slit lamp biomicroscopy intro
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7/28/2019 Slit Lamp Biomicroscopy Intro
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Introduction to Slit Lamp
Biomicroscopy
Edeline Lu, OD
Assistant Professor, SCCO
Slit Lamp Instrumentation
Basic design
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Hardware
Forehead rest
Canthus alignment
Chin rest
Chin rest adjustment knob
Fixation light
Lock for slit lamp base
Table height adjustment
Headrest
Chinrest
Fixation light
Canthus alignment
Chinrest adjustment
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Beam intensity
Slit lamp base lock
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Biomicroscope
Oculars
Convergent optics
Divergent optics
Magnification
Joystick
Vertical control knob
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Biomicroscope
Illumination system On/off
Intensity
Beam height
Beam width
Beam angle
Beam filter:
Neutral density
Red free
Cobalt blue
Click stop
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Beam adjustment
Beam orientation
Beam height
Beam width
Filter selection
Beam angle
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Ancillary attachments
Goldmann applanation tonometer
Anterior segment camera
Laser
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Slit Lamp Biomicroscopy
Types of illumination Direct focal
Diffuse
Parallelepiped
Optic section
Conical beam
Specular reflection
Indirect/proximal
parallelepiped
Sclerotic scatter Retroillumination
direct, indirect
Types of illumination
Direct Focal Illumination
General principle: examiner assesses the
structure in question by looking directly into the
path of the beam of light
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Types of Illumination: Direct
Direct Illuminationat cornea
Adapted from Martonyi, et al.
Direct Illumination
at iris
Types of illumination: Direct Focal
Diffuse Illumination:
gross inspection over a maximum illuminated area
Lids, lashes, lacrimal, conjunctiva
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Diffuse Illumination
Adapted from Martonyi, et al.
Diffuse illumination
Set up
Beam angle: variable
Beam width: 4 mm to maximum
Beam height: maximum
Filter: none
Illumination: low
Magnification: low
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Direct Focal Illumination: Parallelepiped
Definition: beam of light that has two parallel sides
Any beam of light with a width between diffuse and optic
section (usually between 0.5mm and 2.0mm)
Provides a 3-dimensional view (width, height and depth)
Parallelepiped
Adapted from Birinyi
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Direct Focal Illumination: Parallelepiped
Set up
Beam angle: 60°, variable
Beam width: 0.5 mm to 2.0 mm
Beam height: variable, but usually set to
maximum
Filter: none
Illumination: low to moderate
Magnification: low to medium
Parallelepiped
All-purpose evaluation: most commonly
used to evaluate almost every structure
Cornea: edema, epithelium, endothelium,
neovascularization
Lens: vacuoules, cataract, Y-suture
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Direct focal illumination: Optic Section
Definition: slit beam of light used to localize
depth of defects.
Provides a 2-dimensional (height and depth)
view.
Optic Section
Set up
Beam angle: 60° for angle estimation, variable
Beam width: ~0.5mm
Beam height: variable, but usually max
Filter: none
Illumination: moderate to high
Magnification: medium to high
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Optic Section
Uses:
Cornea: to determine depth of lesion
Anterior chamber: to determine depth
Angle estimation
Lens: to determine depth/location/layer
Direct Focal Illumination: Conical Beam Definition: a small round or square beam of light
used to assess the status of the anterior
chamber by oscillating between the cornea and
the lens
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Conical Beam
Set up:
Beam angle: greater than 60°
Beam width: parallelepiped or open
Beam height: 2-4 mm high, or smallest circular
or square aperture
Filter: none
Illumination: maximum
Magnification: high
Conical beam
Uses:
Evaluates anterior chamber for presence of
cells and flare.
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Direct Focal Illumination: Specular
Reflection
Special illumination that judges the quality
of a surface
Angle of incidence of the beam of light
from the slit lamp equals the angle of
reflection of light into the biomicroscope
Only observable through one ocular at a
time
Specular Reflection
Set up:
Beam angle: greater than 45°
Beam width: small parallelepiped
Beam height: maximum
Filter: none
Illumination: high
Magnification: medium to high
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Types of Illumination: Indirect/Proximal Definition: zone of illumination that is adjacent to
the direct focal beam.
Provides a softer, more scattered light to view
abnormalities that would otherwise be washed
out under direct illumination
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Types of Illumination: Indirect/Proximal
Indirect illumination
Adapted from Martonyi, et al.
Indirect/proximal Illumination
Set up:
Beam angle: 60°, variable
Beam width: small parallelepiped
Beam height: maximum height
Filter: none
Illumination: medium
Magnification: low to medium
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Indirect/proximal Illumination
Uses:
Cornea: SEI’s, corneal nerves, scars,
neovascularization
Iris lens
Indirect Illumination: Sclerotic Scatter
Type of indirect illumination in which light
is directed at the limbus to scatter light
internally throughout the cornea
May require examiner to view the cornea
outside of the biomicroscope in the case of
central corneal clouding.
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Sclerotic Scatter
Set up:
Beam angle: 60°
Beam width: small parallelepiped
Beam height: maximum
Beam positioned at temporal limbus
Illumination: medium to high
Magnification: low, but usually viewed outside
oculars
Sclerotic Scatter
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Types of Illumination: Retroillumination
Definition: zone of illumination that utilizes light
bounced off another structure
Objects that are opaque to light appear dark (ie, scars,
pigment, blood vessels)
Objects that are clear will appear light (ie, cornea, lens)
Objects that scatter light will appear light (ie, epithelial
edema, vacuoles)
Two types: Direct, Indirect
Usually used for cornea, but can be used for
lens and iris as well.
Retroillumination
Direct Retroillumination:
Zone of illumination that is directly in the path of
the reflected beam of light
Set up:
Beam angle: 60°, variable
Beam width: small parallelepiped
Beam height: maximum height
Filter: none
Illumination: medium
Magnification: low to medium
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Types of Illumination: Retroillumination
Direct Retro-illumination
Adapted from Martonyi, et al.
Direct Retroillumination
Uses:
Cornea
Iris: transillumination defects
Lens: Posterior sclerotic cataract
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Retroillumination
Indirect Retroillumination
Zone of illumination adjacent to the reflected
beam of light.
Set Up:
Beam angle: 60°, variable
Beam width: small parallelepiped
Beam height: maximum height
Filter: none Illumination: medium
Magnification: low to medium
Types of Illumination: Retroillumination
Indirect Retro-illumination
Adapted from Martonyi, et al.
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Types of Illumination (All)
Direct Illumination
Direct Retro-illumination
Indirect Retro-illumination
Indirect illumination
Adapted from Martonyi, et al.
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Getting Ready to do the Exam
Preparation
Pt education: “I’m going to be using this
instrument to evaluate the health of the front
part of your eye.”
Disinfection:
Clean chin rest, forehead rest
May use tissue for chin rest
Preparation
Parfocal
Bringing the oculars of the biomicroscope into the
same plane of focus as the illumination system of thebiomicroscope.
• Achieving parfocal = light beam is focused at the same
time as the structure in question is focused.
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Parfocaling
Technique: Focus a parallelepiped light beam onto a
focusing/test bar or on the patient’s closedeyelid
Lock slit lamp base
Fog each ocular: turn the eyepiececounterclockwise to most plus
Turn eyepiece clockwise until the parallelepiped
light beam just comes into focus
Repeat with the other eyepiece
Preparation: Alignment
Adjust height of slit lamp and canthus
alignment to optimize patient comfort
Alternative setup:
Children
Obese/well-endowed
Wheelchair-bound
Instruct patient to keep forehead firmly against
forehead rest (teeth together)
Provide a good fixation target
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Troubleshooting
Focusing Problems
Bad technique in parfocaling
Not parfocaled
Forehead falling away from head rest
Chin not firmly against chin rest
Examiner accommodates
Instrument myopia
No view through oculars
Light housing in front of one ocular
Dial turned in between to mag settings
Instrument not on
Instrument not plugged in or becomes loose
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