Diabetic retinopathy – answers and questions
Among the various complications related to diabetes, retinopathy is the main cause of avoidable blindness in the population aged between 20 and 65. This is sufficient reason to warrant regular monitoring. Diabetic retinopathy usually develops without any visual signs. However, 98% of type 1 diabetics and 50% of those with type 2 exhibit lesions after 20 years with this disease. It is of vital importance that diagnosis be made in a phase when treatment is still possible and efficient, through periodic and systematic ophthalmologic observation and subsequent treatment.
What is diabetic retinopathy?
Commonly known as “diabetes of the eyes” (an incorrect term), diabetic retinopathy is the alteration of the cytoarchitecture (anatomy) and function of the retinal structures, in response to vascular damage and consequent inflammation, influenced by several factors. Around 25% of diabetics show some form of diabetic retinopathy and, of these, 2%-10% have diabetic macular oedema (prolonged excess of sugar in the blood that provokes oedema in the ocular blood vessels). This is the complication responsible for the greatest number of cases of loss of visual acuity among those affected by diabetic retinopathy.
I have diabetes. Will I eventually develop diabetic retinopathy?
Evolution of complications associated with diabetes in different organs varies enormously, so the greater the patient’s metabolic control, the fewer associated complications. Nonetheless, the incidence of diabetic retinopathy and diabetic macular oedema increases with the number of years a person has suffered from the disease. With 15 years evolution, 15% of diabetics develop macular oedema, but with a 20-year evolution, more than 90% will suffer some degree of diabetic retinopathy.
Is it possible to prevent diabetic retinopathy?
As mentioned in the previous point, careful metabolic control of the disease by the GP, internist or endocrinologist will delay the start of ocular complications. However, despite the best care and control, the longer you are diabetic, the greater will be the incidence of diabetic retinopathy.
If I am diagnosed with diabetic retinopathy, will I go blind?
Diabetes is considered the principal cause of blindness in the active population in industrialised countries. Diabetic macular oedema is the leading cause of loss of visual acuity and proliferative retinopathy (a more serious form of diabetic retinopathy) is responsible for the most pronounced visual impairment. Nevertheless, the most efficient weapon to combat this scenario is early diagnosis (before the appearance of the first symptoms and complications).
What diagnostic methods are used in the evaluation and classification of diabetic retinopathy?
Several types of complementary exams are used when assessing a diabetic. It is imperative to assess the lesions on the mid and peripheral retina and, at the same time, rule out the presence of diabetic macular oedema (a complication closely related to the loss of visual acuity). The exam known as fluorescein angiography is one of the most important exams in identifying the number and size of retina lesions (especially those that are invisible during an ophthalmic exam).
Another basic test, especially for assessing the macula (area of the retina with the greatest number of photoreceptors essential for good vision) is called an OCT (Optical Coherence Tomography). This exam has the capacity to analyse the retina’s different layers in detail, thus permitting an early diagnosis of macular lesions before they are linked with the loss of visual acuity. The most recent generation of OCT with swept source technology (OCT-A) produces images similar to those of a classic angiograph, but without the need for using intravenous contrast. According to the number and location of the lesions that are observed, we classify the disease and treat it according to this indication.
When is it necessary to treat diabetic retinopathy?
This is a complex subject. However, generally speaking, most ophthalmologists decide to begin treatment when the disease is classified as severe non-proliferative retinopathy (international clinical classification) or when there is diabetic macular oedema. Other complications, such as peripheral retinal ischemia and neovascularisation detected in a Fluorescein Angiography, influence the need for specific ophthalmological treatment. Any complication related to proliferative diabetic retinopathy requires priority treatment.
What treatments are available?
Depending on the patient’s retinal lesions, the ophthalmologist may suggest different forms of treatment. As previously explained, the majority of cases resulting in loss of visual acuity are associated with diabetic macular oedema. Nowadays, the best results obtained in the treatment of this condition are intravitreal anti-VEGF therapy or intravitreal corticosteroids, both of which are administered in antiseptic conditions in the operating theatre. Other options include retinal photocoagulation and vitreoretinal surgery.
By Dr Argílio Caldeirinha
Dr Argílio Caldeirinha is an ophthalmologist at the Hospital Particular in Alvor and the clinic at AlgarveShopping – Guia