Slitlampexamination

1. DR.M Dinesh

2. Introduction
• It is a dynamic examination in which eye and ocular
adnexa are examined anteroposteriorly and
horizontally.
• Slit Lamp term is a misnomer since slit is only one of
the various other diaphragmatic opening present in
the instrument.
• Term “Biomicroscopy” introduced by Mawas in 1925
means “ Examination of living eye by means of
microscope and slit lamp.”

3. • It is one of the important examination tools of
ophthalmologists.
• most important advantages is that one can examine
the eye structure in three dimensions (3D).
• The 3 basic requirements for appreciation of depth
with a slit-lamp.
– 1.the clinician possessing a third grade of
binocular vision called stereopsis.
– 2.the direction of the incoming light source,is
dependent upon the fact that the light beam can
be moved so it comes in from one side or the
other.
– 3.the shape of the slit.

4. History
• 1806 - karl Himley used a convex lens for observation
• 1823 - Purkinje, attempted to develop a slit lamp
-used hand held magnifying lens in one hand
-another hand held lens to focus strong oblique
illumination
• 1863 - Louis de Wecker,
-devised portable ophthalmomicroscope
-combination of small monocular microscope with
condensed lens
-lacks stereoscopic view

5. • 1891 - Albert and Greenough developed binocular
microscope with stereoscopic view
• 1897 - Siegfried Czapski –modified binocular corneal
microscope.
-However, none of the units had sufficient and
adjustable illumination.
• 1911 - Allvar Gullstrand,an ophthalmologist and Nobel
laureate
-introduced the illumination system which had a
slit diaphragm ,for the first time
-therefore credited with the invention of the slit
lamp.

6. Allvar Gullstrand

7. • 1916 - Henker and Vogt
- improved upon Gullstrand’s device by creating an
adjustable slit-lamp
-combined
Czapski’s binocular corneal microscope with
Gullstrand’s slit-lamp illumination.
• 1933 - Hans Goldmann
- improvise by placing all vertical and horizontal
adjustments of slit lamp & slit beam on a single
mechanical stage
- it is marketed as Haag-Streit model 360 slit lamp

8. • 1950 - Littmann
- introduced new optical principle for the
biomicroscope
- incorporated rotatory magnification changer
based on principle of Galilean telescope ,which is fore
runner of current ziess slit lamp series

9. Basic design of slit lamp
• The three main components of the modern slit-lamp
are:
1)Observation system
2) Illumination system
3) Mechanical system

10. Observation system (microscope)
Should have following Characteristics :
• Optimum stereoscopic observation.
• Selectable magnification.
• Large field of view.
• Large depth of field.
• Enough space in front of the
microscope for manipulations on the
eye.

11. Observation system is composed of
• Compound microscope : composed of
-An objective lens: Two planoconvex lenses with
their convexities put together (Composite power +22D)
-Eyepiece: has lens of +10 D
• Pair of prisms: To reinvert the image B/W objective &
eye piece
• Converging tubes: They are converged at an angle of
10-15 degree, to provide good stereopsis.
• telescope

13. Magnification systems
Range of magnification in slit lamp -6x to 40x
Moder slit lamps use one of the following 3 systems to
produce range of magnification
• Czapskiscope with rotating objective
• The littmann-Galilean telescope principle
• Zoom system

14. Czapskiscope with rotating objective
-one of the oldest
-mc used technique
-different objectives are usually placed on a
turrent type of arrangement that allows them to be
fairly rapidly changed during examination
eg:
Haag-streit model
Bausch&lomb model
Thorpe model

15. The littmann-Galilean telescope principle
• The Galilean Magnification changer(G) developed by
litmann in 1950
• G is a completely separate optical system
• Sits neatly b/w objective & eyepiece ,does not
require either of them to change
• It utilises Galilean telescopes to alter the
magnification.
• It has two optical components:
• 1)Positive lens 2)Negative lens

16. • Lenses are arranged in turret arrangement.
• It provides large range of magnifications, typically
five.
• It fits within the slit-lamp microscope along with relay
lens (R) & prism ejector (P)

17. The Galilean Magnification changer
Knob to change
magnification (3
or 5step)

18. Zoom system
• allows continuously various degree of magnification.
• Range of magnififcation 7x-35x
• E.g, Nikon photo slit lamp
Zeiss-75 Sl

19. Magnification can also be changed
by changing the eyepiece power

20. Illumination System
Gullstrand s illumination system comprises of
1.Light source:
-originally Nernst lamp was used
-f/b nitra lamp f/b arc lamp f/b mercury vapour l.
finally halogen lamps
-provides illumination of 2-4x 105 lux
2.Condensor lens system:
-couple of planoconvex lenses with their convex
surfaces in apposition

21. 3.Slit & other diaphragms:
• Height & width of slit can be varied
• There are stenopaeic slits of 2 & 0.5 mm to provide
conical beam of light
• To assist in examination of fundus & angle of ant
chamber
-there is facility to rotate slit away from vertical
meridian
-also ability to tilt projection system about a
horizontal axis

22. 4.Filters :
-diff filters can be inserted
eg.,cobalt blue & red free filters
• 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

23. • 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 free filter.

24. 5.Projection lens :
-forms an image of slit at eye
-its diameter is fairly small
-it has 2 adv:
a)keeps aberrations of lens down qlty image
b) depth of focus of slit better optical section
of eye

25. 6.Reflecting mirror or prism :
-last component of illumination system
-the illumination system of a slit lamp has to be
able to pass easily from one side of microscope to
another, to allow this
projection system is arranged along a vertical axis
With either mirror or prism final reflecting light along
horizontal axis
-use of narrow prism so that illumination axis can
be made coincide with viewing axis ,without
obstructing filed of view

27. • The illumination system of most slit-lamps consists
of 2 designs.
1. The Haag-Streit type illumination
-allows de-coupling in the vertical meridian. -
-vertical de-coupling is useful in
a)gonioscopy to minimize reflections
b)indirect fundus examination to gain
increased peripheral views.
-illumination comes from above

28. • The Haag-Streit type illumination
• illumination comes from above

29. 2. The Zeiss type illumination system :
-the illumination comes from below
-does not allow decoupling in the vertical
meridian.

30. Optics of illumination system
• Koeller illumination system has been used in slit
lamp
• Optically it is identical to that of a 35mm slide
projection with exception that a variable aperture
takes place of slit
• Projection lens has much shorter focal length
The interowen beam path in koeller illumination

31. •The light source L is imaged in the objective O by the collector
system K. The objective in turn produces an image at S in the
mechanical slit located next to the collector system. The image of
the light source at O is the exit pupil of the system.
•The Light source is imaged on to the objective lens but the
mechanical slit is imaged on to the patient’s eye.
MS

32. Mechanical system
It is mainly concerned with:
• Positioning of patient.
• Adjustment for observer and patient.
• Adjustment of illumination and observations
system.
• It generally contains following hard ware.

33. movable Fixation target
Head rest
Canthal alignment mark
Chin rest
Lock for slit lamp base
Joy stick
Power unit

34. Chinrest adjust
-ment knob
Height
adjustment
switch

35. • Mechanical coupling: Mechanical system provides
coupling of microscope and illumination system
along a common axis of rotation that coincides their
focal planes.
• This arrangement ensures that light falls on the point
where microscope is focused.

36. Mechanical coupling disadvantage
• In gonioscopy or using three-mirror fundus lens
-suboptimal images are seen or
-refocussing is necessary because slit
&microscope do not reach a common focal point in
those conditions

37. Technique of biomicroscopy
• Before using the slit-lamp, it is important to ensure
that the instrument is correctly set up.
• The eyepieces should be focused for the observer for
his/her own refractive error.
• Often a little more minus correction is required than
the observer’s actual refractive error due to
accommodation and proximal convergence.
• The Pupillary distance (pd) is adjusted for the
observer (perhaps the pd should be slightly less than
that usually measured to account for proximal
convergence).

38. • Check that the observation and illumination systems
are coupled, and the slit-beam is of even illumination
and has sharply demarcated edge (otherwise
irregularity of the beam may be falsely interpreted as
irregularity of tissues).
• The slit-lamp examination is conducted in a semi
dark room.

39. Patient adjustment
• Patient is seated comfotably in front of slit-lamp on an
adjustable stool in front of slit lamp with his/her chin on
chin-rest and his forehead on the bar of head-rest.
• Adjust the chin-rest so that the patient’s eyes are
approximately level with the black marker on the side of
the head rest.
• Focus the slit-beam on the eye by moving the joystick
either towards or away from the patient.

40. • The examination should be commenced using the X10
eyepieces and the lower powered objective to locate
the pathology and higher magnification should then
be used to examine it.
• There should be min exposure of retina to light
• Select the longest slit-length by means of the
appropriate lever.
• Medications like ointments &anaesthetic e/d produce
corneal surface disturbances which can be mistaken
for pathology

41. BASE LINE EXAM FLOW CHART
lids
conjunctiva
limbus
tears
cornea
AC
iris
pupil
lens

42. MAGNIFICATIONS
• Low magnification:7X - 10X : General eye
– Lids.
– Bulbar conjunctiva/sclera.
– Cornea/limbus.
– Tears.
– Anterior chamber/iris/crystalline lens.

43. • Medium magnification: 20X - 25X : Structure of
individual layers
– Epithelium/epithelial breakdown.
– Stroma.
– Endothelium.
– Contact lens fit/lens condition.

44. • High magnification: 30X - 40X : Details
• Epithelium
– vacuoles
– microcysts
– dystrophies.
• Stroma
– striae
– folds.
• Endothelium
– Polymegathism
– guttata
– blebs
– cell density.

45. METHODS OF ILLUMINATION
• BERLINER Described 7 basic methods
1. Diffuse Illumination
2. Direct Focal Illumination
3. Indirect Focal Illumination
4. Retroillumination
5. Specular Reflection
6. Sclerotic Scatter
7. Oscillatory Illumination of Koeppe

46. Diffuse illumination with slit lamp
The set is as given
1)Angle b/w microscope & illumination - 30-450
2)slit width - widest
3)Filter - diffusing filter.
4)Magnification - low to med
5)illumination- med to high
Beam is only 8-14 mm diameter and therefore
must be moved over the eyelids and ocular surface.
It can reveal location and general pattern of
eyelid, conjunctival, corneal lesions.

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

48. Direct focal slit illumination
• Terminology : Projection , of a narrow slit beam at an
angle, to the corneal surface, producing an optical
section that slices through the cornea and eye.
• Principle: A direct narrow slit beam optically cuts
through the cornea , providing a cross sectional view
that reveals its contour and its internal structure.
• It forms two parallel curved surface, one that follows
anterior corneal surface and one that follows posterior
corneal surface.
• Two surfaces are joined by a block of light scattered in
the stroma to create a geometric figure that resembles
an elongated ice cube.

50. • Angle b/w microscope & illumination - 30-450
• slit width- narrow
• Heterogenous tissues like cornea & lens disperse light
& become visible as bright objects against dark
background
• Direct illumination is carried out utilising 3 slit beam
effects i.e.,
-optical section
-parallelepiped
-conical beam effect

51. Optical section:
is produced by a very narrow slit beam focused
obliquely
Corneal optical section:Consists of segment of arc with
following concentric zones
• Tear layer - bright anterior most zone
• Epithelium - dark line immediately behind tear layer
• BM - bright line
• Stroma - wider granular & greyer zone
• DM & endothelium – posterior most bright zone
(not as bright as tear layer)

52. •

53. • Examination of the optical section of the cornea gives
useful information about
1) Changes in the corneal curvature
2) Changes in the corneal thickness
3) Depth of the corneal pathologies
4) Anterior chamber angle grading by the Van
Herrick method

54. OPTICAL SECTION OF THE LENS
• On examination with the slit lamp the stratification of
the lens into the following layers is seen
1) Anterior capsule (Ca)
2) Sub capsular clear zone (First cortical clear zone C1a)
3) A bright narrow scattering zone of discontinuity
(First zone of disjunction C1b)
4) Second cortical clear zone (C2)
5) Light scattering zone of the deep cortex (C3)
6) Clear zone of the deep cortex (C4)
7) Nucleus

56. • The entire optical section of lens cannot be focused
in one field & thus microscope is shifted forward to
focus more posterior layer
OPTICAL SECTION OF THE VITREOUS
• Optical section of the anterior 1/3rd of the vitreous
can be studied by the slit lamp beam

57. Parallelopiped of the cornea
• Slit width - 2-3mm
• Pathologies of the epithelium and stroma are better
studied
• Corneal scars and infiltrates appear brighter than
surroundings because they have more densities
• Water clefts have decreased optical density and so
appear black in the optical block
• Cells and flare in the anterior chamber can be graded
by a parellelopiped 4mm height x 2mm in width

59. Conical beam
• a small circular beam used to examine the presence
of aqueous flare
• Beam : Small and circular in pattern
• Light source : 45 – 60 degrees temporally and
directed towards the pupil
• Bio microscope : Directly in front of the eye
• Magnification : High ( 16-20X )

60. Focusing :
• Beam is focused b/w cornea & ant. lens surface
• The dark zone b/w cornea & lens is observed
• This zone is normally optically empty and appears
black
• Flare appears as grey or milky and cells are seen as
white dots
• Locating the cells can be facilitated by gently
oscillating the illuminator

62. Indirect illumination
• The slit beam is focused on a position just beside the
area to be examined
• Angle between the slit lamp & microscope - 30-450
• Beam width - moderate
• Illumination - low medium or high
• Slit lamp can be offset

63. It is useful to observe
• Corneal infiltrates
• Corneal micro cysts
• Corneal vacuoles
• Epithelial cells

64. Retro illumination
• Light is reflected off the iris or the fundus, while the
microscope is focused on the cornea
• Graves divided retro illumination as
-direct
-indirect
depending upon the angle between the observer
and the light

65. Principle:
When light of direct focal illumination strikes a
corneal opacity, it scatters and some of the light is
reflected back towards the examiner.
This form of illumination often washes out and
obscures details of the lesion and provide little
information about optical qualities and internal
structure of small lesion.
When retroillumination is used these details
stands out more prominently because the lesion is less
likely to scatter and more likely to obstruct and refract
the reflected light.

66. Slit beam: narrow to medium
slit height : reduced
area of corneal pathology is positioned directly over
the slit beam light reflected from the iris, either by
moving the instrument or by altering the patient’s
gaze.

67. Retroillumination from Iris
Terminology: It is a technique of illuminating an area of
cornea using light reflected from structure
posterior to cornea such as iris.
Direct type:
• Observer is in the direct pathway of light reflected
from structures
• The pathology is seen against an Illuminated
background

69. Direct retroillumination

70. Indirect type : Cornea viewed adjacent to area of
illuminated by the reflected light.
• Observer is at right angles to the observed
structure and therefore not in line with light.
• Hence the pathology is seen against a dark, non
illuminated background

72. Indirect retroillumination

73. • Based on the optical properties, Graves divided the
pathologies as:
1) Obstructive
2) Respersive
3) Refractile
Obstructive :
• These are opaque to light and seen as dark against a
bright back ground
• Eg
Pigment
blood filled vessel

74. • A solid or an opaque object
-seen as a dark area in direct retro illumination
-In indirect retro illumination it will show
reversed illumination i.e the side away from the
illumination will be bright.

75. Respersive :
• These scatter light but do not obstruct light
completely
• The pathology is seen brightly against a dark
background
• Eg
Epithelial edema
precipitates
Infiltrates are
-relucent in direct focal illumination but
-respersive in direct retro illumination

76. Refractile :
• These refractile pathologies distort the view of
junction of illuminated and dark area because their
refractive index is different from the surroundings
• Eg
Vacuole
-seen as an illuminated area bordered by a
dark line in direct retro illumination
- In indirect retro illumination it appears as
a black area with a bright surface towards the
illuminated area i.e unreversed illumination

77. Retroillumination from the fundus:
• Terminology :
Light entering the pupil is
reflected from RPE and choroid and
emerges from the pupil with orange red glow,
commonly called as red reflex.
• When examiner views the cornea against this reflex
he/she is able to detect lesions that are to subtle for
visualization by other techniques.

78. • Technique:
The pupil is dilated and
the slit beam and microscope are made coaxial
then decentered to the edge of the pupil.
• Slit width: Medium and curved at one edge to fit in
pupil.
• Slit height: Reduced to 1/3
• This technique is used to observe cornea lens and
vitreous pathologies

79. • The light is directed so that it strikes the fundus
and creates a glow behind the opacity in the media
• The media opacity creates a shadow in the glow
• The microscope is then focused on the pathology
directly and 10-16X magnification is used
• Retro illumination of crystalline lens to
classify and grade both cortical and posterior
sub capsular cataracts using LOCS (lens opacity
classifying system)

80. • Dense scars -Obstructs the reflected and they appear
as dark silhouettes.
• Translucent/transparent objects:
Corneal guttae,
DM Folds,
Lattice corneal dystrophy,
epithelial oedema stands out as brightly refractile
contours

81. Schematic of
retroillumination from the retina
Light reflected of the retina

83. LOCS

84. SPECULAR REFLECTION
• Reflection of light occurs when a beam of light is
incidental on an optical surface which is called the
zone of discontinuity , may be found in the cornea
and the lens
• When the observer is placed in the pathway of
reflected light a dazzling reflex will be seen which is
called specular reflection
• Surface pathologies will scatter light the light
irregularly and there fore create dark areas in the
reflex

85. • To get specular reflection the patient is asked to look
30 degrees temporally
• Light beam is directed from the opposite side
• Optical block is focused under high magnification, 3-
4mm from the limbus
• Towards the light source a shining reflex is seen on
the cornea
• When the light source is rotated still temporally the
optical block will approach the reflex

86. • When the angle between the microscope and the slit
beam is about 60 degrees i.e when the angle of
incidence becomes equal to the angle of reflection,
at this point a dazzling reflex which is coming from
the tear meniscus will show meniscus irregularities
• At the same time a deeper less luminous glow will be
seen which when focused will show the endothelial
mosaic
• A parello piped beam with high illumination and high
magnification is used in this technique

87. Schematic of specular reflection

88. • Similarly, specular reflection from the anterior and
posterior lens capsule can be obtained
Uses
• Mostly used for examination of the endothelial layer
of the cornea
• Changes in the Corneal Endothelium like
polymegathism ,guttae can be seen
• Using an eyepiece reticule endothelial cells can be
measured and counted
• to study tear film details
Lens surfaces
Corneal epithelium

90. Sclerotic scatter
• It is used to outline even the faintest corneal
pathology
• Light beam is focused at the limbus
• Due to the phenomenon of total internal reflection,
rays of light pass through the substance of the
cornea and illuminate the opposite side of the limbus
• If there is any pathology it becomes visible because it
scatters the rays of light
• Slit width - 0.5 mm
• Illumination - max
• Magnification - 6-10X microscope is directed straight
ahead

91. Uses
• Detect stromal haze, cellular or lipid infiltration
• corneal scars
• fine opacities
• corneal edema
Schematic of
sclerotic scatter.

92. Oscillating illumination of koeppe
• The slit beam is given oscillatory movements
by which it is often possible to see minute
objects or filaments
• Especially when present in the aqueous as
they would otherwise escape detection

93. Uses of slit lamp biomicroscopy
• Diagnostic:
– FFA
– Anterior segment and posterior segment
diseases
– Dry eye

94. Specialized examination that can be accomplished
with slit lamp biomicroscope using accessory devices
are
• Gonioscopy
• Fundus examination
• Pachymetry
• Applanation tonometry
• Ophthalmodynamometry
• Slit lamp photography
• Slit lamp as a delivery system for argon, diode and
YAG laser
• Laser interferometry
• Potential acuity meter test

95. thank u