Glaucoma is one of the leading causes of severe visual impairment
and blindness worldwide1. Primary angle-closure glaucoma (PACG) is a
major cause of irreversible blindness globally particularly in Asia where it
represents the major form of glaucoma2. An estimate shows that 55.3
million people worldwide will be blind owing to PACG by 20203. PACG
needs an urgent management to lower the
intraocular pressure (IOP) and minimize
the risk of vision loss4. The last decade has seen a
paradigm shift in the treatment of angle-closure glaucoma from incisional
surgery to laser surgery as the preferred method for creating an opening in the
irides5. This is because of no need of using retrobulbar
anesthesia, anterior chamber maintainer,
absence of the risk of infective endophthalmitis and it can be applied as an
outpatient procedure6.
Neodymium-Yttrium-Aluminum-Garnet (Nd: YAG) laser iridotomy is
effective in reducing IOP in people with PACG7. Nd:YAG is
a better option than Argon because of easy iris penetration and a lower
incidence of iridotomy closure8. Its efficacy is greater
in light colored irides, but in dark irides alone it is associated with high
risk of failure and complications, like iris hemorrhage occurring in about 40%,
which is severe enough to postpone the procedure9,10. Argon
laser pre-treatment significantly reduces iris haemorrhage11. The
modified laser iridotomy (MLI) is an advanced technique to treat the PACG and
it uses the benefits of both lasers and avoids their disadvantages and
complications12. Therefore in dark Asian irides, it is
probably the best technique to be used12.
A study
from Pakistan on the efficacy of Argon followed by Nd:YAG laser reported that this
technique was useful in controlling IOP in 75% cases after 6 months of
follow-up. They reported postoperative complications like iritis in 80% cases
followed by raised IOP in 45% cases, hyphema in 35% and corneal damage in 5%
cases6. The rationale of this study is to find out if Nd:YAG laser
combined with Argon laser significantly reduces iris hemorrhage and achieves
higher rate of single treatment success in PACG5,12. This
would greatly benefit the patients and also result in less post-operative visit
so reducing overall burden of patients in the outpatient department.
MATERIAL AND METHODS
This study was carried out at Department of Ophthalmology, Liaquat
University of Medical and Health Sciences, Hyderabad, from November 2011 to May
2012. Patients of 40 to 60 years age, with diagnosis of PACG were included in
the study. All those patients in whom angle was not visible due to corneal
opacity or haze, secondary angle closure glaucoma, severe progressive type of
glaucoma in which angle was not visible were excluded from the study.
After taking history regarding previous attack,
treatment and surgery of glaucoma Snellen visual acuity was measured in all
subjects prior to doing fundoscopy. A slit lamp examination
was carried out, looking for ischemic sequelae of angle closure and signs of
secondary glaucoma. Intraocular pressure (IOP) was measured with a tonometer
(Goldmann model, Haag-Streit, Bern, Switzerland). The median of three tonometer
readings were recorded as a base line IOP for each eye. Gonioscopy was
performed with a three mirror Goldmann gonioscopy lens to record the width of
the irido-trabecular recess in the four quadrants. The angle was graded as
occludable or open. An occludable angle was defined as one in which three
quarters of the posterior pigmented trabecular meshwork was not visible in the
primary position of gaze without indentation. Primary angle closer glaucoma was
diagnosed in eyes with an occludable angle and glaucomatous optic neuropathy.
Evidence of glaucomatous optic neuropathy was defined as a cup: disc ratio
(CDR) of > 0.7 or > 0.2 CDR asymmetry. Dynamic (indentation) gonioscopy
using three mirrors Goldmann lens was performed to assess the presence or
absence of peripheral anterior synechiaes (PAS) in each quadrant.
Prior to laser therapy all patients were explained
about the procedure and a written consent was obtained. A combination of Argon and Nd: YAG for laser iridotomy was used in
all the patients. Nd: YAG laser Abraham iridotomy lens was used with
methylcellulose as a coupling solution. The laser settings were, a power of
1000mw of Argon laser with a spot size of 50 microns requiring 50-80 numbers of
shots. The laser settings for Nd: YAG laser were a power of 4 6 mJ requiring
3 5 shots. The iris tissue was thinned to 20% thickness with argon laser.
After this the 2 3 shots of Nd: YAG laser was applied into the depth of the
crater to complete the iridotomy, so that the anterior lens capsule was visible
through the opening made by the iridotomy.
One hour after the laser IOP was checked and all the
patients were discharged on topical steroid (prednisolone acetate) eye drops
four times a day and a topical beta blocker eye drops twice a day for five
days. The patients were followed up at 1st day, 1st week,
and 4 weeks after the treatment. At each
visit the patients were examined for visual acuity, IOP measurement using
applanation tonometry, anterior chamber reaction was noted, patency of
iridotomy and gonioscopy was performed to confirm the extent of peripheral
anterior synechiae.
The
data was entered and analyzed using SPSS version 16.0. Frequencies and
percentages were calculated for categorical variables like gender, raised IOP,
iritis, hyphema and corneal damage. Mean and standard deviation (SD) were
computed for quantitative variable like age.
Data was stratified based on age and gender to see the effect of
modified laser iridotomy. After laser treatment if the IOP decreased greater
than 8 mm Hg from the baseline IOP the procedure was labeled as efficacious,
good if 5 8 mm Hg decrease and poor if less than 5 mm Hg decrease.
RESULTS
There
were 115 patients with PACG, 51 (44.3%) were males while 64 (55.7%) were
females. Average age of the patients included in the study was 52.95 (± 4.52)
years, with range of 41 60 years. The age, gender, laterality and age
distribution among genders is shown in Table 1. Stratification based on age,
gender and side of eye to see the effect modifier is shown in Table 2, Table 3
and Table 4. One day after laser 35.7%
Table 1: Patient Characteristics N = 115
|
Characteristics
|
N (%)
|
|
Gender M:F = 1: 1.2
|
|
|
Male
|
51 (44.3)
|
|
Female
|
64 (56.7)
|
|
Laterality
|
|
Right
|
67 (58.3)
|
|
Left
|
48 (41.7)
|
|
Age at presentation (years)
|
|
Mean ± SD
|
52.95 ± 4.5
|
|
Min Max
|
41 60
|
|
Males
|
|
Mean ± SD
|
53.25 ± 4.1
|
|
Min Max
|
42 59
|
|
Females
|
|
Mean ±SD
|
53.17 ± 4.8
|
|
Min Max
|
41 60
|
|
Age Groups
41-50 Years
Males
Females
50-60 Years
Males
Females
|
09
12
42
52
|
eyes,
while four weeks later 76.5% eyes had IOP reduction of more than 8 mm Hg
(Figure 1). One day and one week after laser, iritis (82.6% and 10.43%) was the
most frequent complication noted (Figure 2). After four weeks of treatment none
of the patients had hyphema, while rise in IOP was noted only in 1 (0.87%)
patient.
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Fig. 1: Intraocular Pressure Reduction after Laser N = 115.
_files/image006.gif)
Fig. 2: Complications after Laser iridotomy N = 115.
DISCUSSION
Glaucoma is a silent thief of vision which affects scores of
people worldwide. PACG is the most dangerous type with profound irreversible
loss of vision. In Asians PACG is the more prevalent form of glaucoma1.
In Mongolia the prevalence of PACG is 1.4%13, with
more than 6.55% of population having occludable angle.
There are a number of treatment options available for PACG, like
anti-glaucoma medicines, laser modalities and surgical options. Anti-glaucoma
medicines are expensive and require regular follow up and good compliance,
while surgical options are
reserved for advanced glaucoma and have a high rate of failure
especially in case of PACG. In developing countries like Pakistan, glaucoma has
a high burden on both patients and economy due to which most patients are not
compliant and lost in follow up. Here comes the significance of looking for
treatment options in which patients do not need to be followed frequently and
also patients do not require expensive anti glaucoma medications. In cases of
PACG, such treatment option with one time treatment, no frequent follow ups and
no need of expensive anti-glaucoma medication required would be in the form of
laser peripheral iridotomy (LPI)14. LPI works by relieving the
relative pupillary block and thus relieving PACG. But LPI may not work in
non-pupillary block PACG.
LPI can be done by Argon laser which causes photocoagulation of
the iris tissue resulting in shrinkage and charring of iris. But the LPI done
by Argon laser alone showed higher failure rate particularly in dark irides14.
It also resulted in many complications including corneal endothelial
burns, endothelial cell loss and retinal burns. Around 10% of the patients
developed endothelial cell loss15.
After these failure results and complications were observed, Argon
laser was replaced with YAG laser LPI, which works by photodisruption16.
Light pigmented irides showed much better results with YAG LPI as
compared to the darkly pigmented irides because they required less energy22.
YAG had less closure rate than Argon LPI but like any other procedure it
had some problems like the use of higher energy levels in dark irides, iritis,
corneal burns, reduction in endothelial cell count, diplopia and hemorrhage16-18.
If LPI is performed with lower energy and peripherally it can prevent
endothelial cell loss, diplopia and hemorrhage.
Considering the pros and cons of individual use of Argon and YAG
laser, a modified Argon YAG laser iridotomy (MLI) was tried. This method was
especially useful in dark irides which otherwise require high energy levels
with individual lasers19,20. With MLI almost half energy
was needed which resulted in less complications and the iridotomy was large and
round in contrast with slit opening of YAG LPI.
In our study, initially after 1 day iridotomy was effective in
lowering IOP more than 8 mm Hg from baseline IOP in 35.7% of patients which
improved to 59.1% after 1 week and finally to 76.5%. Similarly over 30% of
patients had reduction in IOP of <5 mmHg on day 1, which reduced to 17% on
week 1 and finally to 11% after 4 weeks. This shows that IOP lowering effect of
MLI may take 1 month to be fully effective. As far as complications are
concerned, we observed four different complications including iritis, hyphema,
corneal burns and rise in IOP. We observed that only 1.74 % of patients had IOP
rise after one day of MLI which reduced to 0.87% after one week. As stated in a
study by Harada, iris hemorrhages was observed in 17 % of patients when YAG
laser was used, but in our study only 10.43 % of patients had hyphema (on day
1) 21.
In one recent study, they compared iridotomy outcomes in dark
irides by using 1064 nm pulsed Nd: YAG either with pretreatment of Double
frequency YAG laser (just like Argon laser). They observed that when single
frequency YAG was performed alone it resulted in 43% iris hemorrhages, but when
it was pretreated with double frequency YAG this complication was reduced to
13% only (p=0.0126). Around 2 out of 30 of patients in the standard treatment
group (only single frequency YAG was used for LPI) were abandoned due to
significant hemorrhage22. This is a high frequency of
complications as compared to what we have reported in our study. This shows
that sequential argon laser before YAG LPI is not only equally beneficial but
results in much lower complications rate as compared to isolated YAG LPI.
Iritis has been a well reported complication of both YAG and Argon LPI but only
3 patients in our study who underwent MLI had iritis after 4 weeks23.
Schwartz reported a 75% success rate following MLI which is comparable to
our study (76.5%). Other studies have showed variable frequencies of successful
iridotomies in terms of lowering IOP24.
CONCLUSION
Modified
laser iridotomy (Argon followed by Nd: YAG Laser) technique is excellent for
PACG, permitting effective IOP reduction in most of the patients. Although
iritis was a frequently observed complication on day one after laser but with
topical steroids it resolved in almost all the patients by week four. Thus, it
is an effective treatment option for PACG, with few reversible side effects.
Authors
Affiliation
Dr. Azfar Ahmed Mirza
Department
of Ophthalmology, Liaquat University of Medical & Health Sciences,
Jamshoro/Hyderabad, Pakistan
Dr. Noor Bakht Nizamani
Department
of Ophthalmology, Liaquat University of Medical & Health Sciences,
Jamshoro/Hyderabad, Pakistan
Dr. Mahtab Alam Khanzada
Department
of Ophthalmology, Liaquat University of Medical & Health Sciences,
Jamshoro/Hyderabad, Pakistan
Dr. Khalid Iqbal Talpur
Department of Ophthalmology, Liaquat
University of Medical & Health Sciences, Jamshoro/Hyderabad, Pakistan
Role of
Authors
Dr. Azfar Ahmed Mirza
Study Design, collected data, did
critical appraisal of findings.
Dr. Noor Bakht Nizamani
Drafted the manuscript, statistically
analyzed data and reviewed literature.
Dr. Mahtab Alam Khanzada
Data Analysis and interpretation,
critically reviewed the manuscript.
Dr. Khalid Iqbal Talpur
Conceptualized the study and approved the final version
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