Slit Lamp Biomicroscopy - CSB Flashcards
What is direct illumination?
The observer looks directly at the structures illuminated by the focussed beam.
What is indirect illumination?
The observer looks to the side of the illumination.
What is retroillumination?
The observer uses light reflected from a more posterior source to view an object.
When might retroillumination be used in slit lamp?
When the observer uses light from the iris to observe vessels.
Whats an advantage of Diffuse illumination?
Gives good view of eye, lids and lashes.
What are the four type of optical sections viewed on the slit lamp?
Corneal Section
Paralellopied
Lens section
Van Herrick
Corneal Section
Magnification?
Viewing angle?
The greater the angle, the _______ the optical section.
How is the corneal section seen?
6-16x
At least 45 degrees
The greater the angle, the wider the optical section
As a grey arc
What slit lamp method produces this image?
Corneal Section
Label the structures in this image.
Paralellopied
Whats the easiest way to get to a parallelopied section?
Viewing angle?
Beam Angle?
Magnification?
Obtain a corneal section and just widen the beam to 2-4mm.
45 degrees
2-4mm
6-16x
What optical section is this?
Paralellopiped
What is the purpose of the paralellopiped technique?
To scan the cornea
What is the corneal section technique used for?
To determine depth of opacity of cornea
What is the lens optic section technique used for?
To determine depth of opacity of the lens
What are you looking out for in the scelerotic scatter technique?
You are looking for a complete halo around the limbus that has no gaps.
What is the Van Herick’s technique used for?
It allows you to assess space between the corneal endothelium and anterior chamber iris surface.
What technique has been used to produce this image?
Parallelopiped
Lens Section Technique
Magnification?
Angle?
Beam Width?
What is viewed via this technique and how does it appear?
6-16x
30 degrees
0.5-1mm
The crystalline lens in the section will appear to have a bright band at the front and back (anterior and posterior cortex) and several lighter bands , in the centre, giving it a layered (onion-like) appearance.
What viewing technique has been used to produce this image and what is it showing?
Lens section technique. It is showing the anterior surface of the lens.
What technique has been used to produce this image and what is it showing?
It is a lens section and it is showing the centre of a lens
What viewing technique has been used to produce this image and what is it showing us?
Lens section - it is showing us the posterior surface of the lens.
How can you fully view the lens using the lens section technique?
First focus on the iris then move across to the centre of the pupil. you should see all aspects of the lens illuminated at different points.
Why are we concerned about the angle of the anterior chamber?
Closed angle glaucoma.
Who is at risk of closed angle glaucoma ?
Elderly hyperopic patients.
Can an optometrist induce a closed angle attack?
Yes when you dilate a patient
Van Herrick’s Technique
What is it used for?
Beam width?
Viewing angle?
Magnification?
How do you carry out the technique?
What are you assessing?
Used to acess the depth of the anterior chamber
1-2mm
60 degrees
16x
Instruct patient to look directly at the microscope. Position narrow slit beam on the sclera and move across until you reach the limbus and the beam splits in two.
Assess the gap between the iris and the back surface of the cornea to the thickness of the cornea.
What viewing technique has been used to produce this image?
Van Herricks
What are the structures present in this image and what grade would this be?
Grade 4 as the gap is bigger or equal to the thickness of the cornea- ratio is 1:1 (i.e. the angle is wide open).
What viewing technique produces this image and what structures can be seen as a result?
Specular reflection
Beam Width?
Viewing angle?
Magnification?
What is the angle of incidence equal to?
How do you set up for specular reflection illumination?
What can you expect to see?
What are the uses of specular reflection illumination?
2-4mm
45-60 degrees
>16x (high magnifcation)
The angle of incidence is equal to the angle of reflection.
Remind the client to fixate straight ahead. Look into the microscope. Using the joystick, bring the parallelepiped into sharp focus. Movement of the tear film should be visible after the client blinks. Gradually change the angle the illuminating arm makes with the microscope until a bright, dazzling area of the precorneal tear fluid is seen.
You can expect to see the anterior surface of the lens appear like an orange peel.
Details of the precorneal fluid, mucus secretion and lipid elements of the tears are seen. This illumination enables the contact lens fitter to objectively assess the quality of the tear layer.
What viewing technique has been used to produce this image?
Specular reflection
Sclerotic scatter
Beam Width?
Viewing Angle?
Magnification?
What’s the theory behind the technique and thus what should be seen in an ideal eye?
If a microscope is used for this technique then what must be done?
2-4mm
45-60 degrees
With the naked eye.
The light is internally reflected within the cornea and re-emerges around the limbus, therefore, in a normal eye, the cornea appears dark with a halo of light around the limbus.
If the microscope is to be used it must be decoupled from the illumination system.
What viewing technique is used to produce this image?
Sclerotic Scatter
What is Tear Break Up Time (TBUT) ?
Tear Break Up Time (TBUT) is related to the wetting properties of the tears and the rate of tear production.
(It is the time taken to produce tears).
What is normal Tear Break Up Time (TBUT)?
Over ten seconds (anything under ten seconds is abnormal).
In which people is Tear Break Up Time (TBUT) reduced?
The elderly
Those suffering with Xerophthalmia
Those with Sjogrens Syndrome
Contact Lens Wearers
What is Xerophthalmia?
Xerophthalmia is a progressive eye disease caused by vitamin A deficiency.
(Lack of vitamin A can dry out your tear ducts and eyes. Xerophthalmia can develop into night blindness or more serious damage to your cornea).
What is Sjogrens Syndrome?
A chronic autoimmune disease affecting salivary glands and tear glands.
What is used to test Tear Break Up Time (TBUT) and how do you carry this out?
Flourescin.
You instill flourescin into the patient’s eye then view the eye using the slit lamp - here you add the cobalt blure filter. (If the slit lamp has a wrath filter add this too to increase contrast).
Focus on the cornea and observe the green tear film.
Ask the patient to take a blink and then stare straight ahead.
START counting the number of seconds until you observe dark blue patches appearing in the green tear film. When you see this STOP counting. This is your TBUT.
How many purkinje images are there of the eye?
Four
Where is each purkinje image formed?
Purkinji I - tear Film
Purkinji II - Corneal Endothelium
Purkinji III - Anterior Surface of Lens
Purkinji IV- Posterior Surface of lens
Which purkinji image is the brightest?
Purkinji I
Which Purkinji image is the hardest to see?
Purkinji II
What is the Purkinji III responsible for?
The orange peel effect seen in specular reflection illumination (when i = r ) .
Which Purkinji image is this?
Purkinji I
Which Purkinji image is this (the one far right)?
Purkinji II
Which Purkinji image is this?
Purkinji IV
When using Fluorescin what must you always ensure you do & don’t do?
Remember to use Saline and check expiry dates!
NEVER use tap water.
Tap water + Fluorescin –> Pseudomonas (bacteria) which we do not want!
What does Smith’s method allow us to estimate?
It allows us to estimate the anterior chmaber depth at the apex of the cornea.
If a patient has a ratio of 0.5:1 as measured using Van Herrick’s technique, what grade is she given and what is the diagnosis?
Grade 3 . Diagnosis is that angle is open.
If a patient has a ratio of 0.25:1 as measured using Van Herrick’s technique, what grade is she given and what is the diagnosis?
Grade 2. Diagnosis is that it is suspicious and needs to be checked out by gonioscopy.
If a patient has a ratio of <0.25:1 as measured using Van Herrick’s technique, what grade is she given and what is the diagnosis?
Grade 1. Diagnosis is that the angle is dangerously narrow.
What pathology could possibly be seen by sclerotic scatter?
Corneal oedema - this woul look like a spot also being highlighted (as well as the limbus)
Corneal opacity - a highlighted spot within the cornea.
What are slit lamps used for in optometric practice?
Examination of external eye, anterior chamber, iris and crystaline lens.
Fundus examination (requires auxillary lens and mydriasis).
Applanation tonometry (requires Goldmann tonometer attactchment) - allows us to determine intraocular pressure.
Gonioscopy - viewing of the iridocorneal angle.
Pachometry -process of measuring the thickness of the cornea
Inspection of Contact Lenses.
How is a lid eversion conducted and why is it done?
In order to examine the palpebral conjunctiva under the upper lid.
Instruct the patient to look down.
Place a thin rod (e.g. a cotton bud) horizonatlly along the skin of the upper eyelid just above the level of the upper border of the tarsal plate.
Take the upper lid margin and lashes between the index finger and the thumb and draw the lid away from the globe.
press down with the rod and roll the lid back over it. The rod can then be withdrawn and the lid will normally stay up until the patient looks down or blinks.
What is fluorescin used for?
To detect lesions of the corneal epithelium.
To examine the fit of RIGID contact lenses.
In applanation tonometry
To evaluate TBUT (Tear Break Up Time).
To demonstrate the patency (the condition of being open or unobstructed) of lacrimal drainage.
What is fluorescin angiography?
A technique used to examine integrity of retinal vessels.
What are fluorets and why are they used?
Pseudomonas (a type of bacteria) has an affintiy for flourescin and contamination with this organism presents serious risk to the eye. To avoid this risk fluorescin is usually applied using impreganted paper strips called fluorets.
How does the instillation of Fluorescin occur?
The Fluoret is dampened using sterile saline solution or contact lens wetting solution (NEVER tapwater).
Patient is instructed to look UP and NASALLY.
The moistened fluoret touches the exposed bulbar conjunctiva.
It is then ready to view under UV light.
What are the dark blue areas seen when testing Tear Break Up Time (TBUT) using fluorescin?
These are areas where the tear film has evaporated to expose the epithelium.
Why are elderly hyperopic patients at risk of closed angle glaucoma?
As you age the lens gets (shorter) and fatter. As a result volume in the anterior chamber decreases and so pressure increases.
