Astigmatic change as a predictor of intrastromal corneal ring segment late extrusion

To evaluate changes in keratoconic corneas implanted with intrastromal corneal ring segments (ICRSs) that have been explanted because of late extrusion of the segment after >2 years.

Vissum Miranza, Alicante, Spain; OftalmoSalud, Lima, Peru; Minya University Hospital, Egypt.

Retrospective multicenter case series.

23 keratoconic corneas that were implanted for ≥2 years and explanted because of natural extrusion of the segment. Clinical measures of visual, refractive, topographic, pachymetric, and aberrometric data were analyzed. To perform exploratory factor analysis, the Kaiser-Meyer-Olkin (KMO) test was used to evaluate sampling adequacy. Factor analysis with VARIMAX rotation was used to determine the main factors of the inventory.

The mean time interval was 5 years. Topographic findings were reversed nearly to the baseline level after segment explantation (Km: 48.97 ± 3.47 D pre implantation and 47.60 ± 3.67 D after explantation, P =.374). Significant worsened in refractive cylinder was found pre-ICRS extrusion (‒2.54 ± 3.40 D after implantation and ‒3.96 ± 1.72 before extrusion, P < .05). The main factor obtained in the preimplantation moment included keratoconus grade, keratometric readings, and visual acuities. After ICRS implantation, the most strength components were the refractive cylinder, corrected distance visual acuity, and uncorrected distance visual acuity. Corneal aberrations were the main factors in the pre-explantation analysis.

ICRSs were safely extracted, with a reversal of the corneal topographic data to the preoperative level. A significant astigmatic change was shown in patients implanted with ICRSs before late extrusion of the segment, suggesting the role of this parameter as a prognostic factor of extrusion.