The slit lamp is an instrument used to examine the eye and adnexa. It consists of a binocular microscope combined with a light source that provides illumination in the form of an adjustable narrow slit. This allows for stereoscopic examination of the external eye structures at high magnification. The slit lamp utilizes various optical configurations and illumination techniques to evaluate the different layers and structures of the anterior segment of the eye. It is an essential tool in ophthalmic examination and diagnosis.

1. SLIT LAMP
BIOMICROSCOPY
PRESENTER-
HIRA NATH DAHAL

2. PRESENTATION LAYOUT
• Introduction
• Optical principle
• Components
• Examination procedures
• Illumination types
• Uses

3. INTRODUCTION
Slit lamp:
• instrument designed specifically to examine the eye and
adnexa
• Operational components consists of a binocular
microscope and a light source
• provides light in the form of slit to observe various ocular
structures
• Provides stereoscopic view of external adnexa, external
eye, AC, iris, lens and anterior vitreous

4. HISTORY
• Alvar Gullstrand( Stockholm)
• Nobel Prize in medicine and
physiology(1911)
• Vogt(1919)- first to describe use
of specular microscopy
• Mawas(1925)- biomicroscopy
• Various modification by
Kohler, Goldmann

5. OPTICAL PRINCIPLE
• Two systems- illumination and observation
• Mounted on a movable trolley about a common centre
and vertical axis
• Foci on the same plane
• These two systems coupled around the same centre of
rotation to ensure par-focus of microscope and slit beam
• Coplanar, coaxial and copivotal

6. • Works on the same principle of compund
microscope
• Objective lens(+22D) and eye piece(10-14D)
• Adjustable illumination system
• A narrow "slit" beam of very bright light
by lamp. This beam is focused on to the eye
which is then viewed under magnification with
microscope

7. TYPES BASED ON ILLUMINATION
SYSTEM
Zeiss slit lamp biomicroscope-
 Light source at the bottom
Haag streit slit lamp
biomicroscope-
 Light source at the top

8. HAAG STREIT ZIESS

9. OPTICAL PRINCIPLE OF HAAG-STREIT TYPE
Vertical illumination system

10. OPTICAL PRINCIPLE OF ZEISS TYPE
Horizontal prism reflected light source

11. PARTS OF SLIT LAMP
Mechanical support
Forehead rest
Chin rest
Fixation target
Power supply unit
Locking controls
Joystick
Observation system
Binocular eyepieces
Camera/video adapter
Observation tube
Magnification changer

12. ILLUMINATION SYSTEM
• Light source-halogen, xenon, W lamps(200000-
400000lux)
• Condenser lens system- 2 planoconvex lens,
convexities in apposition
• Slit and other diaphragms-stenopaic slits
• Filters(Neutral density filter, cobalt blue, red free filter)
• Projection lens- small diameter
• Reflecting mirror/prism

13. TYPICAL SLIT
LAMP
ILLUMINATION
SYSTEM

15. • The slit within illumination system must have sharply
demarcated edges and be adjustable
• Slit width and height must be adjustable such that any
shaped patch from a slit to circle may be projected-
increase illumination methods
• Graduated slit width- size of lesion
• Ability to rotate lamp housing- if a protractor scale
included
• Must have the facility to displaced of offset
sideways(decoupled)

16. THE LIGHT BEAM IS CONTROLLED BY KNOBS OR LEVERS

18. FILTERS
• Green(red free)-
• Increase contrast when
looking for corneal and
iris neovascularization
• Increase the visibility of rose bengal staining
• ND filters-
• Reduce beam brightness and increase comfort for the pt
• Polarizing filters-
• Reduce unwanted specular reflection and enhance visibility of
subtle defects

19. FILTERS
• Cobalt blue-
• Fluorescein staining
• Keratoconus- fleischer’s ring
• Kodak Wratten No.12(Yellow)
• Barrier filter placed in front of viewing system
• Enhancing green staining

20. GRATICULE
•Measurement and lens fit
•Pupil size, HVID, etc

21. OBJECTIVE SYSTEM
• The resolution of image is governed by NA of
microscope dependant upon-
• The diameter of objective
• The working distance
• The refractive index of medium between objective lens
and eye
• The wavelength of light

22. BIOMICROSCOPE
• Objective(2 planoconvex lens=22D), eye piece(+10D), enlarged image of
near object
• Tubes converged at 10-15° for good stereopsis
• A pair of prisms to re-invert the image
• Range of accomodation- ×6 to ×40
• Czapskiscope with rotating objectives- Haag Streit, B&L, Thorpe
• Littman Galilean telescopic system- Zeiss, Rodenstock, American optical
• Zoom system- Nikon

23. BIOMICROSCOPE
• Variable magnification
• Low 7x-10x general eye
• Medium 20x-25x structure layer
• High 30x-40x details
• Optics of compund microscope
• Two types-
– The Grenough type
– The Galilean changer type

28. MECHANICAL PARTS

29. PROCEDURE
• Position the patient
• Adjust the chin rest height so that the outer
canthus of the patient is at the level of the
mark given
• Forehead on the head rest.
• Turn the switch on – begin with minimum
illumination
• Use the focusing rod to adjust the focus of
the eyepiece
• Now start ur observation.

31. ORDER OF EXAMINATION
• Tears
• Lid margins/Lashes
• Conjunctiva
• Cornea
• Anterior chamber
• Iris
• Lens
• Anterior vitreous

32. HAND HELD SLIT LAMP
• A portable slit lamp
• Used to examine the pt
in supine position
• Fits into lightweight case
• Wider interpupillary dioptic
range and field of view.

33. ILLUMINATION TYPES:
• Diffuse
• Direct
 Wide beam, optic, parallelopiped, conical
 Specular
 Tangential
• Indirect
 Proximal
 Retro
 Sclerotic scatter

34. DIFFUSE ILLUMINATION
• light is spread evenly over the entire observed surface
• most often used in slit lamp photography
• 45 degree angle and fully open slit
• If no ND filter(diffuser), decrease intensity
• least amount of magnification (6X or 10X).
• The cobalt blue and red-free filters also act as diffusers, but white light
is generally used

35. •Observe: eyelids, lashes, conjunctiva, sclera, pattern of
redness, iris, pupil, gross pathology, and media opacities
•CL fit

36. DIRECT ILLUMINATION
• Observation and illumination system focus at the same point
• Vary angle of illumination
• Variable magnification
• Variable width and height of light
• Types:
 Broad beam
 Optic section
 Parallelopiped
 conical

37. BROAD BEAM ILLUMINATION
To examine large area

38. OPTIC SECTION
• Narrow focused light(<0.25mm wide)
• Indicate depths
• Localize:
• Nerve fibre,
• blood vessels,
• infiltrates,
• Cataract
• Anterior chamber angle

39. OPTIC SECTION
Used to evaluate the structural layers of the cornea and lens
Good judgement of the depth of corneal foreign body or position
of cataract

40. PARALLELOPIPED
• Broader view, illuminated block of cornea
• Angle between two systems 40 - 50 deg.
• Slit width: 1 to 2 mm
• Provides a layered view of the cornea and the lens
• Higher magnification than the wide beam to evaluate both the depth
and extent of corneal abrasion, scar of FB

41. Observe corneal stroma, epithelial breakdown, lens surface and
endothelium
Punctate keratitis, corneal nerve fibres in stroma, water clefts

42. CONICAL ILLUMINATION
• Produced by reducing the height of a parallelopiped
• Square spot of light, darkened room
• Used to examine AC cells and flares

43. INDIRECT
(PROXIMAL)ILLUMINATION
• Observation and illumination system are not focused at the same point
• Vary angle of illumination
• Slit beam is off set
• Low to high magnification
• Beam is focused on an area adjacent to the area to be
observed

44. Iris pathology, iris sphinters, epithelial vesicles and erosions

45. RETRO ILLUMINATION
• Object of regard is illuminated by
reflected light
• Vary angle of illumination
• Moderately wide beam
• Slit beam is off set
• Medium to high magnification
• Reflected light from iris or fundus

46. TYPES
• Direct
 Prism or mirror is used so that light reflected from lens or iris is directly aligned
with area under observation
 Pathology is seen against light background
• Indirect
 Prism is offset so that area under observation is between focal light beam and
light reflected from iris/lens
 Pathology is seen against dark background
• Marginal
 Prism is offset so that light reflected from lens/iris at pupil margin is aligned with
area under observation

47. Vascularization, epithelial edema, microcysts,
vacuoles, dystrophies, lens opacities and CL deposits

48. SCLEROTIC SCATTER
• A tall, wide beam is directed onto the limbal area, light undergoes TIR
and comes out from the limbus of next side
• The illuminator should be slightly offset for this technique and directed
from a moderate angle.
• 10X magnification, with the microscope directed straight ahead.
• Normal portion of cornea looks dark and any opacities on the path of
light show grey reflex.

49. Central corneal epithelial edema, corneal abrasions,
corneal nebula and macula, FB in cornea

50. SPECULAR REFLECTION
• Produced by separating the microscope and slit beam by
equal angles from the normal to the cornea
• Separation of 50 deg produces the best specular reflection
• The area of high reflection --- zone of specular reflection
• Small zone of reflection is seen at one time , so we should
instruct the patient to change gaze so that large area can be
examined.
• High magnification is required.(40 times)
• Endothelial cells can be counted and pathology in them can
be viewed.

51. Endothelial cell layer, tear film debris,
tear film lipid layer thickness

52. TANGENTIAL ILLUMINATION
• Angle between the slit and microscope 70 – 80 deg
• Used to see iris freckles and tumors, general integrity
of cornea and iris

53. OSCILLATORY ILLUMINATION
• Quick to and fro movement
• Minutes objects in AC

54. CLINICAL USES
• Diagnostic
– Anterior segment Evaluation
– Goldmann Applanation Tonometry
– TBUT test
– Staining (Fluorescein, Rose Bengal etc.)
– Visiometry
– Gonioscopy
– FFA and Clinical Photography

55. • Therapeutic
–Epilation
–Foreign Body Removal
–Contact Lens (fitting and post-wear
evaluation)
–Corneal epithelial debridement
(herpetic keratitis)
–Insertion of punctal plugs

56. REFERENCES
• Schmidt A.F.T.Slit Lamp Microscopy
• Bhatt S S. Basics of slit lamp microscopy
• IACLE contact lens modules
• Grosvenor T.Primary Care Optometry
• Clinical procedures in optometry