INTRODUCTION INTRODUCTION INTRODUCTION INTRODUCTION The slit lamp biomicroscope is a fundamental piece of optometric instrumentation, he slit lamp biomicroscope is a fundamental piece of optometric instrumentation, he slit lamp biomicroscope is a fundamental piece of optometric instrumentation, he slit lamp biomicroscope is a fundamental piece of optometric instrumentation, especially for fitting of contact lenses. especially for fitting of contact lenses. especially for fitting of contact lenses. especially for fitting of contact lenses. However, it is also vital for observing the health of the anterior eye, estimating the However, it is also vital for observing the health of the anterior eye, estimating the However, it is also vital for observing the health of the anterior eye, estimating the However, it is also vital for observing the health of the anterior eye, estimating the anterior chamber depth and performing Goldmann contact tonometry and Volk lens anterior chamber depth and performing Goldmann contact tonometry and Volk lens anterior chamber depth and performing Goldmann contact tonometry and Volk lens anterior chamber depth and performing Goldmann contact tonometry and Volk lens fundus examination. fundus examination. fundus examination. fundus examination. The slit lamp slit lamp slit lamp slit lamp is an instrument consisting of a high-intensity light source that can be focused to shine a thin sheet of light into the eye. It is used in conjunction with a biomicroscope. The lamp facilitates an examination of the anterior segment, or frontal structures and posterior segment, of the human eye, which includes the eyelid, sclera, conjunctiva, iris, natural crystalline lens, and cornea. The binocular slit-lamp examination provides stereoscopic magnified view of the eye structures in detail, enabling anatomical diagnoses to be made for a variety of eye conditions. BRIEF HISTORY BRIEF HISTORY BRIEF HISTORY BRIEF HISTORY Low Low Low Low–power clinical biomicroscopy power clinical biomicroscopy power clinical biomicroscopy power clinical biomicroscopy of the eye is an essential tool to diagnose ocular disease, and Optometrist routinely uses a slit lamp to examine almost all of their patients. At its root, the adjustable slit is simply a way to allow variable angles of illumination. However, this surprisingly simple concept has enabled the slit lamp microscope to become an indispensable instrument for every Optometrist. Slit lamps have evolved significantly since their advent in the early 1900s, and many of today’s slit lamp biomicroscopes are sophisticated instruments building on the discoveries of the past century. One of the first individuals to apply microscopy to the living eye was Purkinje, Purkinje, Purkinje, Purkinje, who in the 1820s in the 1820s in the 1820s in the 1820s studied the iris with an adjustable microscope by illuminating the field of view. The uniocular slit lamp was born years later when Louis de Wecker Louis de Wecker Louis de Wecker Louis de Wecker would combine an eyepiece, objective and adjustable condensing lens within a tube. Wecker’s Wecker’s Wecker’s Wecker’s invention was improved upon by Siegfried Czapski, Siegfried Czapski, Siegfried Czapski, Siegfried Czapski, who added binocularity to the microscope. However, none of the units constructed by these
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INTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTION
TTTThe slit lamp biomicroscope is a fundamental piece of optometric instrumentation, he slit lamp biomicroscope is a fundamental piece of optometric instrumentation, he slit lamp biomicroscope is a fundamental piece of optometric instrumentation, he slit lamp biomicroscope is a fundamental piece of optometric instrumentation,
especially for fitting of contact lenses.especially for fitting of contact lenses.especially for fitting of contact lenses.especially for fitting of contact lenses.
However, it is also vital for observing the health of the anterior eye, estimating the However, it is also vital for observing the health of the anterior eye, estimating the However, it is also vital for observing the health of the anterior eye, estimating the However, it is also vital for observing the health of the anterior eye, estimating the
anterior chamber depth and performing Goldmann contact tonometry and Volk lens anterior chamber depth and performing Goldmann contact tonometry and Volk lens anterior chamber depth and performing Goldmann contact tonometry and Volk lens anterior chamber depth and performing Goldmann contact tonometry and Volk lens
The slit lampslit lampslit lampslit lamp is an instrument consisting of a high-intensity light source that can be
focused to shine a thin sheet of light into the eye. It is used in conjunction with a
biomicroscope. The lamp facilitates an examination of the anterior segment, or
frontal structures and posterior segment, of the human eye, which includes the
eyelid, sclera, conjunctiva, iris, natural crystalline lens, and cornea. The binocular
slit-lamp examination provides stereoscopic magnified view of the eye structures in
detail, enabling anatomical diagnoses to be made for a variety of eye conditions.
BRIEF HISTORYBRIEF HISTORYBRIEF HISTORYBRIEF HISTORY
LowLowLowLow––––power clinical biomicroscopypower clinical biomicroscopypower clinical biomicroscopypower clinical biomicroscopy of the eye is an essential tool to diagnose ocular
disease, and Optometrist routinely uses a slit lamp to examine almost all of their
patients. At its root, the adjustable slit is simply a way to allow variable angles of
illumination. However, this surprisingly simple concept has enabled the slit lamp
microscope to become an indispensable instrument for every Optometrist. Slit lamps
have evolved significantly since their advent in the early 1900s, and many of today’s
slit lamp biomicroscopes are sophisticated instruments building on the discoveries of
the past century.
One of the first individuals to apply microscopy to the living eye was Purkinje,Purkinje,Purkinje,Purkinje, who
in the 1820sin the 1820sin the 1820sin the 1820s studied the iris with an adjustable microscope by illuminating the field
of view. The uniocular slit lamp was born years later when Louis de WeckerLouis de WeckerLouis de WeckerLouis de Wecker would
combine an eyepiece, objective and adjustable condensing lens within a tube.
Wecker’sWecker’sWecker’sWecker’s invention was improved upon by Siegfried Czapski,Siegfried Czapski,Siegfried Czapski,Siegfried Czapski, who added
binocularity to the microscope. However, none of the units constructed by these
individuals had sufficient and adjustable illumination to be of much clinical benefit.
Allvar Gullstrand, Allvar Gullstrand, Allvar Gullstrand, Allvar Gullstrand, an Ophthalmologist and 1911 Nobel laureate1911 Nobel laureate1911 Nobel laureate1911 Nobel laureate, developed a first
true slit lamp to illuminate the eye. Then, Henker and VogtHenker and VogtHenker and VogtHenker and Vogt improved upon
Gullstrand’s device in the 1910s1910s1910s1910s by creating an adjustable slit lamp and combining
Czapski’sCzapski’sCzapski’sCzapski’s microscope with Gullstrand’sGullstrand’sGullstrand’sGullstrand’s slit lamp illumination. The modern slit lamp
biomicroscope was born, a powerful diagnostic tool capable of stereoscopically
examining optical sections of the anterior segment in great detail. The instrument
was not only important as an essential diagnostic tool in the clinic, but also served to
greatly advance the scientific knowledge fueling Optometry. Alfred Vogt Alfred Vogt Alfred Vogt Alfred Vogt was
instrumental in driving this knowledge base through innovative and meticulous use
of the slit lamp. Vogt would use the slit lamp biomicroscope to study a vast array of
diseases and document his findings in the highly influential publication “Lehrbuch “Lehrbuch “Lehrbuch “Lehrbuch
und Atlas der Spaltlampenmikroskopie des Leibenden Auges”und Atlas der Spaltlampenmikroskopie des Leibenden Auges”und Atlas der Spaltlampenmikroskopie des Leibenden Auges”und Atlas der Spaltlampenmikroskopie des Leibenden Auges” inininin the 1930sthe 1930sthe 1930sthe 1930s. The slit
lamp microscope was thus accepted as an essential diagnostic tool by the accepted as an essential diagnostic tool by the accepted as an essential diagnostic tool by the accepted as an essential diagnostic tool by the
Ophthalmology community, and over time Eye MDsOphthalmology community, and over time Eye MDsOphthalmology community, and over time Eye MDsOphthalmology community, and over time Eye MDs invented new ways to reach
beyond the cornea and anterior segment. For example, the slit lamp, in conjunction
with certain contact lenses, could be used together to examine the anterior chamber
angle in great detail.
Today, the two main components of the modern slit lamp microscope are the
illumination system and observation system. The illumination system on most slit
lamps consists of two different designs. The first designfirst designfirst designfirst design, the HaagHaagHaagHaag----Streit type Streit type Streit type Streit type
illuminationilluminationilluminationillumination, allows de-coupling in the vertical meridian. Such vertical de-coupling
is particularly useful when performing gonioscopy to minimize reflections and for
indirect funduscopy to gain increased peripheral views. The second designsecond designsecond designsecond design, the Zeiss Zeiss Zeiss Zeiss
type illumination systemtype illumination systemtype illumination systemtype illumination system, does not allow de-coupling in the vertical meridian. Many
optometrist argue that the Zeiss illumination’sZeiss illumination’sZeiss illumination’sZeiss illumination’s advantage is that it confers lightness
and compactness onto the slit lamp to make it somewhat easier to use. In either case,
the illumination systems of today are both capable of producing a homogenous,
aberration-free beam of white light. Most slit lamps use halogen bulbshalogen bulbshalogen bulbshalogen bulbs to yield
shorter wavelengths of light, which allow better visualization of smaller structures
compared with longer wavelengths of light (i.e. tungsten bulbs).(i.e. tungsten bulbs).(i.e. tungsten bulbs).(i.e. tungsten bulbs).
PROCEDURES FOR CARRYING OUT SLIT LAMP BIOMICROSCOPYPROCEDURES FOR CARRYING OUT SLIT LAMP BIOMICROSCOPYPROCEDURES FOR CARRYING OUT SLIT LAMP BIOMICROSCOPYPROCEDURES FOR CARRYING OUT SLIT LAMP BIOMICROSCOPY
While a patient is seated in the examination chair, he rests his chin and forehead on
a support to steady the head. Using the biomicroscope, the ophthalmologist or
optometrist then proceeds to examine the patient's eye. A fine strip of paper, stained
with fluorescein, a fluorescent dye, may be touched to the side of the eye; this stains
the tear film on the surface of the eye to aid examination. The dye is naturally rinsed
out of the eye by tears.
A subsequent test may involve placing drops in the eye in order to dilate the pupils.
The drops take about 15 to 20 minutes to work, after which the examination is
repeated, allowing the back of the eye to be examined. Patients will experience some
light sensitivity for a few hours after this exam, and the dilating drops may also
cause increased pressure in the eye, leading to nausea and pain. Patients who
experience serious symptoms are advised to seek medical attention immediately.
Adults need no special preparation for the test; however children may need some
preparation, depending on age, previous experiences, and level of trust.
The slit lamp exam may detect many diseases of the eye, includingThe slit lamp exam may detect many diseases of the eye, includingThe slit lamp exam may detect many diseases of the eye, includingThe slit lamp exam may detect many diseases of the eye, including:
• Cataract
• Conjunctivitis
• Corneal injury such as corneal ulcer or corneal swelling
Once more a parallelepiped is used. This is the only means by which one is capable
to view the endothelial cells of the cornea or the epithelial cells on the backside of
lens. The cells are seen only by one eye and they come out in the ocular opposite
from the direction of the illumination light source.
CONSTRUCTION OF SLIT LAMP BIOMICROSCOPECONSTRUCTION OF SLIT LAMP BIOMICROSCOPECONSTRUCTION OF SLIT LAMP BIOMICROSCOPECONSTRUCTION OF SLIT LAMP BIOMICROSCOPE
The 2 basic parts of the slit lamp biomicroscope are:
• The slit lamp (illumination system)
• The biomicroscope
The illumination system can be
1. Of the Zeiss type
2. Of the Haag Streit type
The slitlamp biomicroscope in its most basic form consists of an illumination source
with a range of light intensity setting (i.e. the illumination system) and a microscope
with a series of magnification setting (i.e. the observation system). Other important
considerations are the mechanical and support and controls.
The second main component of slit lamps is the observation system. Modern slit
lamp microscopes can magnify images between 5X and 25X, with some microscopes
allowing magnification to 40X and even 100X. Magnification is generally achieved
by three methods, namely a flip-type, a Galilean rotating barrel, and a continuous
zoom system. However, magnification of the slit lamp is less important than its
resolution. A slit lamp’s resolution is dependent on the wavelength of light used, the
refractive index between the eye and objective, the working distance, and the
diameter of the objective lens. In practicality, the first three of these factors are not
easily modifiable, but the objective lens diameter can be modified to increase
resolution. However, a very large diameter lens will also introduce optical
aberrations. The observation system is also influenced by the proximity of the
patient’s eye to the examiner’s eyes. This necessitates a convergence system for
binocular viewing, and most modern slit lamp biomicroscopes are designed with 10
to 15 degrees of convergence to minimize eye strain for the examiner. These features
in the illumination and observation systems must be considered when deciding on
the best slit lamp to match a particular clinic.
In the Zeiss type the illumination comes from below;
In the Haag Streit type the illumination comes from above as shown below;
In both types of illumination system the Kohler Kohler Kohler Kohler illumination principleillumination principleillumination principleillumination principle is
used:
The filament is imaged on to the objective lens but theThe filament is imaged on to the objective lens but theThe filament is imaged on to the objective lens but theThe filament is imaged on to the objective lens but the mechanical slit is imaged on mechanical slit is imaged on mechanical slit is imaged on mechanical slit is imaged on
to the patient’s eyeto the patient’s eyeto the patient’s eyeto the patient’s eye....
The biomicroscope: based on the optics of a compound microscope
Two basic types:Two basic types:Two basic types:Two basic types:
– The Grenough typeThe Grenough typeThe Grenough typeThe Grenough type
– The The The The Galilean changer typeGalilean changer typeGalilean changer typeGalilean changer type
Magnification can also be changedMagnification can also be changedMagnification can also be changedMagnification can also be changed by changing the eyepiece powerby changing the eyepiece powerby changing the eyepiece powerby changing the eyepiece power
The slit lamp and the biomicroscope
are maneouvred together on a cross
slide by means of a joysticka joysticka joysticka joystick
The coupling between the slit lamp and the biomicroscope
• This is such as to make the system “parfocal”
• i.e the focus of the slit and the focus of the microscope are at the same point.
• This parfocality may occasionally need to be dissociated as for example in the
technique of sclerotic scatter
The coupling between the slit lamp and the biomicroscope
This allows both the slit and the microscope to rotate about the point of
focus(i.e the eye) as shown below;
Dissociation of parfocality can be done in
“Haag Streit” type slit lamps by loosening
the sclerotic scatter knobscatter knobscatter knobscatter knob
This dissociation of parfocality is useful for indirect illumination, sclerotic scatter
and retroillumination as shown below.
The key to successful examination of the anterior segment is
knowledge of the various methods of lighting which can be achieved by the slit lamp
Diffuse illumination for surfaceDiffuse illumination for surfaceDiffuse illumination for surfaceDiffuse illumination for surface DetailsDetailsDetailsDetails