Condition category
Circulatory System
Date applied
Date assigned
Last edited
Prospectively registered
Overall trial status
Recruitment status

Plain English Summary

Background and study aims
Obesity is a term used to describe somebody who is very overweight, with a lot of body fat. It's a common problem, estimated to affect around one in every four adults and around one in every five children aged 10 to 11 in the UK. People who are obese are at risk of a number of serious and potentially life-threatening conditions, such as high blood pressure. High blood pressure is dangerous because it can have no symptoms, and increases the risk of a heart attack or stroke. It can also cause permanent damage to vital organs, such as the kidney, eye, brain and heart. Normally, high blood pressure can be treated with medications but these medications don’t work very well in obese patients and we’re not sure why. Most information on blood vessel structure comes from blood vessels studied in a laboratory. Here, we are using a technique which allows us to view blood vessels in the patient directly. Eye (retinal) blood vessel analysis is a non-invasive way to measure the structure of small blood vessels in a patient. The aim of this study is to get a better understanding of the differences in small blood vessel structure between obese patients and lean patients.

Who can participate?
Adults with a BMI over 30 or lower than 25.

What does the study involve?
Participants have non-invasive tests to check how well their blood vessels are functioning. Two of these tests are eye tests. There is also a blood test.

What are the possible benefits and risks of participating?
There are no risks or benefits to participating in this study.

Where is the study run from?
Wellcome Trust Clinical Trials Facility, Central Manchester University Hospitals Trust (UK)

When is the study starting and how long is it expected to run for?
June 2015 to January 2017

Who is funding the study?
British Heart Foundation (UK)

Who is the main contact?
Dr A Greenstein (scientific)

Trial website

Contact information



Primary contact

Dr Adam Greenstein


Contact details

Institute of Cardiovascular Sciences
University of Manchester
Core Technology Facility
Grafton Street
M13 9PL
United Kingdom

Additional identifiers

EudraCT number number

Protocol/serial number

V1; 13/4/14

Study information

Scientific title

Identification of cardiovascular changes in obesity using dynamic and static retinal vessel analysis


Study hypothesis

Changes in retinal vessel function can be correlated with obesity, blood pressure, pulse wave velocity and blood metabolic markers.

Ethics approval

North West - Greater Manchester South Research Ethics Committee, 29/07/2015 ref: 15/NW/0548

Study design

Single site cohort observation

Primary study design


Secondary study design

Cohort study

Trial setting


Trial type


Patient information sheet

Not available in web format, please use contact details to request a participant information sheet.


Cardiovascular disease associated with obesity


All participants who express an interest in study participation will be invited to attend Manchester Clinical Research Facility. Following informed consent procedure (estimated to take approximately 15mins), all participants will undergo:
1. Assessment of past medical history and physical examination: height, weight, waist circumference (10 mins)
2. Pupil dilation (Tropicamide eye drops applied taking 2 minutes to perform but up to 20 minutes to take effect)
3. Blood sampling – up to 10ml (2 teaspoon blood) takes up to 10mins to perform
4. Pulse Wave velocity measurement lay in supine position (10 mins)
5. Blood pressure will be recorded at the start and end of procedure but also throughout the assessment using a wrist cuff
6. Dynamic retinal vessel analysis (flicker stimulation) (15 mins)
7. Static retinal vessel analysis (10 mins)
8. Oxygen saturation will be measured by taking a photograph of the fundus of the eye (5 mins)
9. Carbon dioxide inhalation – during the imaging examination of the eye, a mixture of 95% air/5% carbon dioxide will be administered via nasal cannula (procedure takes 2-3 minutes but gas will be administered for only 45 seconds)
10. On completion of the assessment, participants will be given the general advice leaflet for Tropicamide and advised not to drive for 4 hours This completes study participation.
Total duration of assessment not expected to be more than 2 hours.

Intervention type



Drug names

Primary outcome measure

Vascular function measured by degree of response to flicker stimulation, retinal arteriolar-venular ratio (AVR) and blood oxygen saturation on the assessment day.

Secondary outcome measures

Peripheral measurements: blood pressure, pulse wave velocity and blood levels of HbA1c and blood lipids (triglycerides, LDL and HDL cholesterol) on the assessment day.

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Willing and capable to provide consent to participation
2. BMI greater than 30
3. No known ocular diseases
4. No known concurrent clinical problem likely to interfere with participation or completion of the study

Healthy controls:
1. BMI lower that 25
2. No known diabetes
3. No known ocular diseases
4. No known concurrent clinical problem likely to interfere with participation or completion of the study

Participant type


Age group




Target number of participants

30 healthy lean controls and 30 obese patient-participants

Participant exclusion criteria

1. Under 18 years old
2. Intubated/ventilated patients
3. Unwilling to give consent to participation OR advised by consultee that this would be against the patient’s wishes
4. Smoker
5. If eaten with in an hour of the examination
6. If drank alcohol within an hour of the examination
7. If drank coffee within an hour of the examination
8. If overly hungry
9. Recently treated infection
10. Known ocular diseases
11. Known concurrent clinical problem likely to interfere with participation or completion of the study

Additional exclusion for healthy controls:
1. Diabetes
2. BMI above 25

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

Manchester Clinical Research Facility
Oxford Road
M13 9WL
United Kingdom

Sponsor information


The University of Manchester

Sponsor details

Oxford Road
M13 9PT
United Kingdom

Sponsor type




Funder type


Funder name

National Institute for Health Research

Alternative name(s)


Funding Body Type

government organisation

Funding Body Subtype

Federal/National Government


United Kingdom

Results and Publications

Publication and dissemination plan

Planned publication in a peer reviewed journal.

IPD sharing statement:
The datasets generated during and/or analysed during the current study are/will be available upon request from

Intention to publish date


Participant level data

Available on request

Basic results (scientific)

Publication list

Publication citations

Additional files

Editorial Notes

0106/2017: The following changes have been made to the record: 1. The overall trial dates have been updated from 01/06/2015 - 31/01/2017 to 01/02/2015 - 31/12/2020 2. The recruitment end date has been updated from 31/01/2017 to 30/06/2020 3. The name of the trial participating centre has been changed from Wellcome Trust Clinical Trials Facility to Manchester Clinical Research Facility 4. The funder has been changed from British Heart Foundation to the National Institute for Health Research 5. The interventions and IPD sharing statement have been added 24/03/2016: Ethics approval information added.