Intro to opthamology

Question 1

Formation of a focused image on the retina is dependent on…

Answer 1

1) Ocular shape
2) Transparency of the ocular media
3) Ability of the transparent structures to refract light

Question 2

Functions of the sclera…

Answer 2

1) Maintains eye shape
2) Maintains intraocular pressure
3) Barrier to infection and trauma

Question 3

Functions of the cornea…

over the iris and lens

Answer 3

1) Transparency
2) Refraction –> Major refractive component of the eye
3) Barrier to infection and trauma

Question 4

Aqueous humour is formed by…

Answer 4

Active secretion from the ciliary body epithelium.

Question 5

The two drainage routes out of the eye for aqueous humour are…

Answer 5

1) Conventional Route –> 85% drains via the trabecular meshwork into the canal of Schlemn.
2) Uveoscleral Route –> 15% drains through the ciliary body and into the ciliary circulation.

Question 6

What is normal Intra-Ocular Pressure (IOP)?

Answer 6

10-21 mmHG

IOP normally changes throughout the day.

Question 7

Functions of the crystalline lens…

Answer 7

1) Transparent –> Absence of blood vessels
2) Fine focusing –> Age-related, metabolic, or congenital changes in the lens fibres lead to structural irregularity with resultant opacification (i.e. cataract formation)

Question 8

Functions of the vitreous humour…

Answer 8

1) Transparent –> collage type 2
2) Protects the ocular structures –> firm gel that is 80% of the globe volume
3) Passive “transport and removal” of metabolites

Question 9

What are hyalocytes?

Answer 9

Also known as vitreous cells.
Located in the peripheral part of the vitreous body.
Produce hyaluronic acid, collagen,and hyaluronan, glycosaminoglycan.

Question 10

Function of the retina…

Answer 10

1) Transparent

2) Converts light energy into nervous impulses (via photo-receptors)

Question 11

What is the macula?

Answer 11

Central vision area of the retina….

1) Lies lateral to optic disc.
2) Slightly darker than rest of retina due to yellow luteal pigment.
3) Has higher visual acuity than rest of retina.

Question 12

What is the fovea?

Answer 12

The centre of the macula that is rod free and has the highest visual acuity.

Question 13

“The red eye” (pain, redness, photophobia, discharge) indicates problem with…

Answer 13

Front of the eye.

Question 14

Painless loss of vision indicates problem with…

Answer 14

Back of the eye.

Question 15

Distortion of vision/central scotoma indicates problem with…

Answer 15

Macula.

Question 16

Flashes and floaters indicates a problem with…

Answer 16

Vitreous or retina.

Question 17

What is emmetropia?

Answer 17

There is no refractive error and light rays from infinity are brought to focus on the retina.

Question 18

What is myopia?

Answer 18

A term for short-sighted vision where light rays from infinity are brought to focus just in front of the retina.

1) Eye is too long.
2) Or converging power of lens is too strong.

Question 19

What is hypermetropia?

Answer 19

A term for long-sighted vision where light rays from infinity are brought to focus just behind the retina.

1) Eye is too small.
2) Or converging power of the lens is too weak.

Question 20

What is astigmatism?

Answer 20

The cornea is NOT spherical.

Question 21

What is the accommodation-convergence reflex?

Answer 21

A physiological mechanism that allows close objects to be focused on the retina.

Non-accommodating state –> ciliary muscle is relaxed, lens suspensory ligament remain taunt.

Accommodating state –> contraction of ciliary muscle, lens suspensory ligament becomes lax, causing naturally elastic lens to assume more globular (convex) shape.

Question 22

What is presbyopia?

Answer 22

Long-sightedness caused by loss of lens elasticity (i.e. poor accommodation response). Typically occurs over age of 45 and can be corrected by a weak converging (convex) lens.