Practical Opthalmology Flashcards
(42 cards)
How is distance vision tested?
Snellen chart
How is a snellen chart used?
Pt stand 6m away from chart and read smallest line they can
Vision less than 6/6 - repeat with pinhole to eliminate refractive errors
How does the scoring of a snellen chart work?
Numerator = 6 - 6m away (or 20 for 20ft) Denominator = smallest line they can read (60, 36, 24, 18, 12, 9, 6 as go down chart)
What do you do if a patient can’t read the largest letter?
Count how many fingers
See if they can see a hand moving
Check for perception of light
If none - classified as no perception of light
How is near vision tested?
Near reading chart
Smallest = N5 Largest = N48
How is colour vision tested? How is it scored?
Ishihara plates
Numerical score based on no. of correct responses
What is the first thing you check when testing a patients eyes using an ophthalmoscope?
Red reflex
When is a red reflex abnormal?
Asymmetry
Dark spots
Absent reflex
How do you test for gross visual defects?
Confrontation testing
What is the perimeter testing of visual fields?
It is the machine testing that gives in-depth details of visual fields
What are the parts to the perimeter test of visual fields?
Grey scale
Total deviation
Pattern deviation
What does grey scale perimeter show you?
Generalised picture
Done with other plots and not alone for diagnosis!
What does total deviation perimeter show you?
Which parts of patients visual field that are different to age matched norm
What does pattern deviation perimeter show you?
Localised visual field defects by removing generalised defects such as those caused by cataract
What happens in the cover test?
Focus on object in front and one eye occluded for several seconds
Observe for movement of uncovered eye
What does a cover test show?
If eye move out - esotropia
If eye move in - exotropia
(shows misalignment of eyes)
What happens in the alternate cover test?
Focus on object in front
Occluder rapidly switched from one eye to other
What does an alternate cover test show?
Eye move out - latent esophoria
Eye move in - latent exophoria
What is the difference between esophoria and esotropia?
Esophoria - small turning-in of eye
Esotropia - large turning-in of eye
What nerves are involved in the corneal reflex?
Afferent - ophthalmic branch of trigeminal
Efferent - facial nerve
How do you test the corneal reflex?
Approach eye from side (out of line of vision)
Lightly touch thing strand of cotton on cornea
Watch for direct and consensual reflex of blinking and watering
What does the swinging flash light test look for?
Relative afferent pupillary defect
How is the swinging light test conducted?
Patient look at distant target in dimly lit room
Light moved as fast as possible between 2 eyes (2s per eye)
What is a normal swinging light reflex?
When beam swung from eye to eye, bilateral pupil constriction shouldn’t change
Pupils hold constriction
