Clinical context
Diabetes-related retinopathy (DR) occurs as a result of microvascular disease of the retina. It affects up to one in three people with diabetes, and can cause visual impairment and blindness.4 DR also impairs quality of life and the ability to manage diabetes.5
Three distinct forms of DR are:
- macular oedema, which includes diffuse or focal vascular leakage within the macula
- DR caused by microvascular changes:
- non-proliferative DR (NPDR), which includes microaneurysms, intra-retinal haemorrhage, malformation and torturous vessels; may be asymptomatic
- PDR, which involves abnormal vessel growth on the optic disc or retina.
Sight-threatening DR includes:
- severe NPDR
- PDR
- foveal-threatening diabetic macular oedema.
NPDR affects 19.3% of people with diabetes, whereas 2.1% of people with diabetes may have PDR and 3.3% may have macular oedema.6 PDR and macular oedema are associated with an elevated risk of cardiovascular disease.7
In practice
Risk factors for the onset or progression of DR include:
- existing DR
- poor glycaemic management
- raised blood pressure
- duration of diabetes >10 years (DR may be present at the time of diagnosis of type 2 diabetes)
- microalbuminuria
- dyslipidaemia
- anaemia
- pregnancy.
Visual impairment due to diabetes can be avoided for the vast majority of people through recommended screening and the management of risk factors. This involves regular review of fundi, early detection and optimisation of therapy. DR may progress to advanced stages without affecting vision, hence the importance of regular DR screening examinations. A meta-analysis has suggested some increased risk of DR with the use of sulfonylureas.8
Monitoring for diabetic eye disease involves assessment of:
- changes in visual acuity (with correction)
- lens disease (eg cataracts; see below)
- fundal disease (eg fundoscopy with dilation or retinal camera, or refer to an optometrist or ophthalmologist).
Screening methods and intervals for retinopathy are presented in Box 1.
Consider the timing of referral to an ophthalmologist; for instance, non-centre-involving macular oedema and moderate NPDR are less urgent (within 12 weeks) than PDR (within 1 week).
Strategies for delaying the onset and progression of DR include:
- Lifestyle advice to optimise healthy nutrition and activity levels9
- optimising blood glucose10-12
Refer to the section ‘Glucose monitoring ’ for suggested glycated haemoglobin (HbA1c) targets. Note that intensive glucose management in people with DR that is more severe than moderate NPDR on the International Clinical Diabetic Retinopathy Disease Severity Scale may not be beneficial.13,14 Rapid and marked reductions in HbA1c as a result of improved glycaemic management initiated during pregnancy, bariatric surgery or intensified insulin treatment have previously been associated with transitory worsening of DR and should be avoided. Eye examinations should occur at shorter intervals.
- managing blood pressure15
- adding fenofibrate
Indicated for the reduction of DR progression in people with type 2 diabetes who have existing DR. Fenofibrate does not replace managing blood pressure, blood glucose and blood lipids as strategies to delay the progression of DR.16,17
- ophthalmological specialist care:
- laser therapy
- intraocular anti-vascular endothelial growth factor (VEGF) agents (for further information, refer to the Pharmaceutical Benefits Scheme)
- vitreoretinal surgery.
KeepSight, managed by Diabetes Australia, is a free online reminder system for people with diabetes about their next diabetes eye examination.
The National Diabetes Services Scheme (NDSS) and Diabetes Australia send alerts and reminders to people with diabetes registered on the NDSS to have their eyes checked.
A report on diabetes-related eye disease, titled ‘Out of sight’ has been published.6
The article by Yuen et al includes clinical references to support person centred care in diabetes associated eye disease.9
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Box 1. Screening for retinopathy in type 2 diabetes
When to initiate screening1
- At diagnosis (non-pregnant with type 2 diabetes)
- Educate people with diabetes about the link to sight-threatening eye disease, highlighting the importance of regular eye screening to protect their vision.
- At diagnosis (pregnancy with diabetes)
- Examination in first trimester. Routine referral to ophthalmologist. Pregnant women who develop gestational diabetes do not require screening for diabetic retinopathy2
Screening methods1
- Visual acuity should be tested for each eye in turn (with occlusion of the fellow eye)
- Retinal photography, with or without pupil dilation (mydriasis), with disc-centred and macular-centred images of both eyes, with interpretation by a trained reader
- Direct ophthalmoscopy or indirect slit-lamp fundoscopy through dilated pupil, performed by an examiner proficient in the use of these methods
Research on the optimal number of fields to be photographed is still unclear
If retinopathy is present1,3
- Grade retinopathy severity, refer to ophthalmologist as appropriate and establish appropriate monitoring intervals (≤1 year)
- Sight-threatening retinopathy may be treated with laser, pharmacological or surgical therapy by an ophthalmologist*
- Review glycaemic, blood pressure and lipid management, and adjust therapy to reach targets as per guidelines
- Screen for other diabetes complications, especially cardiovascular disease, including peripheral arterial disease and chronic kidney disease
If retinopathy is not present
- Rescreen every year:2
- people with duration of diabetes >15 years
- suboptimal glycaemic management (HbA1c >8% or 64 mmol/mol)
- systemic disease (poorly managed hypertension, lipids; other diabetes complications; foot ulcers)
- Aboriginal and Torres Strait Islander people
- people from a non-English-speaking background
- Uncertainties over the presence of retinopathy or maculopathy (eg unclear retinal photographs) may warrant referral to an ophthalmologist.
- Rescreen every two years:2
- all other people with type 2 diabetes
- Review glycaemic, blood pressure and lipid management, and adjust therapy to reach targets as per guidelines
- Screen for other diabetes complications
For more information, refer to The Royal Australian and New Zealand College of Ophthalmologists (RANZCO) screening and referral algorithm for diabetic retinopathy.2
*Treatment options include fenofibrate, laser therapy, intra-ocular anti-VEGF agents and vitreoretinal surgery. Evidence highlights the importance of regular, life-long participation in retinopathy screening.
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Role of retinal photography
Retinal photography is technically simple and is now usually performed within the Australian community by general practitioners, optometrists and ophthalmologists. Training is required to ensure quality of image interpretation.
Some Aboriginal Community Controlled Health Services are providing their own retinal photography services with support through telemedicine to promote access to screening.
People whose retinal images suggest they may be at increased risk of having, or at some point developing, sight-threatening retinopathy should be referred for assessment by an ophthalmologist.
Retinal photography may serve as a screening tool for retinopathy; however, it is not a substitute for a comprehensive eye exam.5
Note, a Medicare Benefits Schedule item number for retinal photography with a non-mydriatic retinal camera is available for general practice use.