The procedure, involving the saturation of the cornea stroma with riboflavin (vitamin B2) and subsequent UVA irradiation, increases the biomechanical stability of the tissue by forming chemical bonds between collagen fibrils.5 While only recently approved in the United States, there’s a vast amount of data on the stability and visual acuity results of cross-linking for keratoconus in the literature due to its popularity abroad. 4Ĭorneal collagen cross-linking was approved by the FDA in July 2016 for the treatment of progressive keratoconus and post-refractive ectasia. Though not indicated for the stabilization of progression in keratoconus, some have reported stabilization associated with ring segment placement: A five-year study in patients treated with Intacs for progressive keratoconus noted that 92.9 percent of eyes showed no significant progression in steepest K value during the course of follow-up, 3 while a separate study of patients with previously documented progressive keratoconus and Intacs or Keraring placement demonstrated regression in the mean K value by 3.36 D postoperatively at five years. 2 There are mixed results in the literature regarding regression of the flattening effect seen after Intacs implantation. Doing so can often decrease the amount of irregular astigmatism and higher-order aberrations seen in these patients, improve best spectacle-corrected visual acuity, and improve contact lens tolerance. One of the unique properties of ring segments, which are made of polymethylmethacrylate and come in a range of sizes, is the ability to normalize a highly ectatic cornea by centralizing the cone and reducing maximum corneal curvature. Outside of the United States, Ferrara rings and Kerarings (Mediphacos Belo Horizonte, Brazil) are the other two commonly used ICRS models. 1 Placement can be performed using either mechanical or femtosecond-created channels. Candidates for Intacs are patients whose steepest K values are less than 58 D, who have clear visual axes and corneal thicknesses of at least 450 um at the 7 mm optical zone. Intacs were subsequently FDA approved for the correction of myopia and astigmatism associated with keratoconus, in 2004. However, given the advancements and excellent outcomes of excimer laser ablation techniques, intracorneal ring segments like Intacs were largely relegated to treatment of irregular corneas. The intracorneal implants, when placed in the peripheral cornea outside of the optical zone, cause a flattening of the central cornea, thus reducing myopia and mild astigmatism. Intacs corneal ring segments (Addition Technology Fremont, California) are the only ICRS available in the United States they were originally designed for the correction of low degrees of myopia. In this column, I’ll describe my surgical approach of combining intracorneal ring segments with cross-linking for the management of ectatic corneal disorders, and discuss situations in which one approach might be preferable to the other. ![]() Two technologies that have gained recent attention, both independently and used in conjunction with one another, are intracorneal ring segments and corneal collagen cross-linking. New treatment options offer not only stabilization of the progressive nature of these conditions, but also corneal flattening and improved visual outcomes, enabling surgeons to intervene earlier in the disease course and avoid penetrating keratoplasty. T he treatment of corneal ectasias such as keratoconus, pellucid marginal degeneration and post-refractive ectasia has undergone a significant shift in recent years.
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