Intacs are very small clear plastic arcs that are designed to be inserted into the substance of the cornea in people who have keratoconus and who can no longer see properly with glasses or contact lenses. Intacs were approved by the FDA for treatment as an alternative to corneal transplant, which used to be a standard treatment for keratoconus prior to Intacs and cross-linking.

When they are inserted into the eye, Intacs reshape the cornea by flattening it closer to its original dome shape. Although the procedure usually improves uncorrected vision, the patient will often still need glasses or contact lenses after the Intacs are inserted. After the cornea has been reshaped, patients who were once unable to tolerate contact lenses may be able to return to contact lens wear and see even better than they did with the lenses prior to surgery. Some patients may even be able to see well enough to go back to simply wearing glasses.