slit lamp [AS, slitan + Gk, lampein, to shine] , an instrument used in ophthalmology for examining the external, surface, and internal segments of the eye, including the eyelid(s), lashes, conjunctiva, cornea, anterior chamber, pupil, iris, vitreous, and retina. A high-intensity beam of light is projected through a narrow slit, and a cross section of the illuminated part of the eye is examined through a magnifying lens. A second, hand-held lens is used to examine the retina.
