By Eyecare NGEye Conditions | Signs & Symptoms | Diagnosis | Management | Prevention
Diabetes is a group of diseases characterized by high level of sugar in the blood. It can affect the eye in several ways and cause various eye conditions which together are known as diabetic eye disease.
Diabetes affects different structures of the eye including the iris, lens, vitreous and the retina. For instance, when the blood sugar level is high, the lens can absorb more fluid and swell up resulting in blurry vision. Hence, fluctuation in one’s vision could signify that his/her blood sugar is not well controlled.
Diabetic Eye Conditions
Eye conditions that can be caused by diabetes include retinopathy (known as diabetic retinopathy), macula oedema, cataract and glaucoma.
Diabetic retinopathy is a condition in which the retinal blood vessels are damaged by diabetes. When the blood sugar remains high for a long time, it causes changes in the retinal blood vessels such that they begin to leak blood. The blood accumulates in the back of the eye and causes distortion in vision. In advanced cases, new blood vessels that bleed easily grow and proliferate on the surface of the retina and into the vitreous (the gel-like fluid in the eye). These new vessels cause retinal scarring. The scarred tissue can pull on the retina and peel it off (resulting in a condition known as retinal detachment).
There are four stages of diabetic retinopathy.
- Mild non-proliferative diabetic retinopathy or background diabetic retinopathy: This is the earliest stage of diabetic retinopathy. Small areas of balloon-like swelling in the retinal blood vessels called microaneurysms occur. The microaneurysms may leak fluid into the retina.
- Moderate non-proliferative diabetic retinopathy: There are distortions and swelling of the blood vessels.
- Severe non-proliferative diabetic retinopathy: The blood vessels of the retina get blocked, limiting the amount of oxygen that gets to the retinal cells. This causes the retina to start growing new vessels.
- Proliferative diabetic retinopathy: There is a proliferation of new blood vessels in the retina and vitreous. The blood vessels bleed on the retina and into the vitreous. The bleeding causes scarring in the vitreous and on the retina. The scarred tissue can contract and pull on the retina resulting in retinal detachment. Retinal detachment can lead to permanent loss of vision.
Diabetic retinopathy is the most common cause of vision loss among people with diabetes. All diabetics irrespective of the type of diabetes they have are at risk of diabetic retinopathy. The risk increases the longer a person has diabetes.
Diabetic macular oedema
This is a build-up of fluid that leaks from the retinal blood vessels in the part of the retina called the macula. The macula is the retina’s sharpest point of vision and is responsible for the central vision which we use for reading, writing and performing other activities. Diabetic macular oedema is a consequence of worsening diabetic retinopathy and is usually a common cause of vision loss among people with diabetic retinopathy.
Cataract is the clouding of the eye’s natural crystalline lens. When blood sugar level goes very high, the lens absorbs fluid and swells up resulting in changes in the refractive status of the eye (usually observed as blurry vision). This condition reverses when the blood sugar level is reduced or brought back to normal. The alternate swelling and reduction in the size of the lens due to fluctuations in the blood sugar levels cause permanent changes in the lens which over time leads to the development of cataract. Hence, people with diabetes are at higher risk of developing cataract earlier than people without diabetes.
Glaucoma is a group of eye diseases that progressively damage the optic nerve and can lead to permanent loss of vision if not detected and treated early. The blood vessels which develop in diabetic retinopathy can proliferate to the anterior chamber of the eye and clog the channel from which fluid (aqueous humour) drains from the eye. This results in the build-up of fluid in the eye leading to increased intraocular pressure which damages the optic nerve. Learn more about glaucoma.
Signs and symptoms
At the early stage, people who have diabetic eye disease may not observe any symptoms. As the condition progresses, symptoms observed include:
- Blurry vision: This is usually the first symptom observed. The person experiencing this symptom may not know he/she has diabetes and would usually associate the root cause of the blurry vision to an eye problem.
- Fluctuating vision: This is a situation in which vision alternates between blurry and normal as blood sugar level goes high and normalizes respectively. It usually signifies that diabetes is poorly controlled.
- Floating black spots in front of the eyes: This is caused by the leaking of blood from the retinal blood vessels. While the blood accumulates in the fluid in the back of the eye, the individual perceives them as spots in front of the eyes.
- Pain and redness: These may occur if there is an acute rise in eye pressure.
- Flashes of lights: The occurs if there is retinal detachment
- Loss of vision: If blood sugar level is not properly controlled and the resultant eye conditions not treated, vision loss is often inevitable.
The following eye tests are important for the diagnosis of diabetic eye disease:
Visual acuity: For the measurement of the central vision.
Tonometry: For the measurement of eye pressure.
Slit lamp examination: Slit lamp examination is done to obtain a detailed view of the structures of the eye. For a clearer and wider view, the eyes are usually dilated. During the examination, the doctor looks out for the following:
- Changes in the blood vessels of the retina and the retina including the macula.
- Leaking blood vessels and signs of leakages such as fatty deposits
- Changes in the lens
- Damage to the optic nerve tissues
Ocular coherence tomography (OCT): This is similar to ultrasound. It provides detailed images of the structures of retinal tissues that are not visible to the naked eye. It can reveal changes in the thickness of the macular and other parts of the retina among other things.
Fluorescein angiography: This may be done to look out for leaking blood vessels in the retina. A fluorescent dye is injected into the bloodstream and pictures of the retinal blood vessels are taken as the dye reaches the eye.
The management of diabetic eye disease is dependent on eye conditions that develop as a result of diabetes.
Medical control of blood sugar level is important for the prevention of vision loss. The following treatment options for diabetic retinopathy may be provided independently or combined:
- Laser surgery: This is done to shrink proliferating blood vessels, stop bleeding of blood vessels and destroy damaged tissues. This helps preserves central vision, though significant portions of peripheral (side) vision may be lost
- Vitrectomy: This is a surgical removal of vitreous gel in the centre of the eye. It is used to clear severe bleeding into the vitreous including scar tissues that may be pulling on the retina. The vitreous is replaced with a salt solution. If there is retinal detachment, the retina can be repaired at the same time.
Diabetic macular oedema
Treatment options for diabetic macular oedema include:
- Focal or grid macular laser surgery: A number of small laser burns are made to leaking blood vessels in the areas of oedema near the centre of the macula. This destroys the blood vessels slowing down or stopping fluid leakage and swelling of the macula.
- Injections of medications and implants: With this treatment option, some medications are injected into the vitreous gel to block proteins (vascular endothelial growth factor – VEGF) responsible for the growth and proliferation of new vessels in the retina. Anti-VEGF medications can reverse abnormal blood vessel growth and decrease fluid in the retina. Corticosteroids can also be used. They can either be injected directly into the vitreous or in the form of biodegradable implants that release sustained dose of steroids to suppress macular oedema.
At the early stages of cataract, prescription eyeglasses can be used to improve vision. As the cataract progresses and becomes dense such that glasses no longer improves vision, surgery is the only treatment option. Learn more about cataract treatment
There is no cure for glaucoma. The condition is managed to prevent further damage to the optic nerve and loss of vision. Medications (mainly eye drops) are prescribed to control high pressure. Surgery may be required if medications fail to control pressure. Low vision care and rehabilitation is provided for cases with significant vision loss (that does not improve with eyeglasses or other treatment options)
Diabetic eye disease can cause permanent loss of vision. Early detection and proper treatment significantly reduce the risk of vision loss and blindness. The following measures may help in the prevention or delay of vision loss as a result of diabetes:
- Strict control of diabetes by taking medications as prescribed and following up regularly with the physician. This ensures that blood sugar is under control most of the time. This is probably the best measure to reduce the risk of diabetic eye disease as the success of all treatment options depends on how well the blood sugar is controlled.
- Regular eye examination: It is necessary for people with diabetes to have dilated comprehensive eye examination at least once a year. Depending on the progression and severity of the disease, more frequent eye exams may be recommended by the eye doctor
- Exercise and physical activity is important for the control of diabetes and hence for the prevention/reduction in the progression of diabetic eye disease.
- Eat healthy and balanced meals, avoid smoking and drinking alcohol
- Ensure proper control of other chronic health conditions like hypertension.