Researchers in Brazil have found that implantation of intrastromal corneal ring segments (ICRS) in eyes with keratoconus appears to stabilize the disease.
Keratoconic eyes receiving the implantable corneal rings demonstrated improved visual acuity and stable corneal flattening throughout the study’s five-year follow-up period.
What is keratoconus?
Keratoconus (KC) is a degenerative disorder of the eye characterized by a progressive bulging outward of the clear front surface of the eye into an irregular cone shape.
The disorder often causes visual impairment that cannot be corrected with eyeglasses or contact lenses. Severe cases of keratoconus may necessitate a corneal transplant to restore vision.
The exact incidence of KC is unknown, but the National Keratoconus Foundation estimates the condition affects one out of every 2,000 people in the United States.
Corneal rings for keratoconus: Study results
In the Brazilian study, 35 eyes of 28 patients were implanted with Ferrara corneal ring segments and monitored for at least five years.
(Ferrara corneal rings are similar to Intacs intrastromal ring segments produced in the United States. Developed by Brazilian ophthalmologist Paulo Ferrara, MD, Ferrara corneal rings are used throughout Europe and South America to treat keratoconus.)
Data gathered five years after surgery revealed:
- Mean uncorrected visual acuity improved from worse than 20/125 pre-operatively to better than 20/70 after corneal ring segment implantation.
- Mean best-corrected visual acuity improved from approximately 20/50 pre-operatively to approximately 20/32 after implantation of corneal rings.
- Mean minimum corneal curvature decreased from 48.99 diopters (D) pre-operatively to 44.45 D after corneal ring segment implantation.
- Mean maximum corneal curvature decreased from 54.07 D pre-operatively to 48.09 D after corneal rings were inserted.
All corneal flattening was statistically significant and remained stable throughout the study’s follow-up period of five years.
Corneal rings for keratoconus: Conclusions
The researchers concluded that implantation of intrastromal corneal ring segments in keratoconic eyes produced significant improvements in uncorrected and corrected visual acuity and decreases in corneal curvature, and that these changes appear to be stable over an extended period of at least five years.
SOURCE: Long-term follow-up of intrastromal corneal ring segments in keratoconus. Journal of Cataract & Refractive Surgery. October 2009.
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