The retina is a thin layer containing photoreceptor nerve cells that line the back wall of our eyes. It senses light coming into the eyes and sends signals to the brain so that a visual image can be created. In short, the retina is what helps the eyes to see.
Floaters are particles suspended in the vitreous, appearing as lines, dots, or cobwebs that move with the eye. They may be more noticeable when looking at a bright plain background, such as a computer screen or the blue sky. Floaters often develop as part of normal ageing and are very common. The vitreous lies between the lens and the retina – which is the light-sensitive tissue at the back of the eye.
When we are young, the vitreous gel that fills the eye is in contact with the retina. As we grow older, the vitreous also shrinks in volume, separating from the retina. This is a process called posterior vitreous detachment, a normal and common ageing change in the eye. In most eyes that undergo posterior vitreous detachment, the vitreous cleanly separates from the retina. Occasionally, the retina may tear as the vitreous pulls away from it. This can be associated with a sudden increase in floaters. Severe trauma may also cause retinal tears.
If a retinal tear is left untreated, fluid can enter through the tear and lift the retina off, causing a retinal detachment. A person with a retinal detachment may see a shadow in the vision where the detachment is.
If a retinal tear is detected early, a laser can be applied around the tear. This creates scars which seal the retina to the wall of the eye, preventing fluid from entering through the tear and lifting the retina off.
If a retinal detachment has already occurred, you would almost always require surgery to address this. Without appropriate treatment and surgery, a retinal detachment can lead to blindness.
While long-standing stable floaters are usually harmless, you would require a dilated eye examination if you have a recent increase in floaters or flashes, or if you see a shadow in your vision. For the best outcomes, it is important to detect a retinal tear or detachment early, before it affects the central vision. Besides these ageing changes, floaters can occasionally be due to bleeding, inflammation or infection in the eye.