Retina
About the Retina
The retina is a thin layer of light-sensitive tissue lining the posterior of our eye. The retina and cornea both coordinate to function like the film of a camera. With the retina functioning as a lens, it is important for it to remain clear. The retina converts the light rays coming through the eye into electrical impulses that travel through the optic nerve to our brain. The brain then interprets the impulses into images we see. If the normal connection between the retina and the brain is damaged, transmission problems will result and our vision will become disturbed.
Some common retinal conditions include:
- Diabetic Retinopathy
- Macular Degeneration
Diabetic Eye Care
It is important to have a comprehensive eye exam at least once a year if you have diabetes. Individuals with diabetes are at a higher risk of developing diabetic retinopathy, which is caused by damaged blood vessels to the retina. People with diabetes are 25 times more likely to lose vision over time than non-diabetic individuals. Changes in glucose levels and long-term diabetes increase your risk of diabetic retinopathy. Everyone who has diabetes is at risk for diabetic retinopathy; however, not all diabetics develop the condition.
Diabetic retinopathy, a common complication of diabetes, affects the blood vessels in the retina (the thin light-sensitive membrane that covers the back of the eye). This condition primarily occurs due to lack of oxygen flow to the retina. If untreated, it may lead to blindness. If diagnosed and treated promptly, blindness is usually preventable. There are two types: nonproliferative and proliferative retinopathy. Nonproliferative retinopathy is the less severe type in which there may be hemorrhages (bleeding) in the retina and leakage of blood or serum causing a "wet retina." As a consequence, vision may be diminished. Proliferative retinopathy is a more severe type of diabetic retinopathy. New abnormal fragile vessels develop on the surface of the retina and may grow toward the center of the eye. These vessels frequently bleed into the vitreous (the clear jelly in the center of the eye) and can cause severe visual problems. Treatment is by laser surgery or surgery on the vitreous. These techniques can slow the progression of diabetic retinopathy and sometimes will reverse visual loss. However, damage done may be permanent.
Flashes and Floaters
What are floaters?
You may sometimes see small specks or clouds moving in your field of vision. They are called floaters. You can often see them when looking at a plain background, like a blank wall or blue sky. Floaters are actually tiny clumps of gel or cells inside the vitreous, the clear jelly-like fluid that fills the inside of your eye.
While these objects look like they are in front of your eye, they are actually floating within the vitreous gel inside of the eye. What you see are the shadows they cast on the retina, the nerve layer at the back of the eye that senses light and allows you to see.
Floaters can have different shapes: little dots, circles, lines, clouds or cobwebs.
What causes floaters?
When people reach middle age, the vitreous gel may start to thicken or shrink, forming clumps or strands inside the eye. The vitreous gel pulls away from the back wall of the eye, causing posterior vitreous detachment.
Posterior vitreous detachment is more common for people who:
- are nearsighted
- have undergone cataract operation
- have had YAG laser surgery of the eye
- have had inflammation inside the eye
The appearance of floaters may be alarming, especially if they develop suddenly. You should see a specialist at Hawaii Eye Institute immediately if you suddenly develop new floaters, experience flashes of light, and/or a loss of peripheral vision.
What causes flashing lights?
When the vitreous gel rubs or pulls on the retina, you may see what looks like flashing lights or lightening streaks. You may have experienced this same sensation if you have ever been hit in the eye and seen “stars.”
The flashes of light can appear off and on for several weeks or months. As we grow older, it is more common to experience flashes. If you notice a sudden appearance of light flashes, you should visit your ophthalmologist immediately to see if the retina has been torn.
Some people experience flashes of light that appear as jagged lines or “heat waves” in both eyes, often lasting 10-20 minutes. These types of flashes are usually caused by a spasm of blood vessels in the brain, which is called a migraine.
If a headache follows the flashes, it is called a migraine headache. However, jagged lines or “heat waves” can occur without a headache. In this case, the light flashes are called ophthalmic migraines, or migraines without headache.