Retina is a fine layer of nerve tissue. Retina is part of the central nervous system (CNS), and is the only portion of it that is visible from the outside. There are two types of photosensitive cells called Cones and Rods, which are about a 125 million in number, and are distributed all over retina non-uniformly. Cones are color sensitive, are well defined, and less sensitive to light. Rods are very responsive to light, incapable of discerning color, or producing well-defined images.The light is processed by a cascade of chemical and electrical reactions, which gets converted into electrical impulses and carried by the optic nerve to be processed into the image in the brain.

The retina is affected by the other disease conditions of the body as well as its own disorders. Many retinal disorders have very common symptoms like
– Seeing floaters: floating specks, sparks, cobwebs, etc.
– Defects in side vision
– Blurred or distorted vision; straight lines look wavy
– Lost vision
Often, it is necessary to look through individual eyes to notice these abnormalities. It is very important to see an ophthalmologist immediately as these may indicate serious maladies which can deteriorate quickly to total loss of vision.

Retinal disorders
Some of the most common retinal disorders are diabetic retinopathy, retinal tear, retinal detachment, epiretinal membrane, macular hole, macular degeneration, and retinitis pigmentosa, the latter two being degenerative disorders. All of these can lead to blindness.

Retinal tear and detachment: When the gel-like vitreous that fills the eye between the lens and retina contracts and pulls with enough force, the retina develops a tear. When fluid enters through tear and accumulates behind the retina it gets lifted away from the substratum.
Diabetic retinopathy: In diabetic retinopathy, the capillary blood vessels deteriorate and leak fluids into and under the retina causing its swelling or abnormal new vessels to bleed.
Epiretinal membrane: In epiretinal membrane, a new membrane or scar-like tissue that grows over the retina blurring vision.
Macular hole: Macular hole happens when the region is pulled by contraction of vitreous or injury.
Macular degeneration: In Macular degeneration, themacular tissue degenerates.
Retinitis pigmentosa: Retinitis pigmentosa is a group of genetic degenerative diseases destroying retinal tissue.