As you are lying down for bed at night, you suddenly see a bright flash of light off to one side. You wonder if you imagined it, but you sit up and it happens again.

You wake up the next morning and notice a dark circle or cobweb floating around in your vision.

What is going on and is it dangerous?

The eye can be thought of as a hollow sphere. The inside of the sphere is filled with a clear gel-like substance called the vitreous. The retina is another part of the eye where photoreceptors are located.

These photoreceptors are responsible for your vision, which is then transferred, via your optic nerve, to your brain to be processed. The retina lines the inside of the hollow sphere along the back wall of the eye.

The vitreous gel is connected to the retina at multiple locations including the optic nerve, macula, retinal blood vessels, and peripheral retina.

As we age, this vitreous gel liquefies and shrinks in size. If the vitreous pulls away from the retina, it is called a Posterior Vitreous Detachment, or PVD.

This is actually a rather common occurrence with age, and many people have a PVD without ever realizing it.

However, symptoms of new floaters and-or flashes of light in your vision may be indicative of a PVD with more serious consequences. As the vitreous pulls away from the retina, it can pull a hole or tear in the retina.

A PVD in itself is not harmful or dangerous to the eye, but a hole or tear in the retina is. If fluid gets underneath a retinal hole or tear, a potentially blinding condition called a retinal detachment can ensue.

The retina consists of photoreceptors and other cells which assist in maintaining the integrity of the visual information and transmitting this information.

There are no pain receptors in the retina. The only way the retina is able to respond to any stimulus is by producing a visual signal to the brain.

This is why you see a flash of light in your vision when something pulls on your retina, rather than having a shooting pain in your eye.

A symptomatic PVD, one in which you notice flashes or new floaters in your vision, has up to a 15 percent chance of being associated with a retinal tear.

Any time you have these symptoms, you should call your eye care provider for a dilated retinal examination to rule out the more serious complications of a PVD.

Caroline Bundrick, O.D. is an optometrist practicing at Darling Eye Center, with offices in Bluffton and on Hilton Head Island.