Practical Opthalmology Flashcards
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
What swinging light reflex is seen in patients with a relative afferent pupillary defect?
When light shone on abnormal pupil, both pupils appear to dilate as their degree of constriction reduces
Known as a Marcus Gunn pupil
If a patient has an efferent pupillary defect, what is seen on a swinging light test?
Affected eye constriction poor
Consensual pupillary reflex unaffected
What do you look for on fundoscopy?
Optic disk Optic cup Fovea Macula Retinal arteries and veins
What are the uses of mydriatic drops?
Dilate pupil for visualisation of the retina
Paralyse accommodation in management of children with amblyopia
Refraction of children for prescription of glasses
What side effects are associated with mydriatic drops?
Whitening of the eyelids - vasoconstriction (resolve as drops wear off)
Atropine cause redness of face and warm sensation
Sting eyes for few seconds after instillation
Can’t drive - blurring until wear off
What must you inform patients of in consenting for mydriatic drops?
What procedure involve
Can’t drive
Effects - dilation and stinging
Check allergies and CI
How are mydriatic drops applied?
Pt look up and pull inferior eyelid down
Apply one drop from vertical position
Allow pt to blink
Wipe away excess
What must you document following the use of mydriatic drops?
Type of drop
Which eye
How many drops
Time of instillation
What are the types of mydriatic drops?
Atropine
Cyclopentolate
Tropicamide
Phenylephirine
What are the mechanisms by which mydriatic drops work?
Parasympatholytics - atropine, cyclopentolate, tropicamide
Sympathetic agonist - phenyephirine
What are the contraindications for atropine? How long does the effect last?
Hypertension
Untreated narrow angle glaucoma
1-2 weeks effect
What are the contraindications for cyclopentolate or tropicamide? How long does their effect last?
Untreated narrow angle glaucoma
Allergy
Cyclopentolate 25-75 min effect, recovery over 6-24hrs
Tropicamide 15-20 min effect, recovery 4-8hrs
What are the contraindications of phenylephrine? How long does its effect last?
Untreated narrow angle glaucoma
Avoid in children
3-6 hours effect
What are fluorescein drops used for?
Highlight defects in the cornea
Measuring intraocular pressure with tonometry
What adverse drug reactions are associated with fluoroscein drops?
Skin discolouration - 6-12 hrs
What should you warn patients of when giving fluoroscein drops?
Don’t put contacts in for an hour as they could be stained permanently
What is fluorescein angiography used for?
Look at vascular supply of retina and choroid
How is fluoroscein angiography carried out?
IV injection of fluoroscein which delineate retinal vessels
Photographic record made including leakage from retinal vessels over 15 mins
