Slit Lamp Techniques

Question 1

Diffuse - Use

Answer 1

Provide general view of the anterior eye

Typically used to examine the eyelids, conjunctiva, cornea and iris

Question 2

Diffuse - Set up

Answer 2

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

Question 3

Diffuse - Useful in assessing

Answer 3

Limbal hyperaemia 
CLARE
CLAPC
Hyperaemia - interpalpebral, palpebral conjuctiva, sectoral
Blepharitis
Incomplete blink
MGD

Question 4

Optic Section - Use

Answer 4

Allows cornea to be viewed in cross section

The location and depth of opacities can be determined

Question 5

Optic Section - Set up

Answer 5

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

Question 6

Optic Section - Useful in assessing

Answer 6

Corneal abrasion
CLPU
Corneal microcysts and vacuoles
Corneal infiltrates
Corneal opacities

Question 7

Parallelpiped - Use

Answer 7

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

Question 8

Parallelpiped - Set up

Answer 8

The light beam is adjusted to moderate width
Medium to high magnification can be used
Illumination system is typically angled away from the microscope

Question 9

Parallelpiped - Useful in assessing

Answer 9

Corneal microcysts and vacuoles

Corneal oedema - stromal

Question 10

Conical Beam - Use

Answer 10

Useful for assessing the anterior chamber and anterior vitreous
Used to look for cells/flare or pigment in the aqueous or vitreous

Question 11

Conical beam - Set up

Answer 11

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

Question 12

Conical beam - Useful when assessing

Answer 12

Looking for signs of active inflammation - flare (Tyndall effect)
Looking for signs of retinal detachment - pigment (Schaeffers sign)

Question 13

Specular reflection - Use

Answer 13

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

Question 14

Specular reflection - Set up

Answer 14

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

Question 15

Specular reflection - Useful in assessing

Answer 15

Corneal endothelium
Blebs
Polymegathism
Can also be used to assess the tear film

Question 16

Indirect retro-illumination - Use

Answer 16

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

Question 17

Indirect retro-illumination - Set up

Answer 17

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

Question 18

Indirect retro-illumination - Useful in assessing

Answer 18

Corneal epithelium oedema
Corneal opacities
Corneal FB’s 
Corneal vascularisation
IOL opacities
Iris transillumination

Question 19

Sclerotic scatter - Use

Answer 19

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

Question 20

Sclerotic scatter - Set up

Answer 20

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

Question 21

NaFl - Use

Answer 21

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

Question 22

NaFl - Set up

Answer 22

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

Question 23

NaFl - Useful in assessing

Answer 23

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

Question 24

Sclerotic scatter - Useful in assessing

Answer 24

Corneal oedema - stromal

Corneal opacities