What's in Your Blind Spot?

Did you know that the human eye contains a “blind spot?”  This occurs because there is a portion of the retina (the light sensing area of your eye that processes the images we see) that contains no light sensitive cells.  This spot is located where the optic nerve attaches to the retina. 

So why should we care about this trivia question?  Well, this physiological limitation can be a serious hazard, especially when driving a vehicle.  We normally do not notice the blind spot because we are using both eyes.  What lies in the blind spot of one eye is visible by the other eye, so we are not aware of its presence. 

However, when driving it is important to see all the traffic around us, right?  If we simply glance around using eye movement instead of moving our head carefully to scan around, we may fall prey to the blind spot.  Often we see objects with only one eye at a time because vision is blocked to the other eye.  The bridge of our nose, windshield posts, and other obstructions could block the vision of one eye, but not the other.  If an important object, say the car on the left in the photo below, is seen with only one eye due to a glance, it may enter the blind spot of the eye and totally disappear from sight. 

As the weather warms up and bicyclists, motorcycles, walkers and runners emerge from their hibernation, we need to be very aware of our blind spot. Take the “blind spot test” below to see for yourself (this can be done easier if you print the photo, but it can be done using your computer monitor).  Then remember to scan completely when driving… driving blind is not the way to go!

1. Close your left eye while holding this photo about a foot away from your face.
2. Focus your right eye on the car on the left.
3. Slowly move the paper towards your face; the car on the right will disappear as it enters the blind spot of the right eye.  Move it closer and it will reappear!

 A busy intersection.