Exam 2 Vision

Question 1

Is cornea and lens vascular or avascular?

Answer 1

• Avascular
• light bending is the main thing so you can focus it on retina
• blood will mess up the bending of light–>since its avascular it gets its nurtrients from aqueous humor

Question 2

What is the distance between successive waves?

Answer 2

Wavelength

Question 3

What is the number of waves per second?

Answer 3

Frequency

Question 4

What is the difference between wave trough and peak?

Answer 4

Amplitude

Question 5

When the frequency is higher the wavelength is?

Answer 5

Lower

Question 6

What wavelengths can we see? Vissible light

Answer 6

400 nm to 700 nm

Question 7

What are the three layers of tear film?

Answer 7

Posterior layer rich in glycoproteins

—Derived from conjunctival goblet cells

Watery middle layer

—Secreted by lacrimal tissues

Anterior oily layer

—Produced by meibomian glands and the glands in the eyelids

Question 8

What are the three purposes of tear film?

Answer 8

1) Protect
2) Bending of light in cornea and focusing it on retina
3) Keeps it from drying out

Question 9

What is the main function of the cornea?

Answer 9

to protect eye and relfect light

-it cant be directly opened to external environment

Question 10

What two structures present a tough physical barrier to trauma and infection and protects the internal structures of the eye.

Answer 10

Sclera and Cornea

Question 11

•The cornea refracts light.

–The refractive power of the cornea depends on the ________ of light at the air-cornea interface.

-If air is replaced with something that passes light at about the same speed as the eye, the refractive power of the cornea will be eliminated.

Answer 11

slowing

Question 12

–The cornea provides ______ of the refractive power in the eye.

-The cornea has a refractive power of about ________. Parallel light rays striking the corneal surface will be focused 0.024 meters behind it. This is about the distance from the cornea to the ________.

Answer 12

1) most
2) 42 diopters
3) retina

Question 13

What are the three functions of aqueous humor?

Answer 13

–Maintains a stable pressure

–Feeds avascular tissue

–Maintains clear vision (liquid has to be clear in order for light to pass through)

Question 14

What allows light to pass through lens?

Answer 14

The iris

•The iris functions like the diaphragm in a camera to increase or decrease the amount of light entering the eye.

Question 15

–If an aperture is wide, then ______ rays are admitted, resulting in a ______ focus only for parallel rays with a certain focal length.

*more light

–If an aperture is narrow, then only a _______ number of parallel rays pass through, resulting in a ______ focus at the focal plane and for a distance before and after the focal plane.

*less light

Answer 15

1) many, sharp
2) small, sharp

Question 16

•F-number = focal length / aperture diameter

–F-number (f-stop) of the eye is the ratio of the focal length of the eye (from cornea to retina) and physical aperture (pupil opening).

For a clear picture you want?

Answer 16

F number to go up

–Each smaller F-number doubles the area of the opening and therefore doubles the amount of light entering the camera, and reduces the depth of field.

Question 17

–Wide apertures have ____ depths of field (not as clear)

-Narrow apertures have _____ depths of field (clear)

Answer 17

1) Small
2) large

•The F-number gets larger, the aperture gets smaller and the depth of field gets larger.

Question 18

What is the iris innervation?

Answer 18

Question 19

What is the function of the lens?

Answer 19

• The function of the lens is to focus light on the retina
• The shape of the lens can change in order to enable accommodation.

Question 20

What are the steps in accomadation?

Answer 20

1) The ciliary muscles contract.
2) Suspensory ligaments attached to the lens relax.
3) The lens becomes more spherical due to its inherent elasticity.
4) The curvature of the lens surface increases.
5) The refractive power of the lens increases.
6) Objects up close come into focus.

Question 21

What are the other changes occurring during accommodation?

Answer 21

The eyes converge.

The pupils constrict which increases the depth of field.

Question 22

Example: when the left eye is stimulated, neither pupil constricts, as no signals reach the brain from the left eye due to its damaged optic nerve

Example: when the left eye is stimulated, only the right pupil constricts

Answer 22

The ipsilateral direct reflex is lost

Question 23

Example, because light shone into the right eye can signal to the brain, causing constriction of both pupils via the normal oculomotor nerves

Answer 23

The ipsilateral consensual reflex is intact

Question 24

Example, Because light shone into the right eye can signal to the brain, causing constriction of both pupils via the normal oculomotor nerves

Example, Because light shone into both eyes can still signal to the brain, and the pupil on the undamaged side will still be able to constrict via its normal oculomotor nerve

Answer 24

•The contralateral direct reflex is intact

Question 25

Example, because light shone into the eye on the damaged side cannot signal to the brain; therefore, despite the right eye’s motor pathway (oculomotor nerve) being intact, no signals from the left eye are able to stimulate it due to the damage to the sensory pathway (optic nerve) of the left eye)

Answer 25

•The contralateral consensual reflex is lost

Question 26

Example: when the right eye is stimulated, only the right pupil constricts

Answer 26

•The ipsilateral consensual reflex is lost

Question 27

Example, because light shone into the left eye can still signal to the brain via the normal optic nerve, causing attempted constriction of both pupils; the contralateral pupil constricts via its normal oculomotor nerve, but the ipsilateral pupil is unable to constrict due to its damaged oculomotor nerve

Answer 27

The contralateral consensual reflex is intact