management of IOP and to reduce the number of
medications in patients who are on more than one drug. In addition it can be
used in patients who are at risk of rise in IOP after receiving intravitreal
injections21. Majority of the studies reported 25-30% post laser
decrease in IOP22.
Another study reported that if LTP is used earlier in
treatment of POAG the risk of adverse effect is diminished as the number of
medications are decreased to reduce the IOP.23 Stein Et al reported
that LTP is economical and cost effective as compared to medical treatment24.
Limitation of our study is short term follow up period.
Long term follow up is required to determine efficacy of ALT as an adjunctive
therapy for prolonged control of IOP in POAG.
CONCLUSION
We concluded from our study that ALT is a safe and
effective method to control IOP in POAG when used adjunct to medical therapy.
It helps in decreasing the number of topical medications used for management of
POAG and is thus cost effective.
Conflict of Interest: None.
Author’s Affiliation
Dr. Uzma Fasih
FCPS, Associate Professor
Eye department, Karachi medical and
dental college Abbasi Shaheed Hospital.
Dr. Erum Shahid
MCPS, FCPS, Assistant professor
Eye department, Karachi medical and
dental college Abbasi shaheed hospital
Dr. Arshad Sheikh
MCPS, FCPS, professor and Head of
department
Eye department, Karachi medical and
dental college Abbasi shaheed hospital
Author’s Contribution
Dr. Uzma Fasih
Concept design, data collection,
Manuscript writing, Data analysis, Critical
review.
Dr. Erum Shahid
Concept, Design, critical review.
Dr. Arshad Sheikh
Concept design, data collection, Critical
review.
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