After diabetes has been present for some years, changes may occur at the back of the eye in the retina, known as diabetic retinopathy. Your optometrist may use an instrument called an ophthalmoscope and posterior imaging that will clearly show these changes. There are two main types of this condition: non-proliferative (sometimes called background) retinopathy and proliferative retinopathy. The risk of developing retinopathy increases with the length of time you have had diabetes and is also increased when blood glucose levels are not well controlled over time. All diabetics should ensure they visit their optometrist at least every two years for a thorough examination.
Increased glucose concentration in the blood affects the circulatory system in diabetics. Initially this causes the small vessels in the retina to become weak, which can lead to small bulges in the vessels called microaneurysms, or the vessels can leak causing haemorrhages and exudates (collections of lipid residues). This is termed non-proliferative retinopathy. These leaks can cause swelling of the retina, and if this occurs in the macula (responsible for perceiving sharp detail), it can affect the quality of your vision. Occasionally a swelling of the retina may cause hazy vision or straight lines to appear bent. Your optometrist may instruct you in a simple procedure to carry out at home so that you can test your eyes for this condition. Improvements in diabetic control and co-morbidities such as blood pressure and cholesterol can help resolve these changes. Sometimes a focal laser treatment is needed to close off very leaky vessels.
Proliferative changes occur if areas of the retina become starved of oxygen. This leads to fragile new blood vessels growing to resupply the starved tissue. Unfortunately these vessels leak easily and can bleed, causing sudden vision loss. If these new vessels scar and constrict they can pull on the retina and lead to a retinal detachment. Patients may need a procedure where laser burns are used to kill off some of the less-important peripheral retina if the vessels are very leaky. This decreases the oxygen demand of the central retina and helps prevents further changes.
Diabetes sometimes causes the focusing ability of the eye to weaken or fluctuate from day to day due to swelling of the crystalline lens inside the eye. This characteristic has often led to optometrists diagnosing diabetes in their patients. The problem eases when blood glucose levels are well controlled.
This is a distressing but rare complication of diabetes. The condition is usually temporary but it may last for a few months. An optometrist can help to treat it while it has effect. Diabetes is not the only cause of double vision so it is best to have this checked by your optometrist if it occurs.
Diabetics experience higher rates of ocular surface disease such as dry eye. Research shows that most cases of dry eye associated with diabetes are caused by insufficient production of tears due to “autonomic neuropathy” affecting the nerves that control the lacrimal gland. That is, the same process leading to diabetic peripheral neuropathy that causes symptoms like tingling or burning in the hands and feet, can also affect the nerves that normally sense dryness and produce moisture to keep the eyes well lubricated. See our dry eye page for more information here.
Controlling blood glucose over time significantly reduces the risk of developing retinopathy, but does not eliminate it. The best management is to have regular eye examinations so that changes can be detected and treated early. It is advisable for all people with diabetes to have annual eye examinations. People who have been diagnosed as having retinopathy should have eye examinations more frequently than once a year. In addition, regular visits to your general practitioner or endocrinologist may help to control blood glucose levels.
The role of optometry in diabetic management in retinal health is that of close monitoring and communication with other health professionals involved in your diabetic care. If we detect the development of diabetic retinopathy we can instigate changes to the diabetic control with the help of the patient’s general practitioner or endocrinologist. If needed we can also refer to ophthalmology for a surgical opinion.
At Innovative Eye Care we recommend a dilated eye exam to best assess the health of the retina. Dilating the pupils enables us to get a much clearer view of the back of the eye. Dilating drops last for 4-6 hours and may cause glare and blurry vision. Because of this we recommend not driving following a diabetic retinal examination.
We use a range of equipment on the forefront of diagnostics during a comprehensive diabetic health exam. This includes retinal photography to record and monitor subtle signs in the retina, examination using bio-microscopy to stereoscopically assess both the central and peripheral retina, and optical coherence tomography, a technology that can scan the retinal layers to look for swelling and other damage. Some of the additional tests necessary for a comprehensive diabetic retinal examination fall outside of what is covered by Medicare. Because of this there may be additional charges to cover the cost of the equipment and consumables. Find out more about exam billing here.
CAPTION: An image captured by the Heidelberg OCT showing evidence of proliferative diabetic retinopathy (top) and the same retina after treatment with anti-vascular injections.