Anterior Segment Evaluation and Slit Lamp Techniques
Setup
Align the patient's canthus with the height marker, forehead against the band, chin in the rest. Set the interpupillary distance, begin at low magnification with diffuse illumination, and focus with the joystick before increasing magnification. Adjust slit width and angle per technique: optic section for corneal layers and depth, parallelepiped for infiltrates and cells, retroillumination for microcysts and vessels, specular reflection for endothelium, sclerotic scatter for edema, and a diffuse beam for lids and conjunctiva.
Examination sequence
Lids, lashes, and meibomian glands; conjunctiva and sclera; cornea with sodium fluorescein staining and sensation testing if indicated; anterior chamber cells and flare graded 0 to 4+; iris; lens. Evert the upper lid whenever a foreign body is suspected. Measure lesions with the slit beam in millimeters. Van Herick compares peripheral anterior chamber depth with corneal thickness: one-quarter or less indicates a narrow angle and calls for gonioscopy before dilation.
Worked example
A patient reports a foreign-body sensation after grinding metal. The diffuse exam is normal, but eversion of the upper lid reveals a linear rust ring. That is a retained intralid foreign body; the next step is removal under magnification and a repeat check for corneal staining.
Traps
Touching the lashes or globe with the objective. Not disinfecting the chinrest and joystick between patients. Skipping lid eversion. Calling a one-quarter Van Herick "open" and dilating anyway. Failing to record the anterior chamber reaction grade.