Insulin Dependent Diabetes Trust

Information Leaflet Updated April 2001

CONTENTS

Our eyes provide sight which is probably the most important of our 5 senses and so it is understandable that we are all a little nervous that when we have our eyes examined - the underlying fear of 'bad news'.

It is important that everyone has regular, full eye examinations but especially so for people with diabetes. Early detection and diagnosis of many eye conditions means that treatment can start early in order to preserve sight. In the UK everyone with diabetes is entitled to a free eye test.

A review of retinopathy by the University of York NHS Centre for Reviews and Dissemination published in Effective Health Care, August 1999, provides the following information:

- Diabetic retinopathy is the leading cause of blindness in people of working age in industrialised countries. It is estimated that 12% of people who are registered blind or partially sighted in the UK have diabetic eye disease.

- Twenty years after diagnosis almost all those with Type 1 diabetes and 60% of those with Type 2 diabetes will have some degree of retinopathy.

- British screening studies suggest that around 5-10% have sight-threatening retinopathy and up to 40% of people with newly diagnosed Type 2 diabetes have some retinopathy.

Before considering diabetic eye disease we need to understand a little of how the anatomy of the eye and how the eye works.

- IRIS - this regulates the amount of light that enters the eye. It is the coloured part of the eye across the front of the lens. Light enters through a central opening called the pupil.

- PUPIL - is the circular opening in the centre of the iris through which light passes. The iris controls dilation and constriction of the pupil.

- CORNEA - is the clear circular part of the front of the eyeball. It refracts the light entering the eye on to the lens, which then focuses it on to the retina. The cornea is extremely sensitive to pain.

- LENS - is a transparent crystalline structure behind the pupil of the eye. It helps to refract incoming light and focus it on to the retina. A cataract is when the lens becomes cloudy, and then the lens can be removed and replaced with a plastic intra-ocular lens.

- VITREOUS - is a clear jelly-like material in the middle of the eye.

- RETINA - is a light sensitive layer that lines the interior of the eye. It is made up of light sensitive cells known as rods and cones. The rods are necessary for seeing in dim light. And the cones best in bright light and are essential for receiving a sharp accurate image. Cones can also distinguish colours. The retina works much in the same way as film in a camera.

- MACULA - Is the yellow spot on the retina at the back of the eye and is the area with the greatest concentration of cone cells. It is the area of greatest acuity of vision such as reading.

- OPTIC DISK - is the visible portion of the optic nerve on the retina. The optic disk is the start of the optic nerve where messages from cone and rod cells leave the eye and pass along nerve fibres and so transfer all the visual information to the brain. The optic disk is also known as the 'blind spot'.

For sight to take place light must be able to pass to the retina at the back of the eye. The light passes through cornea and enters the eye through the pupil. It then passes through the lens and the vitreous to be focussed on the retina. The focussed light or images of what we have been looking at, are then passed down the optic nerve to the brain.

- If diagnosed early enough diabetic retinopathy is a treatable condition.

- The only treatment for diabetic retinopathy is laser treatment.

- Over the past 15 years laser treatment has been shown to be helpful in either stopping the progress of the condition or in maintaining sight.

- In the UK sight tests for checking for diabetic retinopathy are free.

- There are two vulnerable groups of people susceptible to retinopathy - firstly, pregnant women and secondly, children and adolescents. In the long term children and adolescents are at greater risk of microvascular and macrovascular complications of diabetes. It is recommended [ref1] that surveillance for the earliest evidence of microvascular disease [this includes retinopathy] should begin at puberty and after 3 and 5 years of diabetes.

Retinopathy is usually classified according to its severity. This may not be the same in both eyes. There are two classifications of diabetic retinopathy:

This is the first stage of the development of retinopathy and it is rare before 8 to 10 years of diabetes duration. At this stage the vision is normal and sight is not threatened. If there are diabetic changes present such as small haemorrhages, fatty deposits [exudates] or abnormal blood vessels [microaneurysms] then this is a sign that the retinopathy is worsening and the doctor will be alerted to arrange more frequent follow ups.

This is where the blood vessels [capillaries] block and starve the retina of nutrients causing new vessels to grow. These new vessels grow either in front of the retina on to the back of the vitreous or occasionally on to the iris. These new vessels are fragile and may bleed into the vitreous. This then affects the sight and may cause floaters, dots or lines and if severe may cause clouding of the vision or loss of vision.

If the vessels grow on the iris, they can cause a rise in pressure in the eye and severe, painful glaucoma. The new vessels eventually cause scar tissue and this can lead to a retinal detachment where the retina becomes detached from the back of the eye with a resulting severe loss of sight.

- If diagnosed early enough diabetic retinopathy is a treatable condition.

- Regular eye checks do not prevent retinopathy but do enable early diagnosis and early treatment and this will benefit your sight.

- Small blood vessels in the retina become blocked, swollen or leaky causing oedema and new, fragile vessels grow haphazardly in the retina. This process can continue for years without causing visual symptoms or visual impairment: during this period, retinopathy can only be detected by eye examination.

- Eye checks are free in the UK.

- In insulin treated diabetes, annual eye checks should be carried out after about 5 years of diabetes or after the onset of puberty in children and young people.

- In people with diabetes not using insulin, then eye checks should take place annually from diagnosis onwards.

Retinopathy can affect people with all types of diabetes:

- Anyone with insulin dependent diabetes, both young and old.

- People who treated with tablets

- People on diet only

- People who have well-controlled diabetes can develop retinopathy if they have had diabetes long enough.

No, but early 'good' diabetic control may slow down the rate of progression of the condition. Improving diabetic control rarely has an effect on diabetic retinopathy itself, but it can prevent further deterioration. Therefore you should: