Condition category
Eye Diseases
Date applied
16/01/2008
Date assigned
06/05/2008
Last edited
23/09/2016
Prospective/Retrospective
Prospectively registered
Overall trial status
Ongoing
Recruitment status
No longer recruiting

Plain English Summary

Background and study aims
Glaucoma is the leading cause of irreversible blindness. Primary angle closure glaucoma (PACG) is the more severe of the two major types of glaucoma. If you have healthy eyes, the fluid in your eye drains away through drainage channels. In some people the eye is shaped differently and the drainage area is very narrow (narrow drainage angles). Under certain circumstances the drain can completely close off, so your eye pressure increases, injuring your optic nerve and damaging your vision. This is considered an attack of angle closure glaucoma. Laser peripheral iridotomy (LPI) is the first-line treatment for PACG. LPI uses a laser beam to create a small hole in your iris, unblocking the drainage channels. LPI is also very effective at preventing symptoms developing in the unaffected eye of patients who have suffered the condition in the other eye. However, so far no conclusions can be drawn regarding the use of prophylactic (preventative) LPI in persons with narrow drainage angles and without any symptoms or signs of active glaucoma. To determine the case for performing prophylactic LPI for all people with narrow angles (1 in 5 Chinese women over the age of 60 fall into this category), it is important to identify how many people with narrow angles will eventually suffer acute symptoms or develop glaucoma. Equally, it is important to know if LPI will reduce this risk, and whether there is any significant adverse risk associated with early LPI treatment. This study aims to assess whether LPI is safe and effective at preventing the development of primary angle closure in high-risk angle-closure patients. The study also specifically aims to answer the question of whether there are any particular features that help to predict who will go on to develop angle closure.

Who can participate?
Guangzhou city residents aged 50 to 70 with narrow drainage angles.

What does the study involve?
The right and left eyes of each participant are randomly allocated to LPI treatment or current standard treatment only. Both treated and untreated eyes are examined on follow-up visits after 2 weeks, 6 months, 18 months, 36 months, 54 months and 72 months.

What are the possible benefits and risks of participating?
Participants will obtain regular and careful medical support from a qualified team of medical experts. There are no obvious risks in participating in this study.

Where is the study run from?
University College London (UK).

When is the study starting and how long is it expected to run for?
March 2008 to February 2017

Who is funding the study?
1. Fight for Sight (UK)
2. Sun Yat-sen University (China)
3. Wilmer Eye Institute (USA).
4. Ministry of Education of the People's Republic of China (China)
5. National Natural Science Foundation of China (China)

Who is the main contact?
1. Prof. Paul J Foster (p.foster@ucl.ac.uk)
2. Prof. Mingguang He (mingguang_he@yahoo.com)
3. Prof. David S Friedman (david.friedman@jhu.edu)

Trial website

Contact information

Type

Scientific

Primary contact

Dr Paul Foster

ORCID ID

Contact details

University College London
Institute of Ophthalmology
11-43 Bath Street
London
EC1V 9EL
United Kingdom
+44 (0)20 7608 6899
p.foster@ucl.ac.uk

Additional identifiers

EudraCT number

ClinicalTrials.gov number

Protocol/serial number

1

Study information

Scientific title

A randomised controlled trial of prevention of angle-closure glaucoma in China

Acronym

ZAAP

Study hypothesis

That laser iridotomy helps to prevent primary angle-closure (a major risk factor for glaucoma) in Chinese adults aged 50 years and older.

Ethics approval

1. Ethical Review Board of Zhongshan Ophthalmic Centre (China), November 2002
2. London School of Hygiene and Tropical Medicine (UK), 17/03/2008, ref: 5267

Extension study:
1. Zhongshan Ophthalmic Centre (China), 28/01/2016, ref: Zhongshan Ophthalmic Center Medical Ethical Committee [2007] No.12
2. London School of Hygiene and Tropical Medicine (UK), 05/03/2011, ref: A240 5267

Study design

Single-centre randomised controlled trial (not masked)

Primary study design

Interventional

Secondary study design

Randomised controlled trial

Trial setting

Hospitals

Trial type

Treatment

Patient information sheet

Available in Chinese with English translation upon request

Condition

Angle-closure glaucoma

Intervention

The right and left eyes of each participant will be randomly allocated to the intervention treatment or no treatment (control).

Intervention treatment: Laser peripheral iridotomy (LPI) by sequential argon then Nd:YAG laser. Duration of the laser treatment is about 5 minutes.
Control: No intervention (current standard treatment only)

Each participant will be examined at baseline, 2 weeks, 6, 18, 30 and 42 months.

Added 20/09/2016:
Each participant will be further examined at 54 and 72 months after LPI.

Intervention type

Procedure/Surgery

Phase

Drug names

Primary outcome measures

The following will be assessed on each of the scheduled follow-up (6, 18, 30 and 42 months):
1. Raised intraocular pressure (either with or without symptoms). Intraocular pressure greater than 24 mmHg verified on two consecutive measurements on separate days. These patients will be further identified as having open, partially-closed or completely closed angles on dark room gonioscopy and anterior segment optical coherence tomography (AS-OCT).
2. Peripheral anterior synechiae
3. Glaucomatous optic neuropathy
If participants are felt to have met a failure criterion, they are re-assessed (by examination with one of the senior investigators) within the next 2 weeks to confirm. The failure will then be classified as having occurred at 6, 18, 30 or 42 months (end of the study).

Added 20/09/2016:
Outcomes will also be assessed at 54 and 72 months.
If participants are felt to have met a failure criterion, they are re-assessed (by examination with one of the senior investigators) within the next 2 weeks to confirm. The failure will then be classified as having occurred at 54 or 72 months (end of the study).

Secondary outcome measures

The following will be assessed on each of the scheduled follow-up (6, 18, 30 and 42 months):
1. Specular microscopy measures of corneal endothelial cell loss
2. Formation of lens opacity
3. Anterior segment optical coherence tomography measures (qualitative and quantitative) of ocular anterior segment anatomy
4. Digital iris photograph measures of iris
5. Ultrasound biomicroscopy measurements of ocular anterior segment anatomy
If participants are felt to have met a failure criterion, we will re-assess (by examination with one of the senior investigators) within the next 2 weeks to confirm. The failure will then be classified as having occurred at 6, 18, 30 or 42 months (end of the study).

Added 20/09/2016:
Outcomes will also be assessed at 54 and 72 months.
If participants are felt to have met a failure criterion, they are re-assessed (by examination with one of the senior investigators) within the next 2 weeks to confirm. The failure will then be classified as having occurred at 54 or 72 months (end of the study).

Overall trial start date

01/03/2008

Overall trial end date

28/02/2017

Reason abandoned

Eligibility

Participant inclusion criteria

1. Anatomically narrow drainage angles in the anterior segment of the eye
2. No evidence of primary angle-closure (high pressure or peripheral anterior synechiae)
3. Aged greater than or equal to 50 years

Participant type

Patient

Age group

Adult

Gender

Both

Target number of participants

1,100

Participant exclusion criteria

1. Inability or unwillingness to give informed consent
2. Raised intraocular pressure, peripheral anterior synechiae or glaucomatous optic neuropathy
3. Previous intraocular surgery

Recruitment start date

01/09/2008

Recruitment end date

22/10/2010

Locations

Countries of recruitment

China

Trial participating centre

University College London
London
EC1V 9EL
United Kingdom

Sponsor information

Organisation

University College London (UK)

Sponsor details

Gower Street
London
WC1E 6BT
United Kingdom
+44 (0)20 7608 6854
h.jones@ucl.ac.uk

Sponsor type

University/education

Website

http://www.ucl.ac.uk/

Funders

Funder type

Government

Funder name

Fight for Sight UK

Alternative name(s)

Funding Body Type

private sector organisation

Funding Body Subtype

foundation

Location

United Kingdom

Funder name

Sun Yat-sen University

Alternative name(s)

SYSY

Funding Body Type

private sector organisation

Funding Body Subtype

academic

Location

China

Funder name

Ministry of Education of the People's Republic of China

Alternative name(s)

Ministry of Education of China, MOE

Funding Body Type

government organisation

Funding Body Subtype

Federal/National Government

Location

China

Funder name

National Natural Science Foundation of China

Alternative name(s)

National Science Foundation of China, Natural Science Foundation of China, NSFC

Funding Body Type

government organisation

Funding Body Subtype

Federal/National Government

Location

China

Funder name

Wilmer Eye Institute

Alternative name(s)

Funding Body Type

Funding Body Subtype

Location

Results and Publications

Publication and dissemination plan

The main findings of the ZAP study will be published in peer-reviewed journals before the end of 2017 and presented at academic conferences.

IPD sharing plan
The datasets generated and/or analysed during the current study are available from Prof. Paul Foster (p.foster@ucl.ac.uk) and Prof. Mingguang He (mingguang.he@unimelb.edu.au; mingguang_he@yahoo.com) on reasonable request.

Intention to publish date

31/12/2017

Participant level data

Available on request

Results - basic reporting

Publication summary

2012 results in: http://www.ncbi.nlm.nih.gov/pubmed/22424576

Publication citations

  1. Results

    Congdon N, Yan X, Friedman DS, Foster PJ, van den Berg TJ, Peng M, Gangwani R, He M, Visual symptoms and retinal straylight after laser peripheral iridotomy: the Zhongshan Angle-Closure Prevention Trial., Ophthalmology, 2012, 119, 7, 1375-1382, doi: 10.1016/j.ophtha.2012.01.015.

Additional files

Editorial Notes

20/09/2016: The overall trial end date was changed from 28/02/2011 to 28/02/2017.