A 4-mirror gonio lens is a tool used to visualize the anterior chamber angle. Gonioscopy is either direct or indirect and allows us to visualize the anterior chamber angle by overcoming total internal reflection. Use of this particular lens as an indirect technique allows for dynamic gonioscopy in which gentle pressure is applied to the cornea improving anterior chamber visualization. Clinicians use dynamic gonioscopy to determine whether or not the angle is occluded, occludable, narrow, or open.