Visual outcomes following implantation of intracorneal rings with sharp and round triangular cross-section designs in keratoconus.

PURPOSE: To compare the visual, refractive, corneal curvature, and aberrometry outcomes one year following implantation of two intra-stromal corneal rings (ICRS) with different cross-sectional designs.

METHODS

This retrospective longitudinal study included 40 keratoconus eyes implanted with ICRSs with similar characteristics except for their cross-sectional design, Keraring with sharp corners triangular cross-section (n = 20 eyes) and Keratacx Plus with round corners triangular cross-section (n = 20 eyes). The two rings were similar in terms of arc length (355°) and outer diameter (5.7 mm). The uncorrected and corrected distance visual acuity (UDVA & CDVA), refraction, corneal topography, and aberrometry indices were compared before and one year after surgery.

RESULTS

Despite a significant change in VA, spherical equivalent, astigmatism, and keratometry readings, there was no statistically significant difference in their mean changes between the two rings. (P > 0.05) The mean corneal asphericity expressed by the Q-value showed a statistically significant change toward less prolateness after surgery and was the only parameter with a significant mean change between the two groups (P = 0.04). In comparing the mean changes of corneal aberrometry indices between two rings, a statistically significant difference was seen for total aberration (P = 0.03), lower order aberrations (LOA, P = 0.03), and defocus (P = 0.03). Subgroup analysis based on keratoconus severity (mild and moderate stages) showed a statistically significant difference in Q-value (P = 0.019), total aberration (P = 0.040), LOA (P = 0.041), and defocus (P = 0.027) only for the moderate keratoconus group between the two rings.

CONCLUSIONS

Both rings provided a significant improvement in visual, refractive, and keratometric parameters so that the triangular cross-sectional design of Keratacx Plus with round corners is not superior to Keraring with sharp corners in terms of visual quality and higher order aberrations (HOAs).