Pathology Of The Orbit

Front 1

Major Causes of Blindness

Back 1

Front 2

Age related macular degeneration
STATS

Back 2

›30% of Australians will develop AMD over the age of 70
›10% of AMD convert to “wet” AMD requiring 4-12 weekly intravitreal injections of anti VEGF agents
›Results in loss of central vision
›Unable to read or drive

Front 3

Glaucoma

Back 3

›Age 50yrs 1% Australians are affected
›Age 80 yrs 10% Australians are affected
›50% of Australians who have glaucoma currently Do Not Know they have the condition

Front 4

Cataract

Back 4

›18% of Australians have a cataract requiring surgical removal NOW based on visual acuity and symptoms
›If you live to 100 yrs everyone will develop a cataract

Front 5

Diabetes

Back 5

›1.7 million Australians have diabetes (≈ 8% of population)
›Diabetic retinopathy
-microvascular complication of diabetes,
-affects one-third of people with diabetes
-threatens vision in 10 per cent

COMMONEST cause of blindness in the working age 20-65

Front 6

Acute Ocular conditions

Back 6

Front 7

Visual Acuity

Back 7

A measure of the resolving power of the eye and refers to the spatial limit of visual discrimination

Front 8

Minimum resolvable (ordinary visual acuity)

Back 8

›Visual acuity as measured clinically also called:
-minimum resolvable or minimum separable.
›Measure of the resolving power of the eye
›A spatial discrimination function representing the smallest visual angle at which two separate objects can be discriminated

Front 9

Snellen Chart

Back 9

the letters are stanerdised
- numerator is testing distance
- denominator is wat the patient sees
- young

Front 10

Extent of Visual Field

Back 10

Front 11

Visual field sensitivity and degree of
eccentricity

Back 11

Front 12

Visual field sensitivity and degree of eccentricity (Large) TESTING

Back 12

look at this with one eye and you can still ddx between the C & O

Front 13

Eccentricity further out

Back 13

but as you move out into the peripheral vision the detail decreases

Front 14

Nerve fibre layer arrangement in retina

Back 14

›Optic tract fibres rotate their topographic axis
-Superior retinal fibres rotate laterally
-Ventral fibres rotate medially
›Changes horizontal field defects to vertical field defects

fibres rotate 90 degrees and so then it becomes vertical fields now

Front 15

Iris Anatomy

Back 15

Front 16

Pupil Light reflex
PERLA

Back 16

›Direct reaction – constriction to light
›Consensual – constriction of other pupil with light to ipsilateral eye
›Accommodation reflex
-pupils constrict to near target (& dilate for further distances)
›PERLA
-Pupils Equal React Light (direct & consensual) and Accommodation

Front 17

Neural connections pupil light reflex

Back 17

Front 18

Relative afferent pupillary defect (RAPD)

Back 18

›normal consensual response when illumination of normal side
›diminished pupillary constriction on direct illumination abnormal side
›related to lesions within the anterior visual pathways (retina, optic nerve chiasm and optic tract)
›almost always present in unilateral or asymmetric bilateral optic nerve disease.

Front 19

Sympathetic neural supply to eye

Back 19

pupil constriction
parasympathetic innervation
sphincter pupillae

pupil dilatation
sympathetic innervation
dilator pupillae

Front 20

Macular Landmarks

Back 20

Front 21

Normal Macular appearance OCT & Histology

Back 21

Front 22

Central and peripheral retinal connections

Back 22

1 to 1 in the central retina
100-200 to 3-4 in the periphery

Front 23

Normal Colour Vision

Back 23

much more red and green
less blue

Front 24

Age related macular degeneration
2 types

Back 24

›Two types:
-Dry (non-neovascular) 90% of ARMD cases = slow, progressive decline in central visual function (ATROPHY of cells)
-Wet (neovascular) 10% = rapid, more substantial loss of vision (HEALING response in the centre of the fovea, leading to scars and BV leading to viision loss)

Tx: Inject Ant-VGEF 4/year $2500 each injection

Front 25

Back 25

Dry Age-related macular degeneration

Front 26

Back 26

Wet ARMD Choroidal neovascularisation
leakage
scar

Front 27

Retinal circulation

Back 27

›two sources of blood supply to the mammalian retina:
-central retinal artery
-choroidal blood vessels.
›choroid circulation
-65-85% of blood flow
-vital for maintenance of outer retina (particularly photoreceptors)
›retinal circulation
-20-30% central retinal artery from the optic nerve head
-supply inner retinal layers.
-central retinal artery has 4 main branches in the human retina

Front 28

1. one cherry red spot; because the retina is thin thats the blood here only (but all the connections are loss so no vision)
2. embolism
3. anomylous vessel suppling the fovea from the post. cilliary aa., thus maintain central vision due to anatomically variation

Back 28

Retinal artery occlusion

Front 29

Giant cell arteritis

Back 29

Giant Cell arteritis
- ddx for opthalamic stroke
- inflammation of the blood vessel
- lots of the medium-large aa. are involved with the lumen is ruined
- pale retina without a cherry spot and and the optic nerve is affected so here the choriod and opthalmic aa. are both affected

Front 30

Red Free photo showing nerve fibre defects

Back 30

Note the nerve fibre layer arrangement
and horizontal demarcation

commonly glaucoma

Front 31

Optic nerve structure

Back 31

have to turn 90 degrees in bundles

Front 32

Optic disc assessment

Back 32

›Vertically oval disc is normal.
›Rim width greatest inferior > superior > nasal
> temporal (ISNT rule)
- If not ? Glaucoma
›Concentric enlargement of cup - if increase over
time diagnostic

BV in the centre of the optic nerve
- due to the 90degree bends, the centre of the nerve is hollow anteriorly thus a divot in the cup

Front 33

Glaucomatous optic disc changes

Back 33

›Asymmetry of cups in both eyes > 0.2
›Focal loss of neuroretinal rim /notch / acquired pit
›Changes in vessels on optic disc: nasalisation, bayoneting, flyover vessels, focal narrowing of vessels, disc haemorrhage

Front 34

Glaucomatous visual field defects

Back 34

arching shape
- inferior defect will be seen as a superior visual defect