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1. SLIT LAMP
BIOMICROSCOPY
AHMADINFOTECH
• NAEEM AHMAD
YouTube.com/ahmadinfotech

2. Introduction
★ The slit lamp is indispensable for the detailed
examination of virtually all tissues of the eye
and some of its adnexa.
★ It is routinely used for examination of the
anterior segment, which includes the anterior
vitreous and those structures that are anterior to
it.
★ The lamp facilitates an examination of the anterior
segment and posterior segment of the human eye
which includes the eyelid, sclera,conjunctiva,iris,
natural crystalline lens, and cornea.
★ In addition to physical (visual)examination,
Tonometry, linear measurement of tissues or
lesions, and ophthalmic photography. contact
lens fitting Etc.

3. The binocular slit-lamp examination provides a stereoscopic magnified view of the eye structures in detail,
enabling anatomical diagnoses to be made for a variety of eye conditions. A second, hand-held lens is used to
examine the retina.
❖ The concept come in 1850 by Hermann von Helmholtz
❖ In 1911 the credit goes to Allvar Gullstrand
❖ In 1919 lamp and magnification is introduced by Vogt Henker
❖ In 1926, the slit lamp instrument was redesigned.
❖ In 1927 the stereo cameras has been introduced
❖ In 1930, Rudolf Theil further developed the slit lamp, encouraged by Hans Goldmann.
❖ In 1938 vertical and horizontal movement and joystick was introduced
❖ In 1976 the halogen bulb was introduced.
❖ In 1996 the last major development
History

4. Types
There are two different types of slit lamp based on the
location of their illumination system:
Zeiss type
In the Zeiss type slit lamp, the illumination is located
below the microscope(Integrated illumination type).
This type of slit lamp is named after the
manufacturing company Carl Zeiss.
Haag Streit type
In the Haag Streit type slit lamp, the illumination is
located above the microscope(Tower illumination
type). This type of slit lamp is named after the
manufacturing company Haag Streit.

5. Slit lamp is composed of three basic systems:
❖ Observation system (Microscope)
❖ Illumination system (Slit-lamp)
❖ Mechanical system (Engineering support)
❖ OBSERVATION SYSTEM (MICROSCOPE)
★ It works on the same principle as a compound
microscope.Which is composed of two optical
elements,an objective and an eyepiece.
★ The objective lens (+22 D) is towards the
patient,whose eye forms the object. The
eyepiece is +10 to +14 D and is towards the
examiner.
★ The objective lens consists of two planoconvex
lenses with their convexities facing towards
each other.

6. ❖ ILLUMINATION SYSTEM
1. Light source
2. Slit and other diaphragms
3. Filters
4. Projection lens
Light source,
★ Originally , a Nernst lamp was used as a light
source which was followed by Nitra lamp, arc
lamp, mercury vapour lamp and finally halogen
lamps.
★ It provides an illumination of 2X 10^5 to 4X
10^5 lux.
★ The illuminating system can be adjusted to vary
the width, height and angle of incidence of the
light beam.
★ Slit lamps provide a range of magnification
from 6X to 40X.

7. Slit and other diaphragms,
★ Height and width of the slit can be varied using
two knobs.
★ There are some stenopaeic slit 2.0 and 0.5mm
to provide conical beam of light.
Filters
Different filters can be inserted into the illumination
beam,
1. Cobalt Blue
2. Red free
3. Neutral density
4. Heat absorbing
5. Grey
6. Yellow filter
7. Diffuser

8. Filter Typical symbol Use
Cobalt blue Blue filled circle
Enhances the view of fluorescein dye in the tear film of the
eye. Typically used for fluorescein staining and Goldmann
tonometry.
Red free Green filled circle Enhance the view of blood vessels and haemorrhages
Neutral density Circle with hashed lines Decreases maximum brightness for photosensitive patients
Heat absorbing
Built into most slit-lamps
Decreases patient discomfort
Grey Circle with thick line Decreases maximum brightness for photosensitive patients
Yellow filter
Yellow filled circle Located in the
observation system
For good contrast enhancement when using fluorescein and
the cobalt blue filter
Diffuser
May be a flip-up filter placed on the
illumination source
overall observations of the eye filter placed on the and
adnexa

9. Projection lens
★ Forms an image of the slit at the eye.
This has two advantages:
1. It keeps the aberrations of the lens down,better
quality image.
2. It increase the depth of focus of the slit,better
optical section of the eye.
MECHANICAL SUPPORT SYSTEM
1. Joystick arrangement
2. Up and down movement arrangement
3. Patient support arrangement
4. Fixation target

10. PARTS OF A SLIT LAMP BIOMICROSCOPE
1. EyePieces
2. Reflecting Mirror
3. Chin Rest - Adjustment Knob
4. Joystick
5. Slit width Adjustment Knob
6. Adjustment Knob For Aperture
Height And Slit Tilt
7. Illumination System Arm
8. Illumination System Lock Knob
To Obs. Arm
9. Observation System Arm
10. Observation System Lock Knob
To Base
11. Illumination System Tilt
Adjuster
12. Filter Selector Switch
13. Magnification Selector
14.Binoculars,
Adjustable For PD.
15. Base Axis
16. Axis Rollers
17. Rails
18. Rolling Pad/Plate.
Attached to Table
19.Forehead Rest
20.Chin Rest
21. Light Compartment
22.Patient Grip Handle
23.Power Switch
24.Fixation Light

11. 1.Eyepieces
2. Reflecting
Mirror
3. Chin - Rest
Adjustment Knob

12. 4.Joystick
5. Slit Width
Adjustment Knob
6. Adjustment Knob For
Aperture Height And Slit
Tilt

13. 7. Illumination System Arm
8. Illumination System Lock Knob To Obs.
Arm
9.Observation System Arm
10.Observation System Lock Knob To
Base
11. Illumination System Tilt Adjuster

14. 12. Filter Selector
Switch
13. Magnification Selector
14. Binoculars, Adjustable For PD.
15. Base Axis

15. 16. Axis Rollers
17. Rails
18. Rolling Pad/Plate. Attached to Table
19. Forehead Rest

16. 20. Chin Rest
21. Light Compartment

17. 22. Patient Grip
Handle
23. Power Switch
24. Fixation Light

18. Principles of Slit-Lamp Illumination
The slit lamp is capable of illuminating the
tissues of the eye in several different ways, any
or all of which can be useful, depending on the
clinical situation. The beginning ophthalmology
resident should strive early to master all of these
techniques of illumination, so as to be able to use the slit
lamp to its full advantage.
Types of Illumination
The slit lamp exam is dynamic; the observer uses
multiple types of illumination simultaneously.
❏ The three main categories of illumination are
DIFFUSE, DIRECT, AND INDIRECT.
❏ Diffuse illumination provides an even light over
the entire ocular surface.
❏ With direct illumination techniques, the light is
shone directly onto the area or structure of interest.
❏ With indirect illumination methods, the object of
interest is illuminated by light that is reflected off
of another structure.

19. Methodes of Illumination
There are s basic methods of illumination using
the slit-lamp :-
1. Diffuse Illumination
2. Direct Illumination
a. Parallelopiped
b. Optical section
c. Pinpoint (conical)
d. Tangential
e. Specular Reflection
3. Indirect Illumination
a. Retro Illumination
b. Sclerotic scatter
c. Transillumination
d. Proximal Illumination
Diffuse Illumination
Direct Illumination Indirect Illumination

20. Diffuse Illumination
● Diffuse illumination is still a good starting point of the
eye.(especially the skin).
● Diffuse illumination is used mainly for obtaining an overview of
ocular surface tissues (eg, bulbar and palpebral conjunctiva),
although it can also be useful for examining intraocular structures
(iris, lens capsule).
● Diffuse illumination is most often used in slit lamp photography.
● Angle between microscope and illumination system should be
30-45 Degree.
● Slit width should be widest.
● Filter to be used is diffusing filter.
● Magnification used is low to medium.
● Illumination should be medium to high.

21. ● The cobalt blue and red-free filters also act as diffusers, but white
light is generally used for this technique.
● The red-free filter produces light-green light, facilitating the
evaluation of rose-bengal staining
● Observe: eyelids, lashes, conjunctiva, sclera, pattern of redness,
iris, pupil, gross pathology, and media opacities.
● Contact lens fitting.

22. Direct Illumination
The slit beam and microscope are focused on the same area, and
examination is performed. Changes in the corneal stroma and epithelium
are better noted by this technique.
a. Parallelopiped
b. Optical section
c. Pinpoint (conical beam)
d. Tangential
e. Specular Reflection
Parallelopiped of the cornea is observed using a 2-3mm wide
focused slit.
★ The slit should be 45-60 degree on to the temporally.
★ Set the slit to a medium width, and the angle to vertical position.
★ Increase the magnification for more detailed analysis as required.
★ Magnification is 7-10X.
★ Microscope is placed directly in front of patients cornea.
★ The room should be darkened.

23. ➢ To determine the fit of a contact lens, particularly a rigid lens after
fluorescein has been instilled in the eye and the cobalt blue filter
used.
➢ Examine the crystalline lens.
➢ Used to detect and examine corneal structures and defects.
➢ The white blood cells will reflect the light and be seen as white
dots floating in the anterior chamber.
➢ Cells and flare in the anterior chamber are graded by using a
Parallelopiped 2 mm wide X 4mm high.
➢ To give a broad view of the anterior and posterior corneal surfaces.
➢ To determine anterior surface irregularities.
➢ To examine the endothelium.

24. OPTICAL SECTION
● A thin slice of tissue can be thrown into bright contrast with its
illuminated surroundings.
● Tear layer is seen as a bright anterior most zone.
● Epithelium is seen as a dark line immediately behind the tear
layer.
● Bowman’s membrane is seen as a bright line.
● Stroma is focused as a wider granular and greyer zone.
● Descemet’s membrane and endothelial layers are seen as
posterior most bright zone.
Examination of cornea by optical section gives information about :
● Changes in corneal curvature
● Changes in corneal thickness
● Depth of the corneal pathologies, e.g. location of a foreign body.

25. ➢ The position of the microscope directly in front of the eye to be
examined.
➢ Angle of about 45 degrees to the microscope on the temporal side.
➢ Use low power magnification first.
➢ The slit to a narrow width and the angle to vertical position.
➢ Use the joystick, bring the illuminated "slice" or section into very
sharp focus.
➢ Increase the angle between the microscope and the illuminating
arm to expose a greater area of stroma.
➢ Increase the magnification.
➢ While scanning, as the slit position reaches the corneal apex, swing
the illuminating arm about 90 degrees to the nasal side for viewing
the medial half of the cornea.
➢ Observe: Cornea, Iris, Lens, Vitreous,Nerve Fibers,Blood
vessels,AC Depth Etc.

26. Pinpoint (conical beam)
➢ Also known as "Conical beam", a small circular aperture of light is
focused on a specific point on the cornea, or aimed through the
pupil to reveal anterior chamber details.
➢ Target in the cornea while minimizing the brightness of the beam
for client comfort.
➢ The principle is the same as a beam of sunlight streaming through
a room, illuminating airborne dust particles.This occurrence is
known as Tyndall’s phenomenon.
➢ Angle of about 45 degree to the microscope on the temporal side.
➢ Reduce room lighting to a minimum or to total darkness.
➢ Magnification is high (16-25X).
➢ Pinpoint illumination is easier if the pupil is not dilated.
➢ Observe: cells, flare

27. Tangential
This technique is used to observe surface texture.Examination of
the cornea and the iris using very oblique illumination when the
microscope is aligned in front of the eye being observed. The angle
of the beam is variable.
➢ To evaluate the position and movement of a contact lens with a
minimum of light intensity.
➢ Using a blue filter, to observe Fleisher's ring in keratoconus.
➢ To reveal the topography, integrity, pigmentation and pathology of
the anterior of the iris.
➢ To observe floaters in the anterior chamber.
➢ The microscope directly in front of the eye.Angle, more than 70
degrees, to the oculars.
➢ Use a medium-wide beam of moderate height.
➢ Magnifications of 10X, 16X, or 25X are used.
➢ If you are looking for details on the cornea or lens, dilation is
preferred because this creates a dark background against which to
view those structures
➢ Observe: anterior and posterior cornea, iris, anterior lens.

28. Specular Reflection
➢ It is used to visualize the actuality of the corneal and lens surfaces.
➢ If the surface is smooth, then reflection smooth and regular; if the
surface is broken or rough, then reflection will likewise be
irregular.
➢ Position the illuminator about 30 degrees to one side and the
microscope 30 degrees to the other side.
➢ Angle of the illuminator to the microscope must be equal and
opposite.
➢ To visualize the endothelium, start with lower magnification (10X
to 16X).
➢ The endothelium is best viewed using only one ocular, so you may
want to close one eye. This technique is difficult to master, partly
because the cells have such low contrast, and takes some
experimentation and experience.
➢ Cell counts done strictly by slit lamp observation are not generally
accepted. Contact specular microscopy is much more accurate.
➢ Observe: corneal epithelium and endothelium, endothelial
mosaic, lens surfaces.

29. Indirect Illumination
The light is directed just to the side of the lesion to be examined.Some
of the light enters the lesion, causing it to glow internally.This type of
illumination is most useful for translucent lesions such as some corneal
opacities or iris nodules.
Indirect illumination provides more detail than diffuse or direct
illumination.
The microscope itself is focused at a different depth or plane than the
light source.
a. Retro Illumination
b. Sclerotic scatter
c. Transillumination
d. Proximal Illumination

30. Retro Illumination
➢ Retroillumination is used to evaluate the optical qualities of a
structure.
➢ Object of interest is illuminated only by light reflected from the
structures behind it.
➢ Retroillumination from the fundus is a quick and easy way to
examine the lens, iris, and cornea. The red reflex, the reflection of
light off the back of the eye, can be used to highlight opacities in
the cornea or lens, and defects in the iris.
➢ 10x–16x magnification.
➢ The microscope is focused on more anterior structures within the
reflected light.
There are two types of Retro-illuminations:-
1. Direct Retroillumination
2. Indirect Retroillumination

31. Direct Retroillumination
➢ This illumination method is used to view corneal pathology.
➢ Use a magnification of 16X to 25X, and direct the light from
45degrees.
➢ The microscope is directed straight ahead. The light strikes the iris,
highlighting the corneal pathology on which you focus the
microscope.
➢ Using the joystick, focus the microscope sharply on the cornea.
➢ This technique is best accomplished if the patient is not dilated.
➢ Objects viewed may have one color in direct and a different color
with retroillumination.
➢ Observe: Cornea

32. Indirect Retro-illumination
➢ The observed feature is not viewed in the direct pathway of the
reflected light.
➢ The oculars are moved so that the retro illuminated object is
viewed against a dark, non-illuminated background.
➢ The angle between the microscope and the illuminating arm can be
varied considerably.
➢ Observe: Cornea, Angles

33. Sclerotic scatter
➢ A broad beam of light is focused sharply at the limbus and the
microscope is focused sharply on the cornea.
➢ This method is useful to view the distribution of corneal pathology.
➢ It especially useful in contact lens evaluation.
➢ Use 10X magnification, with the microscope directed straight
ahead.
➢ The angle between the microscope and illuminating arm should be
45 degrees or greater.
➢ This technique is easiest if the patient is not dilated so that the iris
provides a contrasting dark background.
➢ Observe: General pattern of corneal opacities.

34. Transillumination
In transillumination, a structure (in the eye, the iris) is evaluated by how
light passes through it.
Iris Transillumination
➢ This technique also takes advantage of the red reflex.
➢ Use a full circle beam of light equal to the size of the pupil.
➢ Magnification of 10X to 16X is adequate.
➢ Observe: Iris defects (they will glow with the orange light reflected
from the fundus).

35. Proximal Illumination
This illumination technique is used to observe internal detail, depth, and
density.
The light will be scattered into the surrounding tissue, creating a light
background that highlights the edges of the abnormality.
It opaque the foreign body embedded in the cornea.
Observe: Corneal opacities (edema, infiltrates, vessels, foreign
bodies), lens, iris.

36. SLIT-LAMP BIOMICROSCOPY ROUTINE
While performing slit-lamp biomicroscopy, following routine
may be adopted:-
❖ The slit lamp should be set up in a room that is free of dust.
❖ Excessive heat or humidity, as well as exposure to direct
sunlight, should also be avoided.
❖ Patient should be positioned comfortably in front of the
slit-lamp with his/her chin resting on the chin rest and
forehead opposed to head rest.
❖ If the table is too low, or too high, the patient will be
uncomfortable.
❖ Beginning the actual examination you should adjust the
eyepieces of the slit lamp oculars.
❖ If you wear glasses or remove glasses, the oculars must be
set to compensate for your refractive error.

37. ❖ Examination should be carried out in semidark room so that the
examiner’s eyes are partially dark adapted to ensure sensitivity to
low intensities of light.
❖ Diffuse illumination used for short time as necessary.
❖ Medications like ointments and anaesthetic eye drops produce
corneal surface disturbances which can be mistaken for pathology.
❖ Low magnification should be first used to locate the pathology and
higher magnification should be used to examine it.
❖ You will also need to set the pupillary distance (PD) of the oculars.
❖ If your slit lamp has a fixation light, have the patient look at that.If
you do not have a fixation device, you can ask the patient to look
straight ahead at your ear or over your shoulder at a large letter or
other target at the end of the room.
❖ It is a good idea to begin the examination at 6X or 10X
magnification. You can move to 16X or more when you examine
the cornea and internal structures and when you see some
abnormality that warrants closer inspection.

39. During the test, the doctor will examine all areas of
your eye, including the:
● Eyelids
● Iris
● Lens
● Sclera
● Cornea
● Retina
● Optic Nerve
● Cataracts, Which Is An Opacity Or Cloudiness Of The Lens
● Macular Degeneration, An Eye Disease That Destroys The Central
Vision
● Optic Nerve, Such As Glaucoma

40. ● Bleeding In The Eye
● Foreign Body In The Eye
● Conjunctivitis
● Corneal Injury Such As Corneal Ulcer Or Corneal Swelling
● Diabetic Retinopathy
● Fuchs' Dystrophy
● Keratoconus (Fleischer Ring)
● Retinal Detachment
● Retinal Vessel Occlusion
● Retinitis Pigmentosa
● Sjögren's Syndrome
● Toxoplasmosis
● Uveitis

41. There are number of other investigative techniques that
utilise the slit lamp:-
➢ Gonioscopy
➢ Hruby-lens
➢ Fundus examinations
➢ Tonometry
➢ Van Herick’s technique
➢ Pachometry
➢ Tearscopeâ
➢ Photography using 35 mm, video or digital systems
➢ Aesthiometry
Tearscopeâ
Hruby-lens Applanation tonometer
Pachometry
Gonioscopy

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