The document provides a history of the development of the slit-lamp biomicroscope from the early 19th century to modern versions. It describes the key parts of the slit-lamp including the observation system, magnification system, illumination system, and mechanical support system. Finally, it outlines various techniques for illumination using the slit-lamp such as diffuse, direct, indirect, retroillumination, specular reflection, and oscillating illumination and their uses in examining different structures of the eye.

1. Slit-lamp biomicroscopy
By
Loknath Goswami
B.Optom 3rd year
Ridley College of Optometry

2. Presentation layout
• History
• Parts of slit-lamp
• Technique of biomicroscopy
• Methods of illumination
• References

3. HISTORY

4. History
• 1823: Purkinje,
attempted to
develop a type of slit
lamp by using one
hand-held lens to
focus strong
illumination

5. History
• 1863: De Wecker,
devised a portable
ophthalmomicroscope
that combined a small
monocular microscope
which rested against
the face of the patient
with an attached
condenser lens

6. History
• 1891: Albert and
Greenough, developed
a binocular microscope
which provided
streoscopic view
• 1897: Czapski modified
the binocular corneal
microscope, which is
still found in many
modern slit-lamps
Czapski

7. History
• 1911: Gullstrand
introduced the illumination
system which had for the
first time a slit diaphragm
in it
• 1916: Henker developed
the prototype of the
modern biomicroscopy by
combining the Gullstrand’s
slit illumination system
with the Czapski’s
binocular corneal
microscope Gullstrand
Large Gullstrand
Ophthalmomicroscope

8. History
• 1933: Hans Goldmann
improvised the
biomicroscope in
which all the vertical
and horizontal
adjustments for both
the lamp and the slit-
beam were placed on
a single mechanical
stage

9. History
• 1950: Littmann
incorporated the
rotatory magnification
changer based on the
principle of Galilean
telescope

10. Parts of slit-lamp
Mechanical
support
systemIllumination
system

11. Observation system
• The observation system is essentially a
compound microscope which is composed of
two optical elements
– An objective and
– An eyepiece
Also it have
prism housing
here

12. Observation system
• Objective lens consists of two planoconvex
lenses with their convexities put together,
providing a composite power of +22.00 D
• Eyepiece has a lens of +10.00 D to provide a
good stereopsis, the tubes are converged at an
angle of 10-15˚
To overcome the problem of inverted image produced by the
compound microscope, slit-lamp microscope uses a pair of
prisms between the objective and the eyepiece to reinvert
the image

13. Magnification system
• Most slit-lamps provide a range of
magnification from 6X to 40X
• The modern slit-lamps use one of the
following three systems to produce a range of
magnification
– Czapskiscope with rotating objectives
– The Littmann-Galilean telescope principle
– Zoom System

14. Illumination system
• The Gullstrand’s
illumination system is
designed to provide a
bright, evenly
illuminated, finely
focused adjustable
slit of light at the eye

15. Light source
• Originally a Nernst lamp was used as a light
source which was followed by Nitra lamp, arc
lamp, mercury vapour lamp and finally
halogen lamps
• Halogen lamps provides an illumination of 2 X
105 to 4 X 105 lux

16. Light source

17. Condenser lens system
• It consists of a couple of planoconvex lenses
with their convex surfaces in apposition

18. Slit and other diaphragms
• The height and width of the slit can be varied
using two knobs provided for this purpose
Width control
Height control

19. Variations

20. Filters
• Different filters can be inserted into the
illumination beam
• Cobalt blue and red-free filters are provided in
most of the models

22. Cobalt blue filter
• Cobalt blue filter produce light of the
wavelength 450 to 500nm
• This filter is useful for looking for problems in
the eye once it has been stained
with fluorescein
• Dye pods in area where the corneal
epithelium is broken or absent
• The dye absorbs blue light and emits green

23. Cobalt blue filter

24. Fluorescein stain highlighting dendritiform
lesions in herpetic keratitis

25. • 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.
Red free(green)filter

26. Red free(green)filter
• Fleischer ring can also be viewed satisfactorily
with the red free filter.

27. Neutral density filter
• Decreases maximum brightness for
photosensitive patients

28. Yellow filter
• For good contrast enhancement when using
fluorescein and the cobalt blue filter

29. Diffuser
• For general overall observations of the eye
and adnexa

30. Projection lens
• It forms an image of the slit at the eye
• The diameter of the projection lens is usually
fairly small
• This has two advantages
– It keeps the aberrations of the lens down, which
results in a better quality image
– It increases the depth of focus of the slit and
thereby produces a better optical section of the
eye

31. Reflecting mirror or prism
• The illumination system of a slit-lamp has to be
able to pass relatively easily from one side of the
microscope to the other
• To allow this, the projection system is normally
arranged along a vertical axis, with either a mirror
or prism finally reflecting the light along a
horizontal axis
• The use of a narrow prism or mirror means that
when necessary, such as in examination of the
fundus, the illumination axis can be made to,
without obstructing the field of view, almost
coincide with the viewing axis

32. Mechanical support system
• Joystick arrangement
• Up and down movement
• Patient support arrangement
• Fixation target

33. Joystick arrangement
• Movement of the
microscope and
illumination system
towards or away
from the eye and
from side to side is
usually achieved via a
joystick arrangement

34. Up and down movement
• The up and down
movement is
obtained via some
sort of screw device
that moves the whole
illumination and
viewing system up
and down relative to
the chin rest

35. Patient support arrangement
• A vertically moves chin rest and the provision
to adjust the height of the table has been
made to accommodate the persons of all sizes

36. Fixation target
• A movable fixation target greatly facilitates the
examination under some conditions

37. Mechanical coupling
• The mechanical system not only provides a
support but also a coupling of the microscope
and the 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
• It allows either the microscope or the
illumination system to be rotated around the axis
without changing the focus

38. Technique of biomicroscopy
Patient adjustment
Instrument adjustment
Beginning slit lamp

39. Patient adjustment
• The patient should be positioned comfortably
in front of the slit lamp with his or her chin
resting on the chin rest and forehead opposed
to head rest

40. Instrument adjustment
• The height of the chair should be adjusted
according to table housing the slit-lamp
• The microscope and illumination system
should be aligned with the patient’s eye to be
examined
• Fixation target should be placed at the
required position

41. Beginning slit lamp
• Examination should be carried out in a semidark
room so that the examiner’s eyes are partially
dark-adapted to ensure sensitivity to low
intensities of light
• There should be a minimum exposure of retina
to light
• Medications like ointments and anaesthetic
eyedrops produce corneal surface disturbances
which can be mistaken for pathology
• Low magnification should be first used to locate
the pathology and higher magnification should
then be used to examine it

42. Diffuse
Direct
Indirect
Retro
Specular
reflection
Sclerotic
scatter
Oscillating
Methods of illumination
Berliner described 7
basic methods of
illumination using the
slit-lamp

43. Diffuse illumination
• Angle between the
microscope and
illumination system should
be 30-40˚
• Slit width should be widest
• Diffusing filter should be
used
• Magnification used is low to
medium
• Illumination should be
medium to high

44. Diffuse illumination
• General view of the anterior eye and the
palpebral conjunctiva
• Contact lens fitting

45. Direct focal illumination
• In this technique, the slit-beam is regulated
until it coincides with the exact focus of the
microscope
• Light is directed as a narrow slit at an oblique
angle
• Heterogenous tissue like cornea and lens
disperse light and become visible as bright
objects against a dark background

46. Setup for direct illumination

47. Slit-
beam
effects
Optical
section
Parallelopiped
Conical beam
effect

48. Optical section
• It is produced by a very
narrow slit-beam
focused obliquely
• The whole tissue can be
examined by moving
the slit-beam and
simultaneous focus of
the microscope across
the surface

49. Cornea
• Corneal optical section consists of a segment
of arc with following concentric zones :
• Tear layer is seen as a bright anterior most zone
• Epithelium is seen as dark line immediately behind the
tear layer
• Bowman’s membrane is seen as a bright line
• Stroma is focused as a wider granular and greyer zone
• Descemet’s membrane and endothelial layers are seen
as posterior most bright zone

50. Significance
Changes in corneal curvature
and thickness
Depth of the corneal
pathologies
Anterior chamber angle
grading

51. OPTICAL SECTION OF LENS
Optical section of the lens seen with slit-lamp microscope shows
stratification of the lens into following layers(front to back)
Anterior capsule
1st cortical clear zone
1st zone of disjunction
2nd cortical clear zone
Light scattering zone of deep cortex
Clear zone of deep cortex
nucleus

52. Parallelopiped
• Parallelopiped of the cornea is observed using
a 2-3 mm wide focused slit
• Pathologies of epithelium are better studied
under this illumination

53. Parallelopiped
• Corneal scars or infiltrates appear brighter
than surroundings because they have more
density
• Cells and flare in the anterior chamber can be
graded by using a parallelopiped 2 mm wide X
4 mm high

54. Conical beam
• Conical beam is observe using small and circular
pattern beam, light source 45-60˚ temporally
from the microscope and directed into the pupil
• Biomicroscope is in front of the eye
• Magnification - high

55. Conical beam
• It is used to examine the presence of aqueous
flare
• Beam is focused between the cornea and the
anterior the lens surface, and the dark zone
between the cornea and the lens is observed.
This zone is normally optically empty and
appears black. Flare appears grey or milky and
cells may be facilitated by gently oscillating
the illuminator

56. Aqueous cells
• The “cell” are individual
cells, such as WBCs
• It is an early feature of
iridocyclitis
• The cells should be
counted in an oblique slit-
lamp beam, 1mm long
and 1mm wide, with
maximal light intensity
and magnification

57. Aqueous cells
• It is graded as per ‘Standardization of Uveitis
Nomenclature (SUN)’
 - = < 1 cells
 ± = 1-5 cells
 +1 = 6-15 cells
 +2 = 16-25 cells
 +3 = 26-50 cells
 +4 = Over 50 cells

58. Aqueous flare
• It is due to leakage of protein particles into the
aqueous humour from damaged bllod vessels
• It is demonstrated on the slit lamp examination
by a point beam of light passed obliquely of the
plane of iris
• In the beam of light, protein particles are seen as
suspended and moving dust particles. This is
based on the ‘Brownian movements’ or ‘Tyndall
phenomenon’

59. Aqueous flare

60. Aqueous flare
• The flare is graded from 0 to +4. Grade as per
SUN working group grading scheme:
• 0 = no aqueous flare
• +1 = faint i.e., just detectable
• +2 = moderate flare with clear iris and lens details
• +3 = marked flare (iris and lens details hazy)
• +4 = intense flare (Fibrin or plastic aqueous)

61. Indirect illumination
• The slit-beam is focused on a position just
beside the area to be examined
• The set-up required is
– Angle between slit-lamp and
microscope should be 30-45˚
– Beam width used is moderate
– Illumination used is low, medium
or high
– Slit-lamp can be offset

62. Significance
Corneal
Infiltrates
Microcysts
vacuoles
Epithelial
cells

63. Retroillumination
• Light is reflected off the iris or fundus, while
the microscope is focused on the cornea
Retro
illumination
Direct
Indirect

64. Direct

65. Indirect

66. Retroillumination from the fundus
• This technique is used to observe media clarities
and opacities
• The pupil is dilated and the slit-beam and
microscope are made coaxial
• 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.

67. Retroillumination from the fundus

68. Specular reflection
• Reflection of light occurs when a beam of light is
incident on an optical surface, which is called zone
of discontinuity
• Such zones may be found in cornea and lens
• When an observer is placed in the pathway of
reflected light, a dazzling reflex will be seen which
is called specular reflection. The surface from
which reflection is obtained is called zone of
specular reflection
• Surface pathologies will scatter the light irregularly
and, therefore, create dark areas in the reflex

69. Specular reflection

70. Specular reflection
• To get the specular reflection, the patient is asked
to look 30˚ temporally
• Light beam is directed from the opposite side
• Towards the side of the light source, a shining
reflex is seen on the cornea
• When the angle between the microscope and the
slit-beam is about 60˚ ,i.e. when the angle of
incidence becomes equal to the angle of
reflection at this point, dazzling reflex which is
coming from tear meniscus will show the
meniscus irregularities.

71. Specular reflection
• At the same time, a
deeper less luminous
glow will be seen which
when focused will
show the endothelial
mosaic
• A parallelopiped beam
with high illumination
and high magnification
is used in this
technique

72. Sclerotic scatter
• Light beam is focused at the limbus
• Rays of light pass through the cornea and
illuminate the opposite side of the limbus
• If there is any pathology like corneal opacity, it
becomes visible because it scatters the rays of
light
• A magnification of 6-10X is used and
microscope is directed straight ahead

73. Sclerotic scatter

74. Oscillating illumination of Koeppe
• In this, the slit-beam is given an oscillatory
movement by which it is often possible to see
minute objects or filaments especially in the
aqueous which would otherwise escape
detection

76. Diffuse illumination
• Used to observe contact lens fitting
performance

77. Broad beam illumination
• Used to observe debris beneath the contact
lens

78. Specular reflection
• Used to observe lens front surface wetting

79. Retroillumination
• Used to observe contact lens front and back
surface deposits

80. References
• A K khurana, Theory and practice of optics and
refraction, 3rd edition, page no. 351-61
• Monica Chaudhry, Contact lens primer, 1st edition, page
no. 28-40
• A K Khurana, Comprehensive Ophthalmology, 6th
edition, page no. 154-55
• http://www.healthline.com/health/slit-lamp-
exam#results5
• https://www.aao.org/young-ophthalmologists/yo-
info/article/how-to-use-slit-lamp
• https://www.youtube.com/watch?v=YTbYX51zGu8
• https://www.youtube.com/watch?v=p2nK9BKpBT0