This document discusses slit lamp examinations, which use a high-intensity light source focused as a slit and viewed through a microscope to examine the anterior segment of the eye. It describes the two main types of slit lamps, the principles of examination, important historical developments, examination techniques including different magnifications and illumination methods, and the components and optics of the slit lamp biomicroscope.

1. DR RAKESH JAISWAL
SLIT LAMP EXAMINATIONS

2. Introduction
• An instrument consisting of a high-intensity light source that
can be focused to shine as a slit.
• Used in conjunction with a microscope.
• The lamp facilitates an examination which looks at anterior
segment, or frontal structures, of the human eye, which
includes the
– Eyelid
– Cornea
– Sclera
– Conjunctiva
– Iris
– Anterior chamber
– Natural crystalline lens and
– Anterior vitreous.

3. Important historical landmarks
 De Wecker 1863 devised a portable ophthalmomicroscope .
 Albert and Greenough 1891,developed a binocular
microscope which provided stereoscopic view.
 Gullstrand ,1911 introduced the illumination system which
had for the first time a slit diapharm in it
 Therefore Gullstrand is credited with the invention of slit
lamp.

4. TYPES
 There are 2 types of slit lamp biomicroscope
1)Zeiss slit lamp biomicroscope
2)Haag streit slit lamp biomicroscope
 In Zeiss type light source is at the base of the instrument while
in Haag streit type it is at the top of the instrument.

5. Zeiss slit lamp biomicroscope
Haag streit slit lamp biomicroscope

7. PRINCIPLE
 A "slit" beam of very bright light produced by
lamp. This beam is focused on to the eye which is
then viewed under magnification with a
microscope

8. How to start?
• Focus the eye piece
• Adjust the headrest
• Position the fixation target
• Decrease the room illumination
• Start with diffuse illumination
• Use appropriate magnification

9. Basic slit lamp examination
 Patient positioning:
 Head support unit
 Adjust height of table or chair
 Adjust height of chin rest such that patients
lateral canthus is aligned with the mark.
 Adjust ocular eyepieces.

10.  Power up
 Fixation
 Magnification : begin with 6x -10x
magnification
 Focusing
 Special procedures
 Protocol and documentation

12. MAGNIFICATIONS
• Low magnification:
– 7X - 10X : General eye
– Lids.
– Bulbar conjunctiva/sclera.
– Cornea/limbus.
– Tears.
– Anterior chamber/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
• Epithelium
– vacuoles
– microcysts
– dystrophies.
• Stroma
– striae
– folds.
• Endothelium
– Polymegathism
– guttata
– blebs
– cell density.

13. Instrumentation
 Operational components of slit lamp
biomicroscope essentially consist of:
 Illumination system
 Observation system
 Mechanical system

14.  Illumination system
 It consist of:
A bright ,focal source of light with a slit
mechanism
 Provides an illumination of 2*10^5 to 4*10^5
lux.
 The beam of light can be changed in
intensity,height,width,direction or angle and
color during the examination with the flick of
lever.

15. Condensing lens system:
 Consist of a couple of planoconvex lenses with their
convex surface in apposition.
Slit and other diapharm:
 Height and width of slit can be varied by using
knobs.

16.  Projection lens:
 Form an image of slit at eye.
 Advantages,
 1.keeps the aberration of lens down.
 2.increase the depth of focus of slit.

17.  Reflecting mirrors and prisms
 Filters
 Yellow barrier filter
 Red free filter
 Neutral density filter
 Cobalt blue filter
 diffuser

18. Observation system(microscope)
 Observation system is essentially a compound
microscope composed of two optical elements
1.an objective ,2.an eyepiece
 It presents to the observer an enlarged image of
a near object.
 The objective lens consists of two planoconvex
lenses with their convexities put together
providing a composite power of +22D.
 Microscope is binocular i.e. it has two
eyepieces giving binocular observer a

19.  The eye piece has a lens of +10D.
 To overcome the problem of inverted image
produced by compound microscope ,slit lamp
microscope uses a pair of prisms b/w the objective
and eyepiece to reinvert the image.
 Most slit lamp provide a range of magnification
from 6x to 40x

20. Mechanical system
 Joystick arrangement
 Movement of microscope and illumination
system towards and away from the eye and
from side and side is achieved via joystick
arrangement.
Up and down movement arrangement
Obtained via some sort or screw devices.
Patient support arrangement
Vertically movable chin rest and the
provision to adjust height of table.

21. Fixation target:
 A movable fixation target greatly faciliates the
examination under some conditions.
Mechanical coupling :
Provides a coupling of microscope and the
illumination system along a common axis of
rotation that coincides their focal planes.
 This ensures that light falls on the point where
the microscope is focused
 Has advantages when using the slit lamp for
routine examination of anterior segment of eye.

22.  Magnification control :
 Including two or pair of readily changeable
objective lenses and two sets of eyepieces.
 An on and off switch and illumination control .

23. Magnification
may be changed
by
flipping a lever...
Changing filters. biomicroscope
Patient positioning
Alignmen
t mark
Microscope
and light
source rotate
indepedently

24. Filters used in slit lamp biomicroscopy
 Cobalt blue filter
 Used in conjunction with fluorescein stain
 Dye pods in area where the corneal epithelium
is broken or absent.
 The dye absorbs blue light and emits green.
 Uses:
 Ocular staining
 RGP lenses fitting
 Tear layer

25.  Red free(green)filter:
 Obscure any thing that is red hence the red free
light , thus blood vessels or haemorrhages
appears black.
 This increases contrast ,revealing the path and
pattern of inflammed blood vessels.
 Fleischer ring can also be viewed satisfactorily
with the red green filter.

27. Illumination techniques
 Includes
 Diffuse illumination
 Direct illumination
 Parallilepiped
 Optic section
 Conical(pinpoint)
 Tangential
 Specular reflection
 Indirect illumination
 Retro-illumination
 Sclerotic scatter
 Transillumination
 Proximal illumination

28. Diffuse illumination
 Angle between microscope and illumination system
should be 30-45 degree.
 Slit width should be widest.
 Filter to be used is diffusing filter.
 Magnification: low to medium
 Illumination: medium to high.

29. Optics of diffuse illumination Diffuse illumination with slit beam and
background illumination

30. Applications:
 General view of anterior of eye:
lids,lashes,sclera,cornea ,iris, pupil,
 Gross pathology and media opacities
 Contact lens fitting.

31. Direct illumination
 Involves placing the light source at an angle of about
40-50 degree from microscope.
 This arrangement permits both light beam and
microscope to be sharply focused on the ocular tissue
being observed.
 Wide beam direct illumination is commonly used as a
preliminary technique to evaluate large area.

32.  Parallelepiped:
 Constructed by narrowing the beam to 1-2mm
in width to illuminate a rectangular area of
cornea.
 Microscope is placed directly in front of patients
cornea.
 Light source is approximately 45 degree from
straight ahead position.

33. Applications:
 Used to detect and examine corneal
structures and defects.
 Used to detect corneal striae that develop
when corneal edema occurs with hydrogel
lens wear and in keratoconus.
 Higher magnification than that used with wide
beam illumination is preferred to evaluate
both depth and extent of corneal ,scarring or
foreign bodies.
 it is particularly suitable for assessment of
cataracts,scars,nerves,vessels etc.

35. Conical beam(pinpoint)
 Produced by narrowing the vertical height of a
parallelepiped to produce a small circular or square
spot of light.
 Light source is 45-60 degree temporally and
directed into pupil.
 Biomicroscope: directly in front of eye.
 Magnification: high(16-25x)
 Intensity of light source to heighest setting.

36.  Focusing:
 Beam is focused between cornea and anterior
lens surface and dark zone between cornea
and anterior lens observed.
 Principle is same as that of beam of sun light
streaming through a room ,illuminating airborne
dust particles.This occurance is called tyndall
phenomenon.
 Most useful when examining the transparency of
anterior chamber for evidence of floating cells and
flare seen in anterior uveitis.

37. Tyndall phenomenon
 Cells, pigment or proteins in the
aqueous humour reflect the light like a
faint fog.
 To visualise this the slit illuminator is
adjusted to the smallest circular beam
and is projected through the anterior
chamber from a 42° to 90° angle.
 The strongest reflection is possible at
90°.

39. Optic section
 Optic section is a very thin parallelepiped and
optically cuts a very thin slice of the cornea.
 Axes of illuminating and viewing path intersect in
the area of anterior eye media to be examined e.g.
the individual corneal layers.
 Angle between illuminating and viewing path is 45
degree.
 Slit length should be kept small to minimize
dazzling the patient.

40.  With narrow slit the depth and portion of different
objects(penetration depth of foreign bodies,
shape of lens etc) can be resolved more easily.
 With wider slit their extension and shape are
visible more clearly.
 Magnification: maximum.
 Examination of AC depth is performed by wider
slit width .1-.3mm .

41.  Used to localize:
Nerve fibers
Blood vessels
Infiltrates
Cataracts
AC depth.

42. Optical section of lens
1.Corneal scar with wide beam illumination 2.optical section through scar
indicating scar is with in superficial layer of cornea.

43. Tangential illumination
 This technique is used to observe surface texture
 Medium –wide beam of moderate height is used.
 Microscope is pointing straight ahead.
 Tangential light(projected from a oblique angle)
creates shadows
 Magnification of 10x,16x,or 25x are used.

44.  Observe:
 Anterior and posterior cornea
 Iris is best viewed without dilation by this
method.
 Anterior lens (especially useful for viewing
pseudoexfolation).

45. Example of tangential illumination (iris).

46. Specular reflection
 Established by separating the microscope and
slit beam by equal angles from normal to cornea.
 Position of illuminator about 30 degree to one
side and the microscope 30 degree to otherside.
 Angle of illuminator to microscope must be equal
and opposite.
 Angle of light should be moved until a very bright
reflex obtained from corneal surface which is
called zone of specular reflection.

47.  Irregularities ,deposits ,or excavasation in these
smooth surface will fail to reflect light and these
appears darker than surrounding.
 Under specular reflection anterior corneal
surface appears as white uniform surface and
corneal endothelium takes on a mosaic pattern.
 Used to observe:
 Evaluate general appearance of corneal
endothelium
 Lens surfaces
 Corneal epithelium

48. Schematic of specularreflection.
Reflection from
front surface endothelium

49. Indirect illumination
 The beam is focused in an area adjacent to
ocular tissue to be observed.
 Main application:
 Examination of objects in direct vicinity of
corneal areas of reduced transparency e,g,
infiltrates,corneal scars,deposits,epithelial and
stromal defects
 Illumination:
 Narrow to medium slit beam
 Decentred beam
 Magnification: approx. m=12x (depending upon
object size)

50. Retroillumination
 Retroillumination is used to evaluate the optical
qualities of a structure
 The light strikes the object of interest from a
point behind the object and is then reflected back
to the observer
 A vertical slit beam 1-4mm wide can be used.
 Purpose:
 Place object of regard against a bright
background allowing object to appear dark or
black.

51.  Used most often in searching for keratic
precipitates and other debris on corneal
endothelium.
 The crystalline lens can also be
retroilluminated for viewing of water clefts and
vacuoles of anterior lens and posterior
subcapsular cataract

52.  Direct retroillumination from iris:
 Used to view corneal pathology.
 A moderately wide slit beam is aimed towards
the iris directly behind the corneal anomaly.
 Use magnification of 16x to 25x and direct the
light from 45 degree.
 Microscope is directed straight ahead .

53. Schematic of
direct retroillumination from
the iris.
direct retroillumination from the iris.

54.  Indirect retroillumination from iris:
 Performed as with direct retroillumination
but the beam is directed to an area of the
iris bordering the portion of iris behind
pathology.
 It provides dark background allowing
corneal opacities to be viewed with more
contrast.
 Observe:
 Cornea, angles.

56. Retroillumination from fundus(red reflex
photography)
 In this technique, we are seeking to visualize
media clarity and opacities.
 The light is directed so that it strikes the fundus
and creates a glow behind the abnormality
 The defect creates a shadow in the light
 The slit illuminator is positioned in an almost
coaxial position with the biomicroscope.
 A wide slit beam is decentered and adjusted to a
half circle by using the slit width
 The decentred slit beam is projected near the
pupil margin through a dilated pupil.

57.  Focus the microscope directly on the
pathology using 10X to 16X
magnification
Observe:
cornea, lens, vitreous

58. Schematic of
retroillumination from the
retina.
Example of retroillumination from the reti

59. Sclerotic scatter
 A tall, wide beam is directed onto the limbal
area.
 Such an illumination technique causes cornea
to take on total internal reflection.
 The slit beam should be placed approximately
40-60 degree from the microscope.
 When properly positioned this technique will
produce halo glow of light around the limbus
as the light is transmitted around the cornea.
 Corneal changes or abnormalities can be
visualized by reflecting the scattered light.

60.  Used to observe:
 Central corneal epithelial edema
 Corneal abrasions
 Corneal opacities

61. Schematic of
sclerotic scatter. Example of
sclerotic scatter.

62. Proximal illumination
 This illumination technique is used to observe
internal detail, depth, and density.
 Use a short,fairly narrow slit beam.
 Place the beam at the border of the structure
or pathology.
 The light will be scattered into the
surrounding tissue, creating a light
background that highlights the edges of the
abnormality.

63.  Depending on the density of the abnormality,
the light from behind may reflect through,
allowing detailed examination of the internal
structure of the pathology.
 Observe: corneal opacities (edema,
infiltrates, vessels, foreign bodies), lens,
iris

64. Transillumination
 In transillumination, a structure (in the eye, the
iris) is evaluated by how light passes through
it.
 Iris transillumination:
 This technique also takes advantage of the
red reflex.
 The pupil must be at mid mydriasis (3to 4 mm
when light stimulated).
 Place the light source coaxial (directly in line)
with the microscope.
.

65.  Use a full circle beam of light equal to the size of
the pupil.
 Project the light through the pupil and into the eye
.
 Focus the microscope on the iris.
 Magnification of 10X to 16X is adequate
 Normally the iris pigment absorbs the light, but
pigmentation defects let the red fundus light pass
through..
 Observe: iris defects (they will glow with
the orange light reflected from the
fundus)

67. Uses of slit lamp biomicroscopy
 Diagnostic:
 OCT
 FFA
 Anterior segment and posterior segment
diseases
 Dry eye

68.  Procedures:
 Applanation
 Tear evaluation
 Pachymetry
 Gonioscopy
 Contact lens fitting
 Therapeutic:
 Laser
 FB removal
 epilation

69. Injected conjunctiva
Meibomian gland openings
pinquecula,
INSTILLATION OF FLUORESCEIN PALPEBRAL CONJUNCTIVA
EXAMINATION

70. Meibomian gland evaluation
 With the patient at the biomicroscope, use
white light and medium magnification to
inspect the lower eyelid margins.
 Look for capping of the meibomian gland
orifices (yellow mounds), notching of the
eyelid margins (indentations) and frothing of
the tears on the eyelid margins.
 Pull the lower eyelid down and look for
concretions in the palpebral conjunctiva.

71.  With mild pressure, press on the eyelid
margins near the eyelashes and watch the
meibomian gland orifices.
 Clear fluid should be expressed.
 Capping of the orifices, a cheesy secretion on
expression and frothing of the eyelid margins
indicates meibomian gland dysfunction.

72. Van Herrick Technique
 Use to evaluate anterior chamber angle without gonioscopy
 Medium magnification
 Angle 60 degrees
 Narrow beam close to limbus
 Depth of anterior chamber is evaluated it to the thickness of
cornea:
4. grade – open anterior chamber angle 1:1 ratio
3. grade – open anterior chamber angle 1:2 ratio
2. grade – narrow anterior chamber angle1:4 ratio
1. grade – risky narrow anterior chamber angle less
than 1:4 ratio
0. grade – closed anterior chamber , cornea “sits” on iris

73. Van Herrick Technique

74. CENTRAL RETINA PHOTOGRAPHS
WITH A 90-DIOPTER LENS