Indra P Sharma
B.Optom, M.Optom
The magnified tour of the eye with
SLIT-LAMP
BIOMICROSCOPE
Here comes your slit lamp...
...and with it comes your
RESPONSIBILITY
Background
The name
SLIT : A narrow slit beam of very bright light
LAMP : produced by a lamp (illumination
system)
BIO : to view the biological structure (of
eye)
MICROSCOPE : under magnification with a
microscope
Overview
Instrument uniquely designed to give a magnified three dimensional view of the eye and its structuresfor quantitative measurements for documentation.
Because the slit lamp provides a binocular view, the location of abnormalities can be determined with great precision.
The instrument combines variable magnification with controlled illumination.
In simple, to make a magnified tour of the eye.
The History Mystery
History Mystery
Alivar Gullstrand (5 June 1862 – 28 July 1930)
Nobel prize in Medicine and
Physiology (1911) for developing
slit lamp biomicroscope.
Vogt (1919) : Specular
Microscopy
Various modification by Kohler,
Goldmann,
Large reflection free
ophthalmoscope
Manufactured by Zeiss in 1911
Illuminator with Nernst glower
Haag-streit (1920) Bausch and Lomb slit lamp(1926)
Haag-streit 1933 and 1936
Modern Day
The types
1. According to brands
(Company)
According to Brand (company)
Haag-streit
Topcon
Zeiss
2.Illumination types
Horizontal prism reflected light source
Vertical illumination source
3.According to Magnification
exchanger
Grenough type Galilean type
The Optics
Optics
It works on the same principle as a compoundmicroscope.
The objective lens (+22 D) is towards the patient,whose eye forms the object. The objective lensconsists of two planoconvex lenses with theirconvexities facing towards each other.
The eyepiece is +10 to +14 D and is towards theexaminer.
The illuminating system can be adjusted to vary the width, height and angle of incidence of the light beam.
The working principle
Optics
Parfocality : the focus of the slit and the focus
of the microscope are at the same point.
The Parts
Fixation target
Chin rest
adjustment
knob
Joystick
Power switch
Table height
adjustment
Forehead
band
Canthus
alignment
Chin rest
Hand grip
for patients
Lock for slit
lamp base
Low friction plate
Scale for slit
height
Slit height
control
Inclined mirror
Latch to tilt
light column
Light source
Filter control
Centering
screw
Slit width
conrol
Parts of Slit-lamp
1. Illumination system
2. Observation system
3. Mechanical system
1. Observation system
– binocular eyepieces
– camera/video adaptor
– observation tube (demonstration slitlamps)
– magnification changer
2. Illumination system
lamp housing unit
slit width and height control
neutral density filter
cobalt blue light
red-free (green) filter
field size control
diffuser
prism.
3. Mechanical system
Motorized table (Base)
Patient positioning frame
Joystick
forehead rest
chin rest
fixation target
power supply unit
locking controls.
Magnification ranges
Low magnification: 7X - 10X : general eye(Lids, bulbarconjunctiva/sclera,cornea/limbus,tears, anteriorchamber/iris/crystalline lens)
Medium magnification: 20X - 25X : structure of individual layers.
(Epithelium/epithelial breakdown, Stroma, Endothelium, contact lens fit/lens condition)
High magnification: 30X - 40X : details.
(epithelial changes, stromal striae, folds, endothelial folds, polymegethism)
Illumination System: Features
1. Variable light intensity
– low
– medium
– high.
2. Filters
– cobalt blue light
– red-free (green)
– neutral density filter.
3. Width
– optic section
– parallelepiped of Vogt
narrow beam
broad beam
– conical beam.
4. Height
– adjustable slit height
5. Angle
– variable angle formed with the observation
system
– rotation of the prism or mirror enables
observation with an alternate illumination
technique (especially an indirect method).
Controls
Slit width control knob Slit height control knob
The examination procedure
What the Patient Needs to
Know
Instruction to patients:
This instrument is a microscope used to magnify the structures of the eye.
Please keep your chin in the cup with your teeth together and your forehead against the bar. Try not to lean back. The microscope comes close to your facebut will not touch your eye.
Sometimes the light is bright. Unless specifically told not to, you may blink at any time.
Try to keep both eyes open.
This is just a light, not a laser or a camera.
How to start?
Focus the eye piece
Adjust the headrest
Position the fixation target
Decrease the room illumination
Start with diffuse illumination
Order of Examination
Tears
Lid margins/Lashes
Conjunctiva
Cornea
Anterior chamber
Iris
Lens
Anterior vitreous
What is wrong?
Keypoints
Patient education is an important aspect of the slit lamp
exam.
A comfortable patient is a more cooperative patient.
Before beginning, adjust the ocular power and pupillary
distance
(PD).
Using lower voltage settings preserves bulb life.
Manipulate the microscope with one hand on the light
source
and the other hand on the joystick.
Developing and following an examination protocol will help
ensure quality patient care.
Accurate, legible documentation is the last step of any slit
The illumination technique
Illumination Techniques
1. Diffuse.
2. Direct.
3. Indirect.
4. Retro-illumination.
5. Specular reflection.
6. Sclerotic scatter.
7. Tangential.
1. DIFUSE ILLUMINATION
• 45 degree angle between light and
microscope
• Fully open slit
• Diffusing filter
• Variable magnification (low to high)
Overall view of:
Lids and lashes.
Conjunctiva.
Cornea.
Sclera.
Iris.
Pupil.
2. Direct Illumination
Observation and illumination systems are
focused
at the same point.
Vary angle of
illumination
Low to high
magnification
Vary width and height
of light source
2.1 Optic Section: Slit width 1mm or less
Illumination angle 45-60° or more
High illumination & magnification
Application:
Corneal depth, layers, scars, vessels, Lens opacity
2.2 Parallelepiped: wider beam
Slit width 2-4 mm obliquely focusing
quadrilateral block of light illuminate the
cornea Application
To examine corneal epithelial,
stroma
To ascertain depth (FB, abrasion),
breakdown, lens surface and endothelium.
2.3 Conical Beam: Narrow, short & bright slit of light
45°-60° light source directed to pupil
Magnification 16x-25x
Application :
Inflammatory cells, flare, pigmented cells, metabolic
wastes
Assessment of particles floating in the A/C
3.Indirect Illumination
Observation and illumination systems are not
focused at the same point.
Focal light beam is directed adjacent to the
area of observation. Vary angle of illumination
Slit beam is offset
Vary beam width
Low to high magnification
Valuable for observing:
Iris pathology.
Epithelial vesicles.
Epithelial erosions.
Iris sphincter.
4.Retro-illumination
Object of interest is illuminated by light
reflected
from the structures behind it. Vary angle of illumination
Moderately wide beam
Slit beam is offset
Medium to high magnification
Reflected light from iris or
fundus
Valuable for observing: Vascularization.
Epithelial oedema.
Microcysts.
Vacuoles.
Dystrophies.
Crystalline lens opacities.
Contact lens deposits.
5. Specular Reflection
Angle of incidence = angle of reflection
Slit width < 4mm
Magnification 35x
Best view with one eye
Application :
Assessment of surfaces
Corneal epithelium
Corneal endothelium
Lens surface
Assessment of tear film
6. Sclerotic scatter
Light incident on the limbus with 2-4mm slit at
an angle of 45° - 60°
The microscope focused centrally
Total internal reflection of the incoming light at
inner corneal boundaries (endothelium and
epithelium)
Applications
Scars, foreign bodies, corneal
defects
Irregularities in the cornea
Localized epithelial oedema.
7. Tangential
A narrow light beam is projected almost
parallel along the structure to be observed
Elevated structures are visible by shadowing
Illumination angle 70-90°
Magnification 10-25x
Application :
Elevated abnormities or changes in the iris
Tumors, cysts
Key Points
An appreciation of what is normal is necessary
before one can identify that which is abnormal.
Documenting that a structure is normal is just
as important as notating irregularities.
There are variations of normal that you will
learn as you continue to examine eyes with
the slit lamp.
The accessories
Filters
a) Open aperture
b) Heat absorption screen: decreases patient discomfort
c) Grey filter: decreases maximum brightness for photosensitive patients
d) Red free filter- enhances blood vessel and haemorrhage
e) Empty space for extra filter
Cobalt blue filter
Enhance fluorescein stain
Associated instrument
Goldmann applanation tonometry
Lenses
Laser delivery system
Slit lamp is the an important instrument for an
eye health personnel (treat it as an asset)
User level care & maintenance is very much
important to get optimum performance & long
life from it.
An careful eye examination can make a
difference in someones life.
Slit lamp examination is an artof
science.....Practice, practice practice
6/17/2017
optomindra.blogspot.in6/17/2017
Top Related