Slit lamp Flashcards
What is an alternative name for the slit lamp?
biomicroscope
What are 2 benefits of the slit lamp?
- view is magnified
- is stereoscopic
What does the slit lamp consist of?
binocular compound microscope (2 convex lenses) and adjustable illumination system
How are objects brought into focus with the slit lamp and why?
by moving the slit lamp forward or back, because it has a fixed focal plane
How is movement of the slit lamp achieved a) laterally b) vertically?
- a) laterally = joystick
- b) vertically = dial attached to the joystick
What does the total magnification usually range between in split lamps and what can give a greater range?
- usually 10x to 25x, as some have 2 objective settings (1x and 1.6x) and 2 eyepiece options (10x and 16x)
- others have series of Galilean telescopes that can given 6.3x to 40x
What is an alternative, less common way that varying magnification can be achieved with a slit lamp?
zoom system
What are the 4 typical illumination filter options on the slit lamp?
- unfiltered, heat-absorbing filter
- 10% grey filter
- red-free filter
- blue filter
What traditionally is used for the blue filter on a slit lamp?
cobalt blue, optionally with a 495nm peak
Which slit lamp filter is used for high illumination?
heat-absorbing filter
Which slit lamp filter is used for lower illumination?
the grey filter
What is the use of the red-free slit lamp filter?
increases visualisation of the vitreous and retinal nerve fibre layer/vasculature
What is the blue slit lamp filter used for? 2 things
- combined with yellow enhancement observational filter to maximise visualisaion of fluorescein
- blue filter may also assist detection of iron lines
What is used to adjust the beam height and width of the slit lamp?
apertures - beam light incremented in milimetres
What may the incremental adjustment of the beam light height be useful for?
estimating measurements (e.g. disc size, corneal ulcer etc.)
How can the orientation of the slit lamp beam be adjusted from vertical to horizontal, or any other angle?
by swining the superior aspect of the illumination arm to the left or right
When is it useful to adjust the orientation of the slit lamp beam?
gonioscopy or measuring lesions
How can angulation of the slit lamp beam be achieved?
swinging the whole illumination arm to the side (horizontal) or tilting the illumination arm upward (vertical)
Why is it important to be able to adjust angulation of the slit lamp beam?
illumination techniques (direct illumination, retroillumination, sclerotic scatter and specular reflection) require different angulations of the illumination arm
What is ‘uncoupling’ with the slit lamp?
illumination arm uncoupled to displace the beam from teh centre of the field of view
When might it be useful to tilt the illumination beam of the slit lamp vertically?
may reduce troublesome reflections when using handheld lenses
When could it be useful to replace the standard long mirror of the slit lamp with a short mirror?
when using small angulations (3-10 degrees)
What are 2 things that may be used as a fixation target in a slit lamp (for patient to fixate on)?
- standard fixation lamp
- annular target with focusing range -15 to +10D
What is the range of annular fixation target on a slit lamp and why would it be adjusted?
-15 to +10D - adjusted to patient’s refractive error, enabling them to see the target clearly
What is a stereoaviator, found on some slit lamps?
changes angle of convergence from 13 degrees to 4.5 degrees
What are the benefits of the 13 degree vs 4.5 degreee stereoaviator on slit lamps?
- 13 degrees provides better stereopsis
- 4.5 degrees provides larger binocular field of view and thus improved acuity (binocular acuity > monocular acuity)
When might the 4.5 degree stereoaviator setting be useful when using the slit lamp?
for detailed examintion of certain ocular surfaces e.g. corneal endothelium
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