History of Slit Lamp

History of Slit Lamp

A Slit Lamp is used in ophthalmology. It consists of a source of high-intensity that is focussed into eyes too shine a fine film of light for observation. It is helpful in anatomical diagnoses of various eye conditions. An instrument of such complexity and such vast utility was not made in a day or at once. The slit lamp as seen today is the result of decades of enhancement and refinement. The first ever invention in this context was ophthalmoscope, which was made in 1850. Undoubtedly, the history of ophthalmological instruments and that of slit lamps, spanning centuries of research, is worth being known. The lowdown on slit lamps can be seen from microscope to development of ophthalmoscope and so on to date.

Slit Lamp Microscope

Until early 19th century, there really was not any way to observe what goes on in human eyes. A microscope was used to examine the eyes of a living human first by Jan Evangelista Purkyne in 1823. He was among the first of those who used a microscope for the purpose of eye examination. Purkyne discovered a few things as result of his attempt. The important discoveries were:

s Purkinje images or reflections of objects of structures in the human eye

s Purkinje shift – the name given to the changing brightness of blue and red colours due to gradual decrease in the intensity of light at dusk.

His motive behind the experiment was to analyse what happens to vision experience after it is stimulated with the application of electric currents and pressure to the eyeballs. He also altered the lighting situation to study the reaction of the eye. The invention of ophthalmoscope by Hermann von Helmholtz was largely based on the discoveries made by Purkyne and the ophthalmoscope in turn was crucial to the innovation of modern slit lamp.

Invention of Ophthalmoscope

Magnifying aides had been used for the diagnoses of only outer eye diseases until mid-19th century. There was not really any way to observe the choroide and the fundal retina. The first progress towards modernisation of ophthalmology was witnessed in the form of ophthalmoscope, which Helmholtz invented in 1851. However, the instrument was referred to by the term ophthalmoscope first in 1854. It enabled doctors to examine posterior structures of human eye to diagnose and discover the otherwise undetectable and unknown eye conditions. Interestingly, ophthalmoscope is also the basis of fundus camera.

The next major invention was made in 1889, when Louis de Wecker invented monocular microscope, which can also be called the first Slit Lamp. It consisted of a tube with magnifying aide and objective lens light reflection. The monocular microscope that Wecker developed was enhanced into corneal binocular microscope by Rudolph Aubert in 1891. The corneal binocular microscope was refined into corneal surface microscope by Siegfried Czapski in 1899. The instrument was produced by Zeiss. Shortly later, Czapski added movable illumination source to his original desing. Even until then, the Slit Lamp can be called just a microscope with certain enhancement for eye examination.

A real Slit Lamp was demonstrated by Allvar Gullstrand in 1911. The introduction of his invention is of tremendous importance in ophthalmology. The instrument had an illuminator with Nernst glower and was free of reflection. Zeiss was the producer of this instrument too. The illuminator was connected with small stand base to vertically adjustable column. Gullstrand received Nobel Prize for his invention. Gullstrand invented retinal camera too.

Vogt and Henker of Zeiss combined corneal microscope by Czapski and slit illumination by Gullstrand to produce a compact instrument that had illumination source as well as magnifying aide coupled on the same axis. Further improvements made to the slit lamp by Vogt and Henker were:

> Koehler illumination
> Replacement of Nernst glower with incandescent lamp
> Replacement of Nitra lamp with liquid filter carbon arc lamp
> Addition of an arm for support

Hans Goldman began to improve the design in 1933 and made the significant addition of joystick, which facilitated horizontal movement, in 1938. Vertically mounted illumination source was designed by Comberg in the same year. Hans Littman added stereo telescope with common objective magnification-alteration system in 1950. In 1952, Belmonte-Gonzalez installed stereo camera onto the eyepiece of the microscope on the slit lamp.

Improvement in the photographic aspect of slit lamps continued through 1960s and the first proper launch was made in 1966. It was produced for routine examination in 1970. Six years later, Model 110 and 210/211 were launched in the market and each was manufactured from standard modules to facilitate varieties of configurations. The use of halogen lamps for daylight-like illumination was realised in the same year.

Advanced technologies continued to get incorporated to slit lamps and the latest major improvement was made in 1996. Indeed, the efficiency of a slit lamp is due to such long history of experiment and modification.

Author Bio: Tony Rollan provides marketing services for VSI (http://www.patternless.com) and he is an author of many articles on various optical and ophthalmic equipment. Author like to write about medicine, health, alternative healing, sport and wellbeing.