Retina is the inner most layer of the eye. A healthy retina is necessary to transfer the image formed by the eye to the brain. It can be affected by various diseases. The most common of them are:
a) Diabetic Retinopathy
b) Age Related Macular Degeneration
c) Retinal Detachment
4.5% of India’s population is suffering from Diabetes Mellitus and by year 2025 around 57 million people will have this disease. At present diabetic retinopathy is the leading cause of blindness in United States and is becoming an important cause of blindness in the developing countries also. In India, it was the seventeenth cause of blindness twenty years ago. But today diabetes related blindness has rapidly ascended to the sixth position.
Early detection and timely treatment of diabetes can substantially reduce the risk of vision loss or blindness from diabetic eye disease. However most diabetic patients are not aware of the fact that their eyes will be affected due to diabetes and this is especially true for people who have had diabetes for five years or more.
Frequently asked questions :-
Are the eyes of all diabetics affected ?
Eyes of about 80% of the diabetic patients are affected over time. The longer the duration of diabetes greater are the chances of developing retinopathy.
What are all the ways in which diabetes can affect the eye?
Eye can be affected in many ways; important among these are:
b)Early Cataract formation (i.e. clouding of the lens)
c)Glaucoma (i.e. Increase pressure inside the eye)
What is diabetic retinopathy?
Diabetic retinopathy is a disorder of retinal blood vessels resulting from diabetes mellitus. In this condition, the retinal blood vessels are affected causing insufficient supply of oxygen and nutrients needed by the retina to remain healthy. There are bleeding spots and deposits of fatty material with swelling of the retina. Thus the retina is unable to transmit visual messages to the brain resulting in low vision or blindness.
How does it cause low vision or blindness ?
In moderate cases, the visual loss is due to swelling and bleeding within the retina. But in many cases vision is lost due to severe bleeding inside the eye from the abnormal blood vessels in the retina, leading to blindness. In advanced cases it may be because of tractional retinal detachment.
What are the symptoms by which diabetic retinopathy can be identified?
Usually diabetic retinopathy is symptomless . Some people have slight decrease of vision or foggy vision. Some may have normal vision till they develop sudden blindness due to bleeding. As there are no symptoms in early stages diabetic retinopathy. It is essential that diabetic patients undergo a routine checkup by an eye specialist every six months.
How is diabetic retinopathy diagnosed?
1. Retinal Examination: Under dilatation by an ophthalmologist will help to detect diabetic retinopathy in early stages.
2. Fundus Fluorescein Angiography: In FFA, we take photographs of the Retina after injecting a dye in the arm. It helps us to diagnose the stage of Diabetic Retinopathy in selected cases and localizing leaking new vessels which can be lasered later.
How is diabetic retinopathy treated?
1. Early diagnosis of Diabetes Mellitus and effective control of blood sugar through diet, exercise and medication can help reduce your risk of developing these eye problems associated with Diabetes Mellitus.
2. Laser photocoagulation is the main treatment of diabetic retinopathy.
Laser (Light Amplification by Simulated Emission of Radiation) is low energy and highly concentrated light. Each Laser has a specific wavelength. Wavelength generally used for retinopathy is 532 nm.
Laser treatment is an OPD procedure. After putting anesthetic/numbing drops in the affected eye, the patient is comfortably seated on a stool/chair with chin and forehead stabilized. A contact lens is then inserted in the eye and laser beam is focused onto the retina.
The light is absorbed by pigment layer of the retina, where it is converted into heat.
Laser photocoagulation helps to preserve vision by preventing new blood vessel formation. It may also help in reducing the swelling of thickened retina in some cases and prevent further deterioration of vision.
Photocoagulation may not be appropriate for every body. If the condition is too advanced laser treatment is not possible. In such cases, vitrectomy may be required.
Laser is not a one time treatment. Doing laser once will take care of present retinal leakages. Diabetes is an ongoing disease and it may affect retina again and so regular follow-ups are mandatory. Multiple laser treatments over time are sometimes necessary.
3. Vitrectomy: Vitreous surgery is a time consuming (generally takes 2-3 hrs) surgical procedure in which the blood and scar tissue is removed from the vitreous cavity and from the surface of retina. Sometimes silicone oil or gas is required to stabilize the retina. Following vitrectomy, vision improves to a variable level in most patients.
Age Related Macular Degeneration
Age Related Macular degeneration (ARMD) is a disease that causes progressive damage to the macula. Macula is the central part of the retina that allows us to see fine details. When the macula degenerates, people experience blurring or darkness in the center of their vision and tasks such as reading and driving are affected. The words on a page may look blurred, a dark or empty area may appear in the center of vision, or straight lines may look distorted.
Forms Of Macular Degeneration:
Dry macular degeneration is the more common form of the disease and accounts for 90% of all cases of AMD. Most patients of Dry AMD do not suffer from severe vision loss.
Wet macular degeneration form is less common but more severe than the dry form. It accounts for approximately 10% of all AMD but 90% of all blindness from the disease. This form is characterized by choroidal neovascularization (CNV), the development of abnormal blood vessels beneath the retinal pigment epithelium (RPE) layer of the retina. These vessels can bleed and eventually cause macular scarring which can result in profound loss of central vision (disciform scar).
Risk Factors for Macular Degeneration
Aging: Approximately 10% of patients 66 to 74 years of age will have findings of macular degeneration. The prevalence increases to 30% in patients 75 to 85 years of age.
Smoking: The only environmental exposure clearly associated with macular degeneration is tobacco smoking. Not only does smoking increase the risk of macular degeneration development, current or ex-smokers cannot take the vitamin supplements that have beta carotene because the risk of lung cancer increases if they do so. Beta carotene vitamin supplements were recently shown to help in slowing macular degeneration in a NIH supported study (AREDS).
Family history of macular degeneration:Macular degeneration appears to be hereditary in some families but not in others. Since macular degeneration affects most patients later in life, it is difficult to study successive generations in a family. Approximately one fourth of all late-stage macular degeneration appears to have a genetic basis. The lifetime risk of developing late-stage macular degeneration is 50% for people who have a relative with macular degeneration vs 12% for people who's relatives do not have macular degeneration, i.e a four fold higher risk. People who have first-degree relatives with late-stage macular degeneration develop macular degeneration at an increased rate at a relatively young age. Such patients must undergo regular screening for early detection of the disease by a Retina specialist.
Possible Risk Factors
Cardiovascular Risk Factors - high cholesterol, obesity
Progression of Macular Degeneration
If there is macular degeneration in one eye, then the fellow eye is at a high risk of developing macular degeneration as well. The risk of the fellow eye developing macular degeneration was reported to be 55% in the AREDS and 38.7% in the Rotterdam Study.
Dietary Fat & Macular Degeneration Risk
High fat intake is associated with an increased risk of macular degeneration in both women and men.
When a retinal detachment develops a separation occurs between the neurosensory retina and the pigment epithelium.
What are the symptoms of a retinal detachment?
Retinal detachment is generally preceded by the formation of holes(s) or tears in the retina; symptoms of which may include sudden onset of flashes and floaters-multiple black spots or cobweb like floating objects in front of the affected eye.
When detachment occurs, further symptoms may include-shadow in front of eye, curtain like thing in front of eye, decreased vision or total obscuration of vision.
What causes a retinal detachment?
Nearly all retinal detachments develop because of a hole or tear in the retina. This usually occurs when the retina becomes 'thin', which can occur in short sighted people (Myopia) or if the vitreous (the jelly-like substance that fills the eye) separates from the retina. Previous eye surgery and any ocular trauma can occasionally be the cause of a retinal detachment.
The other causes for detachment include:
1. Exudative detachment- in choroiditis/tumors/inflammation of eye
2. Tractional detachment-in diabetic patients.
Examination & Diagnosis
You will have a sight test and a full eye examination. Eye drops are put into both your eyes to make the pupils bigger, which helps the ophthalmologist to examine the back of the eye fully. The effect of these drops will wear off after a few hours, but your vision will be blurred temporarily preventing you from reading and driving.
Avoid driving yourself to hospital or to the local railway station whenever you come to have your retinas examined because your pupils will always need to be dilated.
If you are diagnosed with a retinal detachment, you will be advised to have surgery as soon as possible to reattach the retina.
Depending on the causes and condition of your retinal detachment, there are a number of different treatment options:
A retinal hole or tear
To seal the retina around the tear and prevent the retina peeling off you may be asked to have:
Laser - the retinal hole can be heat sealed (like spot welding) by directing a laser beam of light through the pupil of the eye. The scar produced seals the hole
Cryotherapy - a freezing treatment applied by a pen shaped probe to the outside of the eye. This freezes through to the retinal hole and promotes scar tissues as a seal.
These procedures may be a little uncomfortable but not painful, and are usually performed under a local anaesthetic as an outpatient procedure. However, they are only effective for retinal holes or tears, without any detachment.
A detached retina
In addition to the above treatment a detached retina will need a surgical procedure such as application of an encircling band or sponge to support the detached retina with or without drainage of sub-retinal fluid.
In patients with old detachment where retina is fixed and immobile, complicated vitreous surgery is generally required to put the retina back to its normal position. This is a time consuming surgery and takes 2-3 hrs. Usually silicone oil or gas is injected inside the eye to stabilize the retina.