Corneal rings


Keraring – intrastromalen corneal ring segment (device implant) is a medical device that is implanted in the human corneal stroma to reduce surface irregularities and refractive errors associated with corneal disorder. The product is made of polymethylmethacrylate (PMMA), and implanted into the corneal stroma in a specific surgical technique.

The device acts on the corneal tissue by changing the curvature and shape of the centre, thereby reducing or eliminating morphological irregularities and existing myopia and astigmatism.

The device consists of a semi-circular segment arc of variable lengths (90, 120, 160, 210 degrees), the variable apical diameter (5mm, 6 mm), a variable thickness (150μm, 200μm, 250μm, 300μm, 350μm), having a triangular cross- section 600 micron base. Each ring segment has a 0.2 mm diameter orifice, in order to facilitate manipulation and implantation.


  • Correct indication for implantation of Keraring requires a thorough assessment of topographic and other conditions of the cornea in addition to a full  eye examination.
  • Overall, the implantation of the device can be considered as follows:
  • Keratoconus patients intolerant to contact lenses;
  • Progressive keratoconus;
  • Irregular astigmatism with the following designations – penetrating keratoplasty;
  • Corneal ectasia following designations – in previous photoablative procedures (LASIK, PRK, LASEK, Epi-Lasik);
  • Irregular astigmatism with the following designations – radial keratotomy;
  • Pellucid marginal degeneration;
  • Irregularities of corneal surface after injury as a result of irregular astigmatism