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.
2. WHY SLIT LAMPS ARE SO GREAT
gold standard device.
This is because they provide…
Stereoscopic image
Variable illumination
Variable magnification
Excellent image quality
3.
4. A narrow vertical slit of light is projected on to
the eye and permits microscopic examination of
living tissues in cross-section
5.
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
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
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
22. ILLUMINATION SYSTEM
Comprises of :
• Light source: halogen lamp
• Condenser lens system
• Slit and other diaphragms
• Filters
• Projection lens
• Reflecting mirror
23.
24. MECHANICAL SUPPORT SYSTEM
Consists of :
Joystick arrangement
Up and down movement
arrangement
Patient support arrangement
Fixation target
Mechanical coupling
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
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
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
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
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
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
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.
Editor's Notes
USE : For judging the depth of lesion & examination of the lens.