Although the corneoplastic effects of intra-corneal ring segment implantation generally remain stable for many years [1], cross-linking is often considered a useful adjunct to the procedure to help stabilise the altered corneal shape. The development of this combination treatment is in its early stages and the optimal time to perform each stage of the treatment has yet to be ascertained [2,3]. Combining LASIK with cross-linking may result in improved corneal integrity and thereby reduce instances of post-LASIK keratectasia. Indeed, a recent study investigating this found that patients treated with combined LASIK and cross-linking had a similar or slightly better clinical outcome than those treated with LASIK alone [4].

 The use of cross-linking with topography-guided photorefractive keratectomy (PRK) was first described by Kanellopoulos and Binder [5]. Since then, others have shown that the simultaneous treatment of topography-guided PRK followed by cross-linking for keratoconus results in reduced refractive error and keratometry readings and improvements in visual acuity that remain stable at a mean follow-up of nearly 20-months [6].  However, it is worth noting that in vitro studies have shown that the efficacy of laser ablation is reduced in cross-linked corneas [7] and so it may be necessary to modify existing ablation algorithms for the treatment of cross-linked corneas [7].

Further investigations into the use of cross-linking as a means of stabilising corneal moulding have produced mixed results. Early studies of accelerated cross-linking in combination with microwave keratoplasty, (a novel technique used to induce axial shrinkage of collagen and thereby flatten the keratoconus cornea), found it to be only minimally effective as an adjunct to the procedure as it failed to maintain the flattening effect and regression occurred [8]. Similarly, when used in conjunction with orthokeratology it was found that cross-linking failed to stabilise the shape change. Nevertheless, the combined treatment did result in improved visual acuity, which remained above baseline levels at 1 year post-treatment [9].

[1] Bedi R, et al. Refractive and topographic stability of Intacs in eyes with progressive keratoconus: five-year follow-up. Journal of Refractive Surgery. 2012;28(6):392-6.

[2] Ertan A, et al. Refractive and topographic results of transepithelial cross-linking treatment in eyes with Intacs. Cornea. 2009;28:719-23.

[3] Iovieno A, et al. Intracorneal ring segments implantation followed by same-day photorefractive keratectomy and corneal collagen cross-linking in keratoconus. Journal of Refractive Surgery. 2011; 27 (12): 915-8.

[4] Celik H, et al. Accelerated corneal crosslinking concurrent with laser in situ keratomileusis. Journal of Cataract and Refractive Surgery. 2012;38(8):1424-31.

[5] Kanellopoulos A. and Binder P. Collagen cross-linking (CCL) with sequential topography-guided PRK: a temporizing alternative for keratoconus to penetrating keratoplasty. Cornea. 2007;26:891-5.

[6] Kymionis G, at al. Simultaneous topography-guided photorefractive keratectomy followed by corneal collagen cross-linking for keratoconus. American Journal of Ophthalmology. 2011;152:748-55.

[7] Chen S, et al. Evaluation of the efficacy of excimer laser ablation of cross-linked porcine cornea. PLoS One. 2012;7(10):e46232.

[8] Vega-Estrada A, et al. Outcomes of a new microwave procedure followed by accelerated cross-linking for the treatment of keratoconus: a pilot study. Journal of Refractive Surgery. 2012;28(11):787-92.

[9] Calossi A, et al. Orthokeratology and riboflavin-UVA corneal collagen cross-linking in keratoconus. Journal of Emmetropia. 2010;1:126-31.