Test your body · Vision / 01

Find the gap in your vision.

Each eye has a small blind spot where the optic nerve leaves the retina and there are no photoreceptors. Your vision still feels complete because the brain uses surrounding information to fill in what is missing.

02 minutes01 screenNO equipment
INTERACTIVE LABEXPERIMENT 01 / VISION
Choose an eye
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  1. Cover your left eye. Keep the selected eye open.
  2. Look only at the plus. Keep your gaze fixed and move slowly toward the screen.
  3. Stop when the dot disappears. Do not shift your eyes toward it.

Tip: the effect appears only across a small range of viewing distances.

Inside your eye

The missing information never reached your brain.

The light-sensitive retina lines the back of the eye. At one small location, nerve fibers gather and exit toward the brain as the optic nerve. That exit contains no photoreceptor cells, so light landing there cannot be recorded.

You do not normally notice the gap. The other eye covers some of it, and the visual brain uses surrounding color, texture and edges to construct a continuous scene. It does not place a dark hole over the missing patch. It predicts what belongs there.

LightOptic nerve exit
No photoreceptors

Why your body does this

The blind spot is a structural consequence of the vertebrate retina. The wiring sits in front of the light-sensing layer, so nerve fibers need an exit. Your brain's ability to infer missing visual information keeps that anatomy from interrupting ordinary experience.

What this test reveals

Vision is not a pixel-perfect recording of the outside world. It is a useful model assembled from incoming signals, context and prediction.

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Sources

Read the science

01
Central Projections of Retinal Ganglion CellsNeuroscience, 2nd edition · NCBI Bookshelf
02
The Primary Visual CortexNeuroscience, 2nd edition · NCBI Bookshelf
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