Clinical Trial Details
— Status: Completed
Administrative data
| NCT number |
NCT01549132 |
| Other study ID # |
EKHT RETINAL RESEARCH UNIT |
| Secondary ID |
|
| Status |
Completed |
| Phase |
|
| First received |
|
| Last updated |
|
| Start date |
April 2012 |
| Est. completion date |
March 2014 |
Study information
| Verified date |
September 2023 |
| Source |
East Kent Hospitals University NHS Foundation Trust |
| Contact |
n/a |
| Is FDA regulated |
No |
| Health authority |
|
| Study type |
Observational
|
Clinical Trial Summary
The investigators believe that oxygen saturation measurements in the retina may provide more
information on how well the retina is working and may detect problems in the retina earlier
than the fundus fluorescein angiography (FFA). This may be useful to an ophthalmologist so
that they may identify abnormal areas of the retina and commence or change the treatment so
that they may prevent irreversible blindness.
Most patients with clinically significant macular oedema and/or ischaemic diabetic
retinopathy could have either laser or Intravitreal Anti-VEGF injection treatment provided
they are counseled about the risks. It is known the Anti-VEGF injections reduce oedema and it
is believed that laser treatment of the retina in this condition improves the oxygen supply
to the retina and sometimes reverses the damage. It will be useful to take pictures of these
treated eyes using the Oxymap spectral retinal camera(s) to see whether the investigators can
detect a change in the oxygen saturation in the retina before and after treatment using our
oxygen saturation methods.
Description:
WHAT IS SPECTRAL IMAGING?
This is a way of studying in detail an area that is being imaged. This can be done because
each picture of the same area is taken using different colours of light (wavelength).
Different materials in the picture will absorb and reflect the different wavelengths of light
from a hyperspectral camera differently. It is then possible to look at each point in the
picture and work out what is in the picture. This has been used in satellites and aeroplanes
to identify what is on the ground. For example, it can distinguish the different types of
trees on the ground based on the different way they absorb and reflect different wavelengths
of light.
USING SPECTRAL IMAGING IN MEDICINE. Spectral imaging was found to have uses in medicine
because of its ability to distinguish one thing from another. A lot of Spectral imaging
research has been done to measure the amount of oxygen in the blood. This is because oxygen
is important to all living cells in the human body - without it cells would die or stop
working. Oxygen is carried to living cells by blood in blood vessels known as arteries and
the left over is carried away by veins. Most of the oxygen in the blood is transported by
cells in the blood containing a chemical called haemoglobin. There are two main forms of
haemoglobin called oxyhaemoglobin (haemoglobin binds to oxygen) and deoxyhaemoglobin
(haemoglobin that is not bound to oxygen). The proportion of oxyhaemoglobin to the total
amount of haemoglobin (both oxyhaemoglobin and deoxyhaemoglobin) is called the oxygen
saturation and is presented as a percentage. The normal saturation in the artery is about 97%
because it contains more oxyhaemoglobin and in the vein it is about 75% because it contains
less oxyhaemoglobin. Importantly oxyhaemoglobin (HbO2) and deoxyhaemoglobin (Hb) have
different spectral characteristics - i.e they absorb light differently at various wavelengths
of light. This has been extensively documented in various publications using samples of
blood. This property is the basis of pulse oximetry which is the measurement of the oxygen
saturation (OS) in the finger tip using a saturation probe which is commonly used in the
hospital.
The different spectral characteristics of Hb and HbO2 can also be used in spectral imaging to
calculate the amount of each in the blood to perform oxygen saturation measurements in
certain parts of the body. This has previously been used to study the oxygen supply in the
skin and also to look at the oxygen supply in patients with diabetes which is a condition
that is caused by a lack of a hormone called insulin causing high amount of sugar in the
blood resulting in damage to the blood vessels.
Spectral imaging has only recently started to be used in imaging the eye. The main emphasis
of Spectral imaging in ophthalmology has been on measuring the oxygen saturations in the
retina (the layer at the back of the eye that allows us to see). This is called retinal
oximetry. In essence, the principles of retinal oximetry are similar to that of pulse
oximetry, i.e using the different spectral characteristics of Hb and HbO2 to calculate the
oxygen saturation.
In diabetic retinopathy, the only way the investigators can study the blood supply is by
performing a Fundus Fluorescein Angiogram (FFA). This is an invasive test which involves the
injection of a dye into the arm, this dye is transported by blood to the eye and pictures of
the blood vessels are taken with the dye in it. Also, importantly, there are side effects
(sometimes life-threatening) to injecting this dye into the arm. If there is a problem with
the blood supply in the retina then the dye will not fill up in the blood vessel and is seen
in the pictures as a black area. The FFA provides information on the blood supply but not
directly on the amount of oxygen in it. Loss of sight from diabetic retinopathy and
age-related macular degeneration is believed to be caused by a reduction in the amount oxygen
being supplied to the retina by the blood vessels.
The investigators believe that oxygen saturation measurements in the retina using spectral
imaging could be a more useful test for an ophthalmologist because it may provide more
information on how well the retina is working and may detect problems in the retina earlier
than the FFA. This may be useful to an ophthalmologist so that they may identify abnormal
areas of the retina and commence or change the treatment so that they may prevent
irreversible blindness.
