all about slit lamp. special features, basic designs, principal of observation system, principal of illumination, animations are done for the beginners for easy understanding,pitfalls.

1. DR.NAFIZ MAHMOOD
SLIT-LAMP
BIOMICROSCOPY
Resident
N a t i o n a l I n s t i t u t e o f O p h t h a l m o l o g y a n d H o s p i t a l
Bangladesh

2. WHY SLIT LAMPS ARE SO GREAT
gold standard device.
This is because they provide…
Stereoscopic image
Variable illumination
Variable magnification
Excellent image quality

4. A narrow vertical slit of light is projected on to
the eye and permits microscopic examination of
living tissues in cross-section

6. First concept of slit-lamp was introduced by PROF.
ALLVAR GULLSTRAND IN 1911
And named as LARGE GULLSTRAND
OPHTHALMOSCOPE

7. SPECIAL FEATURES
1. The alignment of viewing & illumination system
- parfocal
2.long working distance.
3.allows to carry out certain manoeuveres like
• FB removal from cornea
• interpose certain optical devices-
condensing lens, goniolens, Goldmann
applanation tonometer

8. 3. Incorporated with prisms
-invert the image vertically and horizontally
-so it appears erect and right way round
4. A bank of Galilean telescopes of different
powers
- to allow the magnification

9. WHAT CAN WE USE THEM
FOR?

10.  Routine examination of
anterior segment
 Problem-based
examination of anterior
segment
 Assessment of anterior
chamber depth and angle
 Contact lens examination
 Gonioscopy
 Fundoscopy
 Ocular photography
 Contact tonometry
(Goldmann)
 Laser photocoagulation
On their own
With accessories

11. BASIC
DESIGN

13. OBSERVATION SYSTEM
composed of 2 lenses
- objective lens
- eyepiece lens
Objective lens :
consists of 2 plano-convex lenses
providing a composite power of +22 D

14. Eyepiece lenses :
magnification : 10×, 16×, 25×
provide good stereopsis as the tubes
converged at an angle of 10°- 15°
Prisms :
to overcome inverted image produced
by compound microscope

15. OL
Fo Fo
O Fe
Fe
i
EL
I
Optics of compound microscope

16. Cross-section of
observation system of
modern slit-lamp

17. MAGNIFICATION

18. • Slit lamps provide variable magnification
• Lower magnifications - general assessment
and orientation
• Higher magnifications -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

19. LITTMANN-GALILEAN
TELESCOPE METHOD
• A separate optical system is placed in
between the eyepiece and the objective
• Utilizes Galilean telescopes to alter
magnifications
• It consists of a rotating drum that houses
Galilean telescopes

20. Galilean telescopes consist of a positive and
negative lens that provide magnification
based on the lens powers

21. Galilean magnification changer (G) is placed between
the slit-lamp objective (O) and the relay lens ( R ).

22. ILLUMINATION SYSTEM
Comprises of :
• Light source: halogen lamp
• Condenser lens system
• Slit and other diaphragms
• Filters
• Projection lens
• Reflecting mirror

24. MECHANICAL SUPPORT SYSTEM
Consists of :
Joystick arrangement
Up and down movement
arrangement
Patient support arrangement
Fixation target
Mechanical coupling

25. Technique of biomicroscopy

26. A.Patient adjustment :
should be positioned comfortably in
front of slit-lamp with his or her chin resting
on the chin rest and forehead opposed to
head rest

27. B. Instrument adjustment :
- height of the table housing the slit-lamp
should be adjusted according to patient’s height
- microscope and illumination system should
be aligned wth patient’s eye to be examined
- fixation target should be placed at
required position.

28. C. Beginning slit-lamp examination : some points
to be kept in mind
I. Room should be semi-dark
II. Diffuse illumination – used for short time
III. Medications like ointments and anaesthetic
eyedrops produces corneal surface disturbance
which can be mistaken for pathology.
IV.Low magnification should be 1st used to locate
pathology and then higher magnification to
examine it.

29. Structures to see through slit-lamp
External : brow, nose, chick
Lid & lash
Conjunctiva & sclera
Cornea
Anterior chamber
Iris
Lens
Anterior vitreous

30. PRINCIPAL OF ILLUMINATION

31. DIFFUSE ILLUMINATION
1
DIRECT FOCAL ILLUMINATION2
SPECULAE REFLECTION3
TRANSILLUMINATION /
RETROILUUMINATION4
INDIRECT LATERAL ILLUMINATION5
SCLEROTIC SCATTER6

32. DIFFUSE ILLUMINATION
LIGHT : Full height
Broad beam
Low brightness
DIRECTION : Temporally or Nasally

33. White light
Eye & adnexa

34. Cobalt blue filter with fluorescein
1.Evaluation of fluorescein dye ( appear
yellow) staining the ocular surface tissue
2.Tear film
3.To discern the fluorescein pattern in
Goldmann Applanation Tonometry
[thin marginal tear meniscus and
inferior punctate erosions stained with
fluorescein ]

35. Red free filter with rose bengal dye
Diffuse illumination with red free filter to enhance visibility
of rose bengal red dye which has stained keratin in
intraepithelial ( squamous ) neoplasia

36. DIRECT FOCAL ILLUMINATION
Lamp Microscope
The light and the
microscope are
both pointed at
the object of
interest

37. Beam :
full height
medium width
medium bright
Direction:
obliquely
Aim :
to focus it on cornea so that quadrilateral
block ( parallelepiped) illuminates the cornea
ANTERIOR SURFACE
CROSS-SECTIONAL ILLUMINATION

38. ANTERIOR SURFACE
CROSS-SECTIONAL ILLUMINATION
POSTERIOR SURFACE

39. Use :
1. to examine the anterior surface &
posterior surface of cornea
2. examination of anterior segment & lens
3. for grading of cells & flares ( when the
height of the beam is reduced to 2-4 mm)

40. OPTICAL SECTION :
when the beam made so narrowed that the
anterior & posterior portion becomes very thin
leaving only cross sectional illumination of
cornea.
Optical section: mostly depth

41. SPECULAR REFLECTION
i r
lamp microscope

42. Beam :
medium – narrow ( must be thicker than
optical section )
Angle between light & microscope : 50° – 60°
Purpose :
• to observe corneal endothelium
.
Careful focusing can
bring up endothelial
cells, like mosaic
pattern

43. RETROILLUMINATION
Lamp Microscope

44. An object of interest is lit by retro-illumination
when the light source is directed onto another
structure (deeper) so that the reflected light must
pass through that object.
Retroillumination of fundus is best performed
with -
• dilated pupil
• viewing and illuminating arm not
parfocal

45. What can be seen
• Blood vessels of cornea,
• abnormalities of post. surface of cornea
• Cataract & PCO
• iris atrophy

46. Directly
illuminated
Retro-illuminated
Blood vessels of cornea, other abnormalities of post.
surface of cornea

47. INDIRECT LATERAL
ILLUMINATION
DIRECTION :
• Light is directed just to the side of lesion to
be examined
• Some of the light enters the lesion so it
glows internally

48. What can be seen:
• corneal infiltrates
• corneal microcyst
• corneal vacule

49. SCLEROTIC SCATTER
BEAM :
medium width
Direction :
on to the limbus - temporally
the viewing system focused to center of
cornea

50. lamp
microscope

51. Sclerotic scatter produces a diffuse glow of limbus and a
backlighting of any corneal opacities, as with cornea
verticillata( whorl-like changes) secondary to epithelial
deposition of the oral drug amiodarone

52. PITFALLS & POINTERS
1. Remember to set the oculars to your
refractive error or to plano if you are using
spectacles.
2. Proper positioning of the patient
3. Intensity of the light at level of patient’s
comfort
4. To take advantage of full value of slit-lamp,
examiner must become skilled in using all
of the methods of illumination and
understand when each is best employed.