Ophthalmoscopy

Question 1

what is the cornea, its function and structure?

Answer 1

highly specialised tissue
main function is refraction and transmission of light
structure is an outer epithelium, and avascular hypocellular stroma and replicating endothelial monolayer
the endothelium pumps water out of the stroma into the anterior chamber; failure leads to loss of transparency

Question 2

what is the uvea composed of?

Answer 2

choroid
ciliary body
iris

Question 3

where is the choroid and what is its function?

Answer 3

consists of blood vessels, connective tissue and pigment cells and is between the retina and sclera
it provides oxygen and nutrition to the outer retinal layers

Question 4

what is Bruch’s membrane?

Answer 4

formed by the basement membrane of the uvea along with the retinal pigment epithelium

Question 5

what is the function of Bruch’s membrane?

Answer 5

acts as a diffusion barrier between choroid and retina

Question 6

what is the ciliary body?

Answer 6

made up of the ciliary muscles and ciliary processes
the 3 sets of ciliary muscles are the longitudinal, radial and circular muscles, and they are responsible for altering the shape of the lens in accommodation, they attach to the lens by the zonules of Zinn

Question 7

what is the iris?

Answer 7

lies on the anterior surface of the lens, it is a thin diaphragm made up of the sphincter and dilator papillae which constrict and dilate the central aperture (the pupil)

Question 8

what is the retina?

Answer 8

composed of several layers, divided into the optic component mad e up of the neural light receptive layer, and pigment layer and the non visual component, which is the anterior continuation of the pigment layer, spanning the ciliary body and posterior surface of the iris

Question 9

what do photoreceptors do?

Answer 9

convert light energy into electrical, transmit it to the ganglion cells via connector neurones

Question 10

where do ganglion cells go?

Answer 10

gangion cell axons pass across the surface of the retina and leave the eye at the optic disc

Question 11

where are cone receptors concentrated?

Answer 11

macula for high quality colour vision

Question 12

name the extra-occular muscles?

Answer 12

• superior oblique
• levator palpebrae superioris
• superior rectus
• lateral rectus
• inferior oblique
• inferior rectus
• medial rectus

Question 13

what does the superior oblique do?

Answer 13

depress and abducts, conjugation with the inferior rectus to move the eyeball inferiorly, receives innervation from CNIV

Question 14

what does the levator palpebrae superioris do?

Answer 14

elevates the superior eyelid, deep layer is innervated by sympathetic fibres

Question 15

what does the superior rectus do?

Answer 15

elevated and adducts, innerated by CN III

Question 16

what does the lateral rectus do?

Answer 16

adducts eyeball CN VI

Question 17

what does the inferior oblique do?

Answer 17

elevates and abducts the eye, works in conjugation with superior rectus to move the eyeball superiorly, innervated by CN III

Question 18

what does the inferior rectus do?

Answer 18

depresses and adducts, innervated by CNIII

Question 19

what does the medial rectus do?

Answer 19

adducts the eyeball, innervated by CN III

Question 20

what is accommodation?

Answer 20

the ability of the eye to maintain focus on an object regardless of the distant by increasing/decreasing the power of the lens

Question 21

describe the process of accommodation with near objects?

Answer 21

as the object comes closer the image would focus behind the retina.
to prevent this the ciliary muscles contract and the zonules of zinn and allowing the lens to return to a rounder more convex shape and focusing the image on the retina

Question 22

describe the process of accommodation with far objects?

Answer 22

as the object goes further the image would focus in front of the retina
to prevent this the ciliary muscles relax and place the zonulas of zinn under tension and pulling the lens into a flatter more concave shape and focussing the image on the retina

Question 23

what is myopia?

Answer 23

the eye is too long and the retina is not in focus without correction
concave (minus) lenses bring the retina into focus

Question 24

what is hypermetropia?

Answer 24

the eye is too short and the retina is not in focus without correction
convex lenses bring the retina into focus

Question 25

what is the red reflex and what is the pathological significance of it being absent?

Answer 25

red-orange reflection observed at the centre of the pupil elicited with the opthalmoscope the absence can suggest severe cataracts or retinoblastoma which show leukocoria (white discoloration of the eye)

Question 26

what is the fundus?

Answer 26

the interior surface of the eye, opposite the lens, it includes the macula, the optic disc, fovea and posterior pole

Question 27

what does direct opthalmoscopy involve?

Answer 27

visualisation of the structures of the funds with an ophthalmoscope

Question 28

describe the process of examining with direct ophthalmoscope?

Answer 28

- hold in right hand - use right eye to examine patients right eye - place top of ophthalmoscope against brow and place free hand against patient forehead - elicit the red reflex whilst at arms length - move In close as possible and adjust focus - identify optic disc and 3cs - examine vascular supply - repeat with other eye

Question 29

what is the red reflex and what does its absence suggest?

Answer 29

- the red orange reflection at the centre of the pupil elicited with opthalmascope - when absent can suggest severe cataracts or retinoblastoma (show leukocoria-white discolouration of the eye)

Question 30

what are the considerations when examining the funds?

Answer 30

- optic disc-cup, colour, contour - macula and fovea - retinal vessels - abnormalities (haemorrhages or exudates) - colour-red-purple - clinical context

Question 31

what are the 3 Cs?

Answer 31

- cup (cup-disc ratio <0.5) - colour (yellow/orange-pink) - contour (margins should be sharp)

Question 32

what is papilloedema?

Answer 32

swelling of the first part of the optic nerve due to increased intracranial pressure

Question 33

what can cause raised intracranial pressure?

Answer 33

cerebral oedema malignant hypertension optic nerve tumours

Question 34

what is glaucoma?

Answer 34

increased pressure in the eye which can lead to vision loss it can be primary or secondary -primary acute (angle closure), chronic (open angle) glaucoma -secondary can present with increased cup:disc ratio

Question 35

what is optic disc atrophy?

Answer 35

degeneration of the optic nerve, visible as pallor of the optic disc

Question 36

what is the macula?

Answer 36

central point of vision dark spot on retina surrounding greatest concentration of cones no vessels may be slightly pigmented abnormalities-fluid, haemorrhage, exudates drusen (small round yellow deposits deep in retinal layer)

Question 37

what is the fovea?

Answer 37

small depression in retina containing largest amount of cones therefore it is the point of greatest acuity

Question 38

what abnormalities may be seen on the fovea?

Answer 38

changes in colour and contour abnormalities such as cherry red spots haemorrhages, drusen, laser scars, exudates, oedema

Question 39

what abnormalities are looked for in the retinal vessels?

Answer 39

``` calibre -excessive narrowing of arteries as in arteriosclerosis -tortuous and dilated veins AV nipping -hypertension -arteriosclerosis abnormality -AV malformation -new vessel formation -sheathing ```

Question 40

what are the characteristics of diabetic retinopathy?

Answer 40

- early disease - dot and blot haemorrhages and micro aneurysms - as capillary non perfusion increases the signs of retinal ischaemia become visible including cotton wool spots, venous dilatation and angiogenesis

Question 41

what are cotton wool spots?

Answer 41

superficial retinal deposits which occur around areas of infarcted retina

Question 42

what are hard exudates?

Answer 42

well defined yellow/white deposits in the retina | caused by lipoproteins leaking from abnormally permeable blood vessels

Question 43

what are micro aneurysms?

Answer 43

first lesions appearing in diabetic retinopathy physical dilations of the smallest intra-retinal blood vessels these lesions appear as small circular red dots having distinct margins and are no larger than a blood vessel width at disk margin

Question 44

what are retinal haemorrhages?

Answer 44

represent actual bleeding within the retina as a result of MAs or when capillaries become leaky enough to let blood out of vessels can be a variety of shape (dot, blot, flame shaped) usually larger than MAs with unevenly indistinct edges and causes

Question 45

what are the other causes of retinal haemorrhages?

Answer 45

``` hypertension trauma retinal breaks subarachnoid haemorrhage retinal vein occlusion sickle cell disease anticoagulants age related macular disease ```

Question 46

what do proliferative lesions suggest?

Answer 46

advanced sign of diabetic retinopathy require treatment aim to reduce retinas need for oxygen and nutrients

Question 47

what is hypertensive retinopathy?

Answer 47

chronic hypertension leads to diffuse or segmental narrowing of arterioles as the vessel walls thicken thickened arterioles cause compression of veins accelerated haemorrhage signs include flame haemorrhage, hard exudates and papilloedma

Question 48

what is the grading for hypertensive retinopathy?

Answer 48

grade 1 - arteriolar narrowing grade 2 - arterio-venous nipping grade 3-exudates, haemorrhages, cotton wool spots grade 4 - papilloedema

Question 49

describe dot and blot haemorrhages of the retina?

Answer 49

lies deep in retina reflecting leakage of capillaries or venues common in diabetic retinopathy

Question 50

describe flame haemorrhages?

Answer 50

these lie within superficial nerve fibre layer, they reflect ischaemic leakage from arterioles or veins under high pressure