Retinopathy Screening - diabetic retinopathy

Diabetic Retinopathy

HEDRSCE Team is proud to announce the release of 'Diabetic Retinopathy', a new guide to Retinopathy Screening published by Oxford University Press, containing information on all key areas of digital diabetic screening and guidance on running a diabetic retinopathy screening service.

Diabetic Retinopathy costs £10. Proceeds will go to the LEOPARD project in Ethiopia. To order copies or make enquiries please contact Jane Pitt or Helen King at HEDRSCE.

Chapter 1: What is diabetes? A Wright

Chapter 2: Diabetic retinopathy? Margaret Clarke

Chapter 3: Anatomy of the eye and the healthy fundus, Laurence Quant

Chapter 4: Diabetes and the eye, Paul M Dodson

Chapter 5: Background diabetic retinopathy, Laurence Quant

Chapter 6: Maculopathy, Rebecca Lone

Chapter 7: Pre-proliferative and proliferative retinopathy, Rebecca Leigh

Chapter 8: Advanced diabetic eye disease, Karen Whitehouse

Chapter 9: Other ophthalmic lesions in the fundus, Jonathan M Gibson

Chapter 10: The screening episode- visual acuity, mydriasis, and digital photography, David Roy

Chapter 11: How to grade? Helen C King

Chapter 12: The principles of a national diabetic retinopathy screening programme, Margaret Clarke

Chapter 13: Programme administration, Helen King and Caroline Harrison

Chapter 14: Models of screening and IT, Andrew Mills

Chapter 16: Medical management of diabetic retinopathy, Paul M Dodson

Chapter 17: Ophthalmic treatment of diabetic retinopathy, Jonathan Gibson

Chapter 1: What is diabetes?

A Wright

Diabetes mellitus is characterized by raised levels of glucose in the blood. This may result in symptoms of excessive thirst, passing of more urine, loss of weight and loss of energy, and eventually damage to a number of tissues.
At present diabetes is classified into type 1, type 2, secondary, and those due to other less common causes.
Acute complications occur when plasma glucose levels fall below normal (‘hypoglycaemia') or are very high with resulting loss of fluid and development of ketones.
Chronic complications may arise with long-term damage to blood vessels, nerves, kidneys, retina, and the lens.
Good control of glucose levels and good management of other vascular ‘risk factors' can maintain health and prevent or delay long-term complications.

Chapter 2: Diabetic retinopathy?

Margaret Clarke

Diabetic retinopathy (DR) is still one of the commonest causes of visual loss in the Western world in the working age population.
Patients with visual loss due to DR often reflect late presentation or non-attendance to diabetes and eye services.
The pattern of blindness in diabetes is that maculopathy is the major cause, particularly intype 2 diabetic subjects, whereas blindness due to proliferative retinopathy is becoming rarer in type 1 diabetes.
DR meets the screening criteria of Wilson and Junger for a successful programme; as it has important adverse effects, laser treatment is effective, it can be easily detected by digital photography, which is an acceptable test, and is cost effective.

Chapter 3: Anatomy of the eye and the healthy fundus

Laurence Quant

The anterior segment
The posterior segment
The appearance of a healthy fundus
Normal variations

Chapter 4: Diabetes and the eye

Paul M Dodson

Diabetes mellitus is still one of the commonest causes of blindness worldwide.
The ophthalmic complications of diabetes include diabetic retinopathy, cataracts, primary open angle and neovascular glaucoma, and cranial nerve palsies.
Retinovascular disease including retinal vein and artery occlusion and non-arteritic ischaemic optic neuropathy are more common in diabetic subjects.
Diabetic retinopathy occurs in approximately 40% of diabetic subjects, with ethnic differences.
The primary abnormalities of diabetic retinopathy are capillary basement membrane thickening, such that it becomes porous, and capillary occlusion with resultant retinal ischaemia.
Diabetic retinopathy occurs in around 40% of the total diabetic population.
In type 1 diabetes, diabetic retinopathy is almost invariable after 15 years of disease duration, In type 2 diabetes 20% have retinal signs at diagnosis of diabetes, rising to a prevalence of 60% after 15 years of known disease duration.
Major modifiable risk factors for diabetic retinopathy include poor glucose and blood pressure control and increasing lipid levels.

Chapter 5: Background diabetic retinopathy

Laurence Quant

Background diabetic retinopathy consists of:
- Microaneurysms
- Haemorrhages
- Exudation
- Cotton wool spots
Background changes are, as its name suggests, not visually threatening.
Background changes if identified for the first time, are a warning sign that microvascular disease is present.
Background changes are common, affecting up to 40% of the diabetic population.

Chapter 6: Maculopathy

Rebecca Lone

Maculopathy is one of the commonest causes of blindness in the Western world.
In diabetic populations diabetic maculopathy causes blindness in 80% of cases due to diabetic retinopathy (DR).
It is defined as a disease of the macula region located within the retina.
Screening for diabetic maculopathy and identification of surrogate markers for clinically significant macula oedema (CSMO) will identify sight-threatening maculopathy at a stage when there is the best potential laser treatment outcome.
There are three different types of maculopathy: exudative, ischaemic, and cystoid maculopathy due to diabetes, all of which have a detrimental effect on visual acuity (VA) if untreated.

Chapter 7: Pre-proliferative and proliferative retinopathy

Rebecca Leigh

Pre-proliferative retinopathy precedes proliferative retinopathy (new vessel growth) and is therefore an indication that the eye will soon be affected by advanced stages of retinopathy
Pre-proliferative retinopathy indicates chronic retinal ischaemia due to blocked capillaries and the clinical signs include:
- Multiple cotton wool spots
- Venous beading and/or looping
- Multiple deep round and blot haemorrhages
- Intra-retinal microvascular abnormalities
New vessels arise on the optic disc (NVD) or on the retinal surface (NVE) due to retinal ischaemia and growth factors (VEGF and others). The new vessels help re-vascularize the hypoxic (oxygen-starved) tissue.
New vessels can easily rupture, leading to haemorrhage and severe visual loss.

Chapter 8: Advanced diabetic eye disease

Karen Whitehouse

Hypoxia of the retina leads to development of new vessels which subsequently may form fibrous and glial tissue.
Gliosis and fibrosis in the new vessels from the retina onto the posterior vitreous interface may cause retinal traction and retinal detachment.
New blood vessels can also grow into the angle of the anterior chamber of the eye (rubeosis iridis) leading to neovascular or rubeotic glaucoma.
Rubeotic glaucoma is a serious complication with visual loss and raised intra-ocular pressure, resulting eventually in acute severe periorbital pain, corneal oedema and optic atrophy.
Advanced diabetic eye disease can remain asymptomatic for a long time, due to the slow progression of proliferative retinopathy.
Diabetic retinopathy screening is an important factor in intervention which, with timely laser, may prevent development of advanced disease.

Chapter 9: Other ophthalmic lesions in the fundus

Jonathan M Gibson

When screening the diabetic population for diabetic retinopathy (DR), many other retinal conditions will be identified.
The most common conditions which may be diagnosed as DR are retinal vein and artery occlusion, hypertensive retinopathy, arterial emboli, and retinal changes due to blood disorders, for example, anaemia. Theses need local protocols for medical management.
Familiarity and pattern recognition are important to recognize common abnormalities, for example, drusen, chorioretinitis, asteroid hyalosis, choroidal naevi, and age-related macula degeneration.

Chapter 10: The screening episode- visual acuity, mydriasis, and digital photography

David Roy

Digital retinal photography has completely revolutionised the accurate detection of diabetic retinopathy (DR), allowing precise diagnosis and resulting in timely and appropriate referral to diabetic eye specialists.
Accurate measurement of visual acuity (VA) followed by adequate pupil dilatation (mydriasis) is an integral part of a DR screening episode.
A visual history is essential to record, as this may affect the clinical outcome of screening.
Obtaining digital retinal photographs (images) of acceptable quality to grade, with a low ungradable rate (<10%), is imperative.
Practice and expertise is needed to ensure avoidance of the pitfalls of digital photography.

Chapter 11: How to grade?

Helen C King

The grading environment should be quiet, with appropriate lighting, and grading undertaken on high–quality computer equipment and screens.
A grader needs good pattern recognition skills and attention to detail.
Graders should adhere to minimum standards and numbers of grades as required by the NSC.
A grading scheme has been formulated comprising a retinopathy grade (R) and a maculopathy grade (M).
Graders should check image quality, and use a step-by-step grading method which may also use image manipulation.

Chapter 12: The principles of a national diabetic retinopathy screening programme

Margaret Clarke

The aim of the programme is to reduce the risk of sight loss among people with diabetes by the prompt identification and effective treatment of sight-threatening retinopathy at the appropriate stage during the disease process.
A diabetic retinopathy screening programme consists of several key components:

• Administration in place

• Digital retinal cameras available

• Trained and accredited screening/grading staff

• Grading pathways- to include quality assurance

• Quality assurance- both internal and external

• Appropriate referrals to ophthalmologist

• Laser treatment and referrals seen in a timely manner

• Information systems to manage and report all of the above

• Comprehensive annual reports

Chapter 13: Programme administration

Helen King and Caroline Harrison

A systematic screening programme should have:
An accurate patient register
Central call/recall for subjects
Tight, monitored and auditable exclusion criteria for subjects
The capacity to produce annual reports
Well organised administrative service.

Chapter 14: Models of screening and IT

Andrew Mills

Screening needs a central storage and computer, ‘the server', to receive and serve data, including images, to users.
At some point use, one client PC collects for, or displays data from, the central unit.
A secure transfer medium is required to communicate data between the client PC and the server.
Image compression provides a useful tool to save storage space and improve response time for data transfers.
Models of screening determine which transfer medium is most appropriate.

Chapter 16: Medical management of diabetic retinopathy

Paul M Dodson

Medical management is focused on the proven benefit of tight glucose and blood pressure control.
Standard management includes multiple cardiovascular risk factor management with angiotensin receptor blockade and statin and fibrate treatment in addition to aspirin.
Targets to achieve include HbA1c <7%, blood pressure <140/80, and serum cholesterol <4mmol/l.
A number of new trials have demonstrated the beneficial effects on diabetic retinopathy (DR) of fenofibrate (lipid lowering), and Ruboxistaurin® (protein kinase C inhibition) with reduction of laser treatment and protection of vision.
A landmark study of an angiotensin receptor blocker is due to complete shortly (DIRECT study) which will provide data on the potential benefit of this treatment on both primary and secondary prevention of DR.

Chapter 17: Ophthalmic treatment of diabetic retinopathy

Jonathan Gibson

Laser photocoagulation remains the main treatment for diabetic retinopathy (DR).
Laser photocoagulation is unlikely to improve vision once it has decreased but is effective in stabilizing vision.
Treatment with intra-vitreal drugs for maculopathy is a major development.
Optical coherence tomography is an invaluable imaging tool for DR.
Pars plana vitrectomy is available for advanced DR.