Microscope today is a product of several innovations and improvements done by several individuals through the course of its history. Microscope is not the invention of a single individual alone but a result of the combined efforts of many individuals. One of it is a slit lamp microscope or biomicroscope. Slit lamp microscope is a kind of microscope that is attached with a light for an eye doctor to examine ones eye. The anterior parts of the eye such as the cornea, conjunctiva, iris, lashes, lens, lids and pupil are viewed using high magnification of this microscope. Slit lamp microscope is derived from the adjustable nature of its light beam. Slit lamp microscope has evolved significantly in 1900s from a simple instrument used by ophthalmologists in examining patients. It was Purkinje, who had first applied microscopy to the living eye in 1820s, modifications gave birth to the slit lamps cousin, the uniocular slit lamp. It was from the skill of Louis de Wecker in combining an objective, eyepiece and adjustable condensing lens all within a tube that made this possible.

Weckers invention to the various modifications employed by more scientific minds like Siegfried Czapski, Allvar Gullstrand, Henker and Vogt, the modern slit lamp microscope was born. This advanced version of biomicroscope is now more than just a diagnostic instruments, it has also become a tool for discovering significant information for more ophthalmological innovation. Modern biomicroscope or slit lamp microscope has two major components. The binocular microscope, which is the observation structure and the movable slit lamp as the illumination structure. A slit lamp microscopes illumination structure usually has two designs. First is the Haag-Streit kind of illumination, which permits separation in the vertical meridian. This feature facilitates the examination of the front part of the eye or gonioscopy as it reduces reflections. Funduscopy is used to examine the back of the eye and also benefits from this feature as it maximizes peripheral views. The other design is the Zeiss kind of illumination structure. This design has attributes that prevents the separation in the vertical meridian. Both of these illumination designs are able to produce homogenous white light. The major part of a slit lamp microscope is the observation structure. The magnification range of modern biomicroscopes are 5x, 25x to 40x for more advance slit lamp microscopes and 100x for research based. The three methods that make the magnification possible include the flip- type, the most basic magnification. Galilean rotating barrel with multiple magnification types, and the zoom system with continuous and most preferred type of magnification. The examination structure of the slit lamp microscope more of a feat is its resolution because it is what dictates the quality of the image. The different factors of the resolution are the lights wavelength, the refractive index difference, the working distance and the objective lens. This four factors, the diameter of the objective lens is the easiest to modify to improve resolution. However, it should be noted that increasing the lens diameter can produce optical irregularities. One of the major applications of the slit lamp microscope is the contact lens assessment. Diagnosing eye disorders such as nearsightedness, pseudoexfoliation, iris atrophy and Krukenberg spindles and diseases such as corneal problems and cataracts is another important use of this microscope. Examination of the lids, lashes and tear film, even the anterior vitreous part of the eye is made possible with the help of attaching other equipment to the slit lamp.