Adjustability of refractive effect for corneal ring segments

To evaluate the safety and efficacy of adjustability of the refractive effect of intrastromal corneal ring segments (ICRS, Intacs).

Data from four patients who had their initial Intacs removed and exchanged for new Intacs of different thickness sizes during a United States Food and Drug Adminstration Phase II clinical trial were evaluated with regard to segment size, reasons for exchange, duration within the cornea before exchange procedure, loss or change of spectacle-corrected visual acuity, change of uncorrected visual acuity, manifest refraction, cycloplegic refraction, topography after exchange, and stability of refraction.

The exchange procedure was performed in two patients due to undercorrection and in two for overcorrection. The length of time the segments remained in the cornea after initial surgery varied from 6 to 15 months (mean, 10.25 +/- 4.03 mo). The most recent examination occurred between 4 to 18 months (mean, 10.0 +/- 6.32 mo) following the exchange procedure and showed improved uncorrected visual acuity with a range from 20/16 to 20/20 and a gain of 2 to 7 lines of uncorrected visual acuity compared to baseline. No eyes lost any lines of spectacle-corrected visual acuity following the exchange procedure and all preserved their preoperative spectacle-corrected visual acuity of 20/16. The intended refractive correction was achieved in the first few days of the exchange procedure and remained stable.

In these four eyes that were over- or undercorrected after initial Intacs placement, segment thickness sizes were exchanged after 6, 8, 12, and 15 months without complication and with final uncorrected visual acuities of 20/16 to 20/20.