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 Patient 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 Without focusing rod 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 Magnification Angle Method 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 Magnification 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 non-illuminated (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 Magnification Angle Method Record 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 Magnification Angle 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 Magnification Angle Method Record Parallelepiped (2-3mm) to examine overall lens condition via retro-illumination Optical section to examine lens structure Magnification 16x Angle Microscope: straight Illumination: for retro-illumination 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 y-sutures 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 Magnification Angle Method Record 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