Ophthalmology basics Flashcards
Drug causes of eye pathology:
Steroids can cause cataract/affect glaucoma
Anticholinergics can cause blurred vision and angle closure glaucoma
Normal vision?
Snellen: 6/6 (UK)
20/20 (US)
Near: N6
Protanopes…
Lack red-sensitive cones
Deateranopes…
Lack green-sensitive cones
Tritanopes…
Lack blue-sensitive cones
Normal visual field?
60 degrees above and 75 degrees below fixation in each eye
Central visual field is 30 degrees from fixation
Blind spot is 15 degrees temporal to fixation
Nasal side 60 degrees to fixation
Temporal side 90 degrees to fixation
What does a lesion at the optic chasm cause?
Bilateral hemianopia
Lateral rectus action =
Abduction
Medial rectus action =
Adduction
Superior rectus action =
Elevation
Inferior rectus action =
Depression
Superior oblique action =
Intorsion
Inferior oblique action =
Extorsion
Outcome of CN III palsy?
Can abduct, elevate and slightly depress the eye
No other movements
What does the superior division of the oculomotor nerve (CN III) supply?
Superior rectus
Levator palpeerde superioris (elevates upper eyelid)
What does the inferior division of the oculomotor nerve (CN III) supply?
Medial rectus
Inferior rectus
Inferior oblique
Parasympathetic efferent to constrictor pupillae and the ciliary muscles for accommodation
Which cranial nerve innervates superior oblique?
CN IV - Trochlear
CN IV - Trochlear nerve innervation:
Superior oblique: actions = intorsion, depression and abduction
How does CN IV trochlear nerve palsy present?
Vertical or diagonal double vision
Deviation more obvious when head tilted to the side as superior oblique is a depressor and when the head is tilted it cannot depress
What cranial nerve innervates lateral rectus?
CN VI - Abducens
CN VI - Abducens innervation:
Lateral rectus: actions = abduction
Features of congenital esotropia/squint:
Affected eye unable to fixate and is inward looking
Cover unaffected and affected eye will fixate
Uncover unaffected eye and it will compensate by moving in
Difference between esotropia and exotropia?
Esotropia is inward looking whereas exotropia is outward looking
What can cause an abnormal red reflex?
Cataracts
Lens opacity
Media opacity
What does a child with a white reflex indicate?
Retinoblastoma
White reflex = leukochorea
Treatment for sub-conjunctival haemorrhage (above sclera)?
Topical lubricants
Treatment for bacterial conjunctivitis with discharge?
Topical abx
Chloremphenicol
What is conjunctival chemosis and how do you treat it?
Fluid under the conjunctiva associate with conjunctivitis
Topical abx
What can herpes simplex keratitis lead to?
Dendritic ulcer
Treatment for herpes simplex keratitis?
Topical antiviral ointments
Avoid steroids unless prescribed by an ophthalmologist
What can dry ocular surface lead to?
Punctate erosions
What can a contact lens problem lead to?
Corneal ulcer and hypopyon (pool of pus at base of cornea)
Eye emergency
Treatment for corneal ulcer?
Topical abx
Urgent ophthalmology referral
What is hypopyon?
A pool of pus at the base of the cornea
What can a mid-dilated pupil and hazy cornea lead to?
Acute glaucoma causing ischaemia of the iris and dilation of the pupil
Refer to an ophthalmologist
What is papilloedema?
Bilateral optic disc swelling with normal visual acuity
Haemorrhage of the optic disc is a classic feature of which condition?
Glaucoma
