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ALPI vs Medical Therapy Effects on Optic Nerve Structure & Function (Iridoplasty)

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT00485238
Recruitment Status : Unknown
Verified May 2008 by National University Hospital, Singapore.
Recruitment status was:  Recruiting
First Posted : June 12, 2007
Last Update Posted : May 15, 2008
Information provided by:
National University Hospital, Singapore

Brief Summary:
The aim is to determine which approach, immediate argon laser peripheral iridoplasty or conventional systemic medical treatment efficiently breaks acute angle closure attack without consequent visual morbidities. The specific objectives are to see whether sudden intraocular pressure(IOP) lowering brought about by laser iridoplasty or medical treatment affects optic nerve head structure and function and identify if immediate decompression is associated with greater incidence of ocular problems like corneal endothelial compromise, optic disc edema, macular edema, decompression retinopathy, cataract formation, progression to chronic angle closure.

Condition or disease Intervention/treatment Phase
Glaucoma Procedure: Argon laser Iridoplasty Drug: Intravenous acetazolamide Phase 4

Detailed Description:

Primary Angle Closure Glaucoma (PACG) continues to be a major concern in Asia. It is a major cause of visual morbidity in the region1 being the most prevalent type of glaucoma especially in Chinese and Mongoloid descent.2,3 During the acute stage of the disease, prompt institution of measures to break the attack is necessary. Two recognized approaches are utilized in practice in lowering intraocular pressure and preparing for the definitive treatment of laser peripheral iridotomy. These are conventional topical and systemic medical therapy and immediate peripheral iridoplasty using either argon or diode lasers.

In the study of Lim, Tan, Chew, Seah et al., laser iridoplasty was noted to have a useful role in the management of medically unresponsive acute angle closure, particularly in those cases where laser peripheral iridotomy (PI) could not be successfully performed4 . Randomized controlled trials of Lam, Lai, Tham et al. comparing immediate laser peripheral iridoplasty plus topical medications and topical and systemic medical treatment found no significant difference in the eventual mean IOP and requirement for glaucoma medications 5 . However, significant difference in efficacy was observed between the two treatment arms within the first two hours of treatment with argon laser peripheral iridoplasty and topical medications lowering IOP faster than conventional medications6. In all the trials cited, there was no mention of sudden IOP lowering effects of either argon laser iridoplasty or conventional medications on the optic nerve head and visual field status, as well as its effect on other ocular structures like the cornea, lens and retina . In our literature search, two papers studied the optic nerve head structure and function in angle closure glaucoma, but not in the immediate period of sudden IOP lowering. Ang, Aung, Chua, Yip and Chew made a comparative assessment of the visual field loss between symptomatic and asymptomatic PACG, with 50% of asymptomatic PACG subjects presenting with end stage visual field loss in contrast to just 7% of symptomatic PACG.7 Lai, Tham, Lam et al. compared the retinal nerve fiber layer measurements of attack eyes and their fellow eyes after a single unilateral attack of acute primary angle closure (APAC) using scanning laser polarimetry six months after the acute attack8. Retinal nerve fiber layer damage was documented in eyes where the duration of the APAC attack lasted more than 48 hours8. Decompression retinopathy following laser peripheral iridoplasty for acute primary angle closure was reported in two cases reported by Lai, Lee, Leung and Chung.9 In order to compare the efficiency of laser peripheral iridoplasty and medical treatment, as well as to identify any morbidity that may come from sudden decompression of the eye, we undertake this randomized controlled trial.

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Study Type : Interventional  (Clinical Trial)
Estimated Enrollment : 60 participants
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)
Primary Purpose: Treatment
Study Start Date : February 2007
Estimated Study Completion Date : December 2008

Resource links provided by the National Library of Medicine

MedlinePlus related topics: Glaucoma

Primary Outcome Measures :
  1. optic nerve head stereometric analysis HRT3 and Stratus OCT,optic nerve head and RNFL & macula thickness average. AGIS scores of HVF is the measure of functional status. [ Time Frame: 1 year ]

Secondary Outcome Measures :
  1. amount and rate of IOP-lowering,gonioscopy and ASOCT changes, change in LOCS grading for cataract, corneal decompensation & edema,macular,retinal edema by Stratus OCT. [ Time Frame: 1 year ]

Information from the National Library of Medicine

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Ages Eligible for Study:   21 Years to 80 Years   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • Age more than 21 years with ability to give informed consent and cooperate for a slit lamp laser procedure
  • Subjects at their first presentation of acute primary angle closure attack.
  • Intraocular pressure levels of 40 mm Hg or higher by applanation tonometry or tonopen
  • Pupillary block as the main mechanism of angle closure
  • No previous treatment

Exclusion Criteria:

  • Age less than 21 years
  • Angle closure due to non-pupil block mechanism (e.g. plateau iris, pseudoplateau, phacomorphic, malignant glaucoma) or other secondary causes (subluxed lens, neovascular, uveitic, traumatic, post-operative)
  • Angle closure patients whose IOP's are not lowered by 20% or more, and are unresponsive to maximum medical IOP-lowering agents after one hour of initiating treatment and needing other intervention/s to lower IOP(e.g. iridoplasty, surgery).
  • Corneal opacities or abnormalities obstructing laser application
  • Use of contact lens
  • Single-eyed patients

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT00485238

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Contact: Paul TK Chew, A/Prof 67725317
Contact: Maria Cecilia D. Aquino, M.D. 67725317

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National University Hospital Recruiting
5 Lower Kent Ridge Road, Singapore, Singapore, 119074
Principal Investigator: Paul TK Chew, A/Prof         
Sponsors and Collaborators
National University Hospital, Singapore
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Principal Investigator: Paul TK Chew, A/Prof National University Hospital, Singapore

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Responsible Party: Paul TK Chew, A/Prof, National University Hospital, Singapore Identifier: NCT00485238    
Other Study ID Numbers: DSRB A/06/177
First Posted: June 12, 2007    Key Record Dates
Last Update Posted: May 15, 2008
Last Verified: May 2008
Keywords provided by National University Hospital, Singapore:
Additional relevant MeSH terms:
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Ocular Hypertension
Eye Diseases
Carbonic Anhydrase Inhibitors
Enzyme Inhibitors
Molecular Mechanisms of Pharmacological Action
Natriuretic Agents
Physiological Effects of Drugs