These are rigid, transparent plastic (PMMA), arc-shaped corneal ring inserts that are surgically introduced within the peripheral cornea.
The SAIs reshape the front surface of the cornea. They reduce the topographical irregularity and off-centering caused by the cone while flattening the center of the cornea.
Patients with intracorneal rings get better visual acuity than before surgery because they keep the central area of the cornea clear and intact. The rings slow or stop the progression of keratoconus by avoiding a cornea transplant. They improve tolerance to contact lenses too.