OP1201 – Basic Clinical Techniques
Part 2
Dr Kirsten Hamilton-Maxwell
A few notes before we beginI am about to describe a systematic procedure that
will seem like a recipeThis 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
HygieneGood 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 binAnything that has come into contact with the eye
needs to go in the yellow biohazard bin
Slit lamp safetySlit lamp 15x irradiance of
ophthalmoscopeMacula injury with fundus
exam possibleIR thermal injuryUV photochemical
damageGreater risk in
ChildrenAphakesMacula pathology
Prior exposure within last 24hrs increases risk
Safe viewing time for fundus with dilated pupil with Haag-Streit21 secs at lowest setting8 at highest
FDA recommendsLimit brightnessUV and short wave blue
filters (<420nm)However, don’t risk
missing important lesions by trying to do the exam without enough light
Set-upSlit lamp preparation
Disinfect yourself and the slit lampFocus eyepiecesAdjust table height
Patient preparationExplain what you are doingAdjust chin height, chair height, and ask patient to rest
forehead against forehead restYou 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 examineAdnexaEyelids and lashesCornea and tear filmTear meniscusAnterior chamberIris including pupillary ruffLensAnterior 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 everythingWe scan from left to right, or right to left, in a systematic
wayThe 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 statedYou will need to refocus (by moving the slit lamp
forwards or backwards) as you go because of the curvature of the eye
AdnexaPatient has eyes closedIllumination
Wide beam with a diffuser
MagnificationLow (6x)
AngleMicroscope: straightIllumination: about 45º
MethodScan across upper and
lower adnexaLook for colour, texture
or elevation changesRecord
Normal and abnormal findings
Draw unusual findings
Xanthelasma
Eyelids and lashesPatient has eyes closed
for superior lid and open for inferior lid
IlluminationParallelepiped (3-4mm)
Magnification10x
AngleMicroscope: straightIllumination: about 45ºRemember to switch
sides
MethodScan across upper and
lower lids and lashesLook for colour, texture,
elevation changes, abnormal eyelid position, meibomian gland appearance, lash colour and regularity
RecordNormal and abnormal
findingsDraw unusual findings
Eyelid margin is vascularised and the Meibomian glands appear blocked
CorneaPatient has eyes open
from now onIllumination
Parallelepiped (2mm)Magnification
Moderate (10x to 16x)Angle
Microscope: straightIllumination: about 45º
MethodDivide 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 non-illuminated (indirect) areas for irregularities
RecordNormal and abnormal
findingsDraw unusual findings
Corneal foreign body with rust ring and associated inflammation
Tear film meniscusThe pool of tears that is
adjacent to the lower lidIllumination
Parallelepiped (2mm)Magnification
Moderate (16x)Angle
Microscope: straightIllumination: about 45º
MethodMeasure 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
RecordMeniscus 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
IrisIllumination
Parallelepiped (2-3mm)Magnification
16xAngle
Microscope: straight Illumination: about 45ºRemember to switch sides
Since the iris is a deeper structure, push the slit lamp forward to bring it into focusThe anterior chamber
should appear empty!
MethodScan across the upper and
lower irisLook for colour, texture,
elevationRecord
Normal and abnormal findings
Draw unusual findings
Iris pigment in a sector of the iris
PupilThis is actually an
examination of the pupillary ruff, pupil shape
IlluminationParallelepiped (2-3mm)
Magnification16x
AngleMicroscope: straightIllumination: 20-30º
MethodInspect the pupillary
ruff and pupil shapeRecord
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 surfaceIdeally, the pupil should
be dilated prior to a thorough lens examination
IlluminationParallelepiped (2-3mm)
Magnification16x
AngleMicroscope: straightIllumination: about 30º
MethodRemember 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 peelRecord
Normal and abnormal findings
Draw unusual findings
Lens surface
Lens bodyIllumination
Parallelepiped (2-3mm) to examine overall lens condition via retro-illumination
Optical section to examine lens structure
Magnification16x
AngleMicroscope: straight Illumination: for retro-
illumination 5-10º, for optical section, as large as pupil size will allow
MethodRetro-illumination as
described in the last lectureFor optical section, scan
temporal then nasal lens, switching sides
Look for irregularities in lensYou’ll know you’re doing it
right when you can see y-sutures
RecordNormal and abnormal
findingsDraw unusual findings
A y-suture in a healthy lensYou’ll need to find this in each other
Nuclear cataract
Posterior subcapsular cataract
Anterior vitreousIllumination
Parallelepiped (2-3mm)Magnification
16xAngle
Microscope: straightIllumination: about 30º
MethodPush the microscope
forward to view the anterior vitreous
Look for vitreous floaters, pigment
A spider web appearance is common
RecordNormal and abnormal
findingsDraw 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 densityHow deep is it?
Optical sectionParallax error (swing beam or microscope from side to side)Focus
Useful tipsWhen 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 forestsWhile you should soon be able to see details as small as one
cell, it is the overall picture that countsUse the full spectrum of lighting techniques and magnifications to
put together a complete story for each and every patientThough 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 equipmentStay 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
Same as the previous lecture