OHD Labs

Illumination techniques on a sit lamp

Diffuse illumination

Allows to view the overall

Achieved by using the slit and scanning across eye

Only illuminates small areas

Doesn’t allow to compare aspects like colour \

Executing diffuse illumination

Place diffuser in front of illumination

Light from beam is diffusing across the whole of the eye and evenly illuminates it

Brightness controlled by increasing brightness or increasing height or slit

Use low mag as gives large depth of field \ask patient to look in diff directions so can look at more areas of the eye

Optical section corneal

Effective for examine depth of corneal damage

Remove diffuser

Thin slit down as much as possible for better resolution

Increase magnification

Increase brightness

Upper and lower part is not in focus due to the curvature of cornea

Reduce height of slit to 3-4 so straighten eye and have all cornea in focus

Magnify image further whilst focusing it

Slit width might need adjusting to get bright image

Increasing angle between illumination system and observation system

Increasing angle section looks broader

Reducing angle make sit thinner \increase mag further layers can be seen more clearly

Move to temporal section of cornea whilst keeping in focus

Why do we move to the temporal side of cornea to view the layers

The temporal side is the thickest part of the cornea so the layers differentiate more

Examination of an anterior model eye

1. Start with wide beam at low mag

2. Control slit lamp with one hand on the joystick and one hand on the illumination system

3. Scan across the eye moving the illumination system to the other side when you reach midpoint

Examination using a parallel piped beam

Remove the diffuser, narrow beam , increase the brightness and increase the mag

Scan across the eye again focusing on the anterior surface of cornea

Creating an optic section

Narrowing the beam further to the thinnest, increasing brightness and magnification

Place the illumination system at an angle to view the Individual layers

After you have focused the slit lamp correctly, you remove the focusing rod and look through the eyepieces at your patients eye. You have not moved the lamp. What’s the most likely reason that the eye appears blurred

Slit lamp too far back

If you’re focused on the cornea and now want to focus on the lens, how would you do this

Move the slit lamp forward

What slit lamp technique is this

Optic section

There are lesions in the cornea shown below. What layer of the cornea is this

Epithelium.

How do you know if you’re correctly focused on the anterior cornea

You can see the tear debris moving when the patient blinks

Apart from cornea what other structure can you view with an optic section

Lens

Once focused eye pieces, where is the slit lamp always focused

Above the pivot point

What of the following words is most appropriate to describe a cornea when appears normal

No abnormalities detected

What angle should the illumination be at when conducting an examination of the eyelid

0 degrees so illumination in line with the observation

Anterior eye examination

1. Focus slit lamp

2. Move light to the eye using low mag and diffuse, move in / out until in focus

3. Scan inner canthus to outer

4. Ask patient to look up

5. Pull down lower lid and check pall conjunctiva. Can remove diffuse and look with wide beam at higher mag

6. Ask to look down and lift lower lid

7. Look straight ahead and scan across again

8. Move slit lamp closer to view iris and scan across - cornea ( blue light) should be out of focus

9. Move even further to focus on lens, should see orange peel texture

Optic section of intracocular lens

Thin slit and can view section of cornea at 16x

Once 1, is achieved, you can see the lens out of focus within the pupil. To focus the lens move lamp forward until clear

Should see 3 layers on the pupil, anterior capsule, epithelium and anterior cortex

Move in further for nucleus , should see dark band with 2 blue bands next to it

To view posterior parts, increase mag 25x reduce angle and move in

Purpose of Specular reflection

Examine surface quality of tissue that reflects light

Corneal endothelial specular reflection

Will allow is to see the cellular structure of endothelial as a standard resolution and mag

How do we achieve specular reflection

Need to observe the reflection of the illumination systems light source

Reflected ray should make an angle to the normal

Should be equal to the angle Of incidence

As cornea is curved, the normal will change across surface

start up of specular reflection

Corneal section formed

Microscope in straight ahead direction

Can see reflection of light source to the left of section

Instructions to perform specular reflection after corneal section is formed

illumination at 45

microscope in straight ahead direction

 Increase mag x16

Adjust slit width and brightness

Move corneal section onto the bright corneal reflex ( purkinje image)

reduce slitheight to the same size as corneal reflex

now will be able to see a section of the endothelium and epithelium  

What is Van Herick used for

Assessing anterior chamber angle to help determine whether patient is at risk of angle closure glaucoma

Or if glaucoma is induced by pupil dilation

How to set up Van Herick

Form clear optic section at the apex of cornea

Reduce height of slit so it’s 3-4mm in height

How to measure van hericks of temporal

Move optic section to temporal cornea

Keep observation system straight ahead

Then angle illumination system 60 degrees temporally

Increase mag 25x

Examine space between corneal section and iris scatter: this space represents the aqueous

Van hericks grading scale

Assessing van Herick of nasal

Ensure angle of observation and illumination is 60 degrees

Locking it in place

nose will get in way of illumination system

So move the observation and illumination System temporally about 5-10 degrees

Ask patient to look at observation system

Measure van hericks

why do we assess the anterior chanber angle

to assess the patients risko developing closed angle glaucoma

what illumination type do we use for a van herick 

optic section

what angle do you set between the illumination and observation systems for Van hericks

60 degrees

what side should the illumination be on for doing temporal van hericks

temporal

to assess van hericks, we compare the slit beam width with what?

the space between the endothelium and the iris 

what do we nee to do for a nasal van hericks

we need to be careful the light from illumination syste isnt obstructed by the patients nose 

we need to be careful not to hit nose 

helful to lock illumination system to maintain the correct angle 

observation and illumination rotated temporally 

px looking at the observation system 

illumination system on the nasal side moving from sclera to cornea 

what grade is this   1:0.75

grade 3

grade  1:1

grade 4 

1:0

grade 0

1:0.1

grade 1

1: 0.3

grade 2

1:0.65

grade 3

1:0.25

grade 2

1:0.15

grade 1

How to measure structures and lesions on the eye using slit lamp

Narrow beam

Rotate slit beam so it’s same orientation as the thing you want to measure

Adjust height so it’s same length

Record length or vertical and horizontal

after you have focused the slit lamp correctly, you remove the focusing rod and look through the eyepieces at your patients eye. You have not removed the slit lamp. what is the most likely reason that the eye appears blurry 

slit lamp is too far back 

cant be too forward as the focusing rod wouldnt have fitted

if you are focused on the cornea and now want to focus on the lens, how would we achieve this 

move the slit lamp forward

what slit lamp technique is being demonstrated in the image 

optic section

what slit lamp technique is benig demonstarted in this 

sclerotic scatter 

what layer of the cornea are the arrows pointing to 

epithelium

how do you know if you are correctly focused on the anterior cornea 

you can see the tear debris moving when the patient blinks  

apart from the cornea, what other structure can you view with an optic section

lens

one you have focused the eyepieces, where is the slit lamp always focused?

above the pivot point

with which slit lamp technique woul dwe decouple the slit lamp

sclerotic scatter

what would we describe a cornea that appears normal

Clear

what angle should the illumination be at when conducting an exam of the eyelids 

variable- the angle should change as you examine across the eyelid 

what slit lamp tecnhique is being demonstrated in the image below 

specular reflection

what abnormalities in the eye can be visualised with sclerotic scatter 

corneal foreign bodies 

corneal scars 

corneal oedema 

when is it useful to decouple the slit lamp

when illuminating one strucure but observing another

which structure of the eye do we observe when performing sclerotic scatter

cornea 

how do you set up the slit lamp for specular reflection

angle of incidence= angle of reflection

which slit lamp technique is this 

conical beam 

what is a conical beam useful for

examining the anterior chamber for sings of inflammation

what structures of the eye can you retroilluminate from

retina

iris

what abnormality is visible in this picture

iris transillumination

I would like to check the corneal endothelium for polymegathism (cell size variability). what slit lamp tecnhique should i use 

specular reflection

what slit lamp technique is being demonstrated on the model eye in this image

optic section

what slit lamp technique is being demonstrated on model eye in this image

parallelpiped 

which slit lamp technique does the angle of incidence need to be equal to the angle of reflection

specular reflection

which direction should the observation and illumination systems be moved for nasal van herick

temporal

what ration would this angle be? 1:

0.3

( between 0.25-0.5)

what grading

grade 3

which layer of the cornea is the green lesion located in?

endothelium

how would you accuratley measure the longest part of the crcled lesion - point A to point B

1. rotate the sit beam so that its orientation matched that of the lesion 

2. adjust the slit height until its the same length as the lesion 

3. read off the slit height as the length 

beam shows 1mm slit length

what measurement would you record for this bit of the lesion

1.3 

what would you record the measurement of beam shows 1mm

1.1 

pulsair NCT 

puff of air to measure IOP 

aods in screening and diagnosisi of glaucoma at 15mm black cross appears, centre the image hear and will fire 

select R for individual readings 

I care rebound

place wristband around wrist

at top is the forhead rest an forhead asjusting wheel

bottom part tsticking out- probe base and collar

black screen is the display

round circle is the select and navigation button

measuring button

how to turn on the icare rebound tonometer

press and hold the measuring button until you hear a beep

load probe into tonometer when it says to load it on the display

open cap and place the single use probe into the probe base 

a green light appears around the probe base when inserted correctly 

blue play button appears on the display when ready to take a reading 

place 

place forhead against rest and align the probe base in centre of cornea- it will show up as green if allgne correctly. 

press and hold the measuring button until long beep is heard 

to take individual readings, press button 6 times

which structure is in focus 

cornea

what side is the light coming from

left side

when trying to perform an optic section of the cornea to determine which layer the green lesion is in, but it doesnt look right. What could I be doing wrong

slit is too wide

slit lamp is too far back so not focused sharply

slit lamp too far forward so not focused sharply on the cornea

what surface is in focus here

cornea 

what structure is the lesion on where red arrow pointing

lens

what surface is red arrow pointing to on lesion if illumination on the left 

anterior lens 

slit lamp technique- sheffers sign

what is shaeffers sign

release of blood cells or pigment clumps into anterior vitreous

indicates if reitnal detachment occurs : if shaeffers sign is positive

how to conduct 

have clear section of cornea in middle 

angle of illumination at 15 degrees 

microscope 15 away from illumin

push slit lamp forward until anterior in focus 

push further in until posterior focus 

then move further in until the anterior vitreous is in focus 

what do we look for in the anterior vitreous

see if there are any piment clumps seen in the beam

switch of light in room to view

ask to look around left right up down to agitate vitroeus and see clumps if there more visible

what are the 4 Ds you should check for before putting a rop into the px eye for dilation?

drug

dose

direction

date

what would a positive shaeffers sign indicate

there is likely a retinal detachment present in the eye

how should the slit lamp be set up for assessing the anterior vitreous

there should be a narrow angle of around 30 degrees between viewing system and the illumination system

where should you instil an eye drop

on the px lower fornix