Ophthalmology Exam Flashcards
What are the main components?
Visual acuity Visual fields Eye movements Pupillary reaction Fundoscopy
What is a layman’s term for visual acuity?
Eyesight
What is visual acuity?
Clarity of person’s vision
What is visual acuity measured using?
Snellan chart
What does testing visual acuity involve?
How well person can identify letters from standard distance
What is the standard distance of measurement for visual acuity?
6 m
In what order should visual acuity be measured?
Unaided
With pinhole
With glasses
Are the eyes tested together in visual acuity?
No, they’re tested separately
What should you remember when the patient is covering their eye?
Hand/paper should be at angle parallel and next to nose to block out all possible light
What are the instructions to the patient for visual acuity?
Stand 6 m away from chart Cover 1 eye Read letters aloud Don't squint to read them Encourage them to continue reading if they get stuck
What denotes a person’s visual acuity?
Row with smallest letters person can accurately read
If get half or more of row correct, that row is included
How is visual acuity recorded?
Eg: 6/18 +2
What is normal vision?
6/6
What reflects abnormal vision?
Denominator greater than 6
What can you do if the person cannot read the biggest letter on the chart?
Count number of fingers held in front of them (CF); if not >
See hand movements (HM); if not >
Perceive any light (LP); if not >
No light perception (NLP) > blind in that eye
What does a pinhole test for?
Refractive problems - usually with lens
What does it mean if a person’s acuity improves with a pinhole?
Probably refractive error
Is visual acuity a specific test?
No
What is the layman’s term for visual field?
Peripheral vision
What is a visual field?
Extent of peripheral vision while looking at target straight in front of them
What can cause defects in visual fields?
Lesions in any point in the visual pathway
Generally, what visual field does a lesion behind the optic chiasm affect?
Visual fields of both eyes
What visual field does a pathology of the eye or optic nerve affect?
Visual field of one eye
What does your visual field have to be to measure a patient’s?
Normal
Mirror exactly
How do you position yourself and the patient for a visual field test?
Sit in front of patient at same level
What do you instruct the patient to do when testing their visual field?
Close and cover one eye (you close your own eye directly opposite)
Look at your eye with open one
Place hand about halfway between the two of you
Wiggle fingers in from periphery from 8 points > like Union Jack
Ask patient to inform you when they can see movement
Compare this to when you see your hand yourself
Repeat for other eye
Is this way of testing the visual field specifically diagnostic?
No, it’s a screening test
If abnormality detected, more detailed mapping required
What is unilateral blindness?
Loss of visual field of one entire eye
Where is the lesion in unilateral blindness?
Optic nerve
What is bitemporal hemianopia?
Loss of temporal visual fields of both eyes
Where is the lesion in bitemporal hemianopia?
Optic chiasm
What is homonymous hemianopia?
Loss of nasal visual field in one eye and temporal visual field in other
Where is the lesion in homonymous hemianopia?
After optic chiasm; eg: optic radiation
Which cranial nerves innervate the extraocular muscles?
CN III
CN IV
CN VI
Which nerve controls the superior oblique?
CN IV
How does the superior oblique move the eyeball?
Down and medially
Which nerve controls the lateral rectus?
CN VI
How does the lateral rectus move the eyeball?
Laterally
Which muscles does CN III control?
Superior rectus
Inferior rectus
Medial rectus
Inferior oblique
What is the muscle that elevates the eye?
Levator palpebrae superioris
What are the functions of CN III in the eye?
Control 4 extraocular muscles
Elevate eyelid
Constrict pupil
What will an oculomotor nerve palsy cause?
Ptosis
Severe ocular movement limitation
Dilated pupil
How do you test eye movements in a patient?
Sit opposite patient Ask them to keep head still Ask them to follow tip of finger/pen with their eyes Draw out H - Start laterally - Move up - Move down - Move medially - Move laterally - Move up - Move down Move slowly Move to extremes of gaze Observe both eyes
What are you looking for when you test eye movements?
Symmetrical movements
No limitation of movement
No double vision
In what light conditions should you test the pupillary response?
Dimly lit room
What is involved in the examination of the pupils?
Sit in front of patient
Observe pupils for shape and symmetry
- Note if equal
Using strong torch, shine light into one eye
Pupil should constrict = direct response
Shine light again into same eye
Other pupil should constrict = consensual response
Repeat in other eye
If either pupil fails to constrict to light, check if constricts to accommodation = look far away > focus on near object > pupil should constrict
Swinging flashlight test
What is the swinging flashlight test?
Compares right and left pupillary responses
When swinging light from right eye to left, left pupil should restrict as light reaches it
Same should happen when you swing light back to right eye
What does it mean if a pupil dilates in response to light in the swinging torch test?
Retinal or optic nerve disease
Called relative afferent pupillary defect (RAPD)
How is the fundus examined?
Done through pupils that have been dilated with mydriatic drops
If not possible achieve pupil dilation by darkening room
Use ophthalmoscope to examine person’s eye with your same eye
Ask patient to look ahead
Shine light of ophthalmoscope into eye and examine fundus
Move head in all points of the Union Jack to see entire fundus
Which muscles elevate and depress the eye when it is abducted?
Elevator = superior rectus Depressor = inferior rectus
Which muscles elevate and depress the eye when it is adducted?
Elevator = inferior oblique Depressor = superior oblique
