Slit lamps are an essential piece of equipment for any ophthalmology practice.  These special microscopes enable doctors to see a patient’s eyes inside and out, in 3D, and they’re typically part of every eye examination, including regular annual checkups.  However, despite its everyday applications, using a slit lamp correctly involves proper technique and skill.

First, it’s important to know what you’re looking for before you use your slit lamp.  For example, if you haven’t determined an order in which you’ll examine the eye (i.e. starting externally and working deeper into the eye), you risk missing seemingly obvious conditions like periorbital neoplasms.

Next, you’ll need to decide on the proper illumination for the exam.  There are several techniques to choose from, all based on which conditions you’re attempting to find:

• Diffuse illumination: This works best for an overall exam of the eye. The open beam hits the eye at a 45-degree angle.
• Sclerotic scatter: The beam is aimed directly at the limbus. Light then scatters through the cornea, which reveals opacities.

Both diffuse illumination and sclerotic scatter use 10x magnification.

• Retroillumination: There are two options here – iris retroillumination reflects light off the deeper iris from an anterior angle; the red reflex test shines the beam through the pupil and off the retina. This is a 10x-16x magnification.
• Van Herick’s technique: Here, a narrow beam is aimed at the limbus at a 60-degree angle. This is a 6x-10x magnification.
• Conical beam: A small, rectangular beam is angled between 45-60 degrees at the aqueous (16x-20x magnification).
• Corneal cross-section: This involves the same angle and magnification as the conical beam, but it involves a thinner beam aimed at the layers of the cornea.

There’s also the option of using light filters (neutral, blue, red, and yellow) to identify more specific issues like leakage, photosensitivity, and legions.

With so many illumination options, it’s critical to know what you’re looking for so that you can choose the right beam strength and technique for the best results.