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.

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.

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