Lab Practical II - The Eye Flashcards
Is the space between the cornea and iris filled with aqueous humor.
anterior chamber
Is a watery-like fluid, produced by the ciliary body; it fills in the front of the eye between the lens and cornea and provides the cornea and lens with oxygen and nutrients.
It drains back into the bloodstream through the canals of schlemm.
aqueous humor
Is where the electrical signals sent from our eyes are processed into vision.
Damage can lead to vision loss if the visual cortex or optic pathways are damaged.
Majority of nerve fibers in the optic tract connect to the LGN.
brain
Structures that are located around the perimeter of the iris. They allow aqueous fluid to drain back into the bloodstream. The trabecular mesh-work along with ? regulate the eyes internal pressure.
In the eye disease called glaucoma, these structures become blocked leading to increased pressure. The increased pressure, from this condition, destroys the optic nerve.
Canals of Schlemm
Is a layer of blood vessels between the retina and sclera; it supplies blood to the retina.
In the disease called macular degeneration, abnormal blood vessels grow into the space between the retina and ? damaging the macula.
choroid
This is where the aqueous humor is produced.
ciliary body
The eye can bring fine print in a phone book into focus, or focus in on the moon over 1/4 million miles away. These change the shape of the lens (called accommodation). It relaxes to flatten the lens for distance vision; for close work it contracts rounding out the lens.
Everyone will develop an eye condition called presbyopia. As we age, these and the crystalline lens lose their elasticity. This is why most people need reading glasses by their 40’s.
ciliary muscle
Is a thin, clear membrane covering the front of the eye and inner eyelids. Cells in this lining produce mucous that helps to lubricate the eye.
This is the eye’s first layer of protection against infection. i.e. “pink-eye”
conjunctiva
This is a clear, dome-shaped surface that covers the front of the eye. It is the first and most powerful lens in the eye’s optical system. To keep it transparent, it contains no blood vessels.
Tears that flow over it and aqueous humor in the chamber behind it keep it nourished. When you hear of eye banks and eye transplants, it is this that is being replaced. It can be damaged from accidents, infections, and genetic defects.
cornea
This structure works like the adjustable lens in a camera. Positioned just behind the cornea, it is responsible for keeping images in focus on the retina. It is adjustable for distance and close work.
A cataract is the lens clouding up. This happens to most people as they age; a few people are even born with cataracts. Modern surgery has all but eliminated cataracts as a cause of blindness in the developed world.
crystalline lens
These are like little video cameras measuring about 1 inch or 2.5 cm in diameter.
If someone’s ? is larger than ?, they will be nearsighted (myopic); if it is smaller than this, they will be farsighted (hyperopic). Having two gives us binocular vision - depth perception. This is due to the flushing of both images in the visual cortex.
eyeball
These specialized hairs protect the eyes from particles that may injure them. They form a screen to keep dust and insects out. Anything touching them triggers the eyelids to blink.
eyelashes and eyebrows
These structures protect and lubricate our eyes. Small oil-producing glands line the inner edge of them. These oils mix with tears when we blink, keeping the eye moist and clean.
eyelids
This is a cone-shaped bony cavity that protects the eye. It is padded with fatty tissue that allows the eye to move easily.
eye socket
This is an indentation in the center of the macula. Its diameter is only 1.5 mm or about 1/16 inch. The small part of our retina is responsible for our highest visual acuity. It is the center of our central vision.
fovea (small pit)
This continually releases tears and other protective fluids onto the surface of the eye. It lubricates and keeps the cornea from becoming dehydrated.
lacrimal gland (tear duct)
This is a tiny pump that drains tears and other debris from the eye. The fluids flow down the nasolacrimal duct into the nose where they help keep the nasal linings moist. This is why your nose runs when you cry.
lacrimal sac
This is the part of the brain that acts as a relay station; it decodes visual information from the optic tract before sending it to the visual cortex for final processing.
Lateral Geniculate Nucleus (LGN)
During modern cataract surgery the outer membrane of the lens is left in place. The artificial intraocular lens is placed in this.
lens sack or capsule
This is the colored part of the eye: brown, green, blue, etc. It is a ring of muscle fibers located behind the cornea and in front of the lens. It contracts and expands, opening and closing the pupil, in response to the brightness of surrounding light.
Just as the aperture in a camera protects the film from over-exposure, this helps protect the sensitive retina.
iris
This is the part of the retina that is the most sensitive. Its diameter is only about 7 mm or about 1/4 inch. It is responsible for our central, or reading vision. This part of the retina gives us 20/20 vision. Without this, you would be blind - legally blind that is. People with certain eye diseases have vision from 20/200 to 20/800.
macula (yellow spot)
This is the part of the brain to receive visual input. Each eye takes a slightly different picture of the world. At this each picture is divided in half. The outer left and right halves continue back toward the visual cortex. The inner left and right halves cross over to the other side of the brain then continue back toward the visual cortex.
optic chiasm
Is the spot on the retina where the optic nerve leaves the eye. Are no sensory cells here, creating a blind spot. Each eye covers for the blind spot of the other eye and the brain fills in the missing information.
optic disk
Each one of these has about 1.2 million fibers. This is the cable connecting the eye to the brain.
optic nerve
The nerves that connect the optic chiasm to the LGN are called this. If one of these is damaged, vision will be lost in one side of each eye.
optic tract
6 of these are in charge of eye movement. 4 of these move the eye up, down, left, and right. The other 2 control the twisting motion of the eye when we tilt our head. Defects in these and the nerves that control them lead to conditions like Nystagmus and Amblyopia (lazy eye).
orbital muscles
The retina is composed of these 2 types of cells. When light falls on one of these cells, it causes a chemical reaction that sends an electrical signal to the brain.
photoreceptor cells
These cells give us our detailed color daytime vision. There are 6 million of them in each human eye. Most of them are located in the central retina - the macula fovea area. There are 3 types - 1 sensitive to red light, another to green light, and the third sensitive to blue light.
cone cells
These cells are about 500 times more sensitive to light than cone cells; they give us our dim light or night vision. Are also more sensitive to motion than cone cells. Are 120 million of these in the human eye. Most are located in our peripheral or side vision.
rod cells
Is the space between the iris and the front of the lens filled with aqueous humor.
posterior chamber
Is the hole in the center of the iris that light passes through. The iris muscles control its size.
pupil
Is the film of the eye.
It converts light rays into electrical signals and sends them to the brain through the optic nerve. Sides of this are responsible for our peripheral vision. The center area, called the macula, is used for our fine central vision and color vision.
Is the area where most of the problems leading to vision occur, 3 of the leading causes of blindness are damage to this area; they are retinitis pigmentosa, macular degeneration, and diabetic retinopathy.
retina
These are vessels in the choroid just beneath the retina. Abnormal growth of these and leaking ones are the cause of vision loss in eye conditions like diabetic retinopathy, ROP, and macular degeneration.
retinal blood vessels
This is a layer of cells between the retina and choroid.
retinal pigment epithelium (RPE)
This is the white, tough wall of the eye. It along with internal fluid pressure keeps the eyes shape and protects its delicate internal parts.
sclera
This is the middle vascular layer of the eye. It is made up of 3 parts: the iris, ciliary body, and choroid.
uvea
This is an imaginary line drawn through the center of the pupil to the center of the fovea. The orbital muscles keep these aligned on the center of what you are looking at (fixation point).
An eye condition called strabismus (misaligned eyes) results when the orbital muscles fail to keep the eyes in alignment. Any damage to eye structures along this area leads to severe vision loss.
visual axis
This is the part of the brain that processes and combines visual information from both eyes and converts it into sight. Damage to this area results in a condition called cortical blindness.
visual cortex
This is the space between the lens and retina filled with the gel-like ? humor.
vitreous cavity
This is a jelly-like liquid that fills most of the eye (from the lens back). As we age it changes from a gel to a liquid and gradually shrinks separating from the retina.
This is when people start seeing floaters, dark specs in their vision. This is a normal sign of aging, but in a few cases the retina can become detached as this separates.
vitreous humor
These are hundreds of string-like fibers that hold the lens suspended in position and enable it to change shape for near or distant vision.
zonules
The retina of each eye has 2 sections: the nasal retina (nose side) and temporal retina (ear side).
For example, with your right eye, you see the right half of the world with your nasal retina; you see the left half with your temporal retina. The picture your eye takes is flipped left for right and upside down; its up to the brain to sort things out.
visual fields
