Diabetes Mellitus, commonly referred to as Diabetes is a metabolic disorder which affects the ability of the blood to utilize glucose which means conversion of the glucose to energy. The entry of glucose from the blood stream into the body cells and its subsequent metabolism to generate energy is dependent on a hormone called insulin secreted by the pancreas. Therefore, Diabetes is generally the result of either underproduction of insulin by the pancreas (Type I Diabetes) or resistance of peripheral body tissues to the action of insulin (Type II Diabetes). The net result of the underutilization of glucose is abnormally high levels of glucose or sugar in the blood. If not properly controlled, this may lead to irreversible damage to the heart, kidneys, nerves and Eye in long-standing cases.
According to data released by the International Diabetes Federation in the year 2020, there are around 463 million people affected by Diabetes worldwide of which 77 million are in India. A survey report released by the Ministry of Health and Family Welfare in 2019 states the prevalence of diabetes in India is 11.9% in people above 50 years of age. Thus, it is a fairly common disease with the ability to cause damage to many vital body organs, if left untreated or inadequately treated. In this article, we shall be discussing the effects of Diabetes on the eye.
How does Diabetes affect the Eye?
Diabetes has the potential to affect different parts of the eye, most importantly the retina. Retina is the neural tissue at the back of the eye which is vital to the process of vision. The damage caused by Diabetes to the retina is called Diabetic Retinopathy.
The excess blood glucose gets deposited in the walls of the small blood vessels of the retina and distorts their normal architecture. This causes the blood vessels to become leaky. Lipids and proteins from the blood leak out and get deposited in the retinal tissue resulting in thickening or swelling of retinal tissue. When this swelling occurs in the central and most important part of the retina called macula, it is called Diabetic Macular Oedema. This results in difficulty in vision for the patient.
Another way in which excess blood glucose affects the retina is by decreasing blood flow through the small retinal blood vessels. Thus, the retina starts becoming hypoxic or oxygen starved. In response to this, new vessels start growing the retina with the aim to bring in more oxygen. But these new blood vessels are often fragile and abnormal. They rupture and bleed causing further and irreversible retinal damage and vision loss. This is called Proliferative Diabetic Retinopathy.
Apart from this, Diabetes also increases the risks of blood vessel blockage in the retina leading to Stroke in the Eye (Central Retinal Artery or Vein Occlusion). Early development of Cataract (Clouding of the lens of the eye) and Glaucoma (Increased eye pressure) are other eye diseases having a strong association with Diabetes.
How do we control eye damage due to Diabetes?
Eye damage due to Diabetes depends mainly on three factors
Duration of the disease is a factor which cannot be modified but the remaining two are modifiable risk factors. Strict control of blood sugar by diet, oral medication or insulin injections as recommended by the treating physician is the cornerstone of prevention of Diabetic Eye Disease. Associated co-morbid conditions like high blood pressure and high cholesterol should also be appropriately controlled.
Regular eye examination, at least once a year by an Ophthalmologist is a must for all patients affected with Diabetes even in the absence of any visual complaints. Diabetic Retinopathy is relatively symptom free in the early stages and causes visual complaints only in the advanced stages. So regular screening of diabetic patients is very important for early detection and management of Diabetic Retinopathy.
Advanced Diabetic Retinopathy is treated with laser to the retina and injection of anti-proliferative drugs into the eye. Multiple sittings of treatment are required which often entail psychological and financial burden on the patient.
Though I have discussed only the eye-related complication of Diabetes in this article, the economic and psychological impact of other Diabetes related complications is quite similar. Therefore, it is very important for every patient affected with diabetes to aim at preventing the development of diabetes related complications, not only to the eye but also other vital organs like heart, kidney and nerves. With meticulous attention to diet, regular exercise, disciplined lifestyle, regular check-ups and appropriate medication as advised by the treating doctor, blood sugar can be kept within acceptable limits so as to prevent associated complications even in long-standing disease.
‘What happens to us in life is perhaps beyond our control but how we choose to deal with it decides what we actually become’
Dr Sudha Seetharam
MBBS, M.S (Ophthalmology)
Author: “Self-assessment and Review of Ophthalmology” for MBBS students