What Your Blind Spot Really Is

A blind spot is a very small gap in the visual field of each eye—an area of your relatively nearby surroundings that you can't see. It may sound like a physical defect, but everyone has a small natural blind spot (physiological blind spot), and it's not usually noticeable.

You have a blind spot because there's a tiny portion of your retina (that area of your eye that normally detects light) without light receptors. This area is located where your optic nerve enters the back of your eye.

How to Find Your Blind Spot

Every human eye has a blind spot. Your blind spot is roughly 7.5° high and 5.5° wide. Its location is about 12–15° temporally (towards your forehead) and 1.5° below your eye. You can't see anything that's located in that small area.

Each of your eyes has a visual field that overlaps with that of the other, and this overlap compensates for your blind spot. Your brain is very efficient at combining the information from both eyes to "fill in" missing information. That's why you don't normally notice your blind spot.

You can find your blind spot with a simple procedure that only takes a few minutes. You need a piece of white paper and a black pen or marker.

• Take a piece of paper and mark an X on the left side.
• About 5 ½ inches away from the X, mark an O. Make sure they are horizontal to each other.
• You need to be about 1.5 feet away from the paper.
• Cover your right eye.
• Look at the O with your left eye. The X should disappear. If it doesn't, move the paper back and forth until it disappears.

Alternatively, you can easily find a blind spot test online.

The location and size of your blind spot are so precise because it corresponds to the location of structures inside your eye. Your optic nerve detects visual input (the things you see). This nerve enters the back of your eye and spreads nerve fibers onto the back of the eye to make up a light-detecting cell layer (the retina). The small round spot where your optic nerve enters the back of your eye is the optic nerve head, also called the optic disc. There are no photoreceptors (light-detecting cells) on the disc, so you can't see anything in your visual field that corresponds to this tiny area.

When to See a Doctor

A noticeable blind spot is not normal. If you think that you have one, see your doctor.

You may want to prepare for your visit by paying attention to these factors:

• Does the blind spot come and go?
• Can you describe exactly where your blind spot is located? Right or left?
• Does the blind spot move?
• Do you have any other symptoms that occur with the blind spot, like flashing lights?
• Does the blind spot only occur in one eye or do you see it in both eyes?

Your doctor will do a full comprehensive exam, which includes a visual acuity test, Amsler Grid testing, automated visual field testing, and a dilated retinal exam.

A Word From Verywell

A blind spot that isn't normal may be described as scotoma, and it can be caused by conditions like a retinal migraine, glaucoma, macular degeneration, or retinal detachment.

A retinal detachment is a disorder in which the retina separates from the layer underneath. Symptoms of retinal detachment include seeing floaters and flashes of light and having decreased vision in the outer part of the visual field. You might feel like a curtain is coming down, blocking your vision. Without prompt and proper treatment, permanent loss of vision may occur. 

Get medical attention promptly if think you have a blind spot in your vision. Your medical team will quickly assess your condition and provide immediate treatment if necessary.