Summary
Light is focused by the lens onto the retina, where rods and cones convert it into nerve signals.
In depth
Light passes through cornea, aqueous humour, lens (adjusted by ciliary muscles) and vitreous to the retina. Rods (about 120 million) work in dim light; cones (about 6 million) give colour in three types. The fovea has highest acuity; the blind spot has no receptors.
The lens adjusts focus by accommodation. Iris controls light. Photoreceptor pigments (opsins) change shape with light, triggering a cascade. Retinal ganglion cell axons form the optic nerve.
Example: colour blindness arises from missing cone pigments.
The retina has 120 million rods (dim light, no colour) and 6 million cones (L, M, S types for red, green and blue light, concentrated in the fovea, which gives sharp vision). Phototransduction: light isomerises retinal in rhodopsin, activates transducin and PDE, lowers cGMP, closes channels and hyperpolarises the photoreceptor, which is unusual, since receptor cells decrease transmitter release in light. Bipolar and ganglion cells process contrast, and optic nerve axons leave at the blind spot.
Accommodation is lens thickening by ciliary muscle contraction. Defects: myopia (long eyeball), hyperopia, astigmatism, presbyopia, cataracts (lens clouding), glaucoma (high pressure damaging the optic nerve), macular degeneration, and colour blindness (about 8 percent of men). Optic chiasm sends left visual field input to the right hemisphere.
Example: night vision needs about 20 to 30 minutes for rhodopsin to regenerate.
Frequently asked questions
What is Eye and Vision?
Light is focused by the lens onto the retina, where rods and cones convert it into nerve signals.
Which area of biology covers Eye and Vision, and how advanced is it?
Eye and Vision is one of the 54 topics in Neuroscience. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Sensory Receptors, Optogenetics, Visual Cortex Processing.
Can you give an example of Eye and Vision?
Myopia means the image forms in front of the retina.
What should I learn before Eye and Vision?
Eye and Vision is a Beginner topic, so no earlier topic is required. Other Beginner topics in Neuroscience that pair well with it include Nervous System, Neuron, Central and Peripheral Nervous Systems.
What topics are related to Eye and Vision?
The closest topics to Eye and Vision are Sensory Receptors, Optogenetics, Visual Cortex Processing, Neuron. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Eye and Vision?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Eye and Vision. To practise the whole of Neuroscience, use the Neuroscience quiz.
How is Eye and Vision different from Sensory Receptors?
Eye and Vision: Light is focused by the lens onto the retina, where rods and cones convert it into nerve signals. Sensory Receptors: Mechanoreceptors, thermoreceptors, chemoreceptors and photoreceptors transduce stimuli into signals. Read both side by side and note what each one explains.
How should I study Eye and Vision step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Sensory Receptors and explain the difference aloud. Finally, take the Neuroscience quiz and come back to this page for any question you miss.