C15 3-5

Question 1

glaucoma

Answer 1

Cause: buildup of aqueous humor leads to increase in intraocular pressure.

Consequence: Compresses retina and optic nerve - blindness.

Glaucoma exam: air puff to determine pressure.

Question 2

cataracts

Answer 2

Cause: Age related hardening and thickening of the lens or secondary consequence of diabetes. Change in the shape of crystallin (loss of conformation).

Consequence: clouded lens, distortion.

Artificial lens can be implanted.

Question 3

Astigmatism

Answer 3

Cause: Unequal curvatures in different parts of the cornea or lens

Consequence: Blurry images.

Question 4

Myopia

Answer 4

Cause: Eyeball is too long. Distant objects focus in front of retina instead of on it.

Consequence: Distant objects are blurred. Nearsightedness.

Concave lenses are corrective - move focal point back.

Question 5

Hyperopia

Answer 5

Cause: Eyeball is too short. Light rays from distant objects focus behind the retina.

Consequence: Close objects are blurry. Farsightedness.

Convex lenses are corrective - move focal point forward.

Question 6

Presbyopia

Answer 6

“Old person vision” Cause: Non-accomodating lens - the lens has lost elasticity and can’t bulge for near vision.

Question 7

Pathway of light to the retina

Answer 7

Cornea –> Aqueous humor –> Lens –> Vitreous humor –> Macula Lutea (Fovea Centralis) –> Photoreceptors –> Bipolar cells –> Ganglion cells –> Optic nerve

Question 8

How is light focused for close vision?

Answer 8

3 adjustments:

1. Accomodation of the lens - lens bulges (parasympathetic contracts ciliary muscle which releases tension in the ciliary zonule (muscle squeezes towards zonule.))
2. Constriction of the pupil (parasympathetic, sphincter pupillae, only picks up rays coming in perpendicular)
3. Convergence of the eyeballs. (medial rectus muscles/oculomotor, eyes pulled toward the object being viewed.)

Question 9

How is light focused for distant vision?

Answer 9

No adjustments needed - our eyes are best adapted for distant vision. Ciliary muscles are completely relaxed, tension in the ciliary zonule stretches the lens flat.

Question 10

Emmetropic

Answer 10

normal vision

Question 11

Far point of vision

Answer 11

Distance beyond which no change in lens shape is needed for focusing.

Question 12

Near point of vision

Answer 12

Closest point on which we can focus clearly (maximum bulge of lens)

Question 13

Refraction

Answer 13

Bending of light rays, happens when light passes from one medium to another. Happens three times in the eye: Cornea, Entering lens, Leaving lens.

Question 14

Focal point

Answer 14

Light rays are bent so they converge or intersect at a single point call the focal point.