This presentation explains in detail about different illumination techniques and filters used in slit lamp examination and the procedure to perform slit lamp examination.

1. SLIT LAMP AND ITS DIFFERENT
ILLUMINATION TECHNIQUES
Presented by-
Abhishek Kashyap
B.Optom 3rd year
Ridley College Of Optometry

2. Layouts
• Introduction
• History
• Designs
• Parts
• Different Illumination technique
• Procedure
• References

3. Introduction
• The slit lamp is a microscope designed
specifically to examine the eye
• It is used to examine the external ocular
adnexa, external eye, anterior chamber,
iris, crystalline lens, and the anterior face
of vitreous

4. • The term “Slit Lamp Biomicroscopy” was
coined because of slit beam emitted by the
illumination system and the microscope
use to examine the living eye

6. History
• Purkinje (1823), attempted to develop a type
of slit lamp by using one hand-held lamp to
magnify an another hand-held lens to focus
strong oblique illumination
• De Wecker (1863), devised a portable
ophthalmomicroscope that combined a small
monocular microscope which rest against the
face of the patient with an attached
condenser lens. It lacked stereoscopic view

7. • Albert and Greenough (1891), developed a
binocular microscope which provided
stereoscopic view
• Czapski (1897), modified the binocular
corneal microscope, which is still found in
many modern slit lamps
• Gullstrand (1911), introduced the
illumination system which had for the first
time a slit diaphragm in it

8. • Henker (1916), developed the prototype of
the modern biomicroscopy by combining the
Gullstrand’s slit-illumination system with the
Czapski’s binocular corneal microscope
• Hans Goldmann (1933), 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. The slit-lamp designed by
Goldman was marketed in 1937 as the Haag-
Streit model 360 slit lamp

9. • Littmann (1950), incorporated the
rotatory magnification changer based on
the principle of Galileon telescope. The slit
lamp designed by Littmann is the
forerunner of the current Zeiss slit-lamp
series

10. Designs of biomicroscopes
Zeiss
Biomicroscope
Haag- Streit
Biomicroscope

11. Parts of slit lamp

12. • The slit lamp biomicroscope is composed
of following parts:
1) Mechanical support
 forehead rest
 chin rest
 fixation target
 power supply unit
 joystick arrangement

13. 2) Observation system:
 objective lens
 eyepiece
 prism
 magnification changer

14. 3) Illumination system
 lamp house unit
 condenser lens system
 slit width and height control
 filters
 projection lens
 mirror or prism

15. Figure: Optics of Slit lamp

16. Illumination techniques
1. Diffuse illumination
2. Direct illumination
3. Indirect illumination
4. Retro-illumination
5. Specular reflection
6. Sclerotic scatter
7. Tangential

17. Diffuse illumination
• Set up:
- angle between microscope and
illumination system should be 30- 45 ̊
- slit width should be widest
- diffusing filter
- magnification: low to medium
- illumination: medium to high

19. • Used for:
- General view of the anterior eye
- contact lens fitting

20. Direct illumination
• Observation and illumination systems are
focused at the same point
• Angle : 30- 60 ̊
• Magnification : low to high
• Variation in the width and height of the
light source will give the following:
- optic section
- parallelopiped
- conical beam

22. Optic section
• It is produced by a very narrow slit beam
focused obliquely
• Used for:
- observation of variation in corneal
curvature
- variation in corneal thickness
- depth of the corneal pathologies
- cataract
- anterior one-third of the vitreous

26. • Anterior chamber angle grading by Van
Herrick method can be done by the use
of optical sections
• An angle of 60 ̊ is set between illumination
and observation systems
• A very narrow slit of 1mm width and 3 mm
height is directed towards the limbus at 3
or 9 o’ clock, normal (90 ̊) to the surface at
the limbus

27. • The anterior chamber depth is compared
with the corneal thickness
• Chamber depth less than or equal to a
quarter of the corneal thickness are of
concern

28. Grading according to Van Herrick

29. Parallelopiped
• The illumination is same as optic section
except that the beam is broader than optic
section
• The width of the beam is 2-3 mm
• Used for:
- observation of pathologies of epithelium
and stroma
- corneal scars or infiltrates (appears
brighter)
- striae and folds

31. Conical beam
• It is a small circular beam use to examine
the presence of cells and flare
• Set up:
 the room should be dark
 beam - small circular pattern
 light source – 45-60 ̊ temporally and
directed into the pupil
 magnification – medium to high

32.  focusing – beam is focused between
the cornea and the anterior lens surface,
and the dark zone between cornea and
lens is observed

33. Indirect illumination
• Observation and illumination systems are
not focused at the same point
• Focal light beam is directed adjacent to
the area of observation
• Set up:
 angle : 30-45 ̊
 beam width used is moderate
 illumination : low – high

35. • Valuable for observing:
- corneal infiltrates
- corneal microcysts
- corneal vacuoles
- epithelial cells
- iris pathology

37. Retroillumination
• Object of interest is illuminated by light
reflected from the structures behind it
• Two types-
 Direct : see the cornea just infront of
the illuminated area
 Indirect : see the corneal area
adjacent to the illuminated area

38. Direct retroillumination Indirect retroillumination

39. • Set up:
- create a parallelopiped
- illuminate the area behind the corneal
area to be seen
- magnification medium to high
- observe the cornea in the reflected light

40. • Valuable for observing:
- contact lens deposits
- crystalline lens opacities
- epithelium oedema
- microcysts
- vacuoles
- dystrophies
- neovascularization

42. Specular reflection
• Angle of incident light is equal to the angle
of reflected light
• Set up:
 the angle between the microscope and
slit beam is about 60 ̊
 create a parallelopiped beam
 high magnification and illumination is
use

44. • Valuable for observing:
- endothelial cells
- tear layer stability and lipid layer
- contact lens surface wetting

47. Sclerotic scatter
• Illumination of the cornea is done by total
internal reflection
• The light beam is directed at the limbal
region while observing the cornea
• Utilizes a parallelopiped technique
• Magnification of 6-10x is used

49. • Valuable for observing:
- corneal opacity
- corneal scar
- foreign bodies in the cornea

51. Tangential illumination
• Large angle of 70-80 ̊ is created between
the illumination and observation system
• Observation system is directed in front of
the eye being examined and illumination
system is directed obliquely
• Valuable for observing:
- iris freckles
- tumours
- general integrity of the cornea and iris

55. Filtered illumination

59. Routine examination of the eye
Lids and
lashes
Conjunctiva
and Sclera
Limbus
Cornea
Anterior
Chamber
Iris
Pupil Lens
Anterior
Vitreous

60. Procedure
1. Ensure that the slit lamp is plugged in
2. Clean forehead and chin rest
3. Bring the table into position in front of
the patient
4. Adjust the chin height to position eyes at
the level of the black indicator line with
head in contact with the forehead band
5. The patient can be instructed to hold the
handlebars

62. 6. Set oculars at ‘0’ and adjust interpupillary
distance like binoculars
7. Unlock the carriage
8. Adjust coarse focus by moving the entire
carriage forward and backward at the
base
9. Move the joystick into position: turn
clockwise to raise, counterclockwise to
lower
10. Turn the power switch on

63. 11. Adjust beam width and intensity
12. Set the light on the correct filter
13. Adjust the height of the beam
14. Move the beam angle by swiveling the
illumination while holding the beam
width knob
15. At the conclusion of the exam lock the
carriage in place
16. Turn off the slit lamp power switch

65. References
• Theory and practice of optics and refraction, 3rd
edition, by A K Khurana, Page No351-361
• Primary care optometry, 4th edition, by
Theodore Grosvenor, Page No167-176
• The IACLE module 1, 1st edition, Page No189-
235
• The slit lamp primer, by Janice K. Ledford and
Valerie N. Sanders, Page No2-85
• https://eyewiki.aao.org/Slit_Lamp_Examinatio
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