[Biology Class Notes] on Structure of Eye Pdf for Exam

Inside the protecting sclera follows the choroid, which, as the name suggests, is permeated by several blood vessels and capillaries. The blood delivers the retina with nutrients and oxygen.

Retina

The retina is situated on the back or inside of the eye. It is made up of different cell layers: the photoreceptors transform the light impulse into an electrical nerve impulse. The light information is bundled in named receptive fields, enlarged, and transmitted to the brain via the visual pathway.

The genuine “visual process” then occurs on the retina. The retina is made of a number of different cell kinds with different responsibilities. First of all, the sensory cells are vital. They convert the light into an electrical impulse.

There are two kinds of vision cells:

• The rods (light-dark vision, active in evening or darkness)

• The cones (accountable for color vision)

Three different kinds of cone cells are essential for color vision:

• Pins for red-visibility (about 46% of all pins)

• Cones for green vision (about 46% of all cones)

• Cones for blue vision (about 8% of all cones)

The three types of cone react to light of different wavelengths. 

If a photon or a light partial with a wavelength in the red region hits a red cone, then it “produces” an impulse at the following cells. The other two cone kinds remain inactive for a “red photon”. They react accordingly when photons reach their exact wavelength. If one of these cone types is not properly made due to a genetic defect, there will be a color vision injury or color blindness we can say as red-green weakness. The genetic irregularities of the eye’s color are as follows:

• Protanomaly: Red vision weakness

• Protanopia: Red blindness

• Deuteranomaly: Green vision weakness

• Deuteranopia: Green blindness

• Tritanopia: Blue blindness

• Tritanomaly: Blauseh weakness

Further Processing on the Retina

The retina involves a large number of other different cells that develop the electrical impulses directed by the visual cells. The visual information from neighboring regions is bundled, compared, and enhanced in contrast. It can be said that only “new” and “relevant” info from the “image” is delivered to the brain This “filtering” of data is very effective and economical. Evolution has advanced the eye in such a way that it uses as little energy as possible. Rationally, you don’t have to see everything to live, but only what is vital.

Stereoscopic Vision

The pre-structured optical evidence is then conveyed to the brain with the help of the optic nerve. The info is collected from both eyes and forwarded together. This is where “stereoscopic vision” is formed. The information from the left and right eye is somewhat different since the angle of incidence is marginally different. From this difference, the brain can conclude something like space. The spatial visual imprint is therefore produced from the different information of the two eyes. Correctly, still, one has to say that the learned information like perspective, sizes, and so on have a bigger share of the three-dimensional visual imprint than stereoscopic vision.

Lastly, the information reaches the brain with the help of the optic nerve – and here it is spread over large areas that are stored to fluctuating degrees (via linked synapses of the single nerve cells). Eventually, this “neural pattern” is what we see as a visual image of reality. This pattern has been continuously developed and modified since the first day of opening the eyes.

More about the Human Eye

The human eye is a part of the sensory nervous system in the human body which helps us in receiving light reflected from the surface of objects. This light signal gets transferred to the brain where it is processed by it and we get the perception of size, color, motion, and other visual properties of objects. 

The human eye is a very complex organ that involves a lot of complex parts. The eye is an example of the human body where biology and physics work hand in hand and make it possible to see the world around us.

The human eye is placed on either side of the nose in a socket in the forehead bone which is known as orbits. Depending on the side of the face where the eye is situated it is known as the left or right eye. The outer layer of the eye is protected by the sclera and eyelids. Eyelids are attached to the eyelashes.

The outer layer of the eye is called the cornea, it gives shape to our eye. In the center of Corona, we have a pupil which is surrounded by iris. The pupil can be thought of as a hole through which the light passes into our eye and the size of the Pupil is controlled by the iris.

Below the pupil, we have an eye lens that is connected with suspensory ligaments of the eye. These muscles change the shape of the lens which helps in refocusing images by the lens. The image created by the lens is projected on the retina which is present at the back of the eye. This acts as a screen that helps us in capturing the images as sensory nerve signals with help of rod and cone cells.