If it’s not the patient asking “What are those floaty things in my vision?”, it’s the optometrist asking “Do you see floating spots?”. What are those strange things in my vision that look like fish eggs, hairs, dust, segmented worms or spider webs and which many of us will see if we look carefully enough? Should I be concerned? Am I crazy to mention it to the optometrist? Maybe it will go away if I ignore it.
Let’s first start with some basic anatomy, followed by some of the common causes. Then we’ll discuss the kind of spots that might represent a “red flag” that should be investigated right away.
The retina is the “image sensor” of our eye. It begins the visual process of seeing the images of our “outside” world, but is also a source of images which are not part of our “outside” world. Coloured lights, a grainy pattern of lights, or dancing lights can be noticed, particularly by children, especially in dark rooms or with eyes closed. We tend to ignore this as we get older. These “inner world” images are the result of normal random firing of the neural retina causing an appearance like a dark grainy digital photo. This background visual “noise” is one of the entopic phenomena. Other entopic phenomena include lights from mechanical pressure to the eye such as with eye rubbing, “after images” after looking away from a bright object, arcing dots of light from stimulation by blood cells flowing in the retinal capillaries, “shooting stars” after coughing or bending over, and more. Light passing through closed or semi closed eyelids can produce some interesting light and colour patterns too.
The vitreous is a clear, gel-like substance which fills much of the inside of the eye. It is positioned immediately in front of the retina and light entering into the eye passes through the vitreous before it reaches the retina. Imagine a fly flying in front of a projection screen. It will cast a shadow on the screen. The closer the fly is to the screen, the clearer is the shadow. Any normal or abnormal irregularities in the vitreous structure can cast a shadow or “floater” onto the retina. It is difficult to look directly at the floater because as we move our eye the vitreous moves with it. Since the vitreous is a bit fluid like, the floater may appear to drift or “slosh” when we move our eyes. As we grow older our vitreous tends to become more liquid like and irregular. We may see more floaters which tend to move or drift more.
As we age into our 50s, 60s and 70s, many of us will develop a posterior vitreous detachment. Because the vitreous is liquefying and shrinking as it ages, it may gradually or suddenly pull away from the retina, where it is most loosely attached. This process frequently causes symptoms of flashes of light and/or new floaters and may include a new large floater, often web-like or “C” shaped. Often the vitreous detaches without causing any damage to the retina. However, sometimes the vitreous can cause a tear in the retina which may lead to a retinal detachment. This retinal damage is can threaten vision and needs to be treated promptly.
Some other abnormal causes of floaters include blood in the vitreous, inflammatory cells in the vitreous, and pigment cells released from a retinal detachment. Damage to the central part of the retina called the macula occasionally causes a more fixed spot to appear in the middle of the vision.
Most of us will see spots and unusual patterns in our vision if we look carefully enough. It is good to take an inventory of what you see. This is easier to do when you look at the sky, light colour wall or computer screen. The floaters, if large or numerous, can be annoying but they are not normally treated because of the risks associated with removal.
If at any time you notice many new spots in your vision that you have never seen before, it is important to call our office right away and have your eyes examined to determine the cause. Early detection of an abnormal cause and treatment can make a significant difference in your visual outcome.
… Oh yes, there is one more rare but documented cause of spots – Rabbititis!