Opthalmology Flashcards
(180 cards)
Types of strabismus
Paralytic: CN3, CN4 or CN6
Convergent = esotropia, most common in children
Divergent = exotropia, in older children, often intermittent
Complication of esotropic squint
Brain suppresses deviated image and pathway may not develop
Diagnosis of strabismus - 2
Corneal reflection - should be symmetrical
Cover test - squinting eye will move to take up fixation when normal eye is covered
Management of strabismus - 3
Optical - determine refractory state with cyclopentolate, and check for any abnormalities. Give glasses to correct refractory error
Orthoptic - patch good eye
Operation - on rectus muscles to align, or botulinum toxin
Appearance of CN3 palsy and causes
CN3 - cavernous sinus lesion, diabetes, posterior communicating artery aneurysm
Complete ptosis and down and out, fixed and dilated (unless diabetes or htn when pupil is spared)
Appearance of CN4 palsy and causes
Diplopia, head tilted - ocular torticolis
Look up in adduction and cannot look down and in
Caused by trauma, diabetes or tumour
Appearance of CN6 palsy and causes
Diplopia
Medically deviated and cannot move laterally
Caused by tumour increasing ICP and compressing nerve on edge of petrous temporal bone, trauma to base of skull, diabetes
3 requirements for good outcomes with strabismus
<7yo
Conscientious and disciplined treatment
Optimal glasses
Pupil reflex pathway
Optic nerve afferent - oculomotor nerve efferent
SNS pupil dilatation via ciliary nerves
Cause of afferent defects - 3
Optic neuritis
Optic atrophy
Retinal disease
Causes of fixed dilated pupil - 5
CN3 palsy Trauma Myriatics Acute glaucoma Coning
Condition causing delayed response to light
Tonic (Adie) pupil - lack of parasympathetic innervation. Initially uni then bilateral
What is Horner’s syndrome
Disrupted sympathetic fibres
Miotic pupil with no dilation in the dark
Partial ptosis
Anhydrosis
Causes of Horner’s syndrome - 6
Posterior inferior cerebellar artery occlusion MS Pancoast’s tumour Hypothalamus lesion Mediastinal mass Aortic aneurysm
Cause of bilateral miosis and other features
Argyll Robertson pupil - neurosyphilis and diabetes
Bilateral miosis, poor pupil dilatation, pupil irregularity
2 features that determine refraction in eye
Distance between cornea and retina
Curvature of lens and cornea
Pathophysiology of myopia and treatment
Short sighted - eyeball long, so closer to eye = focus further back and on retina
Concave glasses
Pathophysiology of hypermetropia and treatment
Long sighted - eyeball short so distant objects focus behind retina
Ciliary muscles contract to make lens more convex, which makes tiredness and convergent squint
Treat with convex glasses
What is astigmatism
Irrregularly shaped cornea
What is the age related sight change
Presbyopia - lens stiffens so ciliary muscles cannot reduce tension in it and make it more convex
When to get help in sudden loss of vision - 3
Retinal artery occlusion <6h
Visual loss <6h unknown cause
GCA
5 questions in sudden vision loss
HELLP
Headache - ESR for GCA
Eye movements hurt - optic neuritis
Like a curtain - amaurosis fugax precedes vision loss from GCA/emboli
Lights/flashes - detached retina
Poorly controlled DM - vitreous haemorrhage
Optic neuropathies - what and 4 signs
Damage to optic nerve:
Monocular vision loss with central scotoma
Afferent pupillary defect
Dyschromatopsia
Papillitis then optic atrophy on fundoscope (pale disc)
2 causes of optic neuropathy
GCA
Anterior ischaemic optic neuropathy - inflammation or atheroma block posterior vascular supply