SENSOR & TRANDUSER
JURNAL INTERNASIONAL (SLIT LAMP)
DI
SUSUN OLEH :
NAMA : FAISHAL SHADDAM
AL HASYIR
NIM : 182151024
DOSEN
PENGAMPU : Pak ADE FIRDAUS
D- IV
TEKNIK ELEKTROMEDIK
FAKULTAS KESEHATAN
2016-2017
Slit lamp
The 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
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 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.
History
Two
conflicting trends emerged in the development of the slit lamp. One trend
originated from clinical research and aimed to apply the increasingly complex
and advanced technology of the time. The second trend originated from
ophthalmologic practice and aimed at technical perfection and a restriction to
useful methods. The first man credited with developments in this field was Hermann
von Helmholtz (1850) when he invented the ophthalmoscope. In ophthalmology and
optometry, the instrument is called a “slit lamp,” although it is more
correctly called a “slit lamp instrument”. Today’s instrument is a combination
of two separate developments, the corneal microscope and the slit lamp itself.
The first concept of a slit lamp dates back to 1911 credited to Alvar
Gullstrand and his “large reflection-free ophthalmoscope. ”The instrument was
manufactured by Zeiss and consisted of a special illuminator connected to a
small stand base through a vertical adjustable column. The base was able to
move freely on a glass plate. The illuminator employed a Nernst glower which
was later converted into a slit through a simple optical system. However, the
instrument never received much attention and the term “slit lamp” did not
appear in any literature again until 1914. It wasn’t until 1919 that several
improvements were made to the Gullstrand slit lamp made by Vogt Henker. First,
a mechanical connection was made between lamp and ophthalmoscopic lens. This
illumination unit was mounted to the table column with a double articulated
arm. The binocular microscope was supported on a small stand and could be moved
freely across the tabletop. Later, a cross slide stage was used for this
purpose. Vogt introduced Koehler illumination, and the reddish Nernst glower
was replaced with the brighter and whiter incandescent lamp. Special mention
should be paid to the experiments that followed Henker’s improvements in 1919.
On his improvements the Nitra lamp was replaced with a carbon arc lamp with a
liquid filter. At this time the great importance of color temperature and the
luminance of the light source for slit lamp examinations were recognized and
the basis created for examinations in red-free light. In the year 1926, the
slit lamp instrument was redesigned. The vertical arrangement of the projector
made it easy to handle. For the first time, the axis through the patient’s eye
was fixed along a common swiveling axis, although the instrument still lacked a
coordinate cross-slide stage for instrument adjustment. The importance of focal
illumination had not yet been fully recognized. In 1927, stereo cameras were
developed and added to the slit lamp to further its use and application. In
1930, Rudolf Theil further developed the slit lamp, encouraged by Hans
Goldmann. Horizontal and vertical co-ordinate adjustments were performed with
three control elements on the cross-slide stage. The common swivel axis for
microscope and illumination system was connected to the cross-slide stage,
which allowed it to be brought to any part of the eye to be examined. A further
improvement was made in 1938. A control lever or joystick was used for the
first time to allow for horizontal movement. Following World War II the slit
lamp was improved again. On this particular improvement the slit projector
could be swiveled continuously across the front of the microscope. This was
improved again in 1950, when a company named Littmann redesigned the slit lamp.
They adopted the joystick control from the Goldmann instrument and the
illumination path present in the Comberg instrument. Additionally, Littmann
added the stereo telescope system with a common objective magnification
changer. In 1965, the Model 100/16 Slit Lamp was produced based on the slit
lamp by Littmann. This was soon followed by the Model 125/16 Slit Lamp in 1972.
The only difference between the two models was their operating distances of 100
mm to 125 mm. With the introduction of the photo slit lamp further advancements
were possible. In 1976, the development of the Model 110 Slit Lamp and the
210/211 Photo Slit Lamps were an innovation by which each were constructed from
standard modules allowing for a wide range of different configurations. At the
same time, halogen lamps replaced the old illumination systems to make them
brighter and essentially daylight quality. From 1994 onwards, new slit lamps
were introduced which took advantage of new technologies. The last major
development was in 1996 in which included the advantages of new slit lamp
optics. See also "From Lateral Illumination to Slit Lamp - An Outline of
Medical History".
General procedure
While a
patient is seated in the examination chair, they rest their 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. Asubsequent
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.
Variations in methods
Observation
by optical section
Observation
with an optical section or direct focal illumination is the most frequently
applied method of examination with the slit lamp. With this method, the axes of
illuminating and viewing path intersect in the area of the anterior eye media
to be examined, for example, the individual corneal layers.
Direct diffuse illumination
If media,
especially that of the cornea, are opaque, optical section images are often
impossible depending on severity. In these cases, direct diffuse illumination
may be used to advantage. For this, the slit is opened very wide and a diffuse,
attenuated survey illumination is produced by inserting a ground glass screen
or diffuser in the illuminating path. "Wide beam" illumination is the
only type that has the light source set wide open. Its main purpose is to
illuminate as much of the eye and its adnexa at once for general observation.
Indirect
illumination
With this
method, light enters the eye through a narrow to medium slit (2 to 4 mm) to one
side of the area to be examined. The axes of illuminating and viewing path do
not intersect at the point of image focus, to achieve this; the illuminating
prism is decentered by rotating it about its vertical axis off the normal
position. In this way, reflected, indirect light illuminates the area of the
anterior chamber or cornea to be examined. The observed corneal area then lies
between the incident light section through the cornea and the irradiated area
of the iris. Observation is thus against a comparatively dark background.
Retro-illumination
In certain
cases, illumination by optical section does not yield sufficient information or
is impossible. This is the case, for example, when larger, extensive zones or
spaces of the ocular media are opaque. Then the scattered light that is not
very bright normally is absorbed. A similar situation arises when areas behind
the crystalline lens are to be observed. In this case the observation beam must
pass a number of interfaces that may reflect and attenuate the light.
Scattering
sclero-corneal illumination
With this
type of illumination, a wide light beam is directed onto the limbal region of
the cornea at an extremely low angle of incidence and with a laterally
de-centered illuminating prism. Adjustment must allow the light beam to
transmit through the corneal parenchymal layers according to the principle of
total reflection allowing the interface with the cornea to be brightly
illuminated. The magnification should be selected so that the entire cornea can
be seen at a glance.
Fundus
observation and gonioscopy with the slit lamp
Fundus observation is known by the ophthalmic and the
use of fundus cameras. With the slit lamp, however, direct observation of the
fundus is impossible due to the refractive power of the ocular media. In other
words: the far point of the eye (punctum remotum) is so distant in front of
(myopia) or behind (hyperopia) that the microscope cannot be focused. The use
of auxiliary optics - generally as a lens – makes it possible however to bring
the far point within the focusing range of the microscope. For this various
auxiliary lenses are in use that range in optical properties and practical
application.
DAFTAR PUSTAKA
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