Vision - Focus Transduction Flashcards Preview

Neurology > Vision - Focus Transduction > Flashcards

Flashcards in Vision - Focus Transduction Deck (26)
Loading flashcards...
1

How does an image form on the retina?

Light waves bend at the cornea and lens (refraction)

2

What happens to the lens when an object is moved closer?

More bending power needed so lens thickens

3

What is accommodation?

The change in focus from distant to close objects

4

What 3 things happen to allow the eye to obtain focused image?

Lens thickens
Pupil constricts
Eyes converge

5

What muscles are involved in thickening the lens?

Ciliary body contracts
Suspensory ligaments become lax

6

What muscle is involved in pupil constriction?

Pupillary constrictor (sphincter pupillae)

7

What muscle allows the eyes to converge?

Medial rectus

8

What is the name given to describe perfect vision?

Emmetropia

9

What is myopia?

Short sight

10

What is the most common cause of myopia?

Eyeball is too long

11

Where is the image formed in myopia?

In front of the retina

12

What are the symptoms of myopia?

Headaches
Divergent squint
Loss of interest in children

13

How is myopia corrected?

Biconcave lenses
Laser eye surgery

14

What is hyperopia?

Long sight

15

What is the most common cause of hyperopia?

Eyeball too short
Cornea and lens too flat

16

Where is the image found in hyperopia?

Behind the retina

17

What are the symptoms of hyperopia?

Eyestrain
Convergent squint

18

How is hyperopia corrected?

Biconvex lenses
Laser eye surgery

19

What is an astigmatism?

Close and distant objects appear hazy

20

What is the cause of an astigmatism?

Bending of light rays along one axis will never be the same as that of the other axis

21

How is an astigmatism corrected?

Cylindrical glasses
Laser eye surgery
Toric lenses

22

What is presbyopia?

Long sight in old age

23

What is the cause of presbyopia?

Lens gets less mobile/elastic
Ciliary muscle not as capable of changing shape during contraction

24

What is phototransduction?

Conversion of light energy to an electrochemical response by photoreceptors (rods and cones)

25

What role does vitamin A play in the visual pigment?

Visual pigment regeneration

26

What are the clinical signs of vitamin A deficiency?

Bitot's spots in conjunctiva
Corneal ulceration
Corneal melting