Floaters

What are floaters?  And why do eye doctors always ask you if you've seen flashes or floaters recently?

Floaters in and of themselves are harmless, albeit annoying.  They are the result of the gradual breakdown of the vitreous (the gel-like substance that makes up most of the inner eye) and are essentially particles of collagen floating in your eye.  What you see as moving gray lines or dots are actually shadows cast on the retina (the light-sensitive tissue that lines the back of the eye) due to collagen's interference with light entering the pupil.  That is why floaters are more noticeable when looking at a bright sky, white wall, or computer screen: more light enters the eye, thus there is a greater potential for shadows to be cast on the retina by the floating collagen particles.

When are floaters more of a concern?

If you notice an increase in the number or frequency of floaters, flashes of light in your vision, or an apparent "curtain" coming down over your vision, this could be a sign of a serious problem with the retina and should be investigated immediately.  Increasing floaters, flashes of light, and a curtain over the vision are all signs of a retinal tear or detachment and could potentially lead to loss of vision.

As proof that you're not imagining your eye floaters, check out this video which shows what the eye doctor sees when he or she looks into the eye of a patient with significant floaters:

http://www.youtube.com/watch?v=sxroMCVgpPk

Find your blind spot!

Do you know that everybody has a natural blind spot in each eye; that is, a spot in one's peripheral vision where nothing can be seen?

Cover your left eye.  Find a spot directly in front of you (a thumbtack on a wall works well).  Extend your right arm straight in front of you, so your thumb covers the spot on the wall.  Slowly move your arm outward (away from your nose, to the right), but continue looking forward at your previously marked spot.  Pay attention to your moving thumb.  Notice that when your thumb reaches a certain point, it disappears! Try it using your left eye and left thumb.

This blind spot exists because your optic nerve (which transmits visual information from the eye to the brain), has no light detecting cells like the rest of the retina does.  You don't typically notice your blind spot because the visual fields of each eye overlaps and your brain is able to "fill in" the missing visual information.  When we test peripheral vision at TotalVision, we use this blind spot, called the "physiological blind spot," as one means of assessing the accuracy and reliability of our peripheral vision testing.