Screening, management of diabetic retinopathy: A comprehensive guide

At the completion of this article, the reader should…

•  Have reviewed screening guidelines to assess diabetic retinopathy based on disease severity and clinical modifiers.

•  Understand the role of digital fundus photography as the standard for DR screening and its advantages in
documenting retinal changes.

•  Integrate digital imaging techniques, including non-mydriatic and ultra-wide-field cameras, in DR screening.

•  Collaborate with healthcare providers to manage and refer patients for timely interventions in diabetic retinopathy.

Dr Amanda Ie
BMedSci, MBBS, FRANZCO
Adult and paediatric vitreoretinal surgeon
Westmead Hospital & Children’s Hospital Westmead

Dr Tracey Phan
BMed, GDip (OphthSci), FRANZCO
Medical retina, glaucoma and cataract specialist

Optometrists are increasingly at the forefront of collaborative diabetes care, playing a crucial role in the early detection of diabetic retinopathy. DR TRACEY PHAN and DR AMANDA IE highlight essential screening guidelines, clinical signs, and referral pathways every optometrist should be aware of.

Diabetes mellitus is a significant contributor to the burden of disease in Australia and worldwide. In 2021, the estimated prevalence of diabetes in Australia was one in 20 (around 1.3 million people),¹ with projected numbers estimated to affect 700 million people globally by 2045.² The National Diabetes Services Scheme reported that around 8% of the Aboriginal and Torres Strait Islander population live with diabetes, and in some remote areas, up to 40% are affected by type 2 diabetes – alarming figures that represent one of the highest documented rates of diabetes in the world.³

Of the diabetic subtypes, type 2 diabetes, remains the most common (86.7%) followed by type 1 diabetes (9.4%).³ Moreover, the prevalence of type 2 diabetes in the last 20 years has tripled and around 500,000 Australians are now estimated to be living with undiagnosed type 2 diabetes,³ providing optometrists a unique opportunity to be the first to diagnose diabetes in susceptible patients.

Optometry at the forefront

Diabetic retinopathy (DR) occurs as a result of microvascular compromise to the retina, affecting up to one third of non-Indigenous and almost 40% of Indigenous diabetics,⁴ and remains one of the top five leading causes of irreversible blindness in adults in Australia.⁵

The sequelae of DR can be potentially devastating, leading to visual impairment with progression to blindness, invariably resulting in poorer quality of life and loss of independence.

The role of the optometrist as a primary care practitioner is critical in the early detection of DR, recognising signs of disease progression, and identifying potentially blinding complications of DR at an early point of intervention. This should occur as part of a holistic model of patient care, with continued encouragement to patients to optimise their glycaemic control and other cardiovascular risk factors.

The three distinct forms of DR are:

1. Diabetic macular oedema (DME) – diffuse or focal vascular leakage within the macula, which affects 3.3% of individuals with diabetes.

2. DR caused by microvascular changes, which can be further categorised as: non-proliferative diabetic retinopathy (NPDR) – including microaneurysms, intraretinal haemorrhages, tortuous vessels (affects approximately 20% of patients with diabetes)

3. Proliferative diabetic retinopathy (PDR), which involves neovascularisation of the disc or retina (occurs in two per cent of diabetics)⁶

Screening recommendations

Screening of diabetic retinopathy is essential as affected patients often remain asymptomatic even at advanced stages of disease. Importantly, visual impairment can be avoided in many of these patients.

Screening for DR at the time of diagnosis is vital, as patients may have had poorly controlled or potentially long-standing diabetes prior to the diagnosis. This visit also presents an opportunity to educate patients regarding the trajectory of diabetic retinopathy to sight-threatening disease and to encourage engagement in regular screening.

Several landmark trials, including the UK Prospective Diabetes Study, the ACCORD trial, and the Diabetes Control and Complications Trial (DCCT), have thoroughly examined the systemic clinical disease modifiers that may contribute to the progression of DR.^8,9 The presence of any of these risk factors will modify screening intervals (see
table 2).

If no DR is present and no associated clinical disease modifiers are identified, screening is recommended every two years. However, annual eye screening is advised if DR is absent but any of the clinical disease modifiers are present. Annual screening is also recommended for patients whose HbA1c level exceeds eight per cent or 64 mmol/mol, or if the patient is of Aboriginal or Torres Strait Islander origin or from a non-English speaking background.

Certain vulnerable groups require special consideration. Children with diabetes should be screened at least every two years from the age of 12, and ongoing screening should follow the guidelines mentioned above (Table 1). The elderly, particularly those with common comorbidities, also require attention.

For pregnant women, routine screening is recommended during the first trimester for those with pre-existing diabetes, as pregnancy can increase the risk of developing DR or worsen existing retinopathy. To avoid exposing pregnant patients to dilating medications, screening may be performed without dilation using a non-mydriatic digital wide-field camera. Pregnant women who develop gestational diabetes mellitus (GDM) do not require screening unless the condition persists postpartum, in which case ongoing screening should be considered according to the guidelines outlined above (Table 1).

Screening procedures

A comprehensive history should be obtained detailing the duration of diabetes, with treatment and recent history of sugar control (with an optimal HbA1C target of less than seven per cent as per the Diabetes Control and Complications Trial (DCCT).⁹

Comorbidities that pertain to risk factors and complications of diabetes should be noted, including hypertension, dyslipidaemia, and any smoking history. Complications including cerebrovascular events, ischaemic heart disease, nephropathy and neuropathy should be documented. The presence of these complications represents a harbinger for severe microvascular changes and thus increase suspicion of diabetic retinopathy.

A comprehensive eye exam includes a thorough anterior and posterior segment examination, with documented best corrected visual acuity and intraocular pressures. Anterior segment examination should pay particular attention to cataractous formation as well as iris neovascularisation (rubeosis) – a late sign of severe and blinding diabetic ocular changes.

The retinal screening examination should be undertaken after adequate mydriasis, with a thorough examination of the posterior pole, looking for signs of neovascular changes at the disc, as well as examining the macula closely for microaneurysms, haemorrhages, exudates, and diabetic macular oedema. The presence of pre-retinal or vitreous haemorrhages should be noted as this may indicate proliferative DR.

A mid-peripheral view of the retina is best to examine for dot-blot haemorrhages, cotton wool spots, venous beading, and intraretinal microvascular abnormalities which are evident in non-proliferative diabetic retinopathy. Signs of neovascularisation elsewhere are found in the mid periphery and often along the retinal arcades. Adequate dilation is essential as these mid peripheral signs may be missed through a constricted pupil.

Initial classification for DR is based as per the Early Treatment Diabetic Retinopathy Study (ETDRS) guidelines and has been further refined by the International Clinical Diabetic Retinopathy and Diabetic Macular Oedema Severity Scale:^10,11

• Non-proliferative diabetic retinopathy
°  Mild disease: microaneurysms only
° Moderate: microaneurysms with at least one of:
– Retinal haemorrhages
– Hard exudates
– Cotton wool spots
– Venous beading

° Severe: any of the following (4-2-1 rule):
– More than 20 intraretinal haemorrhages in each of the four quadrants

– Venous beading in two or more quadrants

– Prominent intraretinal retinal abnormality in one
quadrant

PDR can be diagnosed by either presence of neovascularisation or any vitreous or pre-retinal haemorrhage. High-risk PDR, defined by the Diabetic Retinopathy Study (DRS), is characterised by the following features:

– NVD larger than ¼ to ⅓ of a disc area

– NVD of any size associated with vitreous haemorrhage

– NVE of any size associated with vitreous haemorrhage

The DRS determined that high-risk PDR was an indication for panretinal photocoagulation to reduce the progression of PDR and therefore identification of these characteristics warrants urgent referral to an ophthalmologist.¹²

The role of digital imaging

The RANZCO guidelines state that digital fundus photography is the expected standard for fundus examination.

Screening using imaging can be a valuable tool offering an objective means of documenting the status of the retina. Dilation may not be required if a high-quality image is obtainable through a non-mydriatic or ultra-wide field camera. If the image quality is poor, the pupil must be dilated and 0.5-1% tropicamide drops are required, unless the patient is pregnant.

Ultra-wide field images can be used to screen for diabetic retinopathy, or alternatively, two 45-degree fundus images should be captured, with one centred on the macula, and one on the nasal fundus where the nasal extent of the retina to three disc diameters from the edge of the optic disc is visible. Only 8-15% of patients with DR will have changes outside of this zone alone.

The ZEISS Clarus non-mydriatic camera can capture 133 degrees with one capture, and 200 degrees with two captures, which can be achieved without dilation, giving adequate visualisation of the area most likely to be affected by DR.

Optical coherence tomography (OCT) is another useful adjunct for the detection of diabetic macular oedema, allowing classification as to whether the disease is centre- or non-centre involving, as well as documenting progression or response to treatment.

Importance of collaboration and education

The results of DR screenings should be shared with each patient, and their health care providers including their GP and endocrinologist.

The presence or progression of DR is important to convey as it allows for steps to be taken to improve glucose management and other associated risk factors. When hyperglycaemia, hypertension and dyslipidaemia are managed alongside lifestyle modifications in a
multidisciplinary setting, patients experience better mortality outcomes as well as improved management of their DR.

Regular screening and ongoing patient education at each visit is crucial for the early detection of DR that requires treatment. The timely delivery of any interventions including anti-VEGF injections, laser or vitrectomy can significantly improve patient outcomes.

Conclusion

Understanding of clinical risk factors for worsening diabetic retinopathy is essential in determining the appropriate screening periods.

It also helps to identify vision-threatening features of diabetic retinopathy that require urgent referral to an ophthalmologist when assessing a patient.

The optometrist, as a primary care clinician, plays an important role as the first point of contact for patients with diabetes. Regular reviews of asymptomatic patients enable the early identification of diabetic complications and facilitates timely intervention, potentially preventing devastating vision loss. 

NOTE: References will appear in the online version of this article and are available upon request.

More reading 

Dr James Muecke: The tide is turning on diabetes

Ophthalmic voice prominent in 2024 national diabetes inquiry

AI scan for diabetes has potential to save sight and money

Rererences

1. Australian Institute of Health and Welfare. Diabetes: Australian facts [Internet]. [cited 2025 Apr 2]. Available from: https://www.aihw.gov.au/reports/diabetes/diabetes/contents/summary
2. Saeedi P, Petersohn I, Salpea P, Malanda B, et al, on behalf of the IDF Diabetes Atlas Committee. Global and regional diabetes prevalence estimates for 2019 and projections for 2030 and 2045: Results from the International Diabetes Federation Diabetes Atlas, 9th edition. Diabetes Research and Clinical Practice. 2019 [cited 2025 Apr 2]; 157: 107840. Available from: https://www.diabetesresearchclinicalpractice.com/article/S0168-8227(19)31230-6/pdf.
3. Wong TY, Hayward C, Tapp RJ, et al. Prevalence of Diabetic Retinopathy in Indigenous and Non-Indigenous Australians: A Systematic Review and Meta-analysis. Ophthalmology. 2023 Jan 1;130(1):56–67.
4. Vision 2020 Australia. Clear Insight: The Economic Impact and Cost of Vision Loss in Australia. 2004. 124
5. Tapp RJ, Tikellis G, Wong TY, Harper CA, Zimmet PZ, Shaw JE, et al. Longitudinal Association of Glucose Metabolism With Retinopathy: Results from the Australian Diabetes Obesity and Lifestyle (AusDiab) Study. Diabetes Care. 2008 Jul;31(7):1349.
6. Royal Australian and New Zealand College of Ophthalmologists. RANZCO Referral Pathway for Diabetic Retinopathy [Internet]. [cited 2025 Apr 3]. Available from: https://ranzco.edu/wp-content/uploads/2018/11/RANZCO-Referral-pathway-for-DR-2016.pdf
7. British Diabetic Association. United Kingdom Prospective Diabetes Study (UKPDS): Implications for the Care of People with Type 2 Diabetes. 1998.
8. Nathan DM, for the DCCT/EDIC Research Group. The Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Study at 30 Years: Overview. Diabetes Care. 2013 Dec 11;37(1):9.
9. National Eye Institute, Early Treatment Diabetic Retinopathy Study Research Group. Early Treatment Diabetic Retinopathy Study (ETDRS): Collected Publications 1985-1998. 1999.
10. Wilkinson CP, Ferris FL, Klein RE, Lee PP, Agardh CD, Davis M, et al. Proposed international clinical diabetic retinopathy and diabetic macular edema disease severity scales. Ophthalmology. 2003 Sep;110(9). Available from: https://pubmed.ncbi.nlm.nih.gov/13129861/
11. National Eye Institute. Diabetic Retinopathy Study Research Group. Photocoagulation Treatment of Proliferative Diabetic Retinopathy: Clinical Application of Diabetic Retinopathy Study (DRS) Findings, DRS Report Number 8. 1982. 20 p.