Ocular anatomy

Question 1

What is the orbit of the eye, and what is its purpose

Answer 1

• The bony socket containing the eye
• Protects the eye and provides a mounting point for six striatal muscles to control ocular movement

Question 2

What is intorsion and extorsion in terms of vision

Answer 2

• Internal rotation (intorsion)
  rotating the upper part of the pupil $medially
  (or toward the nose).
• External rotation (extorsion) rotating the upper part of the pupil laterally (or toward the temple).

Question 3

Eye tunics: IMAGE INCLOSE

Answer 3

Question 4

image incloze

Answer 4

Question 5

Which gland produces tears?

Answer 5

Lacrimal gland

Question 6

Three types of tears?

Answer 6

• Basal tears - to maintain a tear film on the corneal surface for optical, metabolic and lubricant purposes
• Reflex tears induced in response to light, cold, irritation
• Emotional

Question 7

What is the precorneal tear film/ ‘three layers theory’, whats the function of it?

Answer 7

• The precorneal tear film consists of a superficial lipid layer, a central aqueous layer and an inner mucus
  layer.
• pH of 7.4
• Prevents corneal drying, transports oxygen and nutrients to the cornea, protect against infection

Question 8

What is the pH of the tear film? What is it buffered by

Answer 8

• pH is 7.3-7.7 (7.4)
• Buffered by bicarbonate ions, proteins and mucins

Question 9

The importance of blinking

Answer 9

• Blinking is a dense mechanism
• It also helps reform eyes tear film. E.g. when eye drops are administered we blink rapidly to reduce tear volume

Question 10

Normal human tear volume

Answer 10

7-9 micro litres

Question 11

Blink rate per minute

Answer 11

15-20
So 5-7s

Question 12

Function of the conjuctiva of the eye

Answer 12

• The conjunctiva of the eye provides protection and lubrication of the eye by the production of mucus and tears
• Prevents microbial entrance into the eye and plays a role in immune surveillance

Question 13

Which layers of the cornea are lipophilic and which are hydrophilic

Answer 13

Question 14

Function of the cornea

Answer 14

• Passage of light
• Refracts light
• Protection

Question 15

What is the aqueous humour

Answer 15

The aqueous humour is a transparent viscous fluid
located in the anterior chamber of the eye

Question 16

Functions of the aqueous humour

Answer 16

• It maintains the intraocular pressure and inflates the globe of the eye
• It provides nutrition for the avascular ocular tissues (posterior cornea
  and crystalline lens);
• May serve to transport ascorbate in the anterior segment to act as an
  antioxidant agent;
• Potential immune response to defend against pathogens
  (immunoglobulins);
• Light refraction

Question 17

What is a crystalline lens

Answer 17

• Avascular, transparent, biconvex structure
• Its focuses light onto the retina

Question 18

What is the vitreous humour

Answer 18

• The vitreous humour is the clear gel that fills
  the space between the lens and the retina
• helps to maintain the normal shape of the globe;
• impedes the diffusion of substances between the
  retina and the anterior segment of the eye;
• small water-soluble substances in the retina may
  diffuse into the vitreous across the blood-retina barrier;
• acts as a reservoir of substances such as oxygen,
  glucose and ascorbic acid;
• acts as a reservoir for metabolic waste products.

Question 19

What are rods and cones

Answer 19

• Rods are activated by low light (night vision) and provide no colour recognition
• Cones are activated by high intensity light, colour and visual sharpness

Question 20

What is colour blindness?

Answer 20

• Inherited genetic trait
• Occurs to a deficient cone cell
• Linked to X rcessive
• The Ishihara test is used for colour blindness detection.