Intracorneal Ring Segments
Intracorneal Ring Segments or ICRS are small plastic rings that are inserted into the cornea to flatten the conical shape of the cornea caused by keratoconus. They are often known under their proprietary names of Intacs or Kerarings or Ferrara rings.
Initially ICRS were used as an alternative to a corneal transplant when a patient could not tolerate contact lenses because of the advanced nature of their keratoconus. They appeared to have the advantage over a corneal transplant of being relatively easy to remove if causing problems. But they proved unsuitable in that scenario due to their moderate corrective effect.
Proponents of ICRS now claim that they are best suited to patients with mild to moderate keratoconus but who are contact lens intolerant. In such cases, ICRS may provide improved uncorrected vision and vision corrected by spectacles. But optometrists say they complicate the fitting of contact lenses and patients may be dissatisfied with their overall vision outcome after ICRS insertion.
Also very few patients are truly contact lens intolerant. Most patients who believe they are intolerant of contact lenses are actually suffering from incorrectly fitted lenses and need to see an expert contact lens fitter for keratoconus for a refit of their lenses.
ICRS do not halt the progression keratoconus and their insertion is therefore usually combined with corneal collagen crosslinking to stabilise the cornea. This is an expensive procedure with an uncertain outcome.
Patients often experience various side effects from ICRS, the most common being problems with night vision, halos, glare, blurry and fluctuating vision, extrusion and infections.
As a result, many patients tend to have ICRS removed after a few years. They are therefore unlikely to provide a long term solution to vision loss caused by keratoconus.