Ocular Therapeutics

Question 1

What is the ocular anatomy and physiology?

Answer 1

1. Bony socket containing eye
2. Formed from several few bones:
   Protect delicate eye
   Mounting point for six striated muscles of the eye that control ocular movement

Question 2

What are internal eye structures? SLCICRO

Answer 2

Sclera: Tough outer protective coat

Lens: Transparent bioconvex structure, suspended by lens

Iris: Regulates light entering eye attached to ciliary body

Choroid: maintains the eye blood supply

Retina: inner layer containing visual photoreceptors (rods and cones)

Question 3

Where are tears produced in the eye and what are their purposes

Answer 3

Lachrymal gland

For lubricant, metabolic and optical purposes

Question 4

What are the layers of the pre corneal film

Answer 4

Lipid- made of sterol esters, phospholipids, triacylglucerol: important to reduce evaporation rate

Aqueous: inorganic salts, glucose, urea, immunoglobulins

Mucus

Question 5

What are the functions of the tear film

Answer 5

1. Helps prevent the cornea layer from drying
2. Provides oxygen and nutrients to the cornea
3. Fights off infection
4. Helps keep it smooth and clean

Question 6

What are the pH of normal tear films and give situations when it changes pH

Answer 6

1. pH of normal tear films are around 7.7-7.9 pH
2. More acidic for contact lense wearers
3. More alkaline for those with eye diseases such as: ocular rosacea, lacrimal stenosis, dry eye: varies between pH 5.2 to 9.3
4. Dependent on buffer capacity of bicarbonate ions, proteins and mucins

Question 7

What is the maximum volume that can be incorporated into pre corneal film without any destabilisation

Answer 7

25-30 microlitres

Question 8

Why is blinking important

Answer 8

Helps to reform the tear film layer

Can block foreign objects from entering into the eye

Allows drainage of tears in lacrimal drainage apparatus

Question 9

How does light enter the cornea

Answer 9

It is refracted at the angle of incidence

Question 10

What is the aqueous humour

Answer 10

Transparent viscous fluids located in the anterior chamber of the eye: composed of 98% water, amino acids

Question 11

What are the functions of aqueous humour

Answer 11

1. Maintains intra-ocular pressure and inflates the globe of the eye
2. Provides nutrition for avascular ocular tissues: posterior cornea, trabecular meshwork, lens and anterior vitreous
3. Serves to transport ascorbate in the anterior segment act as an antioxidant agent
4. Potential for immune response to defend against pathogens (immunoglobulins)
5. LIGHT REFRACTION

Question 12

What is the purpose of the lens

Answer 12

1. Together with the cornea, helps to refract light to focus on retina
2. Lens is elastic and help changes shape
3. Fatter to focus on close objects
4. Thinner to focus on further objects
5. Lens consists of: lens capsule, lens epithelium, lens fibers

Question 13

What is the anatomy of the vitreous humour and its function

Answer 13

1. Anatomy: clear gel that fills the space between the lens and retina
2. Functions:
   Maintains normal anatomic expansion of globe

Impedes diffusion between retina and anterior segment of eye

Small water soluble substances in retina may diffuse into the vitreous humour and across blood brain barrier

Acts as a reservoir for metabolic waste products

Question 14

Where are photoreceptors located and their role

Answer 14

Located on retinal surface

Act in low light levels and do not provide colour and have little spatial resolution

Operate at higher light levels, perceive colour, allow good spatial resolution

Question 15

What are the different kinds of photoreceptors

Answer 15

Cones

Rods

Question 16

How do you activate the optic nerve and explain the sequence of this

Answer 16

1. Rod cone activation causes action potential generation in optic nerve
2. Must pass into skull via optic canal to meet at optic chiasma
3. Nerves project to visual cortex in occipital lobes