Diabetes is defined as “a disease in which the body’s ability to produce or respond to the hormone insulin is impaired, resulting in abnormal metabolism of carbohydrates and elevated levels of glucose in the blood.” India ranks 3rd in terms of the number of people affected with diabetes. The population suffering with this disease has almost doubled in the last 13 years, according to the World Health Organization (WHO).
Diabetes has been dubbed ‘the silent killer by 2030’, as it is the seventh largest cause of death all over the world.
Diabetes is of two types :
· Type 1 Diabetes Mellitus (Insulin dependant/ juvenile diabetes)
· Type 2 Diabetes Mellitus (Non-insulin dependant/ adult onset)
Type 1 diabetes mellitus is a condition, where the beta-islet cells of pancreas are destroyed due to autoimmunity (WBCs attack body’s own cells), drugs, viruses or certain food components. Thus pancreas are not able to produce insulin which in turn increases the blood sugar. Type 1 is more commonly seen in children and young adults.
Type 2 diabetes mellitus is however, more of a lifestyle disease, or an added affect of pregnancy. Here the cells develop a property known as ‘insulin resistance’, which does not allow the insulin to control blood sugar levels. It is common in adults, a consequence of lack of exercise, obesity and some hereditary factors.
Diabetes presents with its famous ‘triad’ of symptoms which are :
è Polyuria – excessive urination
è Polyphagia – increased hunger
è Polydypsia – increased thirst
The buildup of blood sugar in the body over time has damaging effects on the body. Diabetes has the ability to affect various organ systems. Folowing are the complications which are a cause of worry :
· Urinary tract infections
· Cardiovascular disease, such as ischemic heart disease and stroke
· Acanthosis nigricans (brown-black velvety hyperpigmentation of skin)
· Kidney problems
· Sexual dysfunction (common in men)
· Frequent infections
· Delayed wound healing
· Diabetic retinopathy
Here we will discuss how diabetes affects the eyes. It has been stated that diabetes is the leading cause of blindness in the age group of 20-76 years. These effects can be grouped into ‘diabetic eye disorders,’ which include the following :
· Diabetic retinopathy
· Diabetic macular edema (DME)
Diabetic eye disorders are caused by the effects of high blood sugar on the blood vessels, nerves and proteins present in the eyes. The lens, retina, macula and optic nerve are chief targets.
Retinopathy is a disease of the eye which leads to an impairment or loss of vision. It affects about 80% of patients suffering from diabetes for 20 years or longer. The retina consists of many nerve endings which help in detection of light from the source object. This image is then interpreted by the brain.
Hyperglycemia (high blood sugar) causes damage to capillaries located in the retina by narrowing them down. There is decreased blood flow and degeneration of neurons of the reina. The damaged capillaries may give rise to small balloonings (anuerysms) and leakage of blood. Inflammation takes place and other nerve cells also get damaged.
Diabetic retinopathy undergoes four stages –
· Mild non proliferative retinopathy – Blood vessels balloon in this stage (microanuerysms) and may leak intto the retina.
· Moderate non proliferative retinopathy – Blood vesseld thicken and are unable to provide nutrition. Lays grounds for diabetic macular edema.
· Severe non proliferative retinopathy – Inflammatory response because of damage to blood vessels may trigger formation of more blood vessels.
· Proliferative diabetic retinopathy – The excessive formation of new blood vessels makes them very delicate and prone to more leakage. Scar formation may occur on the retina.
Diabetic retinopathy mostly goes undiagnosed in its early stages. But once it happens, it manifests as progressive loss of vision. ‘Floating spots’ are seen in the eyes.
Diabetic Macular Edema (DME):
The macula is that part of the retina which is responsible for the vision with clearest and finest details. Diabetic macular edema is a result of diabetic retinopathy gone bad. Here the fluid leaking from the retinal blood vessels accumulates inside the macula.
DME can be classified into –
· Focal DME
· Diffuse DME
The common symptoms of DME include blurry vision, double vision, floaters and if left untreated may lead to blindness.
Clouding of the lens of the eye is seen in cataract. It has multiple causes, diabetes being one of them. It is the leading cause of blindness in the elderly group of people.
The eye lens is nourished by a fluid called aqueous humor. When blood sugar (glucose) levels rise, it causes swelling of the aqueous humor, decreasing the clarity of vision. Excess of sorbitol, a product of glucose metabolism in the eyes can affect the eye proteins and make the lens more opaque.
Blurry vision, cloudy vision, distorted vision and sensitivity to light are the common signs and symptoms of cataract.
Technically, glaucoma is the loss of sight due to an increase of pressure in the eyeball. People with diabetes are twice as likely to suffer from glaucoma than those who don’t have diabetes. The fluid that drains the eyes is unable to escape into the bloodstream, it thus causes buildup of pressure inside which impinges on the surrounding nerves (especially optic nerve) and blood vessels. This leads to changes in vision.
Types of glaucoma –
· Open angle glaucoma
· Angle closure glaucoma
· Normal tension glaucoma
· Congenital glaucoma
· Variants of open angle and angle closure glaucoma
There has been a strong correlation between diabetes and open angle glaucoma. Neovascular glaucoma (new blood vessels form on the iris), a rare form of glaucoma is also seen in diabetes.
Glaucoma cannot be detected in its early stages.
One starts realising something is wrong when problems start arising in the peripheral vision. Tunnel vision is possible in severe stages along with headache, halos around lights, nausea, vomiting etc.
If untreated, this will lead to complete loss of vision. But to avoid any such risks, one should regularly get tested for glaucoma at least once a year after being diagnosed with diabetes.
Diagnostic tests for diabetic eye disorders:
· Visual acuity test
· Fluorescein angiography
· Dilation test
· Optical coherence tomography
· Non-contact tonometry test (glaucoma)
· Slit-lamp examination
· Retinal exam
· For DME –
Drugs that can slow down growth of new blood vessels and reduce leakage in eyes, such as avastin, eylea. Steroid injections or laser photocoagulation (laser is used to seal off leaking blood vessels) may be of help in later stages.
· For diabetic retinopathy –
Best treatment is to prevent it by controlling the blood sugar levels. Once started, retinopathy cannot be reversed but can only be limited to prevent further damage to the retina. Laser photocoagulation is of some help.
· For glaucoma –
The main aim is to lower the intra-ocular pressure. Thankfully, many options are available. Glaucoma eye drops are first line of treatment They are put directly in the eyes which then enter the blood circulation. Beta-blockers, prostaglandins and alpha-adrenergic agonists are used. In some cases, surgery may be considered. Laser trabeculoplasty, laser iridotomy iridectomies are commonly used methods to decrease the pressure build-up in eyes.
· For cataract –
Many people with cataract often do well with with the help of eyeglasses and other visual aids. Surgery may be required when there are significant changes in vision and the quality of life is affected. Often people are informed about the compulsive need for surgery, but in the end its the patient’s decision after considering all the factors. But cataract does worsen in diabetics.
Simply put, the clouded lens is removed and a new artificial lens is put in place. The region around the eye is numbed with an anesthetic agent and the surgery is performed. It is an outpatient procedure with a recovery time of 8 weeks.
Cataract surgeries with time have greatly advanced in India. Today there are different lenses available with varying techniques of surgery available at an affordable cost. Some techniques are as follows –
· Conventional surgery with stitches
· Keyhole surgery ( SICS – small incision cataract surgery)
· Micro-cataract surgery
· Micro-cataract surgery with PROPACK
· Laser cataract surgery
Diabetes by and large is a lifestyle disease. Efforts to keep the blood sugar in check, weight control and regular exercise can keep further complications at bay. Once diagnosed with diabetes, it is important that one should visit their eye specialist for regular eye check ups.