Image supplied by Charlie Wang, Specsavers Springfield, QLD
Presentation & Pathogenesis
Patients with proliferative diabetic retinopathy (PDR) typically present with symptoms of reduced vision accompanied by obvious clinical signs. Other symptoms may include spots or shadows in vision.
PDR occurs due to neovascularisation triggered by retinal ischemia, which in turn is caused by non-perfusion in the blood supply to the retina. The lack of perfusion gives rise to release of vascular endothelial growth factors (VEGF) and vasoactive factors, which stimulate new vessel growth (neovascularisation).
Neovascularisation can affect various structures within the eye as the proliferation of new weaker, abnormal vessels leak blood, fluid and lipid, triggering further release of these factors. This is a destructive cycle that damages many structures in the eye.
The digital retinal image above shows neovascularisation of the optic nerve extending from the temporal aspect to the superior aspect of the nerve with a distinct, frond-like appearance. This is pathognomonic of PDR.
Thorough retinal examination at the time of presentation is key to identifying the various diabetic changes occurring at the retina. Examination of patients should also include measurement of VA (monocular and binocular), pupil assessment, intraocular pressures, and anterior ocular examination, including anterior chamber assessment (for possible neovascularisation of the iris).
A thorough history will highlight risk factors that predispose patients to progression of non-proliferative diabetic retinopathy (NPDR) or PDR. Risk factors include duration of diabetes, poor glucose control, pre-existing NPDR, co-existing vascular disease (especially if poorly controlled or managed), and ethnicity (Indigenous and Polynesian ethnicities have been found to have a higher risk).
Diabetic retinopathy (DR) can be classified by the severity of clinical signs as observed by the optometrist. It can be defined as mild, moderate, severe NPDR, or PDR. Classic signs of NPDR include:
- Scattered microaneurysms and focal haemorrhages
- Flame haemorrhages
- Macular oedema (fluid leakage and swelling)
- Cotton wool spots
- Intraretinal microvascular anomalies.
Diabetic macular oedema is the most common cause of vision reduction in DR and can occur at any stage of the disease, whereas neovascularisation is a clear indication that the disease has progressed to a proliferative state.
PDR typically follows NPDR, and due to the development of neovascularisation and the resulting sequelae, it can have severe effects on vision. Some of the many causes of vision loss in PDR are:
- Vitreous haemorrhage (bleeding from weaker vessels in the retina into the vitreous)
- Retinal detachment (traction or rhegmatogenous)
- Neovascular glaucoma (ischemia of the optic nerve causing nerve fibre loss and visual field defects).
Progression & Prognosis
PDR is a vision-threatening condition and requires urgent assessment and treatment. Ophthalmologists employ laser treatment, anti-VEGF treatment and / or vitrectomy as key methods of management for patients with DR.
It is integral that ophthalmological treatment is paired with effective management of the factors contributing to the disease. This includes blood glucose control, management of vascular risk factors, lifestyle advice, and referral to allied health practitioners to assess for neuropathy and nephropathy, which are common systemic complications associated with DR.
For this reason, communication between optometrists, GPs, ophthalmologists and other relevant health professionals is vital in preventative management for patients with diabetes.