Oscillatory lighting is sometimes considered a lighting technique. Observation with an optical section or direct focal illumination is the most commonly applied examination method with a slit lamp. The slit lamp consists of two parts, an illumination system and an energy-efficient binocular microscope mounted horizontally. This is the most common method for viewing all of the tissues of the front eye; the observer sees directly the focused slit through the microscope.
The magnification can be increased considerably (from 10x to 40x or more) to see any area of interest in greater detail. For example, it is recommended to fully open the slit lamp beam with low intensity to avoid dazzling the patient when performing an overview with low magnification at the beginning of the examination. The slit lamp offers a variety of lighting and observation methods that not all need to be used in routine exams, but the ability to perform them should be practiced. By activating the latch 11 and tilting the column of the slit lamp, the beam can be introduced up to 20° below the horizontal.
The most commonly used device in eye exams to explore the cornea is slit lamp biomicroscopy (SLB), which allows a detailed evaluation of the front and back segments. When using the slit lamp, direct and indirect lighting are seen simultaneously, the structures seen in the illuminated field are seen under direct lighting, but since this does not occupy the entire field of view, everything that reflects or scatters light from outside the illuminated area is seen indirectly. The slit lamp examination is also known as biomicroscopy because it allows the in vivo study of the living tissues of the eye at a high magnification. When using the slit lamp, it is important to know the various techniques you are using and when to use them.
Undoubtedly, it can be argued that the slit lamp examination is the best method for examining the external eye and should therefore be used with all patients. The following is a suggestion on how a routine technique should be performed; it's by no means the only way to perform a slit lamp routine, and in fact, not all practitioners will.