Anterior segment examination Flashcards
What are 14 stages of anterior segment examination?
- Observe - habitus, face, orbits
- Examine lid margins
- Examine palpebral conjunctiva - invret lids
- Examine fornices
- Examine bulbar conjunctiva/episclera
- Examine sclera
- Examine cornea
- Examine AC
- Examine iris
- Examine lens
- Examine anterior vitreous
- Stain cornea - use fluorescein +- lissamine green
- Check corneal sensation
- Perform applanation tonometry
What are 4 types of illumination that can be used to examine the cornea?
- diffuse illumination
- direct illumination
- sclerotic scatter
- specular reflection
What are 3 types of illumination that can be used to examine the lens?
- direct illumination
- reroillumination
- specular reflection (Purkinje III)
What are 2 things that can be used to stain the cornea?
- fluorescein
- lissamine green
What are 4 types of illumination techniques for anterior segment examination?
- Direct illumination
- Sclerotic scatter
- Retroillumination
- Specular reflection
What is the most commonly used illumination technique?
direct illumination
How is sclerotic scatter achieved?
light source is uncoupled so that the slit beam can be displaced laterally to fall on the limbus, whilst the microscope remains focused on the central cornea
How does sclerotic scatter work and what can it visualise?
total internal reflection results in a generalised glow around the limbus and the highlighting of subtle opacities within the cornea, e.g. early oedema, deposits
How is retroillumination performed?
light source directed at relatively posterior reflecting surface (e.g. iris or retina) and focus on the structure of interest (e.g. cornea, or iris and lens)
What can retroillumination be used for in an undilated eye?
transillumination defects
What can retroillumination be used for in a dilated eye?
lens opacities
What does specular reflection involve?
focus on the tissue of interest and change the angle of illumination until you get a bright reflection, when the angle of incidence equals the angle of reflection, to highlight discontinuities in an otherwise smooth reflecting surface, e.g. examining the endothelium for guttata
What are 3 Purkinje images and what do they represet in specular reflection?
- Purkinje image I = tear film
- II = endothelium
- III = anterior lens)
What are 7 tests that form part of the anterior segment examination?
- Tear film break-up time (TFBUT)
- Seidel’s test
- Shirmer’s test
- Applanation tonometry
- AC depth measurement
- AC acitivity
- Gonioscopy
How is TFBUT ideally assessed?
using specular reflection (peripheral iridotomy) or a specialised instrument imaging a placido disc reflected off the tear film
If peripheral iridotomy or a specialised instrument imaging a placido disc aren’t available for TFBUT what is an alternative?
placing a wetted fluorescein strip (with drop of saline flicked off) onto the lower temporal fornix - ask pt to blink once, then not to blink. observe with blue light and yellow observational filter the time taken until tear film breaks up (dark areas appear)
What is considered an abnormal TFBUT and in whcih group does this vary?
<10s - this is less in Asian eyes
What does Seidel’s test involve in anterior segment examination?
drop of 2% fluorescein placed over area of concern and observed with blue light and yellow observational filter
test is positive if there is a luminous green flow of aqueous indicating aqueous leaking from surgical wound, penetrating injury, or bleb
What does Seidel’s test test for?
aqueous leaking from surgical wound, penetrating injury, or bleb
What is Schirmer’s test?
Whatman test paper (5x35mm grade No. 1) folded at the notch (5mm from the end) and inserted between middle and outer third of lower lid; after 5 min with eyes gently closed, strips removed and length wetted measured
What is the difference between Shirmer’s test I and II?
- I = eye not anaesthetised, is a measure of basal and reflex tearing
- II = test done after addition of topical anaesthetic - gives indication of basal secretion alone
What is an abnormal result for Schirmer’s test I?
<5.5mm
How is applanation tonometry performed?
place drop of local anaesthetic and fluorescein into lower fornix
tonometer dial rotated and pressure recorded at whcih inner aspect of 2 luminous green circles just touch
How are the lines on the prisms usually aligned in applanation tonometry and how does this vary in high astigmatism?
the white line on the prism is usually aligned with the horizontal meridian.
-> in high astigmatism, red line should be aligned with the minor axis
