Repeat Keratoplasty for Failed Therapeutic Keratoplasty for Microbial Keratitis: An Analysis of Characteristics and Risk Factors

Review of the literature on the currently available evidence for the management of infectious keratitis with PACK-CXL

Infectious keratitis (IK) is one of the most common causes of monocular blindness worldwide, especially in developing countries and may account for 5.1%-32.3% of all indications for penetrating keratoplasty (PK). However, performing a therapeutic PK on a "hot eye" is associated with a higher incidence of IK recurrence and graft rejection. Standard treatment includes antimicrobials (ATM) and, once the causative pathogen has been identified, must be continued with targeted treatment, depending on antibiogram sensitivity. However, appearance of multiresistant strains to ATM is progressively increasing at an alarming rate. Besides that, the diversity of the causative microorganisms (bacteria, fungi, parasites, viruses) may hinder the clinical diagnosis and secondarily the proper treatment from the beginning. It is estimated that only 50% of eyes will have a good visual result if the correct therapy is delayed. All these factors make the identification of alternatives to ATM treatment of paramount importance. Due to the ATM properties of photoactivated chromophore (riboflavin, RB) and ultraviolet (UV) light of wavelength (λ) 200-400 nanometers (nm), used in multiple medical and non-medical applications for disinfection, photoactivated chromophore for corneal cross-linking (CXL) of IK (PACK-CXL), as an addition to the therapeutic arsenal for the management of IK has been proposed. It must be differentiated from CXL used for the management of progressive keratoconus (KC). The objective of this review is to update the available evidence on the efficacy and safety of PACK-CXL in IKs.