Diabetes, eyes and vision
Diabetes can affect the eye in many ways, and often you will not know there is anything wrong even with quite advanced disease.
Diabetic maculopathy
In diabetes, high blood glucose levels damage the small blood vessels that bring oxygen to the retina. They become leaky and eventually shut down. In the early stages, small swellings called microaneurysms can leak fluid and fatty substance into the retina. When leakage occurs near the centre of the macula, even small amounts of swelling can affect vision.
Good control of blood sugar, blood pressure and cholesterol delays the development of diabetic eye disease. If detected and treated early, the risk of severe visual loss can be reduced.
Diabetic retinopathy
Over time, damaged blood vessels bleed into the retina and shut down. The retina, starved of oxygen, produces a chemical (VEGF) that stimulates growth of new, abnormal blood vessels. These are fragile and can cause vitreous haemorrhage (bleeding into the gel inside the eye) or tractional retinal detachment.
Diabetic vitreous haemorrhage
If bleeding into the vitreous occurs, you may experience haziness and new floaters with a little bleeding, or significant vision loss with more bleeding. Treatment may involve waiting for the blood to clear, laser treatment, or vitrectomy surgery to remove the blood. Intravitreal injections may also play a role.
Diabetic eye screening
In the UK, people with diabetes are invited for a local photographic eye-screening test once a year. It is important to attend this even if you have already been seen by your optician, as the two examinations focus on different aspects of your eye care.
Tests
OCT scan
Shows the macula in 3D. Particularly useful to detect swelling or fluid. OCT angiography can look at the small blood vessels non-invasively.
Fluorescein angiography
Photographs of retinal blood vessels after dye is injected into a vein in your arm. Most people cope well. You are monitored for up to 30 minutes afterwards.
Treatment
First and foremost: optimise your blood glucose, blood pressure and cholesterol levels, and stop smoking.
Alongside improvements in diabetes control, you may benefit from laser treatment, a course of intravitreal injections, or a combination of the two.
Laser for diabetic macular oedema
Applied as targeted focal laser or diffuse macular grid laser. Both eyes can be treated at the same visit. Newer laser techniques are gentler with fewer visual side effects.
Laser for proliferative diabetic retinopathy
The laser deliberately destroys some peripheral retina to reduce its oxygen demands, which in turn reduces the drive for abnormal blood vessel growth. This can affect peripheral and night vision, and may affect DVLA driving standards.
Laser treatment in patients with high-risk diabetic features reduces the risk of severe visual loss from around 30% to around 15% in the two years after treatment.