Retinal detachment is a serious condition that can lead to severe visual impairment for even total blindness in the affected eye.  It can occur at any age, but it is more common in midlife and later.  It is more likely to occur in people who are extremely nearsighted and diabetes.  Heredity may also play a part since it tends to run in families.

The retina normally lies smoothly and firmly against the inside back wall of the eyeball and functions much like the film in the back of a camera.  Most of the eye's interior is filled with vitreous, a gel-like substance that helps maintain its round shape.  The vitreous contains millions of fine fibers that are normally attached to the retinal surface.  As we age, the vitreous slowly shrinks away from the retina and may at some point be pulled free (this is called a vitreous detachment).  Once in a while, this pulling results in one or more tears or tiny holes in the retina. Any tiny tears or holes in the retina can allow fluid to seep under the retina, separating it from the back wall of the eye. If any part of the retina is lifted or pulled from its normal position, it is called retinal detachment and will cause some vision loss. 

Because retina is such a sensitive part of the visual system, anything that disturbs it will cause visual symptoms.  When it tears, you are likely to have a sudden appearance of floaters-a shower of "cobwebs" in your field of vision-which may be accompanied by "flashes", a sensation of seeing a flashing bright light. Though it is normal to have a few floaters, a sudden increase in their number and size is a warning that small amounts of blood and debris have suddenly appeared in the vitreous.  The flashes are sensations from the retina as it is pulled or torn, or is rubbed by the loosened vitreous. If a tear breaks a larger retinal blood vessel, the blood spilling into the vitreous can cause a massive increase in floaters or even total loss of vision in that eye.  The floaters will usually decrease in a few weeks or months and vision will improve, as long as the retina does not detach.

When the process of retinal detachment begins, you may not notice any change in vision at first if rhe detachment is off to the side.  Later, a "curtain" of darkness will start moving in and block out vision from one direction to the other. When the detachment reaches the central zone of the retina, vision will suddenly and dramatically blur.  As time goes on, the curtain will continue to darken more and more of your vision until you are left only able to see bright light.  The detachment will almost always progress unless it is treated surgically. Therefore, any retinal detachment is always considered an emergency and need prompt management by a qualified ophthalmologist.