History + Investigations Flashcards
What are some general investigations for the eye?
- Ophthalmoscope - to tell which eye you are looking at the optic disc is nasal
- Slit lamp - provides better view of the eye
- Tonometer - measures intra-ocular pressure by measuring the resistance of the cornea to indentation
What is the cup to disc ratio?
Measuring how much optic nerve tissue is visible e.g. in conditions like glaucoma, you lose optic tissue so cup to disc ratio increases.
- <0.3 is good
- > 0.9 is pathalogical
What is a Fundus Fluorescein Angiogram (FFA)?
- Allows us to see blood vessels within the eye better
- Inject fluorescein dye into the vein of a patient
- A camera excites the dye and takes pictures
What do you want to ask in an ophthalmic history?
PC: pain, vision loss, trauma, discharge, redness, photophobia
HPC: duration/rate of onset, recurrent, progression
Past ophthalmic hx: previous surgery/injury, short/long-sighted, contact lenses, ambylopia
FH: glaucoma, dystrophy, blindness
MH: DM, HTN, RA, sarcoid
Drugs: anti-TB, amiodarone, choroquine
SH: occupation, DVLA, carer, smoking/alcohol
What is myopia?
- Short-sighted
- Eyeball (globe) is too big so light refracts in front of the retina
- Struggles with distances but can see things close up
- Requires concave lens
- Glasses minify images
- Higher risk of retinal detachment
What is hypermetropia?
- Long-sighted
- Small eyeball (small globe)
- Problems with near vision
- Glasses magnify image
- Requires convex lens
- Higher risk of acute glaucoma (especially when cataract is growing)
What do you do if the person is unable to read the Snellen chart at 6m?
- Move them closer to the chart
- Try with corrected lenses
- Re-test with pin-holes as this will help determine if acuity is reduced due to refractive error or something organic
- If still can’t read it get them to count fingers
- See if they can see hand movements
- See if they have light perception (with pen torch)
- No Perception of Light (NPL)
What are some ocular emergencies?
- Central Retinal Artery Occlusion (CRAO)
- Orbital Cellulitis
- Retinal detachment
- Acute Angle Closure Glaucoma
- Giant Cell Arteritis
How can you ask about pain in the eyes?
- Are your eyes painful enough today that you would consider taking pain medication?
- Grittiness, dryness, eyes feel tired/want to close
- Sharp stabbing pain “like needles’ - ocular surface problems
- Dull ache - like toothache, uveitis, raised eye pressure, scleritis
What is the red reflex?
Test this first in ophthalmoscopy, by standing at arms width away from patient and shine light in their eye whilst looking through ophthalmoscope.
Red reflex is result of light reflecting directly back from retina - problem with clarity of optica media.
What is tropicamide?
Muscarinic receptor antagonist - inhibits iris sphincter muscle and ciliary muscle contraction (cytoplegia) so pupil dilates (mydriasis). This can cause blurry vision for around an hour (warn the patient).
What is cyclopentolate and phenylephrine?
- Cyclopentolate: anticholinergic, inhibits sphincter muscle of iris and ciliary muscle (dilates pupil)
- Phenylephrine: sympathetic drug (mimics action of epinephrine/norepinephrine), selectively binds to alpha 1 receptors and causes vasconstriction
How do you do ophthalmoscopy?
- Look for cup, colour, contour of optic disc - should be able to see 4 vascular arcades
- Ask the patient to look up, down, left and right to visualise peripheries of eyes and check for swelling
- At the end, ask the patient to look directly into the light to view the macula
