The eyeball has a cavity in the center called the Vitreous Cavity. It is filled with an egg-white type substance called the Vitreous, or Vitreous Humor (sort of means a gas, but not used much anymore). This gel degenerates in time and as we get older there are pockets of fluid or water, and the gel substance. This substances sloshes around in the eye as it moves back and forth and it can, and usually eventually does, detach from the posterior part near the nerve
and over the vessels of the retina. It can, in doing so, cause a tear of a surface vessel which will cause a bleed into the vitreous. Most get Posterior Vitresous Detachments and just have floaters
. But some bleed. Others though, may tear the retina itself. These tears are usually out at the side or front of the retina where the vitreous gel is attached tightly, the vitreous base. These tears can be dangerous as if the liquified gel gets under the retina through the tear, the retina will float into the vitreous cavity. This is called a Retinal Detachment
and can lead to loss of sight. I'd suggest you find a Retina Specialist in your area, not a general ophthalmologist or optometrist and have him take a look at your eye(s). If there are no retina specialists, see a general ophthalmologist but explain your symptoms prior to going there. They may decide to refer you right away to a retina specialist.