What causes flashes in the eyes?

Q: When I take a deep breath, I see some flashes in my vision and also when I read. Why does this happen?

A:Seeing flashes of light indicates a retinal involvement. The most common reason for flashes is that the vitreous (transparent gel that fills the space between the retina and the lens) is undergoing separation from its retinal attachments. During this process (called posterior vitreous detachment), the vitreous gel exerts a traction or pull on the retina causing the sensation of flashes of light. You may also have an increase in the number of floaters or a subjective reduction in vision in the eye. It is very important that you get a dilated fundus examination from an ophthalmologist immediately. The reason is that you could develop a retinal hole (leading to retinal detachment and vision loss) if indeed you have vitreous detachment. In any case, a dilated fundus examination will also rule out any other retinal problems that could be causing flashes of light. A non-retinal cause of seeing flashes or lights is migraine headache.