Slit Lamp Techniques Flashcards
Diffuse - Use
Provide general view of the anterior eye
Typically used to examine the eyelids, conjunctiva, cornea and iris
Diffuse - Set up
A diffuser is placed in front of the light source
Low magnification
Illumination system angled at 45 degrees from microscope
Slit width and light intensity are altered to achieve desired level of illumination
Diffuse - Useful in assessing
Limbal hyperaemia CLARE CLAPC Hyperaemia - interpalpebral, palpebral conjuctiva, sectoral Blepharitis Incomplete blink MGD
Optic Section - Use
Allows cornea to be viewed in cross section
The location and depth of opacities can be determined
Optic Section - Set up
Light beam adjusted to narrow width
Mag increased from diffuse view; medium to high mag can be used
Illumination system is typically angled away from the microscope
Light levels should be increased to compensate for the narrow slit
Optic Section - Useful in assessing
Corneal abrasion CLPU Corneal microcysts and vacuoles Corneal infiltrates Corneal opacities
Parallelpiped - Use
Allows block of cornea to be viewed
A wider area of the cornea can be seen than with optic section
The corneal epithelium, stroma and endothelium are visible
Parallelpiped - Set up
The light beam is adjusted to moderate width
Medium to high magnification can be used
Illumination system is typically angled away from the microscope
Parallelpiped - Useful in assessing
Corneal microcysts and vacuoles
Corneal oedema - stromal
Conical Beam - Use
Useful for assessing the anterior chamber and anterior vitreous
Used to look for cells/flare or pigment in the aqueous or vitreous
Conical beam - Set up
Room lights off and practitioner should take time to dark adapt
Narrow slit width and height reduced until it forms a small circular shape
High magnification
The biomicroscope is focussed on the anterior chamber or anterior vitreous
Detection of pigment/cells is enhanced by asking the patient to move their eyes and looking for any movement as they look straight ahead again
Conical beam - Useful when assessing
Looking for signs of active inflammation - flare (Tyndall effect)
Looking for signs of retinal detachment - pigment (Schaeffers sign)
Specular reflection - Use
Used to view the tear film and corneal endothelium
It is a monocular technique; when set up correctly, the image is only visible in one eyepiece
Specular reflection - Set up
Illumination and observation system are offset at equal angles
A moderately wide beam is used and the microscope is focussed on the structure of interest
Height of the beam can be reduced
The illumination system is moved in order to place the bright Purkinje image (reflection of light source) to coincide with the optic section
High magnification can be used once the structure of interest has been visualised
Specular reflection - Useful in assessing
Corneal endothelium
Blebs
Polymegathism
Can also be used to assess the tear film
Indirect retro-illumination - Use
Uses reflected light from the iris or the fundus to view structures of the anterior eye
The technique is useful in visualising ocular structures and pathologies that show up best in shadow
Illumination and observation system are uncoupled for this viewing technique
Alternatively, the biomicroscope system can remained coupled with the practitioner observing the area of interest to the side of the optic section
Indirect retro-illumination - Set up
If doing so, the illumination system is uncoupled and twisted slightly to one side so it is no longer coincident with the observation system
The light beam is adjusted to a moderate width
Medium to high magnification can be used
The illumination system is typically angled away from the microscope
The microscope is focussed on the area of interest to the side of the light source
Indirect retro-illumination - Useful in assessing
Corneal epithelium oedema Corneal opacities Corneal FB’s Corneal vascularisation IOL opacities Iris transillumination
Sclerotic scatter - Use
Technique uses total internal reflection of the cornea
It allows the cornea to be assessed for the presence of oedema or corneal opacities
Illumination and observation system are uncoupled
Sclerotic scatter - Set up
Illumination and observation system are uncoupled
Low magnification is used
A moderate width light beam is directed at the limbus
The observation system is focussed on the central cornea
When total internal reflection is achieved, the whole limbus is illuminated
NaFl - Use
NaFl is used to anterior eye exam to assess the integrity of the ocular tissues
It is also used to assess the fit of RGP’s and scleral lenses
NaFl - Set up
A drop of NaFl is instilled in the lower fornix
Blue filter is selected and the light beam is adjusted to moderate width
Start with low magnification for a general overview, being increased to observe the area of interest
For the clearest view, a yellow (Wratten) filter should be placed in front of the illumination system
The illumination level will need to be increased to compensate for the introduction of the yellow filter
NaFl - Useful in assessing
Corneal abrasion CLPU Corneal erosion Desiccation Dimple veiling FB tracks Infiltrates Solution toxicity and sensitivity Mucin balls SICS SEAL staining Microbial keratitis CLAPC Lid wiper epitheliopathy
Sclerotic scatter - Useful in assessing
Corneal oedema - stromal
Corneal opacities
