The slit lamp is a binocular microscope that provides the examiner with a stereoscopic (ie, three dimensional) view of the eye (figure 1). It has changed little since its development by Goldman in 1937 . However, there are alternate methods of examining the eye using portable digital photography and videography imaging devices . These newer methods may afford some advantages, but may not offer a stereoscopic view or magnification compatible with a slit lamp. The slit lamp allows the eye to be examined with a beam or “slit” of light (versus diffuse light) whose height and width can be adjusted. The slit of light, when directed at an angle, accentuates the anatomic structures of the eye, allowing close inspection. The slit lamp provides greater magnification (10 to 25 times) and illumination than most handheld devices (eg, Wood's lamp), which is necessary to diagnose a number of traumatic and nontraumatic disorders.
A useful, interactive teaching program on vision care is available free from the University of Michigan Kellog Eye Center at www.kellogg.umich.edu/theeyeshaveit.
This topic review will focus on the steps involved in the examination of the anterior segment of the eye using the basic slit lamp found in most primary and emergency care settings as well as indications and contraindications for its use. Specific diseases and injuries of the eye are discussed elsewhere. (See "Cataract in adults" and "Conjunctivitis" and "Corneal abrasions and corneal foreign bodies: Clinical manifestations and diagnosis" and "Evaluation of the red eye" and "Retinal detachment" and "Approach to the adult with acute persistent visual loss".)
Indications for the use of a slit lamp in the nonophthalmology setting include any acute condition that requires magnification to inspect the anterior segment of the eye (ie, lids, lashes, conjunctiva, cornea, anterior chamber, iris, and lens) or to facilitate ocular foreign body removal. Thus, it is well suited for diagnosing conditions such as corneal epithelial defect, keratoconjunctivitis, hyphema, hypopyon, lens dislocation, herpetic infections, iritis, or evaluation of the red eye.
The slit lamp is less useful in diagnosing conditions of the posterior segment (ie, vitreous, fundus, optic disk) in the primary care office or emergency department. Such conditions include papilledema, vitreous hemorrhage, and retinal detachment. Diagnosis of such conditions with a slit lamp is feasible only if special attachments are available and the examiner has training and experience in their use.