Reversibility and exchangeability of intrastromal corneal ring segments

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Abstract
Purpose: To evaluate the effect of removal and/or exchange of intrastromal corneal ring segments (ICRS, Intacs); specifically the risk factors, degree of reversibility, and visual outcomes. Setting: Gimbel Eye Centres, Calgary, Edmonton, and Vancouver, Canada. Methods: Prospective cohort data were collected on 71 eyes that had ICRS placement by 3 surgeons at the Gimbel Eye Centres between August 1998 and July 1999. Data included patient symptoms, best spectacle-corrected visual acuity, uncorrected visual acuity (UCVA), manifest refraction, reason for removal or replacement, keratometry, corneal topography, and complications. Results: Twenty-four eyes (33.8%) had exchange or removal procedures because of underresponse, 20 eyes; overresponse, 2 eyes; and induced astigmatism and shallow placement, 1 eye each. Secondary procedures were removal and replacement, removal with subsequent laser in situ keratomileusis, and segment repositioning. Two risk factors for secondary surgery were identified: high preoperative refractive astigmatism and postoperative spherical equivalent greater than ±0.5 diopter (D). The 6 eyes that had ICRS removal stabilized to within ±0.25 D of the original refractive error with no surgically induced astigmatism within 1 to 7 weeks (mean 4 weeks) and had a final UCVA of 20/20 or better. In the 15 eyes that had ICRS exchange procedures, the UCVA improved by at least 1 line and median UCVA improved from 20/40 to 20/20. Conclusion: Preliminary data from this study indicate that removal of segments resulted in reversal of the refractive effect.