Introduction to Ophthalmology

Question 1

How is transparency of the cornea maintained?

Answer 1

relative dehydration of the stroma is maintained by impermeable epithelial barrier and active pumping mechanisms of corneal endothelium. regular spacing of individual stromal collagen fibrils

Question 2

What is the sclera? Describe it.

Answer 2

Outer coat of the eye; opaque, mechanically tough. forms posterior 5/6 of the outer coat of the eye. consists of irregularly arranged collagen fibres

Question 3

How can you visually differentiate between the retinal arterioles and retinal veins?

Answer 3

retinal arterioles are thinner and lighter in colour than the veins

Question 4

What forms the aqueous humour and where is it located?

Answer 4

Active secretion by epithelium of the ciliary body in the anterior and posterior chambers; anterior is between the cornea and iris and posterior is between the iris and lens

Question 5

What are three functions of the sclera?

Answer 5

1. maintains the eye shape
2. maintains intraocular pressure
3. barrier to infection and trauma

Question 6

What are the two routes of drainage of the eye? What are the relative proportions of each?

Answer 6

1. Conventional route 85%: drains through the trabecular meshwork into the canal of Schlemm in the anterior chamber angle
2. Uvoscleral route 15%: drains through ciliary body and into ciliary circulation

Question 7

Where is the ciliary body located?

Answer 7

Behind the iris (continuous with it anteriorly, posteriorly continuous with choroid) and encircling the lens, forms part of the uveal tract; divides the posterior chamber from the vitreous

Question 8

Where is the trabecular meshwork located?

Answer 8

Anterior chamber drainage angle; in front of the iris, in angle between iris and cornea

Question 9

What is the range of normal intraocular pressure?

Answer 9

10-21mmHg

Question 10

What maintains the intraocular pressure?

Answer 10

dynamic balance between secretion and drainage of aqueous humour

Question 11

What is the general name of the condition in which there is high intraocular pressure?

Answer 11

Glaucoma

Question 12

What can glaucoma lead to if untreated?

Answer 12

Loss of visual field and eventual blindness

Question 13

What are 3 things that help ensure the lens is transparent?

Answer 13

1. orderly arrangement of the lens fibres
2. small difference in refractive index between the various components
3. absence of blood vessels

Question 14

What are 3 important roles of the vitreous humour?

Answer 14

1. transparent
2. protects the ocular structures
3. passive “transport and removal” of metabolites

Question 15

where is the vitreous humour located?

Answer 15

between lens and retina

Question 16

What are the two key structures present in the retina?

Answer 16

1. Rods/ photoreceptors: 120 million (monochromatic)

2. Cones: 6 million (colour and fine vision)

Question 17

What are the two key structures present in the retina?

Answer 17

1. Rods: 120 million (monochromatic)
2. Cones: 6 million (colour and fine vision)
   (both types of photoreceptors)

Question 18

What are 3 structures present in between the photoreceptors (rods and cones) and optic nerve fibres?

Answer 18

bipolar cells, synapse, ganglion cells

Question 19

What is the macula?

Answer 19

Central vision area of the retina

Question 20

Where is the macula located?

Answer 20

Lies lateral (temporal) to the optic disc: 3-3.5 mm temporal to temporal edge

Question 21

How can the macula be identified/ what does it look like?

Answer 21

Slightly darker than the rest of the retina due to yellow luteal pigment

Question 22

What is the centre of the macula and how is it different?

Answer 22

Fovea; rod free, highest visual acuity

Question 23

What part of the optic nerve fibres are demyelinated?

Answer 23

Nerve fibres are only demyelinated after leaving the eye

Question 24

What is the course of the optic nerve fibres? Include the 6 components

Answer 24

nasal fibres decussate at the optic chiasm (but not temporal fibres). optic nerves –> optic chiasm –> optic tracts –> lateral geniculate nuclei (thalamus)–> optic radiations –> visual cortex (occipital lobe)

Question 25

What is the optic disc?

Answer 25

entry of the optic nerve into the eye, approximately 1.5x1.5mm

Question 26

What are 7 general symptoms and 4 visual symptoms to ask about in an ophthalmological history?

Answer 26

``` General: 1. unilateral/ bilateral 2. onset 3. duration 4. pain 5. photophobia 6. redness 7. discharge Visual: 1. visual loss or distortion 2. field defect, where 3. flashers/floaters 4. diplopia - horizontal/vertical/binocular/monocular ```

Question 27

What is key (in addition to general and visual symptoms) that should be included in an ophthalmological history?

Answer 27

Past ocular history, including refractive (spectacles, contact lenses)

Question 28

Which part of the eye will a red eye be associated with?

Answer 28

Front of eye

Question 29

Which part of the eye will painless loss of vision be associated with?

Answer 29

Back of eye

Question 30

Which part of the eye will distortion of vision/central scotoma be associated with?

Answer 30

Macula

Question 31

Which part of the eye will flashes and floaters be associated with?

Answer 31

Vitreous or retina

Question 32

What are two classes of refractive error?

Answer 32

Emmetropia (no refractive error) and ametropia

Question 33

What are the 3 types of ametropia?

Answer 33

myopia, hypermetropia, astigmatism

Question 34

What is myopia?

Answer 34

Short sightedness; light rays brought to focus in front of the retina as the eye is too long OR the lens is too strong

Question 35

What is an example of when the lens is too strong, causing myopia, and what is this called?

Answer 35

Nuclear sclerotic cataract; index myopia

Question 36

What is hypermetropia?

Answer 36

Long-sightedness; light rays brought to a focus behind the retina as the eye is too short OR converging power of the cornea or lens is too weak

Question 37

What is astigmatism

Answer 37

the cornea is not spherical, i.e. is rugby ball shaped rather than football shaped

Question 38

What is accommodation?

Answer 38

Physiological mechanism that allows close objects to be focused on the retina

Question 39

What changes occur in the ciliary muscle to bring about accommodation?

Answer 39

in the non-accomodative state it is relaxed, allowing the suspensory ligaments to remain taught. in accommodation, the ciliary muscle contracts and suspensory ligaments become lax, causing the naturally elastic lens to assume a more globular (convex) shape

Question 40

What is presbyopia?

Answer 40

with age (usually over 45 years) the lens gradually hardens and is unable to accommodate (as in hypermetropia)

Question 41

How can presbyopia be corrected?

Answer 41

By a weak converging (plus) convex lens

Question 42

What are 5 things to examine in an eye exam

Answer 42

1. Visual acuity 2. visual fields 3. colour vision 4. pupil reflexes (light and accommodation), 5. Ophthalmoscopy (AFRO+ colour vision)

Question 43

Why shouldn't you ask a patient to look into the ophthalmoscope light?

Answer 43

They will accommodate so will constrict, and pupil will also constrict due to light

Question 44

How can you determine whether a patient is hypermetropic or myopic? 2 stages

Answer 44

1. ask them - do you struggle with seeing things up close e.g. reading, or far away e.g. television 2. look through their glasses; if things appear smaller--> myopic, if larger --> hypermetropic

Question 45

How should the ophthalmoscope be adjusted for hypermetropia and myopia?

Answer 45

1. Hypermetropia --> positive i.e. black numbers 2. Myopia --> negative i.e. red numbers (if thicker glasses, dial to a higher number)

Question 46

How should you decide which diaphragm level (Size of light beam) to use in ophthalmoscopy?

Answer 46

use small white beam for undilated pupil, large white beam for dilated pupil

Question 47

What are 4 things to look for/ comment on in opthalmoscopy?

Answer 47

colour of disc, cup:disc ratio, contour of disc, new vessels

Question 48

What is the difference between retinopathy and maculopathy?

Answer 48

haemorrhages and hard exudates etc. don't affect macula in retinopathy but do in maculopathy, which is sight threatening

Question 49

How can pre-proliferative retinopathy be identified?

Answer 49

more than five cotton wool spots

Question 50

What 3 venous changes can occur in pre-proliferative retinopathy?

Answer 50

thickening, tortuosity or beading

Question 51

How can proliferative retinopathy be classified?

Answer 51

NVE - new vessels everywhere | NVD - new vessels of disc