RETINA

The retina is a light-sensitive layer at the back of the eye that covers about 65 percent of its interior surface. Photosensitive cells called rods and cones in the retina convert incident light energy into signals that are carried to the brain by the optic nerve. In the middle of the retina is a small dimple called the fovea or fovea centralis. It is the center of the eye's sharpest vision and the location of most color perception.

Floaters and flashes

As the eye ages, the vitreous gel becomes less solid. As the vitreous gel undergoes this degeneration, parts of the vitreous cast shadows on the retina and are seen as floaters. Floaters appear as gray or black specks, lines, cobwebs or dots in front of the eyes. As the eyes move, the floaters move too.

Flashes occur when the degenerating vitreous gel pulls on the retina. These flashes usually last for only a second or so, but typically occur repeatedly. They may be more obvious with eye movement or in a dark room.

Causes

  • As part of the normal aging process
  • Presence of retinal tears / Retinal detachment

Any new onset or sudden increase in the number of floaters with or without flashing lights should prompt a consultation with an eye specialist.

Retinal Detachment

Pulling away of the retina from the normal position.

Types

  • Rhegmatogenous: The most common. A tear or break in the retina allows fluid to get under the retina and separate it from the retinal pigment epithelium (RPE), the pigmented cell layer that nourishes the retina.
  • Tractional: Scar tissue on the retina’s surface contracts and causes the retina to separate from the RPE.
  • Exudative: Frequently caused by inflammatory disorders and injury/trauma to the eye. In this type, fluid leaks into the area underneath the retina, but there are no tears or breaks in the retina.

Risk factors: (Needs regular consultation with an eye specialist)

  • Myopia or near-sightedness
  • Injury to the eye
  • Previous retinal detachment in the other eye
  • Family history of retinal detachment
  • Complicated cataract surgery

Symptoms

  • Flashes of light
  • New, or increase in, floaters
  • Appearance of a curtain over the field of vision

Treatment

  • Retinal tears without detachment – Laser photocoagulation or cryotherapy is around the tear
  • Retinal tears with retinal detachment:
  • Scleral buckle surgery – a tiny synthetic band, is attached to the outside of the eyeball to gently push the wall of the eye against the detached retina.
  • Vitrectomy – The vitreous gel pulling the retina is removed from the eye and replaced with a special gas or silicone oil.

Age related Macular Degeneration

It is a disease associated with aging that gradually destroys sharp, central vision. AMD affects the macula, the part of the eye that allows you to see fine detail.

Risk factors

  • Age more than 60years
  • Smoking
  • Obesity
  • Hypertension
  • Race: Whites are at higher risk
  • Family history of AMD
  • Gender: Females are at higher risk

Symptoms

  • Blurred vision which go away in brighter light
  • Small but growing blind spot in the middle of field of vision
  • Distortion of images
  • Small/large images

Treatment options available

  • 1. Observation with regular checkups for mild and non progressive forms.
  • 2. Nutritional suppliments containing Selenium,Zinc and Vitamines A,D&E
  • 3. Destruction of abnormal new vessels using Photodynamic therapy(PDT) or direct laser ablation
  • 4. Injections(AntiVEGF agents like Macugen,Lucentis,Avastin or Steroids like Triamcinolone Acetonide) inside the eye to reverse the development of abnormal vessels and control inflammation. You will need multiple injections.
  • 5. Surgery to clear the blood from under the macula

Diabetic Retinopathy

Diabetic retinopathy is the most common diabetic eye disease in India and is caused by changes in the blood vessels of the retina. If you have diabetic retinopathy, at first you may not notice changes to your vision. But over time, diabetic retinopathy can get worse and cause vision loss.

  • Fifty percent of diabetics develop some degree of diabetic eye disease.
  • The risk of blindness is 25 times higher in diabetics than in non-diabetics.
  • Early detection and timely treatment of diabetic eye disease significantly reduces the risk of vision loss.
  • Diabetic retinopathy is often symptomless in the early stages. Since only an ophthalmologist can detect early signs of diabetic retinopathy, all diabetics should have their eyes examined at least once every year.
  • Symptoms include decreased vision and floaters.

Stages

Non-proliferative Proliferative

Non-proliferative: When the blood vessels leak, macular edema may occur, thereby reducing vision.

Proliferative: When new blood vessels grow or proliferate, bleeding into the vitreous may occur and cause severe visual loss.

Risk factors: (Needs periodic review with an eye specialist)

  • Duration of Diabetic
  • Severity of Diabetic
  • Renal function
  • Hypertension
  • Anemia
  • Pregnancy

Treatment

Retina-treatment
  • No treatment is needed for Non proliferative diabetic retinopathy unless you have macular edema. Macular edema is treated with focal laser treatment. To prevent progression of diabetic retinopathy, people with diabetes should control their levels of blood sugar, blood pressure, and blood cholesterol.
  • Proliferative retinopathy is treated with scatter laser treatment Scatter laser treatment helps to shrink the abnormal blood vessels.

How can diabetes affect the eye?


Temporary Blurring - Your vision can become blurred whilst your diabetes is being controlled. Once your diabetes is stabilised it will clear.

Cataract - This can occur in two forms. Young people with diabetes very occasionally develop a special type of cataract. Although their vision gets worse, it can be restored by surgery. Older people with diabetes can be especially prone to developing cataracts. Cataracts can be successfully removed by surgery and usually it is possible to insert a lens implant. However this is unsuitable for some people and you would be told if this is the case.

Diabetic Retinopathy - The most serious diabetic eye condition involves the retina and is called diabetic retinopathy.

Background Diabetic Retinopathy - This condition is very common in people who have had diabetes for a long time. Your doctor may be able to see abnormalities in your eyes, but there is no threat to your sight. There are two types of diabetic retinopathy, which can damage your sight. Both involve the fine network of blood vessels in the retina. They are described below.

Maculopathy - This happens when the blood vessels in the retina start to leak. If the macula is affected, you will find that your central vision gradually gets worse. You may find it difficult to recognise people's faces in the distance or to see detail such as small print. The amount of central vision that is lost varies from person to person. However the vision which allows you to get around at home and outside (navigation vision) will be preserved. It is very rare for someone with maculopathy to lose all their sight.

Proliferative Diabetic Retinopathy - Sometimes diabetes can cause the blood vessels in the retina to become blocked. If this happens then new blood vessels form in the eye. This is nature's way of trying to repair the damage so that the retina has a new blood supply. Unfortunately these new blood vessels are weak. They are also in the wrong place growing on the surface of the retina and into the vitreous jelly. As a result these blood vessels can bleed very easily and cause scar tissue to form in the eye. The scarring pulls and distorts the retina. When the retina is pulled out of position this is called retinal detachment.

• This condition is rarer than background retinopathy and is more often found in people who have been insulin dependent for many years
• The new blood vessels will rarely affect your vision, but their consequences, such as bleeding or retinal detachment can cause your vision to get worse suddenly
• Your eyesight may become blurred and patchy as the bleeding obscures part of your vision
• Without treatment, total loss of vision can happen in proliferative retinopathy
• With treatment most sight-threatening diabetic problems can be prevented if caught early enough

The Importance of Early Treatment
Your vision may be good and you may not be aware of any changes taking place. Most sight loss in diabetes is preventable.
• Early diagnosis is vital
• Have an eye examination every year
• Do not wait until your vision has deteriorated to have an eye test