How Do Cones and Rods Work? Eye Anatomy 101

  
Find A Location
Schedule An Appointment Online
July 15, 2019, by Bard Optical

eye-anatomy

Our eyes are complex systems of the body capable of perceiving incredible amounts of detail, letting us see a wide range of objects both near and far. 

The eye is made up of a network of vessels, muscles, and nerves, but what parts of the eye actually let you see the object you are looking at?

Enter the cone and the rod.

To learn more about cones and rods, we have to zoom in on one of the most important parts of the eye, the retina.

Cones and rods are two types of photoreceptors within the retina. This means that they are responsible for receiving signals (or images), processing them, and sending them to the brain.

The cone and the rod serve different purposes to work towards the same goal: helping you see!

 

Rods Help Your Peripheral Vision And Help You See In Low Light 

The rod is responsible for your ability to see in low light levels, or scotopic vision.

The rod is more sensitive than the cone. This is why you are still able to perceive shapes and some objects even in dim light or no light at all.

It takes your eyes time to adjust from a well-lit room to a dark room, or if you’re outside during nighttime. That’s because it usually takes the rod about 30 minutes to fully adjust to the absence of light. 

In addition to being the receptor that allows you to see in the dark, the rod is also the better motion sensor since it is more sensitive in nature, and has more individual receptors than the cone.

This motion sense is most predominant in your peripheral vision since that is where the rods are positioned.

 

Cones Allow You To See Color 

The cone is made up of three different types of receptors that allow you to see color.

These three different receptors are aptly named the short, medium and long wavelength cones. This size difference represents each receptor’s sensitivity to light.

The most important difference between the cone and the rod is that the cone is more light-sensitive than the rod, and the cone requires much more light to enter it in order to send signals to the brain.

This is the reason that you are unable to differentiate colors in dim light conditions.

Since the cone requires a high level of light in order to send signals, the cones are primarily responsible for your visual acuity (your ability to see objects in fine detail). Defective cones won’t enable you to focus on a certain object or perceive its color correctly, if at all.

As you can see, the rod and the cone are very important to your ability to see objects around you.

The rod sees the level of light around you, and the cone sees the colors and the sharpness of the objects, but together they form the foundation of our normal everyday vision.

The next time you’re trying to find your way through a dark room, or you’re trying to focus on that puzzle in front of you, thank your rods and your cones for making it all possible!

Vision Checklist Download