Visual Field Defects, Diplopia, Optic Disc Swelling Flashcards
Most common presentation of visual field defects
Benign causes
Often asymptomatic - picked up by optometrists on routine screening
-1 eye can compensate for the other
Fatigue, eyebrows/glasses frames encroaching on upper field
Anatomy of the visual fields
-describe the pathway of the normal visual field
Nasal visual field => temporal retina Temporal visual field => nasal retina OPTIC NERVES Nasal retinal axons decussate at optic chaism OPTIC TRACTS -synapse at LGN in thalamus OPTIC RADIATIONS -parietal (inferior field) -temporal (superior field) Both synapse on primary visual cortex
Describe the types of visual defects you get
- lesions anterior to chiasm
- chiasmal lesions
- lesions posterior to chiasm
Anterior to chiasm - unilateral field defect
Chiasmal
- chiasm - bitemporal hemi
- perichiasmal - uninasal hemi
Posterior to chiasm - bilateral defect
The more congruous (similar in size and shape) the defect, the more posterior in the visual pathway lesion
Homonymous hemianopia
- possible location of lesion
- possible causes
Contralateral bilateral - therefore behind chiasm
- optic tract
- optic radiation
- visual cortex
Most common cause - stroke
-tumour
Quadrantopia
- upper location
- lower location
Bilateral - therefore behind chiasm
Upper homonymous quadrantopia - temporal radiations
Lower homonymous quadrantopia - parietal radiation
Bitemporal hemianopia
- location and progression
- most common cause
- pattern of pituitary tumour presentations
Chiasmal lesion
-start incomplete, asymmetrical => compression progresses => more symmetrical
Most common cause - neoplasm
- pituitary adenoma
- craniopharyngioma
- meningioma
Pituitary adenoma - bitemporal sup quadrantopia
-pituitary compresses lower part of chiasm first => more hemi as it progresses
Central visual field defect
- most common cause
- associated symptoms
Most common - AMD
Optic nerve disease - symmetrical, progressive, subacute
-toxic, nutritional, inherited
Associated colour vision defect - highest concentration of cones here
Reduced visual acuity - most focused vision here
Full assessment of visual field defects
- Hx
- key questions
- differentials
- investigations
Central vision loss more likely to be noticed by patient
Sudden or gradual loss? Pain? Floaters, flashers? Neurological review CV review Pituitary review
Retinal detachment Central retinal vein occlusion Optic nerve disease Lesion in visual pathway Glaucoma Stroke Pituitary tumour
Visual fields, acuity, colour vision
Eye movements, ptosis, pupil reflexes
Fundoscopy/slit lamp
Angle and pressure
Causes of diplopia
-pathophysiology
Visual axes of eyes are misaligned
Displacement of eyeball in socket from -trauma -tumours -infection - orbital cellulitis Cranial nerve palsy -isolated or secondary to DM/HTN, MG, Graves
Full assessment of diplopia
-key questions
Type - horizontal, vertical, diagonal images?
1 or 2 eyes?
Onset, duration, constant, intermittent?
Affecting near or far distance
Most noticeable when looking straight ahead or in a specific direction
Do you have to position your head awkwardly to see clearly? - new recent posturing suggests recent onset diplopia
In children
- lazy eye, patching?
- FHx of squints?
Medication, general health
Monocular diplopia
- how this is found on examination
- causes
Diplopia that persists when 1 eye is covered
- corneal abnormalities => changes shape of eye
- uncorrected refractive error
- cataracts
Binocular diplopia
- pathophysiology
- possible causes
- further investigations
Both eyes are misaligned
-eye motor cranial nerve issue?
Visual acuity Abnormal head posturing Eye movements Cover test Refractive error
CN3
- presentation
- possible causes
- function
Painful unilateral 3rd nerve palsy => post comm artery aneurysm
REQUIRES URGENT ASSESSMENT
Pupil sparing palsy => diabetic neuropathy/HTN
Other possible causes
- trauma
- neoplasm
- migraine
- GCA
Supplies SR, MR, IR, IO
-down and out +- dilated pupil
CN3 full assessment
- history
- investigations
Onset
Any pain?
General health
- DM, HTN?
- Any headache or other GCA symptoms
- Neurological review - MS?
BP, DM
Cranial nerve, eye mv, pupillary reflexes
DILATED PUPILS + 3PALSY => SURGICAL PALSY => URGENT
-compression of entire oculomotor nerve
Visual fields
Fundoscopy - fundus, optic nerve head
Temporal artery - tenderness, continuous throbbing
CN4
- presentation
- function
- causes of 4th nerve palsy
- management
SO loss => up and in
- head tilted away from lesion
- vertical diplopia
Unilateral/bilateral Congenital/acquired? DM, HTN MS GCA Tumour Aneurysm
Management
- children - treat amblyopia, refractive error
- prisms
- surgery
