Normal Vision:
The Retina is the nerve cell layer of the eye and acts much like film in a Camera. When light enters the eye it passes through the Cornea and Lens and is focused onto the Retina. The Retina transforms the light energy into vision and sends the information back to the brain through the optic nerve. The macula is the sensitive, central part of the retina and is responsible for sharp, detailed vision.
Diabetic Retinopathy
Diabetic Retinopathy results from the effects of the diabetes on blood vessels that nourish the Retina tissue,which is the innermost layer of the eye wall. It is mainly associated with diabetes and is caused by the blockage of tiny blood vessels in the retina,causing hemorrhages on or in the retina. Diabetes causes retinal blood vessels to leak and grow abnormally.Untreated diabetes or poor disease maintenance greatly increases the risk of diabetic retinopathy. Depending on the severity of the disease, sight can remain near normal or may be lost entirely. Remaining vision may be blurred or distorted or the hemorrhage may cause a deep reddish veil over the field of vision.
Types of Diabetic Retinopathy:
There are two main types of Diabetic Retinopathy:
Non-Proliferative
Proliferative
In Non-Proliferative or Background Diabetic Retinopathy, patients may have normal vision. The damaged retinal vessels leak fluid. Fat and protein particles may leak from these vessels and become deposited in the retina in patches known as Retinal Exudates. The retinal blood vessels may bleed into the retina and result in tiny hemorrhages. If any of the leaking fluid accumulates in the central part of the retina (called the macula), the vision is affected. This condition is called Macular Edema.
In Proliferative Diabetic Retinopathy, new abnormal blood vessels grow, which extend over the surface of the retina. These vessels occasionally invade the gelatinous contents of the eye, the vitreous. The proliferating blood vessels frequently break, causing vitreous bleeding that may significantly decrease vision. Fibrous tissue may grow over the new blood vessels and distort vision.Occasionally, the tissue may contract and pull the retina off the inner surface of the eye, causing a tractional retinal detachment.
Symptoms:
There are no symptoms in the early stages of diabetic retinopathy. Vision may not change until the disease is advanced or the Macula is affected. The earliest sign may be an abrupt change in eyeglass prescription. The blood sugar affects the water content of the lens of the eye and, therefore, spectacle prescription changes. Sudden increase in blood sugar will cause an increase in myopia. This often occurs before the detection of the disease. Diabetic Retinopathy may begin in eyes without one noticing any change in vision. Unfortunately, there may be extensive and severe changes before vision is affected. Thus, it is very important to have the eyes examined regularly at six-month or yearly intervals depending on duration and/or severity of the diabetes.
Detection of Diabetic Retinopathy:
Diabetic retinopathy is detected during an examination of the back of the eye Fundoscopy through dilated (enlarged) pupils and by testing your vision. Dilatation is the method through which, after putting some eye drops, we can see what is inside, to properly evaluate the Retina. We look for evidence of Diabetic Retinopathy. Based on the findings a Fluorescein Angiography may be advised.
Fundus Fluorescein angiography (FFA) :
Fluorescein Angiography is a dye test often used to assess the damage to the retina and its blood vessels. A dye is injected into a vein of one arm. Photographs are taken of the retina as the dye passes through the blood vessels. Since there is a risk of allergic reaction, a history of allergy is important. There may be mild nausea during the procedure.The skin and urine may turn yellow for 24 to 48 hours. These Angiograms show areas of leakage, areas of oxygen-starved retinas, and weak, fragile new vessels. Based on the results a LASER may be advised.
Treatment:
Laser:
The most important treatment for diabetes and its complications including diabetic retinopathy is control of the diabetes. Tight control of blood sugar, weight and blood pressure are important in preventing the ocular complications of diabetes and thus slowing the progression of the disease.
Once retinopathy is diagnosed, Laser therapy is the current modality of treatment. Most patients tolerate the procedure extremely well with little discomfort. Laser surgery is used to treat both diabetic macular edema and proliferative diabetic retinopathy. Laser treatment for diabetic macular edema stabilizes vision by stopping blood vessels from leaking fluid into the retina. Either focal treatment for small discrete areas of leakage is there or a grid pattern is used when the leakage is diffuse in nature. After treatment, the patient may notice small spots of decreased visual sensitivity in the field of vision. Usually these spots become less noticeable with time. It is possible that the vision may get a little worse after laser. However, the laser helps prevent further reduction in vision. Studies have shown that most patients who receive laser for macular edema will have better vision in the future than if they hadn't received the treatment. After instilling an anaesthetic drop in the eye, the retina is treated with LASER using suitable Laser delivery system.
Frequently Asked Question:
Who is at risk of developing Diabetic Retinopathy?
Every person with diabetes is at risk of developing diabetic retinopathy. The longer a person has diabetes the more likely he is to develop diabetic retinopathy. Eye examination at the time of diagnosis of Diabetes and then as advised by the Doctor would reduce the risk of vision loss and blindness. Strict control of Diabetes can delay the development of Retinopathy.
Once diagnosed what is to be done?
After the diagnosis of Retinopathy is done,it is Categorized according to its severity. Fundus Fluorescein Angiography is performed to exactly know the site of blockage and amount of leakage. And accordingly the laser treatment is advised. But sometimes if Retinopathy is with vitreous hemorrhage or Tractional Retinal detachment surgery may be required.
Will My Vision Improve After Laser Treatment?
Laser therapy can only stop the progression of the retinopathy. It cannot reverse the damage already done.
What Happens if the LASER Doesn't Work?
While panretinal photocoagulation is usually successful in halting the proliferative process, some patients progress despite laser treatment. Other patients may have bleeding into the vitreous of the eye. These eyes may require vitreous surgery (vitrectomy). The main indications for vitrectomy are persistent vitreous hemorrhage and tractional retinal detachment. Vitrectomy surgery is a major eye operation. It involves removal of the vitreous from the eye. Frequently, the retina has to be reattached by surgically separating the scar tissue from the surface of the retina. Laser treatment is often applied at the time of vitrectomy. In some cases, a gas bubble is left in the eye following surgery to keep the retina flat against the back of the eye.
Will Glasses Help ?
The glasses that the patient was using earlier can be continued. Many times special vision aids need to be prescribed.Magnifiers and other devices can help.
Can vision loss from diabetic retinopathy be prevented ?
Yes, Severe visual loss can be prevented if diabetic retinopathy is detected early and treated properly. By keeping blood glucose levels within the normal range, one can minimize the risk of visual loss. Take action before you notice any eye-problems.
Retinal Detachment
In Retinal detachment, the retina separates from the outer layers of the eye thus losing its function. If not treated early, retinal detachment may lead to impairment or complete loss of vision.
Cause:
Most retinal detachments are preceded by one of more tears or holes in the retina. Fluid passes through these openings and separates the retina from the adjacent layers of the eye. Near-sighted individuals are more commonly affected due to thinning of the retina. Holes or tears can then develop in the thinned retina. The vitreous (gel fluid in the eye) also plays a significant role by causing tugging on the retina especially when shrinkage occurs. Cataract surgery can also be a precipitating cause. A positive family history of retinal detachment is another risk factor. A combination of factors is usually responsible for retinal detachment. Retinal detachment can also be caused by other diseases in the eye such as tumours, severe inflammations, or complications of diabetes.
Symptoms:
Middle-aged and older persons may see floating black spots called floaters and flashes of light. In most cases, these symptoms do not indicate serious problems.In some eye, the sudden appearance of spots or flashes of light may herald the onset of retinal detachment. A through examination of the retina by an ophthalmologist after dilatation of the pupil is necessary to determine the cause of the symptoms.Some retinal detachments can proceed unnoticed until a large section of the retina is detached. In these instances, patients may notice the appearance of a dark shadow in some parts of their vision. Further development of the retina detachment will blur central vision and create significant sight loss in the affected eye. A few detachments may occur suddenly and the patient will experience a total loss of vision in that eye. Similar rapid loss of vision may also be caused by bleeding into the vitreous which may happen when the retina is torn.
Treatment:
If the retina is torn but detachment has not yet occurred, prompt treatment may prevent the occurrence of a complete detachment. Once the retina becomes detached, it must be repaired surgically.
Laser Photocoagulation:
When new small retinal tears are found with little or no nearby retinal detachment, the tears are sometimes sealed with a laser light. The laser places small burns around the edge of the tear. These produce scars that seal the edges of the tear and prevent fluid from passing through and collecting under the retina.
Freezing Cryopexy :
Freezing through the sclera (white of the eye) behind a retinal tear will also stimulate scar formation and sealdown the edges.
Surgical Repairs:
Successful reattachment of the retina consists of sealing the retinal tear with a silicone material, which is sutured to the Sclera (white of the eye) to indent the eyeball inwards. Freezing applications are then used to bind the retina to the underlying layers.
Newer procedures have been developed to achieve the same result using the injection of a gas into the eye in suitable cases.The surgery may be performed under local or general anesthesia depending on the procedure, age and general health of the patient.In more complex retinal detachments, it may be necessary to use a technique called vitrectomy. This operation removes the vitreous body from the eye. In some cases, when the detached retina itself is severely shrunken or scarred, air of gas may have tobe used to fill the vitreous cavity temporarily.
Prognosis:
Over 90% of all retinal detachments can be reattached by modern surgical techniques. Occasionally, more than one operation may be required. The degree of vision, which finally returns about six months after successful surgery,depends upon a number of factors. In general,there is less visual return when the retina has been detached for a long time of it fibrous growth on the surface of the retina.
Approximately 40% of successfully treated retinal detachment achieve excellent vision. The remainder attains varying amounts of reading vision.
Due to continuous shrinkage of the vitreous and the development of fibrous growth on the retina. not all retinas can be attached. If the retina cannot be reattached, the eye will continue to lose sight and ultimately become blind.