OPHTHALMOLOGY PRESENTATION

1. Slit lamp
examination
DR SIDESH RANGANA(REG.OPHTHALMOLOGY)

2. OBJECTIVES
List the uses of the slit lamp biomicroscope
Identify the main components of the slit lamp; be able to operate
these components
Discuss and perform a series of basic illumination and
magnification techniques

3. IMPORTANT HISTORICAL
LANDMARK
• De Wecker ,1863, developed 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 diaphragm in it.
• THEREFORE,
• GULLSTRAND IS CREDITED WITH THE INVENTION OF SLIT
LAMP.

5. Basic Design
 Viewing arm
 Biomicroscope
 Adjustable focus eyepieces
 Magnification dial
 Illumination arm
 The “slit lamp”
 Slit size, shape and filter controls
 Variable size, shape, colour and brightness
 Biomicroscope and illumination are mechanically
coupled around central pivot point (copivotal)
 Both focus at the same point (parfocal)
 Both arms can swing independently 180º along
horizontal – there is a scale in degrees
 Both always central regardless of angle (isocentric)
 Moveable base plate and joystick control

6. Slit lamp technique
• Start w/ 10x eyepieces & lower powered objective
• (“1x” or “12” on JMC scopes)
• Use lowest voltage setting on transformer
• ensure open aperture
• Select the longest slit length
• Adjust chin rest
• Pt's eyes approx level w/ marker on head rest
• Slit arm in line w/ microscope
• Lamp height w/ slit beam centered vertically on Pt's
medial canthus
• Focus by moving joystick

7. • Slit width
• Wide- survey globe/cornea
• Narrow- depth, width & position of small abnormalities
• beam as wide as cornea is thick
• forms a parallelepiped volume: a box of illuminated tissue is seen
• Thin (slit)- narrowest beam forms an optical section
• so thin it's just discernible
• valuating small changes in clarity & pinpointing depth of pathology
• Light-source intensity
• Medium to high: most purposes
• High: optical section
• Filters
• neutral, cobalt blue (for fluorescein), red-free
• Magnification
• low power (~10x) is used for survey
• medium to high (16-40x) for optic section & parallelepiped
• high (40x) for specular reflection
• normally, light is focused at same point as microscope (“parfocal”)

8. locking nut: loose for free
movementOcular focus to 0
adjust beam height for tall,
narrow vertical beam
adjust width for narrow beam w/
good illumination

9. slit width
adjustmen
t

10. • Magnification adjustment can
be found in various locations,
including btwn the eyepieces
• The filter rheostat can be used
to decrease Pt discomfort under
exam w/ the lamp (neutral
density filter)

11. What can we use them for?
On their own
Routine examination of
anterior segment
Adnexa through to anterior
vitreous
Problem-based
examination of anterior
segment
Contact lens examination
Assessment of anterior
chamber depth and angle
With accessories
Gonioscopy
Fundoscopy
Ocular photography
Contact tonometry
(Goldmann)
Pachymetry
Corneal sensitivity
measurements
(aesthiometry)
Laser photocoagulation

12. Biomicroscope
.

13. A good biomicroscope has…
• Adequate working distance between the microscope and the
eye to allow the practitioner to access the eye
• Convenient size for use in practice
• Adaptable to suit different practitioners
• Good resolution
• Good depth of focus
• A wide range of magnifications

14. Magnification
• Slit lamps provide variable magnification
• Lower magnifications are used for general assessment and
orientation
• Higher magnifications are used for 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

15. Littmann-Galilean telescope
method
A separate optical system is placed in between the eyepiece
and the objective
It consists of a rotating drum that house 2 Galilean telescopes
plus a pair of empty slots
Optics refresher: Galilean telescopes consist of a positive and
negative lens that provide magnification based on the lens
powers and their separation
It is easy to identify whether the slit lamp you are using has
this inside
The magnification dial will click into place as you turn it, and
there will be numbers on the dial that correspond to the
magnification in each position

16. A Galilean telescope
Parallel light enters and exits.
Magnification is typically the intended outcome.
However, if you look from the other side, the image will be minified.

17. Two telescopes produce two magnifications
Mag highest when the convex lens is near objective
Reversal of these two telescopes produces two further minifications
No telescope provides 5th
option

18. Zoom systems
• This tends to be found on high-end Nikon, Topcon and Zeiss
instruments
• Magnification can vary between 7x to ~ 40X
• I find that the image quality is not as good with zoom
magnification

19. Change eyepieces or
objective
Eyepieces
Often two sets provided
with slit lamp
Typical values 10x, 12.5x, 15x or 20x
Inconvenient so rarely used
Generally unnecessary on
modern slit lamps
Objective
Flip arrangement for rapid
change
Usually only two options due
to space confinements
Typical values are 1x and 2x
Lever

20. Illumination
The slit lamp

21. What makes a good slit?
• A good slit needs to be
• Bright
• Evenly illuminated
• Finely focused
• Have well defined, straight edges
• Flexible in terms of size, shape, colour and intensity
• The illumination also needs to
• Provide good colour rendering to detect subtle colour changes

22. Slit width
• Continuously variable (0 to 12-14mm)
• May be graduated to allow
measurement
• Narrow slits are used to “slice”
through the cornea to determine
depth or thickness
• Wide slits are used to inspect surfaces

23. Slit height
May be continuous or set to
fixed heights
Usually a combination of the two
May be graduated to allow for
measurement
Long slits are used to view most
structures in front of the pupil,
while short slits pass through the
pupil much better
Short slit also used to assess the
clarity of the anterior chamber

24. Slit orientation • Achieved by rotating lamp
housing

25. Methods of illumination
Direct
Indirect
Retro-illumination
A combination of these methods is used to
view the anterior eye structures

26. Direct illumination
There are several different forms, named simply by how wide
the slit is
Diffuse (usually not a slit at all)
Wide beam
Parallelepiped
Optical section
CONICAL(pin point)
Tangential
Specular reflection
The slit width will change what you can see
Diffuse/wide beam for an overall view
Wide parallelepiped for broad views of one plane (e.g. Surface of
a structure) and narrow parallelepiped for a balanced view
Optical section to “cut through” a tissue, for thickness and depth

27. Direct illumination
Lamp
Microscope
The light and the microscope
are both pointed at the
object of interest

28. Effect of slit width (cornea)
Wide beam: mostly surface Parallelepiped: balance of
surface and depth
Optical section:
mostly depth

29. Why is the angle important
The angle between the microscope and the illumination arms
is important. Wider angles…
Allow view of deeper layers without interference from reflections
from upper layers
The wider the beam, the greater the angle needed to “see
behind the surface layer”
Allows estimation of depth
Allows better perception of texture
Allows direct/indirect/retro simultaneously
You’ll find a graduated scale located at the pivot point of the
two slit lamp arms
It will give you the total separation between the two arms in
degrees

30. Effect of angle (cornea)
45º: balance of
surface and depth
5º: surface only 85º: depth only

31. Wide beam/Diffuse
Used for general inspection
of eye and adnexa
Good for colour
assessment
Contact lens fit
Wide slit, diffusing
inserted, microscope in
front, illumination angle
30–50°, magnification of 6-
10x
Patients are generally unable
to tolerate the brightness of a
wide beam
This eye has iris naevi (freckles)

32. Parallelepiped
• Default method for
corneal inspection
• Shows a block of tissue
in 3-D, so good balance
between surface and
depth inspection
• Beam about 2 mm,
microscope/illumination
, variable angle, medium
to high mag (10-25x)
This is a narrow parallelepiped being
used to view iris and pupillary margin.
The light first passes through the
cornea but is out of focus there.

33. Optical section
Allows judgement of
thickness or depth
Use the narrowest slit
possible (0.1 – 0.2 mm),
angled beam (largest
angle possible), high
illumination, and a dark
room
You need very sharp
focus

34. Direct Focal Illumination -
Conical Beam
Principle
• assessment of particles
floating in the anterior
chamber by illuminating with
a light beam
• Tyndall‘s phenomenon
• pinpoint illumination 0,3 -
0,5mm
Applications
• assessment of particles in
aqueaous humor
• inflammation cells, pigmented
cells, metabolic waste
-34-

35. Types of Illumination
Tangential Illumination
Principle
• a narrow light beam is
projected almost parallel
along the structure to be
observed
• elevated structures are
visible by shadowing
Applications
• elevated abnormities or
changes in the iris
• tumors, cysts -35-

36. Types of Illumination
Specular Illumination
Principle
• angle of incidence = angle
of reflection
• observation and
illumination have same
angle to perpendicular axis
• slit width < 4mm
Applications
• assessment of surfaces
• assessment of tear film
• endothelial cell layer
-36-
0°
α α

37. Types of Illumination
Specular Illumination
endothelial cells
endothelial cell layer magnified ca. 192x
-37-
0°
α α
Bildquelle: Carl Zeiss Meditec

38. Indirect illumination
A. Retro-illumination
B. Sclerotic scatter
C. Transillumination

39. Indirect illumination
Lamp
Microscope
An object being viewed is
illuminated indirectly when it lit by
reflections/scatter of light that
occur when the light is shone other
than onto the object itself.

40. Indirect illumination
Good for subtle detail, which would be obscured or washed
out by large amounts of illumination
Light internally reflected within the cornea, or reflected by
other surrounding tissue
Opacities scatter light so they will appear light in colour
They are best viewed against the dark pupil (or dark iris, if your
patient happens to have one)
To achieve the effect, keep the slit width narrow to medium
(2-4 mm), and view with a medium to wide angle.
Magnification will vary depending on the size and extent of the
object, but it’s typically medium to high for subtle defects

41. Retro-illumination
Lamp
Microscope
An object of interest is lit by retro-
illumination when the light source is
directed onto another structure so that
the reflected light must pass through that
object.

42. Retro-illumination
Light may be reflected from 2 main structures:
Iris: this back-lights the cornea
Fundus: this back-lights the lens
Opacities will appear dark against a bright
background
For iris retro-illumination, use a narrow-moderate
width slit, a wide angle of illumination, and
magnification appropriate to the object size/extent
Decoupling may be necessary when the magnification high
For fundus retro-illumination, use a short slit with
narrow-moderate width, narrow angle of
illumination (0-10º), and moderate magnification

43. Marginal retro-illumination
• At the border of the zones illuminated by
indirect and retro, therefore viewing technique
is similar for retro with high mag, decoupling
helps
• Objects of higher refractive index show
“reversed illumination”
• Useful to differentiate microcysts (high refractive
index) from vacuoles (low refractive index)

44. Types of Illumination
Sclerotic Scatters
Principle
• Illumination of the limbus
region with a broad light beam
at an angle of 45° - 60°,
decentered slit
• total reflection of the
incoming light at inner corneal
boundaries (endothelium and
epithelium)
Applications
• scars, foreign bodies, corneal
defects
• irregularities in the cornea
cause straylight
-44-

45. Types of Illumination
Sclerotic Scatters
Principle
• Illumination of the limbus
region with a broad light beam
at an angle of 45° - 60°,
decentered slit
• total reflection of the
incoming light at inner corneal
boundaries (endothelium and
epithelium)
Applications
• scars, foreign bodies, corneal
defects
• irregularities in the cornea
cause straylight
-45-

46. Types of Illumination
Iris-Transillumination
Principle
• transillumination of the iris
by indirect light reflected
from the fundus
• half dilated pupil (3 to
4mm)
• Illumination and
observation at ca. 0°
Applications
• Visualization of defects of
the pigment layer of the iris
-46-

47. Types of Illumination
Iris-Transillumination
Albinism
Iris-Transillumination shows the light
transmission of the iris -47-Bildquelle: www.atlasophthalmology.com

48. EXAMINATION USING
FLUORESCEIN
Examination using
Fluorescein
Principle
• Fluorescein is inserted into the
conjunctival sac and fills, for
example, intracellular spaces
• dye is excited with blue light
(λ 450 ... 500 nm)
• contrast reducing straylight is
blocked with barrier filter
(yellow filter λ > 530 nm)
Applications
• corneal lesions / defects
• contact lens fitting -48-

49. (+) Seidel’s test: ruptured globe“Welder’s keratitis”-- diffuse punctate lesions
of the cornea caused by UV radiation
dendritic appearance of HSV keratitis
linear corneal abrasion

50. THANK YOU