The Progression of Slit Lamp Microscope
The progression of Slit Lamp Microscope A Low–power clinical biomicroscopy of the eye is an necessary tool to diagnose ocular disease, and Ophthalmologists typically use a slit lamp to examine almost all of their patients. At its root, the adaptable slit is simply a way to allow changeable angles of illumination. On the other hand, this surprisingly simple perception has enabled the slit lamp microscope to become an essential instrument for every Ophthalmologist. Slit lamps have evolved appreciably since their arrival in the early 1900s, and many of todays slit lamp microscopes are sophisticated instruments building on the discoveries of the past century.
On its own of the first individuals to pertain microscopy to the living eye was Purkinje, who in the 1820s studied the iris with an adaptable microscope by illuminating the field of view. The slit lamp was born years later when Louis de Wecker would join an eyepiece, objective and adjustable condensing lens within a tube. Weckers invention was enhanced upon by Siegfried Czapski, who added binocularity to the microscope. Though, none of the units constructed by these individuals had adequate and adjustable illumination to be of much clinical benefit. Allvar Gullstrand, an Ophthalmologist and 1911 Nobel laureate, developed a first true slit lamp to illuminate the eye.
Then, Henker and Vogt improved upon Gullstrands device in the 1910s by creating an adjustable slit lamp and combining Czapskis microscope with Gullstrands slit lamp illumination. The new slit lamp microscope was born, a powerful diagnostic tool capable of stereoscopically investigative optical sections of the anterior segment in great detail. The instrument was not only significant as an essential diagnostic tool in the clinic, but also served to greatly advance the scientific facts fueling Ophthalmology.
Alfred Vogt was instrumental in driving this knowledge base through inventive and careful use of the slit lamp. Vogt would use the slit lamp microscope to study a huge array of diseases and document his result in the highly influential publication “Lehrbuch und Atlas der Spaltlampenmikroskopie des Leibenden Auges” in the 1930s. The slit lamp microscope was thus established as an essential diagnostic tool by the Ophthalmology community, and over time Eye MDs invented new ways to reach ahead of the cornea and anterior segment. For example, the slit lamp, in conjunction with certain contact lenses, could be used mutually to examine the anterior chamber angle in great detail.
At the moment, the two main mechanism of the modern slit lamp microscope are the illumination system and observation system. The illumination system on most slit lamps consists of two unlike designs. The first design, the Haag-Streit type illumination, allows de-coupling in the vertical meridian .The second design, the Zeiss type illumination system, does not allow de-coupling in the vertical meridian. Many ophthalmologists argue that the Zeiss illuminations benefit is that it confers lightness and compactness onto the slit lamp microscope to make it somewhat easier to use. In either case, the illumination systems of today are both able of producing a homogenous, aberration-free beam of white light. Most slit lamps use halogen bulbs to yield shorter wavelengths of light, which allow better image of smaller structures compared with longer wavelengths of light tungsten bulbs.
A second major component of slit lamps is the observation system. Modern slit lamp microscopes can magnify images between 5X and 25X, with some microscopes allowing enlargement 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. Hence, magnification of the slit lamp is less significant than its resolution. A slit lamps resolution is reliant 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 changeable, but the objective lens diameter can be modified to increase resolution. However, a very large diameter lens will also bring in optical aberrations.
The observation system is also influenced by the closeness of the patients eye to the examiners eyes. This necessitates a convergence system for binocular viewing, and most modern slit lamp microscopes are designed with 10 to 15 degrees of assemblage to minimize eye strain for the examiner. These features in the illumination and examination systems must be considered when deciding on the best slit lamp to equal a particular clinic.
