Intrastromal corneal ring segments
Intrastromal corneal rings (also referred to as intracorneal rings, INTACS, Kerarings, Ferrara rings, or corneal implants) are small devices implanted in the eye to correct vision. In this procedure, an ophthalmologist makes a small incision in the cornea of the eye, and inserts two crescent or semi-circular shaped ring segments between the layers of the corneal stroma, one on each side of the pupil. The embedding of the rings in the cornea is intended to flatten the cornea and changing the refraction of light passing through the cornea on its way into the eye.
Intrastromal corneal rings were originally used to treat mild myopia. For this purpose, they have largely been superseded by excimer lasers, which have better accuracy. They are now mostly used to treat mild to moderate keratoconus. Intrastromal corneal rings were approved in 2004 by the Food and Drug Administration for people with keratoconus who cannot adequately correct their vision with glasses or contact lenses, and for whom corneal transplant is the only other option. They were approved under the Humanitarian Device Exemption, which means the manufacturer did not have to demonstrate effectiveness. According to the FDA, these products should not be used by people who "can achieve functional vision on a daily basis using contact lenses."
- Zadnik K, Lindsley K (2014). "Intrastromal corneal ring segments for treating keratoconus (Protocol)". Cochrane Database of Systematic Reviews. doi:10.1002/14651858.CD011150.
- Rabinowitz YS (2013). "INTACS for keratoconus and ectasia after LASIK". Int Ophthalmol Clin 53 (1): 27–39. doi:10.1097/IIO.0b013e3182774453. PMC 3653443. PMID 23221883.
- Food and Drug Administration (26 July 2004). "INTACS Prescription Inserts for Keratoconus - H040002".