Eye Anatomy Flashcards
Where is the palpebral fissure and what is the average size?
- The palpebral fissure is the elliptical-shaped space between the open eyelids. It’s the entryway to the conjunctival sac.
- The average size is 15mm by 30 mm wide
Describe the characteristics of the cornea
- It is a transparent tissue with no blood supply of its own
- Provides ⅔ refractive power
- The eye has a total refractive power of approx. 60D
- The average size for the horizontal diameter is 11.7 mm while the vertical diameter is 10.6 mm
What does VID stand for?
Visible iris diameter
What does HVID stand for?
Horizontal visible iris diameter
What is the Crystalline Lens responsible for?
It is responsible for ⅓ of the eye’s refractive power
What do you know about the Crystalline Lens
- The average size is 15.00 D to 16.00 D
- Located behind Iris
- Transparent with no blood supply
What is connected to the ciliary muscle that helps shape the crystalline lens?
Zonular Fibers
What do the zonular fibers and ciliary body do with the crystalline lens to see far objects?
- To see objects from far away the ciliary muscle relaxes while the zonular fibers contract making the lends thinner
What is the loss of accommodation called?
Presbyopia
What are cataracts?
- Cataracts are cloudy opacities in the lens
- It is when the vision becomes hazy
How do you get cataracts?
- It could be of old age which ranges between 75-85
- Some infants may be born with cataracts which is known as congenital cataracts
- Other ways are injury, trauma, or disease
What is Aphakic?
It is when the eye is without a crystalline len
What is pseudophakic?
It is when the eye is with an IOL(intraocular implant) which is an artificial lens
What does the retina do?
Captures light rays and converts them into electrical impulses
How many rods does the retina have and what do they do?
It contains 125 million rods that are responsible for night vision
How many cones does the retina contain and what do they do?
- It contains 6-7 million cones responsible for color and light vision.
- Most cones are found in the fovea which is part of the retina and can see the sharpest
What is the center of the retina called and what does it do?
Macula: allows us to see fine details
What is Macula degeneration?
It is a disease that damages the macula, the part of the eye that controls central vision.
What are the symptoms of macula degeneration?
-Symptoms Blurred vision
- Straight lines appearing wavy or crooked
- Loss of clear color vision
- A dark or empty area in the center of the vision
- Difficulty seeing in low light.
What does the optic nerve do?
Carries images from the retina to the brain and creates a blind spot
Why is it important for infants and young children to have eye exams?
To ensure healthy development of the optic nerves.
Where is the optic nerve?
It connects to the back of the eye near the macula.
What do the zonular fibers and ciliary body do with the crystalline lens to see close objects?
-To see objects from close up the ciliary muscle contracts while the zonular fibers relax making the lends thicker
Where is the medial rectus located and what direction does to go towards?
- Medial rectus is located near the nose.
- Moves the eye towards the nose
Where is the Lateral Rectus rectus located and what direction does it go towards?
- Located near the ear
- Moves away from the nose
Where is the Superior Rectus located and what direction does it go towards?
- Located at the top of the eye
- Looks upward
Where is the Inferior Rectus located and what direction does it go towards?
- Located on the bottom of eye
- Moves downward
Where is the Superior Oblique located and what direction does it go towards?
- Located near the superior rectus
- Rotate the top of the eye toward the nose
Where is the Inferior Oblique located and what direction does it go towards?
- Located near the inferior rectus
- rotates the top of the eye away from the nose
What does the Iris controls?
- Controls the light inside the eye
Why are there colors in Iris?
The color comes from melanin
What is accommodation?
The ability of the eye to change focus to see
What is retinal detachment?
- It is when the retina pulls away from the lining of the eye.
What happens to the retina when it is detached from the eye for too long?
- The portion of the retina can atrophy or die; without immediate medical intervention, vision can be lost forever.
What does the macula contain?
- Contains a high concentration of photoreceptor cells that convert light into nerve signals.
What are the tiny dimples at the center of the macula called and what do they contain?
- Fovea
- It contains only cones and is responsible for the sharpest, most brilliant color vision.
Together, what is the mocula and fovea are responsible for?
- responsible for clear, sharp vision, and provide the central part of the vision.
what is the optic nerve?
- It is a bundle of nerve fibers that carries visual information to the brain.
Does the optic nerve have rods or cones?
- No
What happens when the optic nerve is not sending good signals?
- If good signals aren’t sent along both optic nerve pathway during young children/infant development then the optic nerve can atrophy or die and vision will forever be lost.
The average person blinks how many times per minutes?
7 to 12
What part of the optic system is responsible for carrying electrical signals from the retina to the brain?
optic nerves
The crystalline lens is responsible for approximately how much refractive power?
15.00D to 16.00D
The light-sensitive tissue that lines the back of the eye and sends electrical impulses to the brain is called the:
Retina
What are the three fluid chambers of the eye?
- Anterior chamber
- Posterior chamber
- Vitreous Chamber
Where is the anterior chamber located?
- Between the cornea and iris
Where is the posterior chamber located?
- Between the Iris and lens
Where is the vitreous chamber found?
- Between the retina and lens
- Vitreous chamber maintains the shape of the eye.
What are the five layers in the cornea?
- Outer layer: Epithelium
- Second layer: Bowman’s membrane
- Third layer: Stroma
- Fourth layer: Descemet’s membrane
- Inner layer: Endothelium
What are the two muscles in the Iris and what do they do?
- The dilator muscle: opens the iris allowing more light in
- Sphincter muscle: Closes the Iris
Where is the medial canthus located?
The tip area of the eye near the nose
Where is the lateral canthus located?
- The tip area of the eye near the ears
Where is the meibomian glands located?
- Located along the inner margins of the eyelids that holds the secrete of liquid.
Where is the Fornix located?
Located behind the eyelid or palpebra and along the sclera
Where is the lacrimal gland located?
Inside the orbit of the eye
Where is the lacrimal puncta located?
Small opening located at the medial canthus that allow the accumulated tears to drain off the eye
Where is the sclera located?
- The white of your eyes.
- It is thick, tough and fibrous layer that provides structure of the entire eyeball
Where is the limbus Located?
- Where the cornea blends into the sclera
What are the three layers that makes up the eye?
- Fibrous tunic
- Vascular Tunic
- Nervous tunic
What does the fibrous tunic consists of?
- Sclera and cornea
What does the Vascular Tunic consist of?
- The iris, choroid, and the ciliary body
- responsible for nourishment
What does the nervous tunic consist of?
- retina
- it is the inner layer of photoreceptors and neurons.
