Corneal Crosslinking: The Standard Protocol

Abstract

RESUMOO objetivo desta revisão é de determinar as indicações e eficácia da cirurgia que promove novas ligações covalentes entre as fibras de colágeno da córnea, conhecida como Cross-Linking (CXL), assim como esclarecer seus objetivos. O ceratocone é uma doença ectasica da córnea, bilateral, assimétrica, que, principalmente, cursa com encurvamento e afinamentos progressivo, e se inicia em geral na segunda década de vida. O uso primário do CXL tem sido na interrupção da progressão do Ceratocone. Apesar do conhecido encurvamento no estroma da córnea ocorrer nesses pacientes, a fisiopatologia por trás do ceratocone ainda é desconhecida e parece ser multifatorial. Pela evidencia literária disponível até o momento, o CXL da córnea esta, portanto indicado nos pacientes com doença em progressão. Concluímos que existe evidencia suficiente para afirmar que o CXL da córnea é eficaz na estabilização da doença ectásica da cornea.Descritores: Córnea/fisiologia; Córnea/metabolismo; Cross-linking reagentes; Ceratocone/terapia; Riblflavina/administração & dosagem; Protocolos ABSTRACT The purpose of this review is to determine the indications and efficacy of the surgery that promotes new covalent bonds between the collagen fibers of the cornea, known as Cross-Linking (CXL), as well as to clarify its objectives. Keratoconus is a bilateral, asymmetric ectasic disease of the cornea that mainly courses with steepening and progressive thinning, and usually begins in the second decade of life.The primary use of CXL has been in discontinuing the progression of keratoconus. Although known corneal stromal remodeling occurs in these patients, the pathophysiology behind keratoconus is still unknown and appears to be multifactorial. By the literary evidence available to date, the CXL of the cornea is safely indicated in patients with progressing disease. We conclude that there is sufficient evidence to affirm that cornea CXL is effective in stabilizing corneal ectasic disease.

Standard cross‐linking versus photorefractive keratectomy combined with accelerated cross‐linking for keratoconus management: a comparative study

“…Similarly, many authors have reported the good and lasting effect of standard CXL in comparison with AXL. In fact, it has been observed that AXL had a limited corneal flattening influence in topography while standard CXL had an excellent topographic corneal flattening outcome that led to keratoconus stability and postoperative visual improvement (Choi et al 2017;Kymionis et al 2017;Santhiago 2017). Brittingham et al (2014) stated that AXL has negative effect on the demarcation line at 12 months after cross-linking with increased steepening of the anterior corneal surface.…”

<p>Efficacy of Standard and Accelerated (10 Minutes) Corneal Crosslinking in Keratoconus Stabilization</p>

“…Because of the frequent side effects associated with the standard technique, new protocols are needed. 5 Line of sight loss, haze and progressive flattening are already well defined in research studies. Thus, we opted to adhere to pre-and postoperative keratometry measurements without studying other effects.…”

“…4 The physiopathology of corneal steepening is still unknown, but it is assumed that repetitive trauma, such as eye scratching, combined with abnormalities in the corneal connective tissue contribute to the progression of the disease. 5 ABCD classification is used to stage keratoconus from 0 to IV according to progression based on the posterior and anterior corneal curvature, corneal thickness, best corrected visual acuity and corneal scars. 6 Although there have been advances in knowledge, the aetiology of keratoconus has not yet been elucidated.…”

“…9 The most recent discovery for the treatment of progressive keratoconus was corneal crosslinking (CXL), which, in biological terms, stimulates the formation of new covalent bonds between the collagen fibres of the cornea, making the cornea more stable; thus, there is a lower tendency for thinning and steepening. 5 The indication for corneal crosslinking, regarding keratoconus, is stop the progression of the corneal ectasia or stop the steepening of the cornea.…”

“…However, this method can cause progressive flattening, haze and infiltrates. 5 Therefore, other protocols are being used, called Accelerated CXL, with shorter durations and irradiation intensities ranging from 9 minutes with 10 mW/cm 2 to 15 minutes with 7 mW/cm 2 , among others, and variable results have been obtained. 8 Recent studies have concluded that the results of the standard and accelerated protocols are similar, including in children, although the results may vary considering irradiance, time and age, indicating the need for further studies to confirm the efficacy of the Accelerated protocol.…”