The most commonly used illumination method for slit lamp microscopy is: direct focal illumination.
Slit lamp microscope, is an important instrument essential for ophthalmic examination. Slit lamp microscope by the illumination system and binocular microscope, it can not only make superficial lesions observed very clearly, and can adjust the focus and light source width, made of "optical section", so that the deep tissue lesions can also be clearly visible.
As the name suggests, the light illuminates the eye through a slit. It is called a "light knife" because it is a narrow slit light source. This "light knife" will be irradiated in the eye to form an optical section, you can observe the health of various parts of the eye. The principle is to use the British physicist Tyndall's "Tyndall phenomenon".
The Tyndall phenomenon is: when a beam of light through the colloid, from the perpendicular direction of the incident light can be observed in the colloid appeared a bright "pathway", this phenomenon is called the Tyndall phenomenon, also known as the Tyndall effect.
Basic structure
The structure of the slit lamp consists of two parts, namely, the "slit lamp" and the "microscope". In order to facilitate the slit lamp to irradiate various parts of the eye from different angles and the microscope to observe the eye from different angles, both the slit lamp and the microscope are mechanically required to have sufficient left and right oscillating angles.
The slit lamp's light source requires that its slit edges be very flat and that the slit be clearly imaged in the vertical plane of the center of the circle of the left-right swing, and the microscope's focus must likewise be on this vertical plane of the center of the circle.