Organization of Collagen in the Lyophilized Cornea

Review of Gamma-Irradiated Sterile Cornea: Properties, Indications, and New Directions

ABSTRACT

Gamma-irradiated sterile cornea (GISC) is a relatively new graft tissue that follows the 30-year success of irradiation to other tissues (bone and sclera) to lessen antigenic load and infection transmission. It can serve as a graft to cover glaucoma drainage devices, as graft tissue for frank or impending corneal perforations in tectonic keratoplasty, as graft tissue in lamellar keratoplasty, and as carrier tissue for keratoprosthesis. With the limited availability of fresh corneal tissue in less developed countries, GISC may fill a need for corneal tissue worldwide. It can be used in situations where corneal endothelium is not needed and with a greatly reduced risk of rejection and infection because of the effect of irradiation on corneal tissue.

A review of long-term corneal preservation techniques: Relevance and renewed interests in the COVID-19 era

The growth of eye banking in India was showing positive trends until the nation was hit by unprecedented times as a result of the COVID-19 pandemic. The impact of this has led to a downward spiraling in eye banking activities globally. Several measures had to be implemented to tide over the crisis and strategies planned for future to prepare for the needs of corneal transplantation. While eye banks in India have been practicing short- term and intermediate storage preservation media, there is a definite need to evolve other methods of very long-term preservation. This review discusses various methods of long term corneal preservation, their relevance and applications in the present times. We reviewed relevant medical literature in English from PUBMED with the key words “Corneal preservation”, “Cryopreservation”, “Glycerol preservation”, Gamma Irradiation”, “Eye Banking” ,”COVID-19”.

The use of X-ray scattering techniques to determine corneal ultrastructure

The manner in which X-rays are scattered or diffracted by the cornea provides us with valuable insights into the fine structure of the corneal stroma. This is because when X-rays pass through a cornea a diffraction pattern is formed due to scattering from regularly arranged collagen molecules and fibrils that comprise the bulk of the stromal matrix. Collagen provides the cornea with most of its strength, and its proper organisation is believed to be important for tissue transparency. Ever since 1978, when the first X-ray diffraction patterns were obtained from the cornea using radiation from a powerful synchrotron source, biophysicists have recorded and analysed a huge number of X-ray diffraction patterns from many different corneas. This article aims to explain the ideas that underpin our use of X-ray diffraction to investigate corneal ultrastructure, and show how the knowledge gained to date has far-reaching implications for tissue biomechanics, disease changes and transparency.

A synchrotron x-ray diffraction study of developing chick corneas

To study some ultrastructural aspects of developing chick corneas we performed a synchrotron x-ray diffraction analysis of 22 specimens obtained daily from developmental day 10 through day 19. Before day 12 of development in chicks we were unable to detect a meridional x-ray diffraction pattern from cornea. Neither were we able to record a first-order equatorial x-ray reflection at this time. Normally, these reflections are present in corneal x-ray patterns, arising from, respectively, the periodic axial electron density of fibrillar collagen and the lattice-like arrangement of the fibrils. By day 12 of development we could detect the third- and fifth-order meridional reflections (indicating increased amounts of collagen) and a first-order equatorial reflection (implying that more collagen was regularly arranged). The third- and fifth-order meridional reflections became more intense as the tissue matured, suggestive of a continued deposition of fibrillar collagen, and the scattering angle of the interfibrillar maximum increased, suggesting that regularly arranged collagen was becoming more closely packed with maturation. In embryonic chick corneas, the establishment of an orderly, fairly compacted matrix of collagen fibrils may be one of the main events underlying the acquisition of corneal transparency.