Laser Iridotomy Versus Phacoemulsification in Acute Angle Closure

2014-08-27 03:43:35 | BioPortfolio


This is a randomised controlled clinical trial to compare laser peripheral iridotomy (LPI) and primary phacoemulsification with intra-ocular lens implantation (phaco/IOL) in the treatment of acute primary angle-closure glaucoma (APACG). Following successful medical lowering of raised intra-ocular pressure (IOP) and control of intraocular inflammation, patients presenting to Singapore National Eye Centre and Singapore General Hospital with acute primary angle-closure glaucoma who meet the eligibility are randomised to one of the two treatment arms: laser peripheral iridotomy and primary phacoemulsification with intra-ocular lens implantation. These patients will be monitored closely for 2 years post-operatively.



The objective of this study is to conduct a randomised controlled clinical trial to compare LPI and primary phacol/IOL in the treatment of APACG.

The specific aim is to compare long-term IOP control in patients who undergo LPI with patients who undergo primary phaco/IOL. At the same time the following will be studied.

1. To evaluate the safety of these two techniques for the treatment of APACG

2. To assess the development of PAS

3. To establish if LPI and primary phaco/IOL are as effective in preventing the recurrence of acute attack in eyes with APACG


Initial Medical Treatment

Patients with APACG will be treated initially for the acute attack with medical treatment. The initial treatment is standardized to the following:

1. Intravenous acetazolamide (Diamox) 500 mg stat

2. Oral acetazolamide 250 mg tid to qid with Span K 1.2 g om

3. Topical beta-blocker (Timolol 0.5%) bid or Brimonidine bid if beta-blockers are contra-indicated.

4. Topical pilocarpine 4% qid

5. Topical steroids

6. Intravenous mannitol 20% at 1-2g/kg at 4 hours after initiation of treatment if IOP is not reduced by 20% of initial IOP unless contra-indicated due to systemic disease eg. Congestive heart failure.

7. A second infusion of intravenous mannitol 20% at 2g/kg at 12 hours after initiation of treatment if IOP is still not reduced by 20% of initial IOP

Response to Initial Treatment and Evaluation of Cataract

Patients are divided into 2 categories based on IOP after 24 hours of initiation of medical treatment: (a) APACG with IOP £ 30 mmHg (b) APACG with IOP > 30 mmHg.

Patients with IOP £ 30 mmHg are evaluated clinically for the presence of cataract and further divided into those with cataract and those without cataract. Patients with cataract are defined as those with best corrected visual acuity equal or less than 6/15 due to lens opacity in the opinion of a consultant grade ophthalmologist.

Note: Eyes with intumescent cataract (phacomorphic glaucoma), subluxated lens or anterior chamber depth differing by more than 0.3 mm are excluded.

Eligible patients with informed consent are randomised.

Laser Peripheral Iridotomy

1. In addition to the consultants, LPI may be performed by registrars, senior registrars and fellows who have observed and been taught by the glaucoma consultants and are deemed to be able to perform the procedure to a high standard.

2. LPI is performed when the cornea is sufficiently clear (usually within 72 hours) following the lowering of the IOP medically.

3. Technique for LPI to be standardized to sequential argon-Nd-YAG Laser PI.

4. LPI should be sited at the superior nasal or superior temporal quadrant.

5. The size of opening should be ³ 200mm.

6. Following successful LPI, topical eyedrops are continued for one week after the procedure. Oral Diamox is discontinued.

7. If the initial attempt is unsuccessful, LPI at a second alternative site will be attempted. If the second attempt remains unsuccessful, patient will be considered as failure .

Phacoemulsification with Intra-ocular Lens Implantation

1. All phacoemulsification with intraocular lens implantation are to be performed by consultant surgeons. The panel of surgeons is formed from the group of co-investigators of this study.

2. Phacoemulsification will be carried out between 5 to 7 days following the lowering of the IOP. This is to allow for improved corneal clarity and reduction of intra-ocular inflammation.

3. Gutt pilocarpine to be stopped on morning of operation.

4. Pre-operative intravenous mannitol 20% at 1-2g/kg is given 2 hours before the start of operation for those subjects with an IOP persistently raised above 21mmHg.

5. Clear corneal incision.

6. Viscoelastic agent to be injected 360 degrees circumferentially in the angles to deepen the anterior chamber. There will be no other angle augmentation procedure using surgical instruments.

7. A standard foldable IOL (Type of IOL: Acrysof MA60)

8. Viscoelastic agent should be removed at the end of operation as far as possible.

9. Oral Diamox 250 mg to be given stat post-operatively to reduce post-operative IOP spike.

10. Following successful phacoemulsification with IOL implantation, topical steroids and antibiotics are given. Topical pilocarpine, timolol and oral Diamox are stopped.

IOP Lowering Medication

With regard to the determination of endpoints IOP evaluation will be considered from post-operative week 3 onward. This is to allow for treatment of short-term surgery related IOP fluctuation.

During the follow up period, if a rise of IOP occurs, i.e. IOP is between 22 to 24 mmHg on two occasions within one month or IOP ³ 25 mmHg on one occasion, IOP lowering medication will be started.


Post operation visit Window period

1st week ± 2 days 3rd week ± 5 days 6th week ± 7 days 3rd month ± 2 weeks 6th month to 2nd year ± 3 weeks

At the completion of the trial patient will receive normal clinical follow up of 4-6 monthly thereafter whilst the data will not be collected for this study.

The primary objective of the study is to compare IOP control between these two treatment groups.


Sample Size Calculation:

The primary objective of the study is to compare long-term intra-ocular pressure (IOP) control between the two groups.

The proportion of the subjects whose IOP are not successfully controlled in the LPI group can be estimated as 60% (Aung T 2001). And the proportion of the subjects whose IOP are not successfully controlled in the phacoemulsification with intra-ocular lens implant group is about 20% under clinical estimation. Hence, the study needs a sample size of 70 patients (Machin, Campbell, Fayers & Pinol, 1997), 35 in each group. This will be sufficient to detect a 60% vs. 20% of proportion of the subjects who develop increasing IOP between two groups with a two-sided test with a power 90% while the significance level is controlled at 5%.

Statistical Analysis Plan

All statistical analysis will be carried out on an intention-to-treat basis. In the event of lost to follow-up, patients will still be included in the analysis for the duration that they are observed, and the last IOP which is assessed before lost to follow-up will be used for data analysis.

To compare long-term IOP control between two treatments, Pearson χ2 test or Fisher’s exact test will be used. The evaluation of the incidence of recurrence of an acute attack in eyes with APACG will be carried out using Fisher’s exact test. Logistic regression will be carried out to adjust for relevant covariates.

The time interval for the subsequent increase in IOP to occur after LPI or phacol/IOL is to be recorded. Kaplan-Meier life table analysis can be applied to assess the survival time (failure being defined as any need for further glaucoma treatment) of two groups, and Log rank test will be used to compare the two survival curves. In addition, The Cox regression will be used to adjust for covariates where applicable.

An interim statistical analysis will be carried out after all patients have completed 6 months follow-up.


1. Acton J, Salmon JF, Scholtz R. Extracapsular cataract extraction with posterior chamber lens implantation in primary angle-closure glaucoma. J Cataract Refract Surg. 1997 Jul-Aug;23(6):930-4.

2. Aung T, Ang LP, Chan SP, Chew PT. Acute primary angle-closure: long-term intraocular pressure outcome in Asian eyes. Am J Ophthalmol. 2001;131(1):7-12.

3. Chylack LTJ, Wolfe JK, Singer DM, et al. The Lens Opacities Classification System III. Arch Ophthalmol 1993;111:831-836.

4. Fleiss JL. Statistical methods for rates and proportions. New York:Wiley, 1981:2nd edition.

5. Greve EL Primary angle closure glaucoma: extracapsular cataract extraction or filtering procedure? Int Ophthalmol. 1988;12(3):157-62.

6. Gunning FP, Greve EL. Uncontrolled primary angle closure glaucoma: results of early intercapsular cataract extraction and posterior chamber lens implantation. Int Ophthalmol. 1991 Jul;15(4):237-47.

7. Gunning FP, Greve EL. Lens extraction for uncontrolled angle-closure glaucoma: long-term follow-up. J Cataract Refract Surg. 1998 Oct;24(10):1347-56.

8. Ho T, Fan R. Sequential argon-Yag laser iridotomies in dark irides. Br J Ophthalmol 1992; 76:329 –331.

9. Hoffer KJ. Axial dimensions of the human cataractous lens. Arch Ophthalmol 1993; 111(7):914-8.

10. Hong C, Kitazawa Y, Tanishima H. Influence of argon laser treatment of glaucoma on corneal endothelium. Japan J Ophthalmol 1983;27(4):567-74.

11. Ishikawa H, Ritch R, Liebmann J. Quantitative assessment of the anterior segment using Ultrasound Biomicroscopy. Current Opinions In Ophthalmology. 2000;11:133-139.

12. Lim L, Seah SKL, Lim ASM. Comparison of argon laser iridotomy and sequential argon laser and Nd:YAG laser iridotomy in dark irides. Ophthalmic surgery and lasers 1996;27(4):92-95.

13. Lowe RF. Aetiology of the anatomical basis for primary angle-closure glaucoma:biometrical comparisons between normal eyes and eyes with primary angle-closure glaucoma. Br J Ophthalmol 1970; 54(3):161-9.

14. Lowe RF: Primary angle-closure glaucoma: a review of ocular biometry, Aust NZ J Ophthalmol 1977; 5:9.

15. Lowe RF. Clinical types of primary angle-closure glaucoma. Aust NZ J Ophthalmol 1988;16:245-50.

16. Obstbaum SA. Glaucoma and intraocular lens implantation. J Cataract Refract Surg 1986;12:257-61.

17. Pavlin,CJ, Foster,FS. Ultrasound biomicroscopy in glaucoma. [Review]. Acta Ophthalmologica - Supplement. 1992;7-9.

18. Roberts TV, Francis IC, Lertusumitkul S, Kappagoda MB, Coroneo MT. Primary phacoemulsification for uncontrolled angle-closure glaucoma. J Cataract Refract Surg 2000;26:1012-16.

19. Teekhasaenee C, Ritch R. Combined phacoemulsification and goniosynechialysis for uncontrolled chronic angle-closure glaucoma after acute angle-closure glaucoma. Ophthalmology. 1999 Apr;106(4):669-74.

20. Wishart PK, Atkinson PL. Extracapsular cataract extraction and posterior chamber lens implantation in patients with primary chronic angle-closure glaucoma: effect on intraocular pressure control. Eye. 1989;3 ( Pt 6):706-12.

Study Design

Allocation: Randomized, Control: Active Control, Endpoint Classification: Safety/Efficacy Study, Intervention Model: Parallel Assignment, Masking: Open Label, Primary Purpose: Treatment


Angle Closure Glaucoma


Laser Preipheral Iridotomy and phacoemulsification


Singapore National Eye Centre




Singapore National Eye Centre

Results (where available)

View Results


Published on BioPortfolio: 2014-08-27T03:43:35-0400

Clinical Trials [1435 Associated Clinical Trials listed on BioPortfolio]

Comparison of Superior vs Nasal/Temporal Laser Peripheral Iridotomy in Primary Angle Closure

The purpose of this study is to determine if location of laser peripheral iridotomy (LPI) that is the standard of care treatment for angle closure glaucoma is related to changes in post-op...

Laser Peripheral Iridotomy Plus Laser Peripheral Iridoplasty for Primary Angle Closure

This is a 10-centre randomized controlled clinical trial to explore whether laser peripheral iridoplasty (LPIP) plus laser peripheral iridotomy (LPI) is more effective than single LPI to c...

Effect of Peripheral Laser Iridotomy Placement on Post-operative Visual Function

To evaluate the influence of superior versus temporal laser peripheral iridotomy location on post-operative visual acuity and contrast sensitivity.

Comparing Nd:YAG Laser and Sequential Double Frequency YAG-Nd:YAG Laser Iridotomy

No single type of laser or set of laser parameters is appropriate for all type of irides. Pure Nd:YAG laser iridotomy is very effective in the light color irides. It was considered as the ...

Intraocular Pressure (IOP) Lowering Effect of Selective Laser Trabeculoplasty Versus Prostaglandin Analogues in Angle Closure Glaucoma

Glaucoma affects 66 million people worldwide and is the leading cause of irreversible blindness, and Primary angle-closure glaucoma (PACG) is a major form of glaucoma in Asia. Laser perip...

PubMed Articles [3835 Associated PubMed Articles listed on BioPortfolio]

Early Phacoemulsification After Acute Angle Closure in Patients With Coexisting Cataract.

The purpose of this study is to evaluate the effect of early phacoemulsification on the management of acute angle closure glaucoma in patients with coexisting cataract after initial treatment with med...

Iridotomy to slow progression of visual field loss in angle-closure glaucoma.

Primary angle-closure glaucoma is a type of glaucoma associated with a physically obstructed anterior chamber angle. Obstruction of the anterior chamber angle blocks drainage of fluids (aqueous humor)...

Contemporary Approach to the Diagnosis and Management of Primary Angle-Closure Disease.

Primary angle closure disease spectrum varies from a narrow angle to advanced glaucoma. A variety of imaging technologies may assist the clinician in determining the pathophysiology and diagnosis of p...

Bilateral acute angle-closure glaucoma induced by duloxetine.

Introduction - To present a rare case of bilateral acute angle-closure glaucoma secondary to duloxetine administered for the treatment of depression. Case presentation - A 46 year old woman developed ...

Quantitative assessment of changes in anterior segment morphology after argon laser peripheral iridoplasty: findings from the EARL Study Group.

Argon laser peripheral iridoplasty (ALPI) could be effective in widening residual angle closure following laser peripheral iridotomy (LPI).

Medical and Biotech [MESH] Definitions

Loss of CORNEAL ENDOTHELIUM usually following intraocular surgery (e.g., cataract surgery) or due to FUCHS' ENDOTHELIAL DYSTROPHY; ANGLE-CLOSURE GLAUCOMA; IRITIS; or aging.

A technique utilizing a laser coupled to a catheter which is used in the dilatation of occluded blood vessels. This includes laser thermal angioplasty where the laser energy heats up a metal tip, and direct laser angioplasty where the laser energy directly ablates the occlusion. One form of the latter approach uses an EXCIMER LASER which creates microscopically precise cuts without thermal injury. When laser angioplasty is performed in combination with balloon angioplasty it is called laser-assisted balloon angioplasty (ANGIOPLASTY, BALLOON, LASER-ASSISTED).

A form of glaucoma in which the intraocular pressure increases because the angle of the anterior chamber is blocked and the aqueous humor cannot drain from the anterior chamber.

A cloprostenol derivative that is used as an ANTIHYPERTENSIVE AGENT in the treatment of OPEN-ANGLE GLAUCOMA and OCULAR HYPERTENSION.

A cloprostenol-derived amide that is used as an ANTIHYPERTENSIVE AGENT in the treatment of OPEN-ANGLE GLAUCOMA and OCULAR HYPERTENSION.

More From BioPortfolio on "Laser Iridotomy Versus Phacoemulsification in Acute Angle Closure"

Quick Search


Relevant Topics

Clincial Trials
In a clinical trial or interventional study, participants receive specific interventions according to the research plan or protocol created by the investigators. These interventions may be medical products, such as drugs or devices; procedures; or change...

Ophthalmology is the branch of medicine that is devoted to the study and treatment of eye diseases. As well as mild visual defects correctable by lenses, ophthalmology is concerned with glaucoma, uveitis and other serious conditions affecting the eye, ...

Searches Linking to this Trial