Ophthalmology 2 Flashcards
Visual acuity
the ability of the vision system to resolve (‘see’) a gap between two objects.
spatial resolution
your visual system can no longer resolve the gap as you move your head away from fine lines
how do you record visual acuity
You state however many meters you tested the eyes at e.g. 6 and then you state the line that the smallest text was seen on as a fraction e.g. 6/18
LogMAR Visual Acuity
Logarithm of the Minimum Angle of Resolution
Main difference in design of LogMAR visual acuity
- Same number of letters on each line with proportional spacing to the size of the letter
- Only uses ‘square’ shaped equally legible letters (Sloan)
Advantages of LogMAR
- ‘Crowding’ phenomena is therefore equal for each line (unequal spacing between lines on Snellen)
- The letters change size by equal logarithmic steps (unequal changes in letter size in Snellen)
- You end up with a ‘number’ which is much easier to analyse statistically (rather than a x/y result in Snellen)
‘Blind’ or Severe sight impairment (SSI) =
Worse than 3/60
Partial Sight’ or Sight Impaired (SI) =
> 6/60 to 3/60
Driving vision =
Better than or equal to 6/12
Causes of an RAPD - relevant afferent pupil defect
- Asymmetrical disease of the retina or optic nerve
- Retinal detachment
- Optic neuritis
- Anterior ischaemic optic neuropathy(AION) • Tumour pressing on the optic nerve
Fundal reflex test
- Quick
- Non-invasive
- Assess clarity of ‘media’ • Corneal scars
- Cataract
- Vitreous Bleeds
- Retinal tumours
how do you perform a fundal reflex test
use ophthalmoscope to see “red eyes” in white children bu appears more white and bluish in black children
What is the main abnormality seen here on fundal reflex test
loss of left retinal reflection
Fundal Reflex Test can identify
- corneal scars
- cataract
- retinoblastoma
What is the main abnormality seen here on fundal reflex test
central dark opacity in the left eye
what is this
swollen disc
• Pseudo swelling
– Small Discs
– Calcium deposits ‘Drusen’
• Genuine swelling
• Optic Neuritis (VA reduced) • Raised ICP (VA normal) – SOL – IIH – Hydrocephalus
What are the three key elements that should be commented on when examining the optic nerve head?
Margin, colour and cup
What systemic disease is associated with the clinical sign seen at this optic nerve head?
diabetes
Eye Movements are controlled by what muscles
- 6 extra-ocular muscles
- 2 horizontal recti (medical and lateral)
- 2 vertical recti (superior and inferior)
- 2 oblique (superior and inferior)
3rd CNP
• Vertical diplopia • Eye is ‘down & out’ • Diplopia every where • Pupil dilated and ptosis • Can be associated with an aneurysm – needs urgent brain imaging and angiogram] THINK ANEURYSM
4th CNP
• Oblique diplopia • • Head tilt away from side • of the lesion • Diplopia worse away from • the side of the palsy if unilateral (adduction) • Common after head • injury • Bilateral - might be congenital
THINK CONGENITAL OR TRAUMA
6th CNP
- Horizontal diplopia
- Worse in far distance
- Worse towards the side of the palsy if unilateral
- Bilateral - concerned that raised intracranial pressure is present
THINK CRANIAL PRESSURE
What is the main cause of blindness in low income countries
CATARACT
What is the main cause of blindness in ‘wealthy’ countries
Age related macular degeneration
