Class 1 And 2

Question 1

What is aqueous humor?

Answer 1

A clear alkaline fluid that fills the anterior and posterior chambers of the eye.

Question 2

How is aqueous humor formed?

Answer 2

It is formed by ciliary processes at a rate of 2-3 uL/min, continuously formed and reabsorbed.

Question 3

What is the mechanism of active secretion in aqueous humor formation?

Answer 3

Na*-K-ATPase pumps Na followed by passive diffusion of Cl and HCO3, formed by Carbonic anhydrase.

Question 4

What causes osmosis of water in aqueous humor formation?

Answer 4

Osmosis is caused by Na, Cl-, and HCO3.

Question 5

What substances are transported in the formation of aqueous humor?

Answer 5

Glucose, amino acids, and ascorbic acids are transported by diffusion or active transport.

Question 6

How does the composition of aqueous humor differ from plasma?

Answer 6

Aqueous humor has less glucose and protein due to the presence of the blood-aqueous barrier.

Question 7

What is the outflow pathway of aqueous humor?

Answer 7

Aqueous humor flows from the posterior chamber through the pupil to the anterior chamber, then to the canal of Schlemm and episcleral vein.

Question 8

What are the functions of aqueous humor?

Answer 8

1) Supplies nutrients and O2 to the avascular cornea and lens. 2) Drains metabolites. 3) Acts as one of the optical media of the eye. 4) Maintains intraocular pressure.

Question 9

What is the vitreous humor?

Answer 9

A transparent gelatinous mass located between the lens and retina.

Question 10

What is the composition of the vitreous humor?

Answer 10

It contains albumin and hyaluronic acid, which is responsible for its high viscosity.

Question 11

What are the functions of the vitreous humor?

Answer 11

It supports the retina and supplies it with glucose.

Question 12

How do substances behave in the vitreous humor?

Answer 12

Substances can diffuse slowly, but there is little flow of fluid.

Question 13

What is intraocular pressure (IOP)?

Answer 13

The relation between eyeball volume and ocular contents, primarily dependent on aqueous humor.

Question 14

What is the normal value for intraocular pressure?

Answer 14

12 - 20 mmHg.

Question 15

When is intraocular pressure highest and lowest?

Answer 15

Highest in the morning and lowest in the evening.

Question 16

How is intraocular pressure maintained?

Answer 16

It is maintained constant as the rate of drainage equals the rate of formation.

Question 17

What regulates intraocular pressure?

Answer 17

1. Variation in resistance to outflow from the anterior chamber into the canal of Schlemm.
2. Pupil diameter changes (e.g., mydriasis).

Question 18

What happens during pupil dilatation (mydriasis)?

Answer 18

It closes the angle, leading to an increase in intraocular pressure.

Question 19

What are the functions of intraocular pressure?

Answer 19

1. Maintains the spheroid shape of the eye.
2. Supports normal focusing mechanisms.

Question 20

What is TIOP in relation to glaucoma?

Answer 20

TIOP refers to the tension in intraocular pressure, which is a factor in glaucoma.

Question 21

What happens to the lens during accommodation for near vision?

Answer 21

The suspensory ligaments relax, allowing the lens to become more spherical and increase its power.

Question 22

What is the definition of glaucoma?

Answer 22

Intraocular pressure (IOP) greater than 21 mmHg.

May occur with normal range of IOP due to changes in the optic nerve.

Question 23

What are the types of glaucoma?

Answer 23

1. Open angle glaucoma
2. Closed (narrow) angle glaucoma

Question 24

What causes open angle glaucoma?

Answer 24

Resistance to outflow.

Question 25

What causes closed angle glaucoma?

Answer 25

Forward movement of the iris via trabecular spaces into the canal of Schlemm, leading to obstruction of drainage.

Question 26

What are the results of glaucoma?

Answer 26

1. Disturbance of accommodation for near vision
2. Severe pain
3. Blindness due to pressure on the optic nerve and retinal artery.

Question 27

What is the treatment for open angle glaucoma?

Answer 27

1. Medical: Drugs such as carbonic anhydrase inhibitors (oral Diamox, topical dorzolamide), parasympathomimetic drugs (topical eserine & pilocarpine), and prostaglandin analogs.
2. Surgical/laser treatment to open spaces of Fontana.

Question 28

What is the treatment for closed angle glaucoma?

Answer 28

Surgical treatment after medical control of intraocular pressure.

Question 29

What are the causes of corneal transparency?

Answer 29

A. Non keratinized Surface epithelium.
B. Avascular - Obtains nutrients from aqueous humor and O2 from aqueous humor & atmosphere.
C. Supplied by Sensory: unmyelinated trigeminal nerve ending.
D. Specific structure - Collagen fibers of substantia propria, uniform in diameter, parallel, with regular spacing between fibrils.
E. Relative dehydration - Inner epithelium has Na-K pump that pumps Na out of cornea into aqueous fluid, causing osmosis of water out of cornea.

Corneal hydration causes cloudiness as water interferes with the arrangement of the fibers. Corneal opacities are treated with corneal grafts, which have a high success rate due to the cornea being avascular with no mediators for immune response.

Question 30

What is the importance of the cornea?

Answer 30

1. Acts as a fixed powerful convex lens (45D), providing 2/3 of the refractive power due to high degree of curvature and a refractive index of 1.38.
2. Regular curvature helps in the formation of sharp retinal images.
3. Protective function - Corneal reflex: Stimulus is touching the cornea of one eye by a foreign body, with afferent response from the ophthalmic division of trigeminal and efferent response from bilateral facial, resulting in blinking of both eyes. This tests the integrity of trigeminal and facial nerves.
4. Absorbs ultraviolet rays.

Corneal reflex is a superficial reflex.