Slit lamp biomicroscopy
OP1201 – Basic Clinical Techniques
Part 2
Dr Kirsten Hamilton-Maxwell
A few notes before we begin
 I am about to describe a systematic procedure that
will seem like a recipe
 This is strictly for beginners!
 As you get better at slit lamp, the lighting and
magnification changes become second nature, and
your routine will start to flow
 It won’t be long before you can examine both eyes
within 10 minutes
Hygiene
 Good hygiene is very important!
 Clean the chin and forehead rest of your slit lamp
between patients using an alcohol wipe
 Wash and dry your hands thoroughly before and after
each patient; do this when the patient can see you
wherever possible.
 As a patient, you have the right to ask your practitioner
if they have washed their hands
 Dispose of any used tissues immediately in the bin
 Anything that has come into contact with the eye
needs to go in the yellow biohazard bin
Slit lamp safety
 Slit lamp 15x irradiance of
ophthalmoscope
 Macula injury with fundus
exam possible
 IR thermal injury
 UV photochemical
damage
 Greater risk in
 Children
 Aphakes
 Macula pathology
 Prior exposure within last
24hrs increases risk
 Safe viewing time for
fundus with dilated pupil
with Haag-Streit
 21 secs at lowest setting
 8 at highest
 FDA recommends
 Limit brightness
 UV and short wave blue
filters (<420nm)
 However, don’t risk
missing important lesions
by trying to do the exam
without enough light
A basic slit lamp routine
Set-up
 Slit lamp preparation
 Disinfect yourself and the slit lamp
 Focus eyepieces
 Adjust table height
 Patient preparation
 Explain what you are doing
 Adjust chin height, chair height, and ask patient to rest
forehead against forehead rest
 You are now ready to begin
How to focus eyepieces



With focusing rod
Insert the rod into the slit lamp – you will find
the correct hole at the pivot point for the
illumination and biomicroscope arms. Turn
the rod so that so that the flat part is facing
the eyepieces.
Adjust the slit to a width of about 1mm.
Swing the illumination from side to side to
ensure that the slit remains still.
 If it moves, the previous user has
“decoupled” the system, or the slit lamp
needs to be returned to the
manufacturer for servicing
 Without focusing rod
 Adjust the slit to a width of about 1mm
and position on the flat part between
your patient’s eyebrows.
 Without looking through the eyepieces,
move the slit lamp backwards and
forwards until the slit is as sharp as it
can be. Swing the illumination from
side to side to ensure that the slit
remains still. It must be still for this to
work.
 The dioptric focus of both eyepieces should be screwed towards the plus as far as
possible (usually anti-clockwise).
 Close one eye, look at the slit beam image through one eyepiece and gradually
turns the eyepiece clockwise (towards minus) until the surface of the rod is just in
focus.
 Repeat for the other eyepiece.
 Look through both eyes; do you have clear comfortable vision?
 This will take some practice to get right, because you will need to learn to relax your
accommodation.
What to examine
 Adnexa
 Eyelids and lashes
 Cornea and tear film
 Tear meniscus
 Anterior chamber
 Iris including pupillary ruff
 Lens
 Anterior vitreous
What does “scan” mean?
 Since we are using a narrow beam of light, we need to
move the slit across the eye to see everything
 We scan from left to right, or right to left, in a systematic
way
 The scanning procedure is always the same
 When viewing the temporal eye, the light should be on the
temporal side
 When you reach the midline, switch the light to the nasal
side and continue scanning – watch out for the nose
 The slit should be set at full height unless otherwise stated
 You will need to refocus (by moving the slit lamp forwards
or backwards) as you go because of the curvature of the
eye
Adnexa
 Patient has eyes closed
 Illumination
 Wide beam with a
diffuser
 Magnification
 Low (6x)
 Angle
 Microscope: straight
 Illumination: about 45º
 Method
 Scan across upper and
lower adnexa
 Look for colour, texture
or elevation changes
 Record
 Normal and abnormal
findings
 Draw unusual findings
Xanthelasma
Eyelids and lashes
 Patient has eyes closed
for superior lid and open
for inferior lid
 Illumination
 Parallelepiped (3-4mm)
 Magnification
 10x
 Angle
 Microscope: straight
 Illumination: about 45º
 Remember to switch
sides
 Method
 Scan across upper and
lower lids and lashes
 Look for colour, texture,
elevation changes,
abnormal eyelid position,
meibomian gland
appearance, lash colour
and regularity
 Record
 Normal and abnormal
findings
 Draw unusual findings
Eyelid margin is vascularised and the Meibomian glands appear blocked
Cornea
 Patient has eyes open
from now on
 Illumination
 Parallelepiped (2mm)
 Magnification
 Moderate (10x to 16x)
 Angle
 Microscope: straight
 Illumination: about 45º
 Method
 Divide the cornea into
thirds and scan central,
upper, lower separately
 For lower cornea, ask
patient to look up
 For upper cornea, ask
patient to look down and
hold lid against upper
brow
 Look in the illuminated
(direct) and nonilluminated (indirect)
areas for irregularities
 Record
 Normal and abnormal
findings
 Draw unusual findings
Corneal foreign body with rust ring and associated inflammation
Tear film meniscus
 The pool of tears that is
adjacent to the lower lid
 Illumination
 Parallelepiped (2mm)
 Magnification
 Moderate (16x)
 Angle
 Microscope: straight
 Illumination: about 45º
 Method
 Measure directly by
matching to slit height
and reading off scale
 If you have a slit lamp
with set positions only,
set a fixed height and
calculate meniscus
height via comparison
 Record
 Meniscus height in mm
Tear meniscus stained with fluorescein
Conjunctiva
 Illumination
 Parallelepiped (3-4mm)
 Magnification
 Moderate (10x to 16x)
 Angle
 Microscope: straight
 Illumination: about 45º
 Method
 Scan nasal, temporal, inferior,
superior bulbal conjunctiva
separately
 You can see the inferior tarsal
conjunctiva and fornix but not
the superior counterparts
without lid eversion
 Remember to ask your
patient to look right, left, up,
down, so that you can see the
full extent of the conjunctiva
 Use your fingers to move the
eyelids when necessary
 Look in the illuminated
(direct) and non-illuminated
(indirect) areas for
irregularities
 Record
 Normal and abnormal
findings
 Draw unusual findings
Pinguecula
Concretion
Iris
 Illumination
 Parallelepiped (2-3mm)
 Magnification
 16x
 Angle
 Microscope: straight
 Illumination: about 45º
 Remember to switch sides
 Since the iris is a deeper
structure, push the slit lamp
forward to bring it into focus
 The anterior chamber
should appear empty!
 Method
 Scan across the upper and
lower iris
 Look for colour, texture,
elevation
 Record
 Normal and abnormal
findings
 Draw unusual findings
Iris pigment in a sector of the iris
Pupil
 This is actually an
examination of the
pupillary ruff, pupil
shape
 Illumination
 Parallelepiped (2-3mm)
 Magnification
 16x
 Angle
 Microscope: straight
 Illumination: 20-30º
 Method
 Inspect the pupillary
ruff and pupil shape
 Record
 Normal and abnormal
findings
 Draw unusual findings
Persistent pupillary membrane (not easy to see in photographs)
The pupillary ruff is the brown ring at the edge of the iris
Lens surface
 Ideally, the pupil should
be dilated prior to a
thorough lens examination
 Illumination
 Parallelepiped (2-3mm)
 Magnification
 16x
 Angle
 Microscope: straight
 Illumination: about 30º
 Method
 Remember that the
anterior lens is in the
same plan as the pupil
margin, so little
refocusing needed
 Use direct illumination
and/or specular reflection

Look for the texture of
orange peel
 Record
 Normal and abnormal
findings
 Draw unusual findings
Lens surface
Lens body
 Illumination
 Parallelepiped (2-3mm) to
examine overall lens
condition via retroillumination
 Optical section to examine
lens structure
 Magnification
 16x
 Angle
 Microscope: straight
 Illumination: for retroillumination 5-10º, for optical
section, as large as pupil
size will allow
 Method
 Retro-illumination as
described in the last lecture
 For optical section, scan
temporal then nasal lens,
switching sides
 Look for irregularities in lens
 You’ll know you’re doing it
right when you can see ysutures
 Record
 Normal and abnormal
findings
 Draw unusual findings
A y-suture in a healthy lens
You’ll need to find this in
each other
Nuclear cataract
Posterior subcapsular cataract
Anterior vitreous
 Illumination
 Parallelepiped (2-3mm)
 Magnification
 16x
 Angle
 Microscope: straight
 Illumination: about 30º
 Method
 Push the microscope
forward to view the
anterior vitreous
 Look for vitreous floaters,
pigment
 A spider web appearance
is common
 Record
 Normal and abnormal
findings
 Draw unusual findings
Recording results
What if I see something?
 Where is it? (Location)
 Exact location with regard to landmarks.
 Distances in mm and directions according to a clock face.
 How big and how many? (Extent)
 Size of anomaly and/or the number of them
 Colour and density
 How deep is it?
 Optical section
 Parallax error (swing beam or microscope from side to side)
 Focus
Useful tips
 When beginning your exam, position (left/right,
up/down) and focus (back/forth) the slit by looking
around the microscope – you can then fine tune
through the microscope
 The tear film often has a globular structure and this
moves with each blink – if you see this, the cornea is
almost in focus
 If you get “lost”, reduce the magnification to increase
the field of view and try again
 Do not lose sight of the forest for the trees!
Trees and forests
 While you should soon be able to see details as small as one
cell, it is the overall picture that counts
 Use the full spectrum of lighting techniques and magnifications to
put together a complete story for each and every patient
 Though slit lamp seems extremely technical, don’t get caught
up on small details (eg. Specific slit widths or angles)
 General recommendations are typically provided for each
technique
 In reality, the exact setting required will vary depending on the
practitioner, patient and the equipment
 Stay within the recommended ranges while you are learning, but
you’ll soon realise that you’ll be guided by what you need to see,
and not by a set of numbers
Recommended reading
Same as the previous lecture