New technique for enhancing the astigmatic correction of intracorneal ring segments in keratoconus eyes with a central cone.

Abstract

Purpose: The purpose of this study was to present a case series describing a new simple technique of intrastromal corneal ring segment (ICRS) implantation that shortens the effective arc length of a segment and amplifies its effect on the corneal cylinder.

Methods: A 150° ICRS designed to be implanted in the 6-mm optical zone (OZ) (Intacs^® SK) was instead implanted in a 7-mm OZ channel using a femtosecond laser.

Results: The decrease in manifest refraction spherical equivalent (MRSE) at 6 months was significantly less for the SK-7 group compared to the SK-6 group (2.21 ± 0.86 D vs. 8.87 ± 3.22 D, P = 0.004, respectively). The average central corneal power was also more pronounced in the SK-6 group (-2.19 ± 0.98D vs. -4.50 ± 2.87D, P = 0.20, respectively). Greater reduction in corneal and refractive cylinder magnitude (SimK) and vector was observed when Intacs^® SK segments were implanted at 7-mm instead of 6-mm OZ. The SK-7 group gained more Corrected distance visual acuity (CDVA) lines at 6 months. The vector analysis variables including surgically induced astigmatic vector, difference vector, correction index, and index of success were all better when Intacs^® SK was implanted at 7 mm.

Conclusion: Shortening the effective arc length of the ICRS to 129° resulted in greater astigmatism correction with less effect on overall corneal flattening and MRSE. This technique would allow the surgeon to obtain a different effective ICRS arc length from the actual one and can be useful to reduce the inventory of ICRS in a given center.