Understanding the slit lamp
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Transcript of Understanding the slit lamp
Eye Emergencies
Dr Carmel Crock FACEM
Director, Emergency Department, RVEEH
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Cornea
• 5 layers
• Depth
0.5-0.8mm
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Normal Cup/Disc ratio 0.3
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Normal retina
Optic disc swelling
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Malignant hypertensive retinopathy.
Grosso A et al. Br J Ophthalmol 2005;89:1646-1654
©2005 by BMJ Publishing Group Ltd.
Anatomy of a Slit Lamp
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Features
• Illumination system
• Magnification via binocular microscope
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Basic Components: illumination
• Bulb• Filters• Slit height
control• Slit rotator• Mirror• Slit width
control
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HeightFilters& Cobalt blue
Filters
1.Unfiltered
2. Heat absorbing
3. 10% Grey
4. Red free
5. Cobalt blue
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1 2 3 4
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Width
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Basic Components: magnification
• Eye pieces• Magnification changer• Joy stick• Lock• Base carriage
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Magnification
Most slit lamps have:• 2 objective settings (1 and 1.6)
• 2 eye piece options (10x and 16x)
• Total magnification ranges thus from 10x-25x
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Use of the Slit Lamp
• Seat patient comfortably
• Adjust table, chair
• Position patient’s head
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Focus the Microscope by 1. Adjusting
inter-puplillary distance
2. Adjusting the eye pieces (set at 0 or dial in your refraction)
3. Checking magnification is on 1x setting
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Focus Patient’s Eye
• Microscope straight• Light column 20-30
degrees from side• Microscope moves via
joystick• Move laterally• Move in and out• Bimanual
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Adjust the Illumination
• Brightness: filters
• Width: slit vs broad beam
• Height: long vs pinpoint
• Cobalt blue
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Trouble Shooting: unable to turn it on
• Check all connections
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Trouble Shooting: power on - but no light
• Slit width closed• Slit height too small• Bulb burned out• Bulb not positioned
correctly
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Trouble Shooting: difficulty moving instrument
• Unlock• Check patient position
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Trouble Shooting: difficulty focusing
• Check eye-pieces on correct setting
• Make sure patient’s head in correct position
• Adjust joy stick in and out
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Trouble Shooting: misalignment of slit and view
• Check magnification changer
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Anterior Segment Examination
• Systematic examination of the eye from front to back
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Lashes/ Lids
Conjunctiva
Cornea
Sclera
Anterior chamber-deep and quiet
IrisLens
no FB no FB
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32http://eyelearn.med.utoronto.ca/default.htm
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Normal cornea
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Assessment of Depth
http://eyelearn.med.utoronto.ca/default.htm
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Do not remove deep CFB
Oedematous thickened cornea from deeply embedded FB
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Assessment of Depth Corneal Lesion
• Thin beam of light
• Illumination column 35-45 degrees
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Stain Cornea
• Use fluorescein
(+/- do Seidel’s test)
http://eyelearn.med.utoronto.ca/default.htm
Corneal abrasions
Fluorescein
• Absorbs light in blue wavelength• Emits green fluorescence
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Tips - fluorescein
• Don’t forget to use it eg. HSV• Measure size abrasion• Total vs nil staining - chemical injury• Fluorescein under lid – upper lid abrasion• Seidel’s + or –ve -document• Self sealing wounds• Apply fluorescein then wait for bit to see
more subtle staining
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Measuring Size of Lesion
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Anterior Chamber
Setting up to look at anterior chamber-darkened room
• 1mm beam height• Bright intensity illumination• High magnification
• Is the anterior chamber deep and quiet?
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Grading of AC Cells (counted with 1x1 mm slit)
Activity Cells+ 6-15
++ 16-25
+++ 26-50
SUN 2005 Am J Opthalmol 2005: 140: 509
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Removing a Foreign Body
Removal of corneal foreign body with needle and with burr
Step by step guide – how to use slit lamp - summary
1. clean
2. practice turn on and using
3. bring in patient - adjust chin rest, lat. canthus at line, forehead against band
4. prepare microscope - interpupillary distance, oculars set at 0, low mag
5. prepare light - low volt, 10% grey, wide beam
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Step by step guide – how to use slit lamp - summary
6. Examine lids, lashes, conj, sclera, cornea, iris, lens
7. Use narrow beam to examine corneal lesion – measure depth
8. Set up to look at anterior chamber - depth, cells, flare - bright/1mm beam/high mag
9. Use fluorescein –measure size lesion
10.Turn off and clean
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