Vision & Human Eye Study Questions

We can see both in very bright light and very dim light. How does the eye deal differently with visual processing in these two situations?

Bright light: eye focuses light on fovea centralis, where cones are located. this allows for a focused/colorful image Dim light: light focuses on ring of cells around fovea centralis (macula lutea) where rods are located

What are the causes and treatments for the following conditions: cataract, glaucoma, macular degeneration, retinal detachment.

Cataract: lens becomes cloudy, light cannot pass through well; treated by surgery that removes the damages lens and replaces it with a plastic lens Glaucoma: blindness caused by increased fluid pressure cutting off retinal blood supply; surgical treatment Macular degeneration: damage to fovea centralis that gets worse over time, causing loss of vision; cannot be treated, only slowed down by medication Retinal detachment: retina become detached from inner eye; requires laser surgery to treat

Where are the visual centers in the brain?

Colored/Detailed Vision Center: Fovea centralis Dim Light Vision Center: Ring of cells just outside the fovea centralis (macula lutea) Peripheral Vision Center: further out from fovea centralis

Define and explain: farsighted, nearsighted, astigmatism. How can each of these visual defects be corrected by lenses or contacts?

Farsightedness: eyeball is too short; image focuses behind retina; cannot see close up; need convex lenses to fix Nearsightedness: eyeball is slightly too long; image focuses in front of retina; cannot see far distances; need concave lenses to fix Astigmatism: irregular lens curvature; makes vision blurry; need irregular lens shape to even out abnormality to fix

Why is our visual acuity so different in using the "peripheral vision" as opposed to looking directly at an object?

Light is not directly focusing on cone cells when using peripheral vision, causing the image to be less detailed/colorful

What are the anatomical parts and how does it work?

Parts: lens, retina, pupil, iris, sclera, cornea, fovea centralis, optic nerve, rectus muscles, optic disk, and vitreous body How it works: the lens focuses light on the light sensitive tissue (retina) to form an image, the brain processes information from the retina through the optic nerve

Explain the structure and function of the following types of visual sensory structures --planarian ocelli (eyespots), Arthropod compound eyes.

Planarian Ocelli: Structure (black dots; simple black eyes) Function (light/dark detectors; no image formed) Arthropod Compound: Structure (composed of cluster units; ommatidia) Function (light stimulates ommatidia to form an image; have a lens that focuses light on photoreceptor cells)

Explain the structure and function of the human eye.

Structures: lens, iris, pupil, retina, rods, cones, and optic nerve Function: lens focuses light to produce an image (appears upside down and backwards)

Why do we have a "blind spot" In our visual field?

The "blind spot" occurs at the optic disk (where optic nerve meets retina) because there are no photoreceptor cells there

How does the lens change its focusing power when we look at objects far away and then those that are close to us (accommodation)?

The lens is able to "accommodate" to view images that are close/far away because the lens can change shape (becoming thicker/thinner) Far Away = Thinner Lens Close Up = Thicker Lens (relaxed) (accommodation is lost with old age)

Why do we say that the retina "analyzes" the image that is focused on it?

The retina takes an image and through the use of photoreceptor cells (rods+cones) analyzes the colors/details of the image

All animals do not have color vision but humans do have the ability to see color: Explain the basis of color vision?

There are 3 types of cone cells (red, blue, green). they respond to different wavelengths of light and our perception of color is based on the degree of light stimulation from these wavelengths

Referring to the structure of the human retina, explain why you see better in dim light if you don't look directly at an object but look slightly to one side of it?

When looking at something in dim light, if you look slightly to the side of the object, the light focuses on the retinal area with the highest rod density (dim light cells)

Why is it so difficult to distinguish colors when using the peripheral vision?

When using the peripheral vison, light is not being focused on the cone cells (color/detail detector cells) resulting in difficulty distinguishing colors

Why is it harder to see color in dim light?

cone cells (color vision detectors) only work well in strong light. dim light is not strong enough to allow cone cells to work optimally, aka none to little color

What does the brain have to do with what we see?

the brain turns the image right side up and forwards and displays the colors/details given by the retina, allowing us to view the world as we do