ORIGINAL ARTICLE  
Efficacy of Microwave Pulse Diode Laser and Argon  
Laser Trabeculoplasty in Patients with Primary Open  
Angle Glaucoma  
Asma Shams1, Narain Das2, Noman Rashid3, M. Nasir Bhatti4, Beenish Khan5, Jai Kumar6  
1,2,4,5,6Departments of Ophthalmology and 3Phsiology, Shaheed Mohtarma Benazir Bhutto Medical College Lyari  
5UM & DC, Karachi  
ABSTRACT  
Purpose: To compare the efficacy of the microwave pulse diode laser and argon laser trabeculoplasty in primary  
open angle glaucoma.  
Study Design: Quasi experimental study.  
Place and Duration of Study: Shaheed Mohtarma Benazir Bhutto Medical College Lyari and Sindh Government  
Lyari General Hospital, Karachi, from October, 2017 to March, 2018.  
Material and Methods: One hundred and sixty patients, between 42 to 61 years with visual acuity of perception  
of light to 6/36 were enrolled. Patients diagnosed with POAG were included and patients with intraocular pressure  
of more than 40 mm Hg, previous glaucoma surgery or laser treatment and narrow angle on gonioscopy were  
excluded. Ophthalmic examination included visual acuity, slit lamp examination, fundus examination and visual  
field status using Humphrey perimeter. Patients were divided into two groups. Group A received microwave pulse  
diode laser (810) and Group B received argon laser trabeculoplasty. Average follow up period was 6 months.  
Success was assessed objectively by measuring intra ocular pressure and subjectively by visual acuity.  
Results: The average time-period for each procedure was 15 ± 5 minutes. In Group A, mean IOP at first week,  
first month, third month and sixth month was 20.79, 16.34, 16.21and 16.09 mm Hg respectively. While in Group  
B, IOP at first week, first, third and sixth month was 16.52, 15.76, 13.62, and 12.54 mm Hg at (P < 0.001 in both  
groups).  
Conclusion: Both microwave pulse diode laser and argon laser trabeculoplasty are effective in lowering intra  
ocular pressures in patients with primary open angle glaucoma.  
Key Words: Open angle glaucoma, Argon laser trabeculoplasty, Diode laser trabeculoplasty, Intra ocular  
pressure (IOP).  
How to Cite this Article: Shams A, Das N, Rashid N, Bhatti MN, Khan B, Kumar J. To Compare the Efficacy of  
the Microwave Pulse Diode Laser and Argon Laser Trabeculoplasty in Patients with Primary Open Angle  
Glaucoma. Pak J Ophthalmol. 2020; 36 (3): 211-215.  
Doi: 10.36351/pjo.v36i3.1008  
blindness in the world, while it is 3rd most common  
INTRODUCTION  
blinding disease in Pakistan1-2. According to WHO  
Glaucoma is the second most common cause of  
program of blindness, 16% of total blindness for year  
____________________________________________  
Correspondence to: Asma Shams  
2020 will be from glaucoma3. Glaucoma affects an  
estimated 67 million people, most of them are not  
aware of the disease4. Glaucoma is a threatening eye  
disorder in which the permanent optic nerve damage  
may occur and results in visual field loss5. Early  
therapeutic intervention is pivitol for stopping  
Shaheed Mohtarma Benazir Bhutto Medical College  
Lyari, Karachi  
Email: dr.shaikh82@yahoo.com  
Received: March 3, 2020  
Accepted: May 4, 2020  
Revised: May 4, 2020  
Pakistan Journal of Ophthalmology, 2020, Vol. 36 (3): 211-215  
211  
Asma Shams, et al  
complete blindness. Glaucoma is diagnosed on the  
basis of intra ocular pressure, visual field testing and  
optic nerve appearance on ophthalmoscopy. In  
glaucoma, retinal ganglions cells axons are lost  
causing thinning or atrophy of retinal nerve fiber layer  
in superior and inferior arcuate bundles with exposed  
smaller retinal vessels. Primary Open Angle Glaucoma  
(POAG) accounts for about 50% of glaucoma  
blindness6. The first line of treatment for glaucoma is  
medical therapy in the form of eye drops7. Several anti  
glaucoma medications are effective in lowering the  
IOP and thus preventing the optic nerve damage.  
Failure of medical treatment leads to interventional  
laser trabeculoplasty or trabeculectomy8.  
patients. Ophthalmic examination included, record of  
visual acuity, slit lamp examination of the anterior  
segment, Fundus examination with slit lamp using +90  
D lens to assess neuroretinal rim, CD ratio, vascular  
status and macula. Visual field status was analyzed  
using Humphrey perimeter.  
The procedure was explained to all the patients  
with its benefits and complications. Informed written  
consent was taken. IOP was measured before the  
procedure. The patients were seated comfortably.  
Topical Proparacaine 0.5% eye drops were instilled in  
the eye to be treated. Ritch trabeculoplasty lens was  
filled with hydroxy propyl methyl cellulose and  
applied. Alcon Ophthalmus 532 Eyelite frequency  
doubled Nd-yag laser Photocoagulator was used. The  
aiming beam was focused at the junction of pigmented  
and non pigmented trabeculum. The ideal reaction was  
transient blanching or the appearance of a minute gas  
bubble at the point of impact. Forty to sixty burns were  
applied at regularly spaced interval. Single drop of  
topical diclofenac sodium 0.1% was instilled into the  
eye after procedure. IOP was checked 3 hours after the  
procedure. All patients were prescribed diclofenac  
sodium 0.1% eye drops 4 times a day for 5 days to  
control inflammatory response.  
Over the years, ophthalmologists are trying to  
achieve an ideal treatment for glaucoma and the role of  
microwave pulse diode laser trabeculoplasty (MDLT)  
and Argon laser trabeculoplasty (ALT) in management  
of POAG. It is a procedure in which tiny holes are  
created in trabecular meshwork with the help of laser  
thereby which improves the facility of out flow. Both  
argon and microwave pulse diode lasers have been  
used for this purpose. It is reported that ALT success  
rate is 90%9. A study regarding MDLT has shown  
success rate to be 75%10.  
Purpose of our study was to compare the efficacy  
of ALT and MDLT in a tertiary care hospital of  
Pakistan.  
All patients were followed up regularly at 1 week,  
4 weeks and 6 months after the procedure. At each  
visit, IOP was measured, gonioscopy was done and  
fundus examination was performed with slit lamp  
using 90 D lens. The final outcome was monitored at 6  
months. The treatment was labeled successful if IOP  
was < 21 mm Hg at 6th month. Cases failed to reduce  
to that level were labeled failed and were treated with  
either additional laser application sessions or anti-  
glaucoma drugs.  
MATERIAL AND METHODS  
The study was conducted at Shaheed Mohtarma  
Benazir Bhutto Medical College Lyari and Sindh  
Government Lyari General Hospital, Karachi for  
duration of six months from October, 2017 to March,  
2018. The study was approved from institutional  
review committee. One hundred and sixty patients  
were selected from glaucoma clinic. Patients  
diagnosed with POAG, both gender and age > 40 years  
and < 70 years were included. Patients with Intraocular  
pressure of more than 40 mm Hg, previous glaucoma  
surgery or laser treatment and narrow angle on  
gonioscopy were excluded from the study. Patients  
were divided into two groups. Group A was treated  
with microwave pulse diode laser while Group B was  
treated with Argon laser. The data regarding reduction  
in IOP < 21 mm Hg and efficacy were entered in  
already designed Proforma. All patients were  
evaluated by taking thorough history and examination.  
General physical examination was carried out in all  
RESULTS  
Male to female ratio was 2:1. Mean age of the patients  
was 55.69 years (range 41 – 69 years). Table 1 shows  
the distribution of patients by gender and age group in  
each intervention group. According to sample size, 80  
eyes of 73 patients were examined and treated in the  
Group A with Microwave pulse diode laser (810).  
There were 57 (71.3%) males and 23 (28.8%) females  
in this group. The mean age of the patients in this  
group was 55.8 years (Range 42 – 69). The mean pre-  
212  
Pakistan Journal of Ophthalmology, 2020, Vol. 36 (3): 211-215  
Efficacy of the Microwave Pulse Diode Laser and Argon Laser Trabeculoplasty in Patients with Primary Open Angle  
treatment IOP of 80 eyes (of 73  
Table 1: Gender Distribution in Each Group According to Age Group (n= 160,  
80 in each group).  
patients) was 31.8 ± 5.32 mm Hg.  
The mean IOP was 19.24+4.9 mm  
Hg at 6 months postoperatively.  
Age  
Group A (n = 80)  
Male Female Total  
Group B (n = 80)  
Male Female Total  
Total No.  
of Eyes  
55  
(Years)  
41 – 50  
51 – 60  
61 – 70  
Total  
18  
25  
12  
55  
11  
10  
04  
25  
29  
35  
16  
80  
16  
31  
10  
57  
08  
09  
06  
23  
24  
40  
16  
80  
Group B was treated with  
Argon laser trabeculoplasty. There  
were 56 (70%) males and 24  
(30%) females in this group. The  
mean age of patients was 55.56  
years (range 41 – 69 Years). Mean  
pre-treatment IOP of 80 eyes (of  
77 patients) was 30.6 ± 5.32 mm  
Hg. There was mean drop of IOP  
to 17.63 ± 4.6 mm Hg at 6 months  
postoperatively. Table 2 gives a  
comparison of the mean IOP  
before and after intervention in the  
two groups.  
56  
49  
160  
Table 2: Comparison of Pre Treatment and Post Treatment (After 6 Months)  
Intra Ocular Pressure (IOP).  
Diode Laser (Group A)  
Mean ± SD mmHg  
(n = 80)  
Argon Laser (Group B)  
Mean ± SD mmHg  
(n = 80)  
Pre-Treatment IOP  
31.79 ± 5.38  
30.66 ± 4.63  
Post Treatment IOP  
19.24 ± 4.99  
17.63 ± 3.65  
(Six Months After Treatment)  
(P < 0.001)  
(P < 0.001)  
and 72.7% at 1 year, but only 9.2% were controlled at  
the end of 4 years.  
DISCUSSION  
Ingvoldstad et al16 and colleagues presented a  
study at the 2005 ARVO meeting. They showed the  
results of ALT and MDLT during a three-month  
follow-up. They noticed similar reduction in IOP with  
these two procedures. There was 18.9% decrease with  
ALT and 18.3% with MDLT.  
Primary argon laser trabeculoplasty has a definite role  
in the management of Primary Open Angle Glaucoma.  
It is useful in decreasing the number of medications  
and delays the surgical intervention11. The other major  
advantage of argon laser trabeculoplasty in addition to  
intraocular pressure reduction is to reduce the spikes  
of the diurnal variation of intraocular pressure. Laser  
therapy causes shrinkage of trabecular beams and  
necrosis of cells resulting in widening of spaces12. The  
mechanism of action of both procedures are  
comparable13.  
Diode laser produces histological changes  
comparable to the argon laser, and early clinical trials  
have shown it to be an effective instrument for  
performing photocoagulation of the trabecular  
meshwork but in current study we did not compare  
such changes in both groups. The similarity of lesions  
produced by current laser modalities, and the  
advantages of diode lasers regarding their portability  
and reliability, certainly will stimulate further interest  
in their therapeutic potential for the treatment of  
glaucoma.  
In our study, argon laser trabeculoplasty as a  
primary therapy was useful in controlling the intra  
ocular pressure in 90% of patients after 6 months  
follow up. It caused mean reduction of intra ocular  
pressure measuring at 12.5 mm Hg at the final follow  
up. Agarwal9 in a study done in Indian population,  
reported a success rate of 90% at 6 months.  
Odberg and Saduik14 reported from Norway that  
there was mean reduction in IOP of 8.8 mm Hg at 1  
month after primary argon laser trabeculoplasty  
therapy with success rate without medication of 77%  
after 2 years, 67% after 5 years and 67% after 8 years.  
Our study showed mean reduction of IOP after six  
months to be 12.54 mm Hg.  
We found from our study that LT yields excellent  
results in controlling rise in IOP. LT has its own  
advantages. The overlying conjunctiva does not  
require breaching as in trabeculectomy surgery  
therefore it is painless and does not cause bleeding.  
The risk of infection and conjunctival scarring are  
minimized and strict aseptic techniques are not  
required. Topical antibiotics or corticosteroid are not  
required after laser trabeculoplasty.  
Another report from India found the effect of  
argon laser trabeculoplasty in Indian eyes which were  
not controlled on maximum medical treatment15. There  
were 93% patients who were controlled at 3 months  
The disadvantages encountered with laser  
trabeculoplasty are that it causes iritis, transient rise in  
IOP and peripheral anterior synechiae. We used  
Pakistan Journal of Ophthalmology, 2020, Vol. 36 (3): 211-215  
213  
Asma Shams, et al  
topical NSAIDS to all our patients for a period of 1  
week to help relieve the mild discomfort and  
inflammation induced by laser.  
controlling IOP then microwave diode laser  
trabeculoplasty.  
Age selection in our study was between 51 – 60  
years with an average of 53 years. Other studies  
Ethical Approval  
The study was approved by the Institutional  
review board/Ethical review board.  
showed a similar age group selection14-16  
.
A study was published in American Journal of  
Ophthalmology17which showed that the diode laser  
patients had mean intraocular pressure of 21.6 ± 2.0  
mm Hg before procedure and 19.0 ± 3.3 mm Hg (or a  
2.4% ± 16.9% mean reduction) at 3 months after  
procedure. In the argon laser patients, mean intraocular  
pressure was 24.4 ± 3.5 mm Hg and 15.5 ± 1.2 mm  
Hg (or a 30.0% ± 16.5% mean reduction) at 3 months  
after laser treatment. The difference between the two  
techniques in reduction of intra ocular pressure was  
statistically significant at 3 months (P < 0.05) after  
treatment.  
Another research18 reported the results of argon  
laser trabeculoplasty in 211 eyes of primary open  
angle glaucoma. The success rate was 81% at 1 year,  
48% at 5 years and only 11% at a ten years. Few other  
studies have also shown MDLT is not as effective as  
Conflict of Interest  
Authors declared no conflict of interest.  
Authors’ Designation and Contribution  
Asma Shams; Senior Registrar: Study Design and  
Procedures.  
Narain Das; Assistant Professor: Compilation of  
data and Procedures.  
Noman Rashid; Associate Professor: Manuscript  
Writing and Review.  
M. Nasir Bhatti; Professor: Manuscript Review.  
Beenish Khan; Assistant Professor: Statistical  
Analysis and Results.  
ALT.  
A
recent study published in Acta  
Jai Kumar; Consultant Ophthalmologist: Data  
Collection.  
Ophthalmologica suggested that 180º MDLT is a safe  
but less effective treatment in patients with open angle  
glaucoma19. These similar results were found in our  
study.  
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reported successful outcomes for primary open angle  
glaucoma20. Another study suggested that hypotensive  
effects and success rates of diode laser trabeculoplasty  
were comparable to argon laser trabeculoplasty  
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