Outcome Analysis of Intracorneal Ring Segments for the Treatment of Keratoconus Based on Visual, Refractive, and Aberrometric Impairment

Abstract

PURPOSE: To analyze the outcomes of intracorneal ring segment (ICRS) implantation for the treatment of keratoconus based on preoperative visual impairment. DESIGN: Multicenter, retrospective, nonrandomized study.METHODS: A total of 611 eyes of 361 keratoconic patients were evaluated. Subjects were classified according to their preoperative corrected distance visual acuity (CDVA) into 5 different groups: grade I, CDVA of 0.90 or better; grade II, CDVA equal to or better than 0.60 and worse than 0.90; grade III, CDVA equal to or better than 0.40 and worse than 0.60; grade IV, CDVA equal to or better than 0.20 and worse than 0.40; and grade plus, CDVA worse than 0.20. Success and failure indices were defined based on visual, refractive, corneal topographic, and aberrometric data and evaluated in each group 6 months after ICRS implantation.RESULTS: Significant improvement after the procedure was observed regarding uncorrected distance visual acuity in all grades (P < .05). CDVA significantly decreased in grade I (P < .01) but significantly increased in all other grades (P < .05). A total of 37.9% of patients with preoperative CDVA 0.6 or better gained 1 or more lines of CDVA, whereas 82.8% of patients with preoperative CDVA 0.4 or worse gained 1 or more lines of CDVA (P < .01). Spherical equivalent and keratometry readings showed a significant reduction in all grades (P £ .02). Corneal higher-order aberrations did not change after the procedure (P ‡ .05).CONCLUSIONS: Based on preoperative visual impairment, ICRS implantation provides significantly better results in patients with a severe form of the disease. K ERATOCONUS IS AN ECTATIC DEBILITATING corneal disorder characterized by a progressive corneal thinning that results in corneal protrusion, irregular astigmatism, and decreased vision. 1 A variety of options have been described for the management of this pathologic condition, such as rigid gas-permeable contact lenses, 2 corneal collagen cross-linking, 3 intracorneal ring segment implantation, 4-11 or keratoplasty. 12 In a number of studies intracorneal ring segments (ICRS) have been demonstrated to be effective in improving visual acuity and reducing the refractive error and the mean keratometry in selected cases of keratoconic eyes. 4-11 Such a positive therapeutic effect is considered to be based on the induction of a remodeling of the corneal anterior and posterior surface's topography, which improves the optical quality of the cornea and reduces the optical aberrations, with consequent improvement in best-corrected visual acuity. [4][5][6][7][8][9][10][11] Although in the healthy cornea, the sectorial arcuate addition to the corneal local volume caused by these implants at the corneal midperiphery induces a flattening of the central cornea in an arc-shortening effect, with the consequence of a decrease in myopic spherical equivalent attributable to the overall reduction in the optical power of the cornea, 13 such corneal modeling effect may be different in structurally abnormal corneas such as in keratoco...

Aberrometric Outcomes of Intrastromal Corneal Ring Segment (KeraRing 355) Implantation Using PocketMaker Microkeratome in Patients with Keratoconus

“…These results are in agreement with studies of Jadidi et al [30], Jabbarvand et al [33], Alio et al [29] and Sansanayudh et al [32]. The similar results in these studies can be related to similar 6 mm diameter and larger arc of rings.…”

“…Notwithstanding that in Jabbarvand study, patients with larger pupil than 5.5 millimeter were excluded from the study. Furthermore, In spite of secondary comma error, Trefoil error did not increase significantly, which is consistent with study by Jabbarvand et al [29]. In the face of Vega-Estrada et al [27] and Shayebak et al [14] studies showing significant decrease in comma-like errors, our result shows little statistically insignificant increase in this type of error.…”

“…Many other studies found less decrease in Keratometric data which is probably because of smaller arcs and larger diameters of implanted rings [8,14,[32][33][34][35][36][37][38]. As mentioned by Jabbarvand et al [29] and Alio et al [25], it seems that complete rings could correct corneal curvature more effectively because of their stronger arc-shortening effect. Second order defocus error decreased 4.21 microns after intervention.…”

“…Jabbarvand [29] and Haddad [28] found significant decrease for this type of error in their studies. The difference can be attributable to differences in mean of follow-up times and implanted rings, and difference in surgical technics, differences in stages of KCN between study population and different techniques to measure errors.…”

“…Arcuate length variability results in better correction of astigmatism in keratoconus patients [22] To our knowledge, there are limited studies investigating Keraring 355 with high attention in KCN treatment. On the other hand, most studies measuring corneal aberration used topography [26][27][28][29][30][31][32][33]. In the present study, we investigated Keraring intrastromal segment effect on optical aberrations in KCN treatment using wave front analyzer which evaluates 80.000 points compared to topography evaluating 6.144 points [34].…”