a comprehensive presentation on Slit-lamp in which i have described about the history, optics and also the uses of different illuminations by Dr. Paresh Nichlani
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Slit lamp – biomicroscopy of eye
1. SLIT LAMP – BIO MICROSCOPY OF EYE
By- Dr. Paresh Vijay Nichlani
Moderators- Dr. K Srikanth
Dr N Swathi
2. NEED OF SLIT LAMP ???
Magnified View
Stereoscopic view
Quantitative measurement
3. EVOLUTION OF SLIT LAMP
Purkinje (1823)- One hand held lamp and one hand held lens
De Wecker (1863)- mono-ocular microscope
Albert & Greenough (1891)- Binocular microscope
Czapski (1897)- binocular corneal microscope
Gullstrand (1911)- Illumination system with a slit
Henker (1916) – Combined the two
Hans Goldmann (1933) – Both the lamp and slit beam with
horizontal and vertical adjustment were placed on single stage,
Haag-Streit model
Littmann (1950) - incorporated rotatory magnification changer-
galilean teliscopee – zeiss slit lamp
4. PARTS OF MODERN SLIT LAMP
Observation system (Microscope)
Illumination system
Mechanical system
5. BRUSHUP
• Ray of light
passing from
optical center will
not be refracted.
• Rays coming
from infinity ( zero
vergence ) will
converge to focal
point
• Rays originating
from focus will
come parallel after
refracting
7. OBSERVATION SYSTEM
1. Objective lens – two Plano convex
lens, convexities put together -
+22.00 D
2. Eye piece - +10.00 D, Tubes
converged at an angle of 10-15
degrees- stereopsis
3. Prisms- rectify problem of inverted
image
10. PRINCIPLE OF ILLUMINATION SYSTEM
Kohler illumination principle
Converts light source to a beam of homogenous
brightness with minimal glare
Advantage is that a very sharp and bright light is
obtained
11. ILLUMINATION SYSTEM
1. Light source – nerst lamp > arc lamp > Mercury
vapour lamp > halogen Lamp> LED lamps
Illumination – 2*105 to 4*105 lux
2. Condenser lens – coupled Plano convex lens
3. Slit and other diaphragm – horizontal and
vertical diaphragm
4. Filters – cobalt blue filter, red free filter
5. Projection lens - diameter of lens is smaller
- Better quality image
- Increases depth of focus of slit
– better optical section.
6. Reflecting mirror/ prism – illumination axis do
not obstruct field of
vision
14. TYPES OF ILLUMINATION
Depending upon the structures and there
different optical property we use different
types of illumination.
15. 1. DIFFUSE ILLUMINATION
Settings
- Slit fully opened (annular diaphragm)
- Inserted diffuser
- Microscope positioned at 0°
-Angle of slit illumination system approx. 30° - 50°
-Magnification – 5-12x
Uses
- general surveys of anterior eye segments
- general observation of the surfaces
of crystalline lens and cornea
- assessment of the lachrymal reflex
-assessment of soft contact lenses
-It can be used with filters
18. 2. DIRECT FOCAL ILLUMINATION
• Slit beam is regulated until it
coincides with exact focus of the
microscope
• Settings – Narrow slit at oblique
angle (30), slit 2-3mm , 5-45x
• 3d layered view
- cornea lens and ant.
Phase of vitreous disperse light and
gets visible against dark back
ground.
• This type of illumination can be
used with 3 types of different
beam
1. Optical Section
2. parallelepiped
3. conical beam effect
19. OPTICAL SECTION
A narrow slit is focused obliquely 2-
3mm, 30-45, – knife like histological
sections of cornea, lens & ant. phase
of vitreous
Optical section of cornea –
1.Tear layer- ant. Most bright zone
2. Epithelium- dark line
3. Bowman’s membrane – bright line
4. Stroma- Wider granular grey zone
5. Descemet’s membrane – bright
zone
Uses – 1. corneal curvature
2. Corneal thickness
3. Location of corneal pathology
4. Van Her-rick method of ac depth
20.
21. OPTICAL SECTION OF LENS
Optical section of lens
1. Ant capsule 2. sub capsular clear zone – c1 3. Bright narrow zone of discontinuity 4.second clear
cortical zone – c2
5.Light scratting zone of deep cortex – c3 6.Clear zone of deep cortex. 7. Nucleus
22. Parallelopiped – 2-
3mm wide focal slit –
used for pathologies
on epithelial and
stroma
Conical beam- small
circular beam –
examining aqueous
for cells and flares –
at 45-60 degrees, at
high mag.
23. 3 INDIRECT ILLUMINATION
Slit beam is focused beside the
area to be observed- The axes of
illuminating and viewing path do
not intersect at the point of image
focus.
Angle-60, variable, slit max height
Uses –
1. Corneal infiltrates
2. Corneal microcytes
3. Corneal vacuoles
4. Epithelial cells
24. 4RETRO ILLUMINATION
• Light is reflected off from iris
or fundus
• system and observation axis are
set to 0°.
• it is essential that the pupil is
• dilated as otherwise the resulting
relatively small field of view
through a normal size pupil
makes observation
• almost impossible.
25. • Direct- Observer is in direct pathway of light reflected from structure. Pathology-
against illuminating background.
• Indirect – observer right angled to observing structure. Not in line with light ,
Pathology – against dark non illuminated background.
26. GRAVES – PATHOLOGY- OPTICAL PROPERTIES
Obstructive- opaque to
light- dark against bright
background eg- pigments
Respersive- scatter light
but do not obstruct –
brightly against dark
background epithelial
edema, precipitates.
Refrectile- distort view as
refrective index is different
from surrounding. Eg –
vacuole.
27. 5. SPECULAR REFLECTION
Reflection accurse – beam
of light incident on optical
surface- zone of
discontinuity
Observer in path of
reflected light – dazzling
reflex - specular reflex –
dark areas in reflex
Technique – Pt to look 30
degree temporally , light
beam focused from opp.
side, focused under high
magnification, 3-4 mm from
limbus- slit is rotated more
temporally to about 60
degree (i=r)
Uses – endothelial cell
count
29. COBALT BLUE FILTER
This throws a blue
light,
Principle –
fluorescence – these
substance absorbs
light of a colour and
then emit a light of
other colour in this
case it absorbs blue
and emits yellowish
green.
Uses – corneal ulcer,
scidel test etc, tear
BUT etc.
30. RED FREE FILTER
This filter emits green
light – This causes
obscure red colour
Blood vessels and
haemorrhages appear
black
Areas of episclera with
lymphocyte appears
yellow
Fleischer ring
32. WHAT DO WE KNOW??
WHAT WE HAVE LEARNT??
Evolution of slit lamp
Parts of slit lamp
Optics of slit lamp
Uses
Types of illumination
Accessory devices
The future- dime
illumination coupled
with electronic light
amplification system
De wecker- heand helf-restedon face- condencer lens,
Zero vergence
Eye piece stronger, objective less power
Afocal system
Objective plus (low power) eye piece minus (hig power)
Ray diagram
Filament imaged on lens , slit imaged on patient eye
Narrow beam- scattered background light is removed
Tindal phenominon narrow beam and dark pupilary background
2 % fluorescein dye
FDDt- prolonged stay in fornex – defective drainage . Jones 1- dye put – collected in inf meatus. Jones 2 – press saline if dye – occlusion of nld if not canallicular occlusion non fn pump
Fleischer ring – pigment ring in pereferal cornea - ieon deposition in basel epithelial cells - keratoconous .... Kayser f ring copper – willson’s