DR.NAFIZ MAHMOOD
SLIT-LAMP BIOMICROSCOPY
Resident
Nat iona l Ins t i tu te o f Ophtha lmo logy and Hosp i ta l Bangladesh
WHY SLIT LAMPS ARE SO GREAT
gold standard device.
This is because they provide…Stereoscopic imageVariable illuminationVariable magnificationExcellent image quality
WHY NAME SLIT LAMP
BIOMICROSCOPE
A narrow vertical slit of light is projected on to the eye and permits microscopic examination of living tissues in cross-
section
History
First concept of slit-lamp was introduced by PROF. ALLVAR GULLSTRAND IN 1911
And named as LARGE GULLSTRAND OPHTHALMOSCOPE
SPECIAL FEATURES1. The alignment of viewing & illumination
system - parfocal2.long working distance. 3.allows to carry out certain manoeuveres like
• FB removal from cornea• interpose certain optical devices-
condensing lens, goniolens, Goldmann applanation tonometer
3. Incorporated with prisms
-invert the image vertically and
horizontally -so it appears erect and right
way round
4. A bank of Galilean telescopes of different
powers
- to allow the magnification
WHAT CAN WE USE THEM FOR?
Routine examination of anterior segment
Problem-based examination of anterior segment
Assessment of anterior chamber depth and angle
Contact lens examination
GonioscopyFundoscopyOcular photographyContact tonometry
(Goldmann)Laser
photocoagulation
On their own
With accessories
BASIC DESIGN
Observation system
Illumination system
Mechanical support system
OBSERVATION SYSTEMcomposed of 2 lenses
- objective lens- eyepiece lens
Objective lens :consists of 2 plano-convex lenses
providing a composite power of +22 D
Eyepiece lenses :magnification : 10×, 16×, 25×provide good stereopsis as the tubes
converged at an angle of 10°- 15°
Prisms :to overcome inverted image produced
by compound microscope
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Fo FoO Fe Fe
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EL
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Optics of compound microscope
Cross-section of observation system of
modern slit-lamp
MAGNIFICATION
• Slit lamps provide variable magnification• Lower magnifications - general
assessment and orientation• Higher magnifications -detailed
inspections of areas of interest• There are several ways to do this
- Common methods: Littmann-Galilean telescope and zoom systems- Less common methods: Change the eyepieces and/or change the objective lens
LITTMANN-GALILEAN TELESCOPE METHOD
• A separate optical system is placed in between the eyepiece and the objective
• Utilizes Galilean telescopes to alter magnifications
• It consists of a rotating drum that houses Galilean telescopes
Galilean telescopes consist of a positive and negative lens that provide magnification
based on the lens powers
Galilean magnification changer (G) is placed between the slit-lamp objective (O) and the relay lens ( R ).
ILLUMINATION SYSTEM
Comprises of :• Light source: halogen
lamp• Condenser lens system• Slit and other diaphragms• Filters• Projection lens• Reflecting mirror
MECHANICAL SUPPORT SYSTEM
Consists of :Joystick arrangementUp and down movement
arrangementPatient support arrangementFixation targetMechanical coupling
Technique of biomicroscopy
A.Patient adjustment :should be positioned comfortably in
front of slit-lamp with his or her chin resting on the chin rest and forehead opposed to head rest
B. Instrument adjustment :
- height of the table housing the slit-lamp
should be adjusted according to patient’s
height
- microscope and illumination system
should be aligned wth patient’s eye to be
examined
- fixation target should be placed at
required position.
C. Beginning slit-lamp examination : some points to be kept in mind
I. Room should be semi-darkII. Diffuse illumination – used for short timeIII.Medications like ointments and anaesthetic
eyedrops produces corneal surface disturbance which can be mistaken for pathology.
IV.Low magnification should be 1st used to locate pathology and then higher magnification to examine it.
Structures to see through slit-lamp
External : brow, nose, chick
Lid & lashConjunctiva & sclera
CorneaAnterior chamber
IrisLens
Anterior vitreous
PRINCIPAL OF ILLUMINATION
DIFFUSE ILLUMINATION1
DIRECT FOCAL ILLUMINATION2
SPECULAE REFLECTION3
TRANSILLUMINATION / RETROILUUMINATION4
INDIRECT LATERAL ILLUMINATION5
SCLEROTIC SCATTER6
DIFFUSE ILLUMINATION
LIGHT : Full height Broad beam Low brightness
DIRECTION : Temporally or Nasally
What structures can be seen
White light
Eye & adnexa
Cobalt blue filter with fluorescein1.Evaluation of fluorescein dye ( appear
yellow) staining the ocular surface tissue
2.Tear film3.To discern the fluorescein pattern in
Goldmann Applanation Tonometry
[thin marginal tear meniscus and inferior punctate erosions stained with fluorescein ]
Red free filter with rose bengal dye
Diffuse illumination with red free filter to enhance visibility of rose bengal red dye which has stained
keratin in intraepithelial ( squamous ) neoplasia
DIRECT FOCAL ILLUMINATION
Lamp Microscope
The light and the microscope are both pointed at the object of interest
Beam :full height medium widthmedium bright
Direction:obliquely
Aim :to focus it on cornea so that
quadrilateral block ( parallelepiped) illuminates the cornea
ANTERIOR SURFACE
CROSS-SECTIONAL ILLUMINATION
ANTERIOR SURFACE
CROSS-SECTIONAL ILLUMINATION
POSTERIOR SURFACE
Use :1. to examine the anterior surface &
posterior surface of cornea 2. examination of anterior segment &
lens3. for grading of cells & flares ( when the
height of the beam is reduced to 2-4 mm)
OPTICAL SECTION :when the beam made so narrowed that the anterior & posterior portion becomes very thin leaving only cross sectional illumination of cornea.
Optical section: mostly depth
SPECULAR REFLECTION
i r
lamp microscope
Beam :medium – narrow ( must be thicker than
optical section )
Angle between light & microscope : 50° – 60°
Purpose :• to observe corneal endothelium.
Careful focusing can bring up
endothelial cells, like mosaic pattern
RETROILLUMINATION
Lamp Microscope
An object of interest is lit by retro-illumination when the light source is
directed onto another structure (deeper) so that the reflected light must pass
through that object.Retroillumination of fundus is best performed with -• dilated pupil• viewing and illuminating arm not
parfocal
What can be seen• Blood vessels of cornea, • abnormalities of post. surface of cornea• Cataract & PCO• iris atrophy
Directly illuminate
dRetro-illuminated
Blood vessels of cornea, other abnormalities of post. surface of cornea
INDIRECT LATERAL ILLUMINATION
DIRECTION : • Light is directed just to the side of lesion
to be examined• Some of the light enters the lesion so it
glows internally
What can be seen:
• corneal infiltrates• corneal microcyst• corneal vacule
SCLEROTIC SCATTER
BEAM :medium width
Direction :on to the limbus - temporallythe viewing system focused to center of
cornea
lamp
microscope
Sclerotic scatter produces a diffuse glow of limbus and a backlighting of any corneal opacities, as with cornea verticillata( whorl-like changes) secondary to epithelial
deposition of the oral drug amiodarone
PITFALLS & POINTERS1. Remember to set the oculars to your
refractive error or to plano if you are using spectacles.
2. Proper positioning of the patient3. Intensity of the light at level of patient’s
comfort4. To take advantage of full value of slit-
lamp, examiner must become skilled in using all of the methods of illumination and understand when each is best employed.
Thank you
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