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PM3A copy (dvw) - S AL > (PM3A) Ocular Therapeutics > Flashcards

(PM3A) Ocular Therapeutics Flashcards

1
Q

What is the orbit?

A

Boney socket containing the eye

Formed from a number of fused bones

Mounting point for 6 striatal muscles

Protection of delicate eye

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2
Q

What are the internal eye structures?

A

(1) Sclera

(2) Lens

(3) Cilliary body

(4) Iris

(5) Choroid

(6) Retina

(7) Optic nerve

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3
Q

What is the sclera?

A

Internal eye structure

Tough

Outer protective coat

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4
Q

What is the lens?

A

Transparent biconvex structure

Suspended by lens zones

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5
Q

What is the cilliary body?

A

Internal eye structure

Provides attachment for lens zonules

Changes the focusing power of the lens

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6
Q

What is the iris?

A

Internal eye structure

Regulates light entering the eye

Attached by cilliary body

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7
Q

What is the choroid?

A

Internal eye structure

Maintains the eye’s blood supply

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8
Q

What is the retina?

A

Internal eye structure

Inner layer containing visual photoreceptors

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9
Q

What is the optic nerve?

A

Internal eye structure

Transmits images from photoreceptors to brain

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10
Q

What is the lachrymal gland?

A

Tear production

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11
Q

What is responsible in the eye for tear production?

A

Lachrymal gland

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12
Q

What are the different types of tear?

A

(1) Basic tears

(2) Reflex tears

(3) Emotional

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13
Q

What are basic tears?

A

To maintain tear film on the corneal surface

For optical, metabolic and lubricant purposes

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14
Q

What are reflex tears?

A

Response to chemical or mechanical irritation

e.g. cold/ light

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15
Q

What is the ‘three layers theory’?

A

Comprises the precorneal tear film

(1) Superficial lipid layer

(2) Central aqueous layer

(3) Inner mucous layer

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16
Q

What is the lipid layer in the eye?

A

Consists mainly of sterol esters, triacylglycerols and phospholipids, free sterols and free fatty acids

Spreads over the aqueous layer during eye opening

Reduce the evaporation rate

Maintain normal tear osmolarity

17
Q

What components comprise the aqueous layer in the eye?

A

Inorganic salts
Glucose
Urea
Retinol
Ascorbic acid
Various proteins
Lipocalins (tear-specific pre-albumins)
Immunoglobulins
Lysozyme
Lactoferrin
Glycoproteins

18
Q

What is the function of the tear film?

A

(1) Prevent cornea drying

(2) Transport of oxygen and nutrients to cornea

(3) Maintain clean + smooth cornea

(4) Protects against infection

19
Q

What is the pH of the tear film?

A

7.3 – 7.7 (mean value 7.4)

Can also vary between 5.2 and 9.3 depending on age + diseases

20
Q

How does the tear film buffer its pH?

A

Bicarbonate ions, proteins + mucins

21
Q

How does the pH of the tear film vary in contact lens wearers?

A

Tears are more acidic

Less efflux of carbon dioxide

22
Q

How does the pH vary in patients with dry eye?

A

More alkaline

23
Q

What is the normal human tear volume?

A

7-9mcL

24
Q

What is the maximum volume of fluid that can be held in the lower eyelid sack?

A

25-30mcL

25
Q

What volume of tears comprises the precorneal film?

A

3mcL

26
Q

Why do eye drops cause rapid reflex blinking?

A

Sudden increase in tear volume

27
Q

What is blinking?

A

Important defence mechanism of the eye

Reflex fast enough to prevent high speed foreign bodies entering the eye

Periodic reformation of the tear film

Activates a pumping mechanism for the drainage of tears

28
Q

Describe the lipophilicity of the epithelium of the cornea.

A

Lipophilic

29
Q

What is the function of the cornea?

A

(1) Passage of light

(2) Refraction of light

(3) Protection of the eye

30
Q

What is the aqueous humour?

A

Transparent viscous fluid

Located in the anterior chamber of the eye

98% water

31
Q

What is the function of aqueous humour?

A

(1) Maintains intraocular pressure + inflates globe of the eye

(2) Provides nutrition for the avascular ocular tissues

(3) Light refraction

(4) Potential immune response

32
Q

Describe the structure of the lens?

A

Elastic - can change shape

Thicker - close focus

Thinner - long sight

(1) Lens capsule
(2) Lens epithelium
(3) Lens fibres

33
Q

What is the vitreous humour?

A

Clear gel that fills the space between the lens + retina

34
Q

What is the function of vitreous humour?

A

(1) Maintain normal anatomic expansion of the globe

(2) Impedes the diffusion of substances between the retina and the anterior segment of the eye

(3) Reservoir of substances such as oxygen, glucose and ascorbic acid, which support the metabolism of adjacent structures

35
Q

Describe the composition of the vitreous humour.

A

99% water

Network of collagen fibrils

Large molecules of hyaluronic acid

36
Q

What are photoreceptors?

A

Located on retinal surface

Rods act in low light levels, no colour + poor spatial resolution

Cones operate at higher light levels, colour + good spatial resolution

37
Q

How is an action potential generated in the optic nerve?

A

(1) Rods/ cones (photoreceptors) activated

(2) Action potential generated

38
Q

How do action potentials enter the skull?

A

Via optic canal

Meet at optic chiasma

39
Q

What are stages in perception of sight?

A

(1) Light enters eye and activates photoreceptors (rods/ cones)

(2) Activation of photoreceptors generates an action potential in the optic nerve

(3) Action potential travels from optic nerve to optic canal to optic chiasma

(4) Nerves project to visual cortex in occipital lobes

PM3A copy (dvw) - S AL (28 decks)

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