Visual Perception and Imagery
Retina
The retina is a thin layer of tissue that lines the back of the eye on the inside.
It is located near the optic nerve. The purpose of the retina is to receive light
that the lens has focused, convert the light into neural signals, and send these
signals on to the brain for visual recognition
Photoreceptors:
The retina processes light through a layer of photoreceptor cells. These are
essentially light-sensitive cells, responsible for detecting qualities such as
colour and light-intensity. The retina processes the information gathered by
the photoreceptor cells and sends this information to the brain via the optic
nerve. Basically, the retina processes a picture from the focused light, and the
brain is left to decide what the picture is
Photoreceptors are the cells in the retina that respond to light. Their
distinguishing feature is the presence of large amounts of tightly packed
membrane that contains the photopigment rhodopsin or a related molecule.
The tight packing is needed to achieve a high photopigment density, which
allows a large proportion of the light photons that reach the photoreceptor to
be absorbed. Photon absorption contributes to the photoreceptor’s output
signal
There are two types of
photoreceptors in the human
retina, rods and cones:
Rods are responsible
for vision at low light
levels (scotopic vision).
They do not mediate
colour vision and have a
low spatial acuity. One
type
Cones are active at
higher light levels
(photopic vision), are
capable of colour vision
and are responsible for
high spatial acuity. The central fovea is populated exclusively by cones. There
are 3 types of cones which we will refer to as the short-wavelength sensitive
cones, the middle-wavelength sensitive cones and the long-wavelength
sensitive cones or S-cone, M-cones, and L-cones for short
The light levels where both are operational are called mesopic
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller Penny97. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £3.99. You're not tied to anything after your purchase.
