Diabetic Retinopathy
What is Diabetic Retinopathy?
Diabetic retinopathy is a complication of diabetes, both type 1 and type 2. Risk of developing diabetic retinopathy is higher in people whose blood sugar levels are poorly controlled and the longer they have been diabetic. This is because prolonged high blood sugar levels cause damage to the small blood vessels all around the body, including the retina. This damage can lead to the blood vessel walls becoming thicker, as well as more leaky. This can lead to small bleeds (haemorrhages) in the retina that will be picked up on your regular eye exams.
Causes of Diabetic Retinopathy
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Diabetic retinopathy is a serious eye condition that affects people with diabetes, impacting 100 million people worldwide.[1] It occurs as high blood sugar levels can damage the blood vessels in the retina, the light-sensitive tissue at the back of the eye. If left untreated, it can lead to vision impairment and blindness. However, with early detection and proper management, the progression of diabetic retinopathy can often be slowed or even prevented.
Early disease
As the vessels in the retina become damaged and permeable, small bleeds known as haemorrhages may be visible on retinal exam. The vessels may also leak fatty deposits called exudates that appear as yellow spots on the retina. Small vessels may also become blocked and this can lead to cotton wool spots which appear as pale white patches. The smallest vessels in the body and retina are known as capillaries. Microaneurysms form as these capillaries can become dilated (swollen) and distended, which may also leak and rupture.
Advanced disease
Vitreous haemorrhage : Blood can pool in the jelly in the centre of the eyeball, in a complication known as vitreous haemorrhage. This can cause sudden profound loss of vision and may require surgical intervention.
Proliferative diabetic retinopathy : Thickened blood vessels may become too narrow to allow the passage of red blood cells, which carry oxygen around the body. Loss of blood vessels causes oxygen starvation (ischemia). This in turn can lead to new abnormal vessels growing from remaining areas of healthy tissue (neovascularisation), but these vessels are not useful, and are fragile and prone to bleed (haemorrhage). This is known as proliferative diabetic retinopathy (PDR).
New blood vessels can also cause additional damage from scarring, causing tugging and lifting of the retina away from the wall of the eye, which can lead to a condition known as tractional retinal detachment.[2]
New vessels may grow in the peripheral retina, at the optic nerve or sometimes in the iris at the front of the eye. When blood vessels reach the iris this is known as rubeosis. Rubeosis can block the drainage of the fluid which fills the front of the eye, cause high intraocular eye pressures and loss of vision through secondary glaucoma. It can also cause bleeding in the front of the eye.
Diabetic Macular Oedema : Leaky blood vessels cause swelling. This swelling can occur in the macula, which is the central area of the retina needed for fine and detailed vision. This is known as diabetic macular oedema (DMO) and can result in reduced & distorted vision.
Diabetic changes to the retina (illustration)
Symptoms of Diabetic Retinopathy
In the early stages, diabetic retinopathy may not cause noticeable symptoms. It is possible to have vision-threatening disease without symptoms. Patients may experience:
Blurred vision: You may notice increased difficulty reading or recognising aces
Sudden changes to vision: Worsened vision should be immediately reviewed by an ophthalmologist
Floaters: Dark spots or strings floating in the vision
Distorted Vision: Straight lines may appear wavy or bent
Dark or Empty Patches: Missing patches in vision may develop in advanced disease.
Management of Diabetic Retinopathy
The management for diabetic retinopathy depends on the stage of the condition:
Managing blood sugar: Controlling blood sugar levels is crucial in preventing and slowing the progression of diabetic retinopathy. Follow treatment and monitoring plans set by your GP, endocrinologist or diabetes educator.
General health: Other factors such as high blood pressure and high cholesterol can also increase risk of retinopathy so should be carefully managed in accordance with advice from your GP.[3]
Lifestyle: Maintain a balanced and colourful diet. Keep up regular exercise that increases your heart rate, such as walking, swimming and pilates. Avoid smoking which is a known risk factor for diabetic retinopathy.
Regular eye exams: Patients with diabetes should have regular eye exams. If there is no retinopathy, every 2 years is adequate, but more frequent exams may be necessary if there is retinopathy already or if there is gestational diabetes. For patients with type 2 diabetes, an eye exam should be scheduled soon after diagnosis, as it is possible to have diabetes for many years before developing symptoms
Proliferative diabetic retinopathy treatment
Pan retinal photocoagulation (PRP) laser
PRP laser is used to treat proliferative diabetic retinopathy, which is an advanced disease occurring due to abnormal blood vessel growth. The aim of the laser is to burn small scars in the oxygen starved (ischemic) peripheral retina. This is a destructive treatment, but the scar tissue that is left after treatment helps reduce the abnormal blood vessel growth. This is because the scar tissue does not release blood vessel growth factor hormones like VEGF. The scar damage destroys tissue needed for peripheral vision, but the oxygen starved tissue does not work properly in any case. PRP laser can impair peripheral vision, which can have an impact on driving, and also reduce night vision. It can also temporarily worsen DMO and some people might notice pain during the procedure.
Timely treatment is essential to achieve best possible results, with a recent study showing that patients who received PRP treatment on day of diagnosis with PDR had visual outcomes 3 lines better at 12 months post treatment than those who were treated >31 days after diagnosis.[4]
Intravitreal injections
PRP is still the gold standard therapy for PDR, although other options exist such as intravitreal injections of antiVEGF medication which causes temporary regression of new blood vessels. However, AntiVEGF therapy is not currently funded by the Australian Government Pharmaceutical Benefit Scheme (PBS) for proliferative diabetic retinopathy.
Treatments
Causes of Diabetic Retinopathy
Vitreous haemorrhage
Proliferative diabetic retinopathy
Diabetic Macular Oedema
Diabetic changes to the retina (illustration)
Management of Diabetic Retinopathy
Proliferative diabetic retinopathy treatment
Pan retinal photocoagulation (PRP) laser
Intravitreal injections
Diabetic Macular Oedema (DMO) Treatment
Intravitreal injections
Illustration of before and after Treatment
Diabetic Macular Oedema treatment
Intravitreal Injections
Diabetic macular oedema (DMO) is swelling of the retina at the point of central, detailed vision so can cause rapid decline in vision. Your doctor may recommend intravitreal injections as an effective treatment for DMO. These medications block the activity of hormones such as VEGF (Vascular endothelial growth factor A) and more recently, Angiopoietin-2. These hormones are responsible for triggering the growth of blood vessels in the eye and are typically abnormally high in people with DMO. Regular treatment with these intravitreal injections can reduce blood vessel growth and the associated leakage and swelling in the macula.
Studies show the average result of regular intravitreal injections for DMO is a 2 line improvement in vision over 2 years.[5]
What can I expect for my first intravitreal injection?
You will initially see an orthoptist who will review your history, check your vision and perform an initial eye exam. You will receive dilating eye drops that allow a complete retinal exam which can blur your vision over the next few hours and cause light sensitivity. You will have a scan of your retina performed (OCT) which provides images of the macula and layers of the retina.
You will then see your treating doctor for further eye examination and discussion of your disease. You will have the chance to discuss the risks and learn about how the treatment will work within the eye. You can also ask any questions you might have and learn what you might expect after the injection. The injection will be performed with prior antiseptic (cleaning) and anaesthetic (numbing) for your comfort. You will be given instructions to keep the eye clean post-injection and you should arrange a safe way to get home as you need to avoid driving after your appointment.
Laser : Focal or grid laser is less commonly used today for Diabetic Macular Odema as antiVEGF (medication) therapy is more effective and does not create scars. It may still be a useful add-on treatment in certain circumstances.
Conclusion
Diabetic retinopathy is a serious complication of diabetes, but with early detection, proper management, and lifestyle changes, its impact on vision can be minimised. Regular eye examinations and adherence to the treatment plan prescribed by healthcare providers are vital in preserving vision and overall eye health for individuals with diabetes.
References
[1] Mitchell, P., Liew, G., Gopinath, B., & Wong, T. Y. (2018). Age-related macular degeneration. Lancet, 392, 1147–1159.
[2] Cheung, N., Mitchell, P., & Wong, T. Y. (2010). Diabetic retinopathy. The Lancet, 376, 124–136.
[3] Liu, L., Quang, N. D., Banu, R., Kumar, H., Tham, Y. C., Cheng, C. Y., Wong, T. Y., & Sabanayagam, C. (2020). Hypertension, blood pressure control and diabetic retinopathy in a large population-based study. PLoS ONE, 15(3).
[4] Ohlhausen, M., Payne, C., Greenlee, T., Chen, A. X., Conti, T., & Singh, R. P. (2021). Impact and Characterization of Delayed Pan-Retinal Photocoagulation in Proliferative Diabetic Retinopathy. American Journal of Ophthalmology, 223, 267–274. https://doi.org/10.1016/j.ajo.2020.09.051
[5] Flaxel, C. J., Adelman, R. A., Bailey, S. T., Fawzi, A., Lim, J. I., Vemulakonda, G. A., & Ying, G. shuang. (2020). Diabetic Retinopathy Preferred Practice Pattern®. Ophthalmology, 127(1), P66–P145. https://doi.org/10.1016/j.ophtha.2019.09.025