What is a Slit Lamp...History of a Slit Lamp...iBEX LED Slit Lamps

What is a 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, or frontal structures and posterior segment, of the human eye, which includes the eyelid, sclera, conjunctiva, iris, natural crystalline lens, and cornea. The 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. An additional hand-held lens is used to examine the retina.[1]

History of a Slit Lamp

To fully understand the development of the slit lamp one must consider that with this invention and its improvements, it had to be accompanied by the introduction of new examination techniques. Two conflicting trends emerged in the development of the slit lamp. One trend originated from clinical research and aimed at an increase in functions and the introduction and application of 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 and the applications of the instrument. The first man credited with developments in this field was Hermann Von Helmholtz (1850) when he invented the ophthalmoscope.

In ophthalmology and optometry, the term “slit lamp” is the most commonly referred to term however it would be more correct to call it the “slit lamp instrument”. Today’s instrument however is a combination of two separate developments in instruments. The two developments are the corneal microscope and that of the slit lamp itself. Though the slit lamp is a combination of these two developments, the first concept of the slit lamp dates back to 1911 credited to Alvar Gullstrand and his “large reflection-free ophthalmoscope.” The instrument was manufactured by the company Zeiss and consisted of a special illuminator that was connected by 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 and 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 shining Nernst glower was replaced with the brighter and whiter incandescent lampSpecial 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 slit projector (slit lamp) made it an easy to handle instrument. For the first time, the axis through the patient’s eye was fixed at a common swiveling axis. This was a fundamental principle that was adopted for every slit lamp instrument developed. A limitation still with the instrument was it lacked a coordinate cross-slide stage for instrument adjustment but only a laterally adjustable chin rest for the patient. 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, a man named Rudolf Theil presented the further development of the slit lamp was encouraged by a company named 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 then improved again in 1950. In 1950, a company named Littmann redesigned the slit lamp again. The 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 optic.[2]

How Slit Lamp excellence was created

 In 2005 iBEX LED Slit Lamps were introduced, designed and built by Appasamy & Associates in collaboration with Trevi Technology. With Appasamy’s 2500 employees and a 600+ research and development team leading the way, Appasamy and Trevi promote a creative environment where research, development, clinical testing and manufacturing work seamlessly. The work is carried out with one objective — to build performance products that enhance clinical eye exams.

With modern optical design typical of high end surgical microscopes, iBEX Slit Lamps deliver high definition observation with reduced reflections and the widest field of view. Ultimately, the user achieves improved diagnosis and less observation strain.

LED Illumination

The proprietary LED delivers the industry’s brightest and most uniform illumination. Wavelengths are full spectrum and synced to maximize anterior and posterior observation. Most importantly, heat to the patient’s eye has been reduced by nearly 80% less compared to traditional illumination, resulting in greater patient comfort during intense and prolonged observation.

EZ Shipping and Setup

We’ve made the process simple. iBEX Slit Lamps are 95% pre-assembled and shipped direct to your office by FedEx. Unpacking and installation takes 20 minutes or less.

To learn about LED Powered Slit Lamps….Contact:

Trevi Technology, Inc.
info@ibexeye.com

Certifications

References:
1.  Wikapedia
2. Wikapedia

                                                             

                                                           

How the human eye works

 The human eye is the organ which gives us the sense of sight allowing us to see and interpret the shapes, colors, and dimensions of objects in the world by processing the light they reflect or emit.  The eye is able to detect bright light or dim light, but it cannot sense objects when light is absent.

Light enters the eye

Light waves from an object  enter the eye first through the cornea, which is the clear dome at the front of the eye.  The light then progresses through the pupil, the circular opening in the center of the colored iris.

Fluctuations in incoming light change the size of the eye’s pupil.  When the light entering the eye is bright enough, the pupil will constrict or get smaller, due to the pupillary light response.

Initially, the light waves are bent or converged first by the cornea, and then further by the crystalline lens (located immediately behind the iris and the pupil), to a nodal point (N) located immediately behind the back surface of the lens.  At that point, the image becomes reversed (turned backwards) and inverted (turned upside-down).

The light continues through the vitreous humor, the clear gel that makes up about 80% of the eye’s volume, and then, ideally, back to a clear focus on the retina, behind the vitreous.  The small central area of the retina is the macula, which provides the best vision of any location in the retina.  If the eye is considered to be a type of a complex camera, the retina is equivalent to the film inside of the camera, registering the tiny photons of light interacting with it.

Within the layers of the retina, light impulses are changed into electrical signals.  Then they are sent through the optic nerve, along the visual pathway, to the occipital cortex at the posterior (back) of the brain.  Here, the electrical signals are interpreted or seen by the brain as a visual image.

Actually, then, we do not see with our eyes but, rather, with our brains.  Our eyes merely are the beginnings of the visual process.

myopia, hyperopia, astigmatism

When  the incoming light from a far away object focuses before it gets to the back of the eye, that eye’s refractive error is called “myopia” (nearsightedness).  When incoming light from something far away has not focused by the time it reaches the back of the eye, that eye’s refractive error is “hyperopia” (farsightedness).

In “astigmatism,” one or more surfaces of the cornea or lens (the eye structures which focus incoming light) are not spherical (shaped like the side of a basketball) but, instead, are cylindrical or toric (shaped a bit like the side of a football).  As a result, there is no distinct point of focus inside the eye but, rather, a smeared or spread-out focus.  Astigmatism is the most common refractive error.

presbyopia

After age 40, and most noticeably after age 45, the human eye is affected by presbyopia.  This natural condition results in greater difficulty maintaining a clear focus at a near distance with an eye which sees clearly far away.

Presbyopia is caused by a lessening of flexibility of the crystalline lens, as well as to a weakening of the ciliary muscles which control lens focusing.  Both are attributable to the aging process.

An eye can see clearly at a far distance naturally, or it can be made to see clearly artificially, such as with the aid of eyeglasses or contact lenses, or else following a photorefractive procedure such as LASIK (laser-assisted in situ keratomileusis).  Presbyopia eventually will affect the near focusing of every human eye.

eye growth

The average newborn’s eyeball is about 18 millimeters in diameter, from front to back (axial length).  In an infant, the eye grows slightly to a length of approximately 19½ millimeters.

The eye continues to grow, gradually, to a length of about 24-25 millimeters, or about 1 inch, in adulthood.  A ping-pong ball is about 1½ inch in diameter, which makes the average adult eyeball about 2/3 the size of a ping-pong ball.

The eyeball is set in a protective cone-shaped cavity in the skull called the “orbit” or “socket.”  This bony orbit also enlarges as the eye grows.

extraocular muscles

The orbit is surrounded by layers of soft, fatty tissue.  These layers protect the eye and enable it to turn easily.

Traversing the fatty tissue are three pairs of extraocular muscles, which regulate the motion of each eye: the medial & lateral rectus muscles, the superior & inferior rectus muscles, and the superior & inferior oblique muscles.

eye structures

Several structures compose the human eye.  Among the most important anatomical components are the cornea, conjunctiva, iris, crystalline lens, vitreous humor, retina, macula, optic nerve, and extraocular muscles.