Condition category
Eye Diseases
Date applied
Date assigned
Last edited
Prospectively registered
Overall trial status
Recruitment status
No longer recruiting
Publication status

Plain English Summary

Background and study aims
Glaucoma is a treatable condition and is the second most common cause of blindness in the UK, and the world’s leading cause of irreversible blindness affecting nearly 7 million. Based on information given by the International Glaucoma Association (IGA) website, glaucoma is the leading cause of preventable blindness in the UK and is estimated to affect over 500,000 people. Additionally, the information provided by the Royal National Institute for the Blind (RNIB) statistics, states that glaucoma is the second leading cause of blindness registered in the UK. Cataract is the most common cause of treatable blindness worldwide. Modern, small incision cataract extraction by phacoemulsification (small incision cataract surgery) with foldable intraocular lens implantation allows rapid visual rehabilitation and has a very high success rate. Phacoemulsification (small incision cataract surgery) is the most commonly performed cataract procedure in the developed world. Modern cataract surgery usually lowers eye pressure in eyes with glaucoma. The underlying mechanism of this is believed to be related to the increase in the flow of fluid out of the eyeball (fluid outflow), but little is known about these changes of fluid outflow in the eye after surgery (the drainage of the fluid is one of the determinants of eye pressure). The aim of this study therefore is to investigate the outflow facility changes in eyes with, and without, primary open angle glaucoma after phacoemulsification cataract surgery.

Who can participate?
Adults over 21 years old with reduced vision and glaucoma, and adults of the same age with reduced vision and no glaucoma.

What does the study involve?
All participants receive standard treatment, however the fluid outflow (drainage rate) from the front segment of the eye is also measured. This is done using tonometry, which is a standard procedure in which a local anaesthetic (numbing) drop is put in each eye and a small smooth instrument touches the surface of the eye for a few seconds to measure the eye pressure, and Shiotz Tonography, which involves lying down for 10 minutes while a technician makes a recording of the eye pressure in each eye for 4 minutes. An anesthetic drop is used so that participants do not feel the tonometer touching their eye while the tracing is made. Participants come back to the clinic after 3, 6 and 12 months so that the tests can be repeated.

What are the possible benefits and risks of participating?
There are no direct benefits involved with participating in this study. The procedures used in this study are not considered risky, however participants may experience a scratchy feeling of the eye and blurred (not clear and foggy) vision is commonly observed following the tonography test which usually lasts less than 30 minutes. As with any other test in which contact with the eye is required, such as tonometry, there is always a small chance of conjunctivitis (eye surface infection).

Where is the study run from?
St Thomas’ Hosptial (UK)

When is the study starting and how long is it expected to run for?
October 2009 to October 2012

Who is funding the study?
EyeHope (UK)

Who is the main contact?
Mr Kin Sheng Lin

Trial website

Contact information



Primary contact

Mr Kin Sheng Lim


Contact details

St. Thomas' Hospital
Westminster Bridge Road
United Kingdom
+44 (0)20 7188 2289

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

Phacoemulsification and changes in outflow facility in eyes with and without glaucoma


Study hypothesis

Changes of outflow facility after phacoemulsification in eyes with and without primary open angle glaucoma.

Further reading:
7. Moorfields manual of ophthalmology, 2008 Timothy Jackson, Mosby publications

Ethics approval

St. Thomas' Hospital Research Ethics Committee, 16/11/2009, ref: 09/H0802/103

Study design

Single-centre case-control study

Primary study design


Secondary study design

Case-control study

Trial setting


Trial type


Patient information sheet

Not available in web format, please use the contact details to request a patient information sheet


Glaucoma; outflow facility; phacoemulsification


1. Visual acuity: using Snellen chart
2. Slit-lamp examination: including examination of the cornea for development of any signs of stromal oedema, gonioscopy using Zeiss or Goldmann gonioscopy lens in dimmed light (to determine angle grade). Angle grading will be according to the Shaffer’s system. Prior to instillation of fluorescein or dilating pupil, aqueous flare and cells will be graded using a slit lamp beam with the height of 3 mm and width of 1 mm directed across the pupil.

Anterior chamber cells grading
Grade 0 = no cells
Grade 1 = 1 - 4 cells
Grade 2 = 5 - 19 cells
Grade 3 = greater than 20 cells
Grade 4 = presence of fibrin

Anterior chamber flare grading
Grade 0 = none
Grade 1 = visible flare
Grade 2 = iris details obscured

3. Goldmann applanation tonometry: A topical anaesthetic and fluorescein drop will be used. The study eye’s IOP will be measured 3 times and the average will be recorded as the IOP.
4. Anterior chamber depth measurement. This non-contact measurement is done by using an ultrasound machine (IOL master, Carl Zeiss). This is a standard measurement needed for all patients prior to cataract surgery to measure their axial length and corneal power in order to calculate the power of replacement intraocular lens needed.
5. Outflow facility: The facility of outflow will be measured from the rate of decay of intraocular pressure in the supine position during application of a recording Schiötz tonometer over 4 minutes time. The "R" values of the curve at every 30 second time point will be manually entered into the McLaren tonography computer based program. The program fits a second degree polynomial by least squares to the nine data points and determines the best fit values for time 0 and time 4 minute by extrapolation. These initial and final values of the tonometer scale reading will be used to look up the value for the facility of outflow using 1955 scale approved by the Committee on Standardization of Tonometer.

Intervention type



Not Applicable

Drug names

Primary outcome measure

Outflow facility is measured using electronic Shiotz tonography at 3, 6 and 12 months post cataract surgery

Secondary outcome measures

1. Anterior chamber depth is measured using IOL master at baseline
2. Intraocular pressure is measured using Goldmann applanation tonometer at baseline, 3, 6 and 12 months
3. Intra- or post-operative complications is measured using clinically intra-operatively and post operatively
4. Development of glaucoma is measured using clinically and Humphrey visual field at baseline and 12 months

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Aged greater than 21 years
2. Lens opacity deemed enough to be causing reduced vision
3. Diagnosis of primary open angle glaucoma (POAG) (Group 1) or no glaucoma (Group 2). POAG defined as glaucomatous optic neuropathy together with an intraocular pressure (IOP) greater than 21 mmHg on at least one occasion, visual field defects (using the 24-2 test pattern on a Humphrey Field Analyser) and a gonioscopic angle width of 3 or 4 and normal in appearance.
4. Patient's willingness to participate in the study and ability to give informed consent

Participant type


Age group




Target number of participants

20 patients in each groups

Participant exclusion criteria

1. Previous intraocular surgery
2. Previous ocular trauma that can cause damage to the drainage angle (e.g. angle recession)
3. International normalised ratio (INR) greater than 3.0 on the day of surgery (for the patients on warfarin)
4. Anterior segment neovascularisation
5. Chronic use of systemic or topical steroid
6. Any other concurrent ocular disease e.g. uveitis, diabetic retinopathy, corneal diseae, etc.

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

St Thomas' Hospital
Westminster Bridge Road
United Kingdom

Sponsor information


Guy's and St. Thomas' NHS Foundation Trust (UK)

Sponsor details

3rd Floor Conybeare House
Guy's Hospital
St. Thomas' Street
United Kingdom
+44 (0)20 7188 5731

Sponsor type

Hospital/treatment centre



Funder type


Funder name

EyeHope (UK)

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Planned publication in a peer reviewed journal.

Intention to publish date


Participant level data

Available on request

Basic results (scientific)

Publication list

2018 results in:

Publication citations

Additional files

Editorial Notes

16/04/2018: Publication reference added. 04/08/2016: The overall trial dates have been updated from 18/01/2010 - 18/08/2010 to 01/10/2009 - 01/10/2012. The timepoints and methods of measurement have also been added to the secondary outcome measures. In addition, the participant information sheet has been uploaded and plain English summary added. 18/07/2016: No publications found, verifying study status with principal investigator.