Optic disc (blind spot)
This is known as the blindspot. It is where the optic nerve leaves the eye. There is no room for photoreceptors due to the amount of blood vessels in this area, so no image is formed at this particular spot.
The lens of the eye is held in place by strong ligaments. It is the ligaments that contract and expand in order to focus on an image. This happens before the image reaches the retina. Smoking can damage the part of the retina called the macula. There are also indications smoking can cause the blood vessels in that area to constrict.
When light is passed through the lens and cornea, it is focused to a portion in the back of your eye. This light, not looking at it as a picture but a beam of light, is then shone on to a patch of photoreceptors that make up the retina. This is the most important part of the eye because this retina is responsible for changing the physical energy, light, into electrical energy, neural impulses. So when this light hits the retina the photoreceptors, like the rods and cones that produce color and shape, they take that energy and transduction it into electrical energy. This energy is them passed through the back of the eyes by the neural cords that attach to the eyes and sent to the brain. Once the eyes send that energy and it reaches the brain, it is sent to the visual association area of the brain, either in the pre-frontal cortex or another area around there (A little unsure). From there this association area takes those neural impulses that the retina created and pieces together pictures. Then from the information that was given to this area it can associated those neural impulses as certain objects or colors and you then can perceive the picture you are seeing. Thank, TS
It actually depends on the lens. For the image to be sharp on the retina, all the rays of light coming off the object must meet together at the same point on the retina. If the rays of light meet somewhere in front of the retina, the lens focuses by stretching itself and becoming thinner. This spreads out the rays of light, making them go further into the eye until they reach the middle of the retina. If the rays of light are behind the retina, the lens thickens to focus.
The fovea centralis. It is the area of sharpest vision because it contains the highest proportion of cones with almost no rods.
Small area storms formed by the strong upward movement of warm, moist air are called storm surges.
the retina
Light waves are bent as they pass through glass - parallel light from the object is focused on a small area (so the image is larger).
The highest concentration of cones is in the macula. The fovea centralis, at the center of the macula, contains only cones and no rods. The macula is a small, yellowish central portion of the retina. It is about 5.5 mm in diamter and is the area providing the clearest vision.
Macula
The apportioning of proportionally more space on the cortex to the representation of specific areas of sensory receptors. For example, a small area on the retina in or near the fovea receives more space on the cortex than the same area of peripheral retina. Smilarly, the fingertips receive more space on the somatosensory cortex than the forearm or leg.
It is because of the functional anatomy of the eye. Basically, when you look at an object, the image of the object falls on the photoreceptors (light sensitive receptors) in the retina of the eye. From these photoreceptors, the nerves carry the impulses to your brain, and you're able to "see". The area in the retina where all these nerve fibres converge to form the "optic nerve" and leave the eyeball is devoid of photoreceptors. So any image falling in that area of the retina will not be sensed. This area is known as the "blind spot". This area is located a little outward to the point of focus in the field of vision. so when you focus on the X and move the paper in and out, you would not be able to see the dot when it exactly in the blind spot. Kokilan.