Part of the book: Astigmatism
Deep anterior lamellar keratoplasty (DALK) has been recently introduced as an alternative to penetrating keratoplasty (PK) for corneal pathologies not involving corneal endothelium. DALK does not rely on donor endothelium and requires less rigid criteria for donor corneal tissue quality. Therefore, it provides a greater availability of donor corneas that do not need perfectly healthy endothelium and high endothelial cell density to be suitable for PK. Furthermore, as lamellar corneal surgery expands the potential use of acellular corneal tissue, long-term preservation techniques are being revisited as a way to increase availability of corneal tissue to alleviate constraints of availability, cost, storage, and transportation in many countries. The recent alterations in the technique of corneal transplantation and hence the type of donor cornea tissues used for each technique, may require eye banks and corneal surgeons to reassess their selection criteria but it is important for any changes to be evidence-based. The purpose of this chapter, therefore, is to present an updated analysis on the type and quality of donor corneas used for PK and DALK, to evaluate the impact of donor and eye bank variables on the suitability of corneas for transplantation and then go on to determine whether any of these donor factors affect clinical outcomes, complications, and graft survivals.
Part of the book: Advances in Eye Surgery
A large subset of corneal pathologies involves the formation of new blood vessels, leading to compromised visual acuity. Additionally, neovascularization of the cornea worsens the prognosis of subsequent penetrating keratoplasty, keeping the patient in a vicious circle of poor prognosis. Ocular angiogenesis results from the upregulation of proangiogenic and downregulation of antiangiogenic factors. There is a tremendous need for developing effective measures to prevent and/or treat corneal neovascularization. Topical steroid medication, cautery, argon and yellow dye laser, and fine needle diathermy have all been advocated with varying degrees of success. The process of corneal neovascularization is primarily mediated by the vascular endothelial growth factor family of proteins, and current therapies are aimed at disrupting the various steps in this pathway. This article aims to review the clinical causes and presentations of corneal neovascularization caused by different etiologies. Moreover, this chapter reviews different complications caused by corneal neovascularization and summarizes the most relevant treatments available so far.
Part of the book: Physiologic and Pathologic Angiogenesis
Mustard gas is a lipophilic, highly cytotoxic agent that rapidly penetrates tissue, and the eye is one of the organs mostly affected. Mustard gas-related ocular injuries can be divided into immediate, chronic, and delayed-onset phases. Late complications, developing after 1–40 years, can cause progressive and permanent reduction in visual acuity and even blindness. A wide range of late ocular involvements have been reported, which include chronic blepharitis, limbal ischemia and stem cell deficiency, and corneal scarring and neovascularization. The majority of corneal involvements are limited to the anterior stroma, leaving the posterior stroma and endothelium relatively intact. Therefore, lamellar keratoplasty is appropriate for the management of corneal involvements in the majority of victims. This procedure can be performed alone or in combination with limbal stem cell transplantation.
Part of the book: Causes and Coping with Visual Impairment and Blindness