15 Slit Lamp Biomicroscopy 2

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



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


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


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



Iris pigment in a sector of the iris

PupilThis is actually an

examination of the pupillary ruff, pupil shape


Magnification16x

AngleMicroscope: straightIllumination: 20-30º

MethodInspect the pupillary

ruff and pupil shapeRecord



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


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



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



A y-suture in a healthy lensYou’ll need to find this in each other

Nuclear cataract

Posterior subcapsular cataract

Anterior vitreousIllumination


16xAngle


MethodPush the microscope

forward to view the anterior vitreous

Look for vitreous floaters, pigment

A spider web appearance is common



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

15 Slit Lamp Biomicroscopy 2

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