Reshaping procedures for the surgical management of corneal ectasia Mohammed Ziaei, MBChB (Hons), FRCOphth, Allon Barsam, MD, FRCOphth, Neda Shamie, MD, David Vroman, MD, Terry Kim, MD, Eric D. Donnenfeld, MD, Edward J. Holland, MD, John Kanellopoulos, MD, Francis S. Mah, MD, J. Bradley Randleman, MD, Sheraz Daya, MD, FACP, FACS, Jose G€ uell, MD, PhD, for the ASCRS Cornea Clinical Committee Corneal ectasia is a progressive, degenerative, and noninflammatory thinning disorder of the cornea. Recently developed corneal reshaping techniques have expanded the treatment armamen- tarium available to the corneal specialist by offering effective nontransplant options. This review summarizes the current evidence base for corneal collagen crosslinking, topography-guided pho- torefractive keratectomy, and intrastromal corneal ring segment implantation for the treatment of corneal ectasia by analyzing the data published between the years 2000 and 2014. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2015; 41:842–872 Q 2015 ASCRS and ESCRS Corneal ectasia is a progressive, noninflammatory thinning disorder of the cornea that compromises the stromal collagen matrix, resulting in protrusion and alteration of corneal shape. The types of ectasia include keratoconus, pellucid marginal degeneration (PMD), keratoglobus, posterior keratoconus, and post laser refractive–surgery ectasia. The incidence of keratoconus, the most common type of ectasia, is 1.3 to 25 per 100 000 1 with a reported prevalence of 50 to 230 cases per 100 000. 2 There is a strong association of ectasia with atopy, 3 and a growing body of evidence suggests genetic factors play an important role in its pathogenesis. 4 Although the total corneal collagen content of keratoconic eyes is normal, changes in epithelial basement membrane structure, stromal collagen fiber and extracellular matrix components, keratocyte morphology, and cell matrix interactions result in lamellar/fibrillar slip- page, leading to a reduction in corneal stiffness by a factor of 0.7. 5,6 This in turn leads to protrusion of the corneal apex and an increase in corneal power. 7 Pellucid marginal degeneration is a rare, idiopathic, progressive, nonhereditary, and noninflammatory ectatic disease classically affecting the inferior aspect of the cornea. 8 Histopathologic evaluation of PMD shows a thin or irregular Bowman layer, 9 while elec- tron microscopy studies reveal fibrous long collagen with a periodicity of 100 to 110 nm scattered among re- gions of otherwise normal collagen fibers. 10 Post laser refractive–surgery ectasia is an uncommon and complex entity that has been reported following both laser in situ keratomileusis (LASIK) 11 and photore- fractive keratectomy (PRK), 12,13 with a reported prevalence of 1/2500 14 and 1/3000, 15 respectively. Iat- rogenic ectasia has been associated with laser refractive Submitted: May 1, 2014. Final revision submitted: July 15, 2014. Accepted: July 23, 2014. From Moorfields Eye Hospital (Ziaei), Luton and Dunstable Univer- sity Hospital (Barsam), and Centre for Sight (Daya), East Grinstead, London, United Kingdom; Department of Ophthalmology (Kim), Duke University Eye Center, Durham, North Carolina, Carolina Cataract and Laser Center, Ladson, South Carolina (Vroman), Ophthalmic Consultants of Long Island (Donnenfeld), Rockville Centre, and Department of Ophthalmology (Kanellopoulos), New York University Medical School, New York, New York, Cincinnati Eye Institute (Holland), Cincinnati, Ohio, University of Pittsburgh School of Medicine (Mah), Pittsburgh, Pennsylvania, and Emory University School of Medicine (Randleman), Atlanta, Georgia; Laservision.gr Eye Institute (Kanellopoulos), Athens, Greece; Insti- tuto de Microcirug  ıa Ocular (G € uell), Barcelona, Spain. Corresponding author: Mohammed Ziaei, MBChB (Hons), FRCOphth, Moorfields Eye Hospital, 162 City Road, London, United Kingdom. E-mail: mohammed.ziaei@moorfields.nhs.uk. Q 2015 ASCRS and ESCRS Published by Elsevier Inc. 842 http://dx.doi.org/10.1016/j.jcrs.2015.03.010 0886-3350 REVIEW/UPDATE