Introduction to Ophthalmology

Question 1

What is the cornea?

Answer 1

transparent front ‘window’ of the eye - major refractive surface

Question 2

What is the sclera?

Answer 2

thick outer coat of the eye - normally white and opaque

Question 3

What is the limbus?

Answer 3

Junction between the cornea and sclera

Question 4

What is the conjunctiva?

Answer 4

The thin, mostly transparent, vascular mucous membrane covering the inner aspect of the eyelids (palpebral conjunctiva) and sclera (bulbar conjunctiva)

Question 5

What is the anterior chamber?

Answer 5

The space that lies between the cornea anteriorly and the iris posteriorly. The chamber contains a watery fluid called aqueous humour

Question 6

What is the iris?

Answer 6

The coloured part of the eye that screens out light, primarily via the pigment epithelium, which lines its posterior surface

Question 7

What is the pupil?

Answer 7

The circular opening in the centre of the iris that adjusts the amount of light entering the eye.

Question 8

What is the ciliary body?

Answer 8

The structure that produces aqueous humour.

Question 9

What is the vitreous cavity?

Answer 9

The relatively large space (4.5cc) behind the lens that extends to the retina. The cavity is filled with a transparent jelly-like material called vitreous humour

Question 10

What is the optic disc?

Answer 10

The portion of the optic nerve visible within the eye. It is composed of axons whose cell bodies are located in the ganglion cell layer of the retina

Question 11

What is the retina?

Answer 11

The neural tissue lining the vitreous cavity posteriorly.

Question 12

What is the macula?

Answer 12

The area of the retina at the posterior pole of the eye responsible for fine, central vision. The oval depression in the centre of the macula is called the fovea.

Question 13

What is the choroid?

Answer 13

The vascular, pigmented tissue layer between the sclera and the retina. The choroid provides the blood supply for the outer retinal layers

Question 14

What does the outer layer of the eye consist of?

Answer 14

Cornea (continous with the sclera)

Question 15

What is the next deeper layer after the outer layer?

Answer 15

Choroid

Question 16

What lies anterior to the lens?

Answer 16

Iris and pupil

Question 17

Where do the retinal blood vessels originate from?

Answer 17

Centre of the optic disc
larger vessels: veins

pale, thinner vessels: arteries

Question 18

How should the optic disc be described?

Answer 18

Colour
contour
cup

Question 19

What is the normal cup disc ratio?

Answer 19

Less than 0.4

Question 20

Describe the course of the visual pathways?

Answer 20

Nasal side of the eye sees the temporal field and temporal side of eye sees nasal field

Information passes back to optic chasm - 50% of fibres cross from the inside of the eyes (temporal fields)

Fibres pass backwards towards lateral geniculate ganglion - then through the optic radiation to occipital cortex

Question 21

Describe how the pupil light reflex occurs?

Answer 21

Nerve fibres from retinal ganglion cells bypass the lateral geniculate ganglion and synapse in the pretactile nucleus

Signal –> Edinger-Westphal nucleus

Some fibres cross to the opposite side (contralateral response)

Fibres reach inferior division of 3rd nerve (stimulates pupils)

Question 22

What does perception of colour depend on?

Answer 22

Cone cells - different wavelengths according to the peaks of their spectral sensitivities:
Short (S) - blue
medius (m) - green
long (l) - red

Question 23

How is perception of colour achieved?

Answer 23

Complex process - output of cone cells in retina

finalised in the visual cortex and associative areas of the brain

Question 24

How is colour vision assessed?

Answer 24

Ishihara plates

Question 25

Describe the presentation o conjunctivitis

Answer 25

Not painful | Red borders of sclera - originates from edges of eye to centrally

Question 26

Presentation of herpes simplex keratitis

Answer 26

Cornea and limbus - generally painful and very red, especially around the cornea Minimal discharge, but substantial watering and blurring Staining with fluorescein dye - dendrite deposits on the cornea

Question 27

Presentation of iridocyclitis

Answer 27

Inflammation of the iris (coloured part of the eye and of the ciliary body Marked redness that is uniform across the eye - pupil is oval and the iris is ballooned forward

Question 28

Giant cell arteritis presentation?

Answer 28

Pale and swollen optic disc

Question 29

What is drusen?

Answer 29

small focal thickenings of Bruch's membrane (layer on which retinal pigmented epithelium lies)

Question 30

what are exudates?

Answer 30

lipoprotein material that has been deposited on the retina due to fluid that has leaked from the vasculature

Question 31

What are cotton wool spots?

Answer 31

poorly defined micro infarcts of nerve fibre layer of the retina

Question 32

What is neovascularisation?

Answer 32

very fine, irregularly blanching blood vessels form on the optic disc or retina seen in PDR

Question 33

What is the presentation of central retinal vein occlusion?

Answer 33

yellow surface with red splashed across it poorly defined swollen, optic disc - cotton wool spots, flame shaped haemorrhages and dilated tortuous veins Cheese and tomato pizza

Question 34

What is AV nipping?

Answer 34

Where arteries cross veins - arterial walls thicken which narrows the vein and causes some degree of occlusion