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Efficacy of laser peripheral iridoplasty and iridotomy on medically
refractory patients with acute primary angle closure: a three year
outcome
Abstract
Background: To evaluate the efficacy of argon laser peripheral iridoplasty
(ALPI) and laser peripheral iridotomy (LPI) on patients with severe acute
primary angle closure (APAC), who have responded poorly to medical therapy.
Methods: Thirty-six patients (8 men and 28 women) were identified as
medically refractory APAC, who still had ocular pain, red eye, hazy cornea,
closed anterior chamber (AC) angle, and intraocular pressure (IOP) of ≥21
mmHg after two days or more of anti-glaucoma medication. All enrolled
patients underwent ophthalmologic examinations including measurement of
visual acuity (VA), best corrected visual acuity (BCVA), IOP, biomicroscopy
and gonioscopy followed by ALPI immediately in the APAC eye and LPI in both
eyes.
Results: All patients were affected unilaterally, with average age of 54.6 ±
11.7 years (range, 37-75) years. The mean IOP value of the affected eyes
dropped from 31.6±7.7 mmHg (range, 21-39) at enrollment to 18.4±8.7 mmHg
(range, 10-27) two hours after ALPI. At follow-up day 7, the mean IOP value
maintained at 14.8±4.2 mmHg (range, 9-21), which was significant (P=0.000)
compared with baseline. The average decrease of IOP in the APAC eyes was
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16.8 ± 7.4 mm Hg (range, 12-21). At follow-up three years later, the mean IOP
of the APAC eyes stabilized at 16.3±3.2 mmHg (9 to 20) with at least 180
degrees of AC angle opened.
Conclusions: ALPI and LPI lower the IOP of medically refractory cases of
APAC though they have responded poorly to anti-glaucoma medication.
Key words: glaucoma; acute primary angle closure; argon laser
peripheral iridoplasty; laser peripheral iridotomy; management
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Introduction
Acute primary angle closure (APAC) is an ocular emergency in that the
highly and rapidly elevated intraocular pressure (IOP) may lead to irreversible
blindness quickly1-7. Prompt and efficient lowering of the elevated IOP in the
affected eyes is one of the most important principles of the management of
APAC 7-11.
Medical therapy is commonly used as the initial treatment for APAC
because it is safe and usually effective, especially for new or mild cases.
However, for advanced or severe cases, in which the IOP is highly elevated
and the peripheral anterior synechiae (PAS) is substantial, the efficacy of
medical therapy is not promising. It is not uncommon in clinical practice that
patients with severe APAC respond inefficiently to anti-glaucoma medications
and need further treatments. In such circumstances, laser therapy or filtration
surgery has to be performed.
So far, there is no preferred practice pattern (PPP) for medically refractory
patients with APAC, who have not responded well to medical therapy. The
choice between laser and surgery may be variable among different
practitioners. Surgical procedures including iridotomy, trabeculectomy, or
paracentesis can lower the elevated IOP quickly, though operation on an
inflamed eye would be risky12-14. Comparatively, laser treatment, mostly
peripheral iridoplasty and/or LPI, is easy and safe to perform, but is less
effective in lowering the IOP.
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So far, the literature regarding IOP-lowering effect of laser therapy on
patients with intractable APAC is limited. The aim of this study is to evaluate
the efficacy of argon laser peripheral iridoplasty (ALPI) with adjunctive LPI on
medically refractory APAC patients.
Patients and methods
Patients
APAC was defined as a red painful eye, blurry vision, hazy cornea, fixed
dilated pupil, and elevated IOP (>21mmHg) in the presence of a closed AC
angle. The inclusion criteria in this study were as follows: a history of
unsuccessful anti-glaucoma medication including topical pilocarpine,
beta-blocker, as well as steroids; and systemic carbonic anhydrase inhibitor
and intravenous Mannitol for ≥2 days; IOP remained ≥21 mmHg after medical
treatment. The exclusion criteria included a history of intraocular surgery, laser
therapy on the iris or AC angle; IOP ≥40mmHg; severe iris atrophy; acute
episode of APAC in both eyes; secondary AC angle closure; BCVA less than
20/40 in the non-affected fellow eye; and age below 18 or above 80 years.
This study was conducted in Beijing Tongren Eye Center, a tertiary
referral center in north China, with permission from the institutional review
board and ethics committee. All patients provided informed consent after
detailed information about the management protocol was performed.
Intervention
ALPI and LPI were performed in all enrolled patients under topical
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anaesthesia with Alcaine (proparacaine, Alcon, Fort Worth, TX), after a
complete acquisition of detailed medical and ocular history and ophthalmologic
examinations including measurement of visual acuity (VA), best corrected
visual acuity (BCVA), body weight, and IOP, biomicroscopy. Gonioscopy and
fundus examination was performed posterior to 3% saline solution instillation,
which relieved the corneal edema.
ALPI was performed immediately on the affected eyes after admission.
Large spot size of 500 microns with long duration of 0.5 seconds was used.
Energy started from 150 milli-watt and was tuned up till the iris contraction
were clearly seen around the laser spot with no air bubble. The laser burns
were delivered to the peripheral iris through an Abraham lens. Six to eight
shoots were delivered in each quadrant with an average interval of 1.5 to 2
diameters of the laser spot. On completion of the laser treatment, prednisone
phosphate eye-drop was instilled to the conjunctival sac of the treated eyes
immediately and on post-treatment 1 and 2 hours. The regimen was then
changed to three times daily from day 1 to 7. LPI was performed in both eyes
with Neodymium-doped yttrium aluminium garnet (Nd:YAG) laser immediately
posterior to ALPI or on follow-up day 1 when the cornea in the affected eye
becomes clear.
IOP was measured two hours later after ALPI. Oral glycerin (Osmoglyn)
and acetozolamide as well as topical pilocarpine 2% and timolol 0.5% would
be prescribed if the post-treatment IOP was ≥ 21 and <30 mmHg.
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Trabeculectomy would be performed if the IOP in the affected eye remained
≥30mmHg after ALPI and LPI. For all patients, follow-up visits followed on
day1, day 7, one month, six month, and every other six month.
Statistical Analysis
The means of post-treatment IOP one week later were compared to baseline with
paired sample t-test. The significance level was set at 5%. All statistical analyses
were done using Statistical Package for the Social Sciences (SPSS) version 12.0
(SPSS, Chicago, IL, USA).
Clinical Trial Registration
Clinical trial registration of this study was done on Chinese Clinical Trial Registry
website (www.chictr.org), where the registration information is public available.
The registration number of the current study is ChiCTR-TNC-10001168.
Results
Thirty-six patients (8 men and 28 women) were identified as having
medically refractory APAC and enrolled in this study, with mean age of 54.6 ±
11.7 years (range, 37-75). All the patients were affected unilaterally and had
been treated with anti-glaucoma medications including topical pilocarpine,
beta-blocker, and systemic carbonic anhydrase inhibitor and hyperosmotics for
≥ 2 days before enrollment. The average medication time before ALPI was 3.2
± 1.1 days (range, from 2 -5).
On admission, the mean IOP value of the APAC eyes and the fellow eyes
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were 31.6±7.7 mmHg (range, 21-39) and 15.3±4.5 mmHg (range, 11-19),
respectively. All APAC eyes have conjunctival congestion, corneal edema,
fixed dilated pupil and closed AC angle. Two hours after ALPI, the average IOP
value in the APAC eyes decreased to 18.4±8.7 mmHg (range, 10-27), which
was significant compared to baseline (p=0.000). Of all the patients, 75% (27/36)
gained sufficient IOP control of < 21 mmHg two hours after the laser treatment,
the other nine were prescribed with adjunct anti-glaucoma medications
because the IOP posterior to ALPI was ≥ 21 mmHg and <30 mmHg. No
trabeculectomy was needed in anyone of the enrolled patients.
On day 1 follow-up visit, ocular pain resolved in all APAC eyes with
improved vision when hazy cornea and conjunctival injection relieved. The
mean IOP value in the APAC eyes was 15.9±4.7 mmHg (range, 8-21).
On follow-up day 7, the average IOP value of the APAC eyes was
14.8±4.2 mmHg (range, 9-21), which was significant compared to baseline
(p=0.000). The average decrease of IOP in the APAC eyes was 16.8 ± 7.4 mm
Hg (range, 12-21). All treated eyes except one gain sufficient IOP control after
the laser treatment. The exceptional APAC eye, which had an IOP of 21mmHg
on day 7, was prescribed Pilocarpine 1% twice daily. There were no symptoms
and the corneal edema disappeared in all APAC eyes. But the pupils were still
moderately dilated with slow pupillary light reflex. Iris atrophy and
depigmentation were seen in 17 APAC eyes. On dynamic gonioscopy, the AC
angles were shallow but mostly (≥180 degrees) open. Pigment granules were
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commonly seen on the trabecular meshwork and Schwalbe’s line after the
laser therapy, especially in the inferior quadrant. On follow-up six months later,
majority of the pupils (20 of 36) in the APAC eyes recovered to normal and
were reactive to light illumination. The fellow eyes were unremarkable after the
prophylactic LPI.
During the following follow-up visits, phacoemulsification was performed
in three eyes of three patients due to cataract formation and uncorrectable VA,
one of which was receiving Pilocarpine for uncontrolled IOP before the surgery.
In this particular patient, goniosynechialysis was performed during the cataract
surgery. Gonioscopy revealed that the AC angle reopened fully in 29 cases
including whose received phacoemulsification. The other nine had remnant
PAS but all less than 180 degrees.
At the last follow-up visit three years later, the average IOP of the APAC
eyes and fellow eyes were 16.3±3.2 mmHg (9 to 20) and 13.9±3.3 mmHg
(11-20), respectively. No recurrence was discovered in anyone of the case
series. Thirty-four pupils of the APAC eyes recovered to normal and reacted to
light illumination. The other two had dilated pupil, iris atrophy, and
glaukomflecken. BCVA in the APAC eyes was all better than 20/200.
Discussion
In this study, we evaluated the efficacy of ALPI adjunct with LPI on 36
intractable APAC patients who had responded inefficiently to anti-glaucoma
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medications for ≥2 days. The results were impressive in that all treated eyes
achieved a substantial average decrease in IOP of 16.8 ± 7.4 mm Hg (range,
12-21). No safety problems or recurrence was observed in anyone of these
patients after laser treatment.
Apposition of the iris against the trabecular meshwork as a result of
pupilary block, plateau iris syndrome, pupil dilation, or phacomorphic
mechanism is thought to cause APAC15-21. Prompt separation of the peripheral
iris from the trabecular meshwork and restoration of the aqueous humor
outflow are main principles of the management of APAC. It is no more a big
problem to abort an episode of APAC in well equipped special eye hospitals or
clinics. For if medical therapy does not have a satisfactory result, laser
treatment or surgery could be soon performed to save the endangered eye.
What the fact is, in remote areas of developing countries like China or some
other south-east Asian counties, in which the prevalence of APAC is relatively
high, there is serious shortage of trained glaucoma doctors and laser or
surgical equipement12,22-24. Medication is the only choice available to treat
APAC. In these areas, patients with severe APAC can hardly receive further
treatment unless they are referred to tertiary referral centers. For mild cases,
especially those have lower IOP and short duration, anti-glaucoma medication
usually has satisfactory results. However, in severe or delayed cases,
medication alone may not achieve good result because the adhesion between
peripheral iris and trabecular meshwork become more substantial. It is not
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uncommon in tertiary referral centers to see patients with APAC still have
ocular pain, conjunctival congestion, and uncontrolled IOP after intensive
anti-glaucoma medications.
So far, there is no identical definition for “severe” or “medically
unresponsive or refractory” APAC in literature. In this study, we arbitrarily
defined “medically refractory APAC” as: APAC patient with an unsuccessful
history of medical therapy including topical pilocarpine, beta-blocker, as well as
steroids; and systemic carbonic anhydrase inhibitor and intravenous mannitol
for ≥2 days; and the post-treatment IOP is ≥ 21mmHg posterior to medication.
When enrolling patients for this study, we excluded those with post-medication
IOP ≥40 mmHg because patients with such high pressure would be much
more probable to have visual disability without instant effective intervention.
ALPI reopens the closed angle in APAC through contraction laser burn on
peripheral iris, which drags the iris root from the trabecular meshwork and
restores the aquous outflow pathway. The literature has demonstrated that
ALPI is effective in APAC in the early stage and might be considered as initial
treatment for this sight threatening disease7,14,16,24-29. However, for those tough
cases, which had a long history and did not respond to medication, the IOP
lowering effect is unknown. Theoretically, long existence of appositional angle
closure would be likely to turn into synechial if the episode is not aborted timely.
Synechial angle closure would be more challenging for ALPI because it is
more substantial and thus difficult to dissect. The present study was set to
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address whether ALPI have a good IOP-lowering effect in medically failed
cases of APAC. The result is quite impressive in that all treated eyes gained
sufficient IOP control with no side-effects. After three years of follow-up, the
patients still have controlled IOP and opened AC angles. No filtering surgery
was needed for these cases after the laser treatment. Our study complements
the literature about the role of ALPI and LPI in the management of medically
refractory cases of APAC.
LPI is performed in both eyes of the patients in order to relieve pupilary
block, a common cause of angle closure. In the affected eyes, LPI helps to
prevent recurrence of APAC or reformation of PAS, For the fellow eyes, it
serves as a prophylactic treatment to prevent episode of APAC.
Thirty-six patients were enrolled consecutively according to the inclusion
and exclusion criteria. Majority of them (28/36) were women. This complied
coincidently with the epidemiological findings that acute attack of APAC is
three times more common in females than in males30-32.
A limitation of the current study is that it was a non-comparative cohort
study. Further research, especially a randomized, multicenter, prospective,
controlled study, is needed to provide more powerful evidence. Nevertheless,
the patients we have enrolled in this study were only “mild or moderate” cases
of refractory APAC. Those with post-medication IOP≥40 mmHg were excluded.
As a result, the efficacy of ALPI and LPI on the most serious medically
refractory APAC patients is still not clear.
11
In summary, based on the current study, we concluded tentatively that
ALPI with adjunctive LPI lowers IOP in medically intractable APAC patients
safely, which could be considered before surgery.
12
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