Human visual system

Main

The visual system detects, transduces and interprets information concerning light within the visible range to construct an image and build a mental model of the surrounding environment. It is divided into the optical system (cornea and lens) and the neural system (retina and visual cortex). The visual system performs tasks such as the formation of monocular images, stereopsis, depth perception, motion perception, pattern recognition, motor coordination, and color vision.

Phases of vision:

1. Light enters the eye through the cornea and pupil

2. The lens focuses the light onto the retina

3. Photoreceptors in the retina convert light into electrical signals

4. The optic nerve transmits these signals to the brain

5. The visual cortex processes and interprets the visual information

Elements of the visual system:

• Cornea: The transparent front part of the eye that helps focus light

• Lens: Adjusts its shape to focus light onto the retina

• Retina: Contains photoreceptors (rods and cones) that convert light into electrical signals

• Optic nerve: Transmits visual information from the retina to the brain

• Visual cortex: Processes and interprets visual information in the brain

Terms

• Mental model: A cognitive representation of the external world, created by the brain based on sensory information, prior knowledge, and expectations. The visual system plays a crucial role in building and updating mental models of the environment.

Analogy

The visual system can be compared to a camera. The eyes, like the lens of a camera, focus light onto the retina (similar to the camera's sensor). The brain then processes this information, just as a computer processes the digital data from the camera to create an image.

Misconception

A common misconception is that the eyes are solely responsible for vision. In reality, the brain plays a crucial role in interpreting and making sense of the visual information captured by the eyes. Without the brain's processing, the raw data from the eyes would be meaningless.

How to use it

1. When spending time outdoors, wearing sunglasses can protect your eyes from harmful UV rays and reduce the risk of developing cataracts or other eye problems.

2. Regular eye check-ups, including tests for corneal health, can help detect and prevent vision problems early on, ensuring that your visual system functions optimally.

3. If you experience visual fatigue or strain when reading or using digital devices, wearing appropriate eye glasses can help reduce the strain on your visual system and prevent long-term damage.

Facts

• The human eye has approximately 125 million photoreceptors.

• The retina contains about 1 million ganglion cells, which compress and transmit visual information to the brain.

• The visual field spans approximately 200° horizontally (monocular) and 135° vertically.

• Visual acuity is highest in the central region of the retina called the fovea, which covers about 1-5° of the visual field.

• The eyes actually capture images upside down, but the brain processes and inverts the image so that we perceive the world right-side up.