slit lamp bio microscopy,magnification, uses, advantages

1. Md. Didarul alam
2nd year
B. Optom,ICO,CU
Slit lamp Biomicroscopy
optometrist

2. Introduction
• Biomicroscope derives its name from the fact
that it enables the clinician to observe the
living tissue of eye under magnification.
• It not only provides magnified view of every
part of eye but also allows quantitative
measurements and photography of every part
for documentation.

3. Important historical landmarks
• De Wecker 1863 devised 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 diapharm in it
– Therefore Gullstrand is credited with the
invention of slit lamp.

4. Large Gullstrand
Ophthalmomicroscope
(1911)

5. TYPES
 There are 2 types of slit lamp biomicroscope
1)Zeiss slit lamp biomicroscope
2)Haag streit slit lamp biomicroscope
 In Zeiss type light source is at the base of the
instrument while in Haag streit type it is at the
top of the instrument.

6. Zeiss slit lamp biomicroscope
Haag streit slit lamp biomicroscope

7. PRINCIPLE
• A "slit" beam of very bright light produced
by lamp. This beam is focused on to the eye
which is then viewed under magnification
with a microscope

9. Topcon slit lamp model SL-3E
Light beam is controlled by knobs
Joy stick arrangement
Chin rest
Reflecting mirror
biomicroscope
Illumination control

10. Magnification
may be changed by
flipping a lever...
Changing filters. biomicroscope
Patient positioning
Alignment
mark
Microscope
and light
source rotate
indepedently

11. Instrumentation
• Operational components of slit lamp
biomicroscope essentially consist of:
–Illumination system
–Observation system
–Mechanical system

12. • Illumination system
• It consist of:
A bright ,focal source of light with a slit
mechanism
• Provides an illumination of 2*10^5 to 4*10^5
lux.
• The beam of light can be changed in
intensity,height,width,direction or angle and
color during the examination with the flick of
lever.

13. Condensing lens system:
–Consist of a couple of planoconvex lenses
with their convex surface in apposition.
Slit and other diapharm:
Height and width of slit can be varied by
using knobs.
The illumination and observation systems
coupled around a common centre of
rotation to ensure that the microscope is
always focused at the same point as where
the slit beam is focused.

14. Observation system(microscope)
 Observation system is composed of two
optical elements
1.an objective ,2.an eyepiece
 It presents to the observer an enlarged
image of a near object.
 The objective lens consists of two
planoconvex lenses facing towards the
patient
providing a composite power of +22D.
 Microscope is binocular i.e. it has two
eyepieces giving binocular observer a
sterescopic view of eye.

15. • The eye piece has a lens of +10D to + 14D
towards the examiner.
• To overcome the problem of inverted image
produced by compound microscope ,slit lamp
microscope uses a pair of prisms b/w the
objective and eyepiece to reinvert the image.
• Most slit lamp provide a range of
magnification from 6x to 40x

16. Mechanical/Physical support
• A joystick control is employed to enable
instrument to be moved left-right/forward-
backward (= focus)/ and up-down.
• A chin rest, head rest and fixation target is also
required. Some slit lamps have a tilting
mechanism to enable the lamp to be directed
from different angles.

17. – Used in conjunction with fluorescein stain
– absorbs blue light and emits green with
fluorescein stain.
 Uses:
• Ocular staining
• RGP lenses fitting
• Tear layer

18. Continue……..
 Obscure any thing that is red hence the red free
light , thus blood vessels or haemorrhages
appears black.
• is used to see the vascular pattern of choroid and
see any abnormalities in the disc of fundus.
• Fleischer ring can also be viewed satisfactorily with the
red FREE filter
• Yellow filter is used for general view of anterior segment.

19. Illumination techniques
– Diffuse illumination
– Direct illumination
• Parallilepiped
• Optic section
• Conical(pinpoint)
• Tangential
• Specular reflection
– Indirect illumination
• Retro-illumination
• Sclerotic scatter
• Transillumination

20. Diffuse illumination
• Angle between microscope and illumination
system should be 30-45 degree.
• Slit width should be widest.
• Filter to be used is diffusing filter.
• Magnification: low to medium
• Illumination: medium to high.

21. Optics of diffuse illumination Diffuse illumination with slit beam and
background illumination

22. Applications:
–General view of anterior of eye:
lids,lashes,sclera,cornea ,iris, pupil,
–Gross pathology and media
opacities
–Contact lens fitting.
–Assessment of
lachrymal reflex.

23. Dirrect illumination
Slit beam and
microscope are focused
on the same area
Vary angle of
illumination
Low to high
magnification
Vary width and height of
light source

25. Optic section
• Optic section is a very thin beam of light and
optically cuts a very thin slice of the cornea.
• Angle between illuminating and viewing path is 45
degree.
• Used to localize:
– Nerve fibers
– Blood vessels
– Infiltrates
– Cataracts
– AC depth.

26. Optical section of lens
1.Corneal scar with wide beam illumination 2.optical section through scar indicating scar
is with in superficial layer of cornea.

27. • Parallelepiped:
–Constructed by narrowing the
beam to 1-2mm in width to
illuminate a rectangular area of
cornea.
–Microscope is placed directly in
front of patients cornea.
–Light source is approximately 45
degree from straight ahead
position.

29. –Applications:
• Used to detect and examine corneal
structures and defects.
• Used to detect corneal striae that
develop when corneal edema occurs with
hydrogel lens wear and in keratoconus.
• Higher magnification than that used with
wide beam illumination is preferred to
evaluate both depth and extent of
corneal ,scarring or foreign bodies.

30. Conical beam(pinpoint)
– Produced by narrowing the vertical height of a
parallelepiped to produce a small circular or
square spot of light.
– Light source is 45-60 degree temporally and
directed into pupil.
– Biomicroscope: directly in front of eye.
– Magnification: high(16-25x)
– Intensity of light source to heighest setting.
Uses
Most useful when examining the transparency of anterior
chamber for evidence of floating cells and flare seen in
anterior uveitis.

32. Indirect illumination
• Lights enter the eye through a narrow to
medium slit (2 to 4 mm) to one side of the
area to be examined
• Illumination
 narrow to medium slit width
 decentred slit
• Magnification
• approx. M= 12x (depending on object size)

34. Observe
valuable for observing
• Epethelial vessicles
• Epithelial erisons
• Irish pathology
• Irish spincter

36. Schematic of
retroillumination from the
retina.
Example of retroillumination from the retina.

38. Retroillumination

39. Specular reflection
• Established by separating the microscope and slit
beam by equal angles from normal to cornea.
• Position of illuminator about 30 degree to one side
and the microscope 30 degree to otherside.
• Angle of illuminator to microscope must be equal
and opposite.
• Angle of light should be moved until a very bright
reflex obtained from corneal surface which is called
zone of specular reflection.

40. Reflection from front
surface endothelium

41. Sclerotic scatter
• It is formed by focusing a bright but narrow slit beam
on the limbus and using microscope on low
magnification.
• total internal reflection occurs here
• The slit beam should be placed approximately 40-60
degree from the microscope.
• When properly positioned this technique will
produce halo glow of light around the limbus as the
light is transmitted around the cornea.
• Corneal changes or abnormalities can be visualized
by reflecting the scattered light.

42. • Used to observe:
–Central corneal epithelial edema
–Epithelial defects
–Corneal endothelial cell counts
–Corneal abrasions
–Corneal nebulae and maculae.

43. Schematic of
sclerotic scatter. Example of sclerotic
scatter.

44. Tangential illumination
• Requires that the illumination arm and the
viewing arm be separated by 90 degree.
• Medium –wide beam of moderate height is
used.
• Microscope is pointing straight ahead.
• Magnification of 10x,16x,or 25x are used.

45. • Observe:
–Anterior and posterior cornea
–Iris is best viewed without dilation by this
method.
–Anterior lens (especially useful for viewing
pseudoexfolation).

47. Order of Examination
• Tears
• Lid margins/Lashes
• Conjunctiva
• Cornea
• Anterior chamber
• Iris
• Lens
• Anterior vitreous

48. Clinical Use
Diagnostic
– Anterior segment Evaluation
– Goldmann Applanation Tonometry
– TBUT test
– Staining (Flurescein, Rose Bengal etc.)
– Visiometry
– Gonioscopy
– FFA and Clinical Photography
– Tear evaluation
– Pachymetry

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

50. References
• Clinical ophthalmology- jack j kanski
• Comrephensive ophthalmology- A K Khurana
• Clinical procedurs in optometry(CPO)
• Optics & refraction – A K khurana
• internet