9 September 2020 Author : Pedro Brito What is the cornea and what are its functions? The cornea is a transparent, multilayered tissue that covers the anterior region of the eye: it covers the pupil (in the dark center of the eye), the iris (the colored region around the pupil) and a part of the sclera (the white of the eye) . Cornea is an avascular tissue (it has no blood supply) that has protective functions for the eye, transmits and helps to concentrate the light on the retina and is the main structure responsible for the focusing power of the eye. For the cornea to perform its functions, it is essential that it maintains its transparency and integrity. However, various inflammatory, infectious, and degenerative diseases, as well as certain types of eye injuries, can irreversibly damage the delicate cellular organization of the cornea and contribute to a significant loss of visual acuity. The treatment of the problems that affect them has evolved a lot and corneal transplantation currently plays an important role in many cases. There are corneal diseases, some serious, that can be indicated and can potentially be cured using modern corneal transplantation techniques. What are the main indications for a corneal transplant? In many cases changes in the transparency of the cornea can be solved with a corneal transplant. Among the most common diseases that can affect the transparency of the cornea are: Keratoconus and other morphological degenerative diseases; Congenital or acquired corneal dystrophies; Scars from infections, such as herpes or fungal keratitis; Chemical burns of the cornea or damage caused by other traumatic injuries; Decompensation of the corneal endothelium due to eye complications. How is the transplant done and what types of transplant exist? A corneal transplant is a surgery in which a donor cornea is used and applied to the diseased eye of the recipient. Depending on the underlying disease and the number of layers of the cornea that need to be transplanted, different types of transplantation can be performed: Penetrating keratoplasty or corneal transplantatio n, if all layers are transplanted; Lamellar keratoplasty or corneal transplantation , if only some of the layers of the cornea are substituted. Lamellar keratoplasty can also be of two types: Endothelial posterior lamellar keratoplasty (DSAEK, DMEK) In cases where the corneal disease affects only the endothelium, such as Fuchs' endothelial dystrophy and bullous pseudophakic keratopathy, it allows the diseased layer to be transplanted through a small incision. The recovery of visual acuity is much faster than in penetrating corneal transplants. Deep anterior lamellar keratoplasties (DALK) When the cornea is deformed, as in situations of keratoconus and ectasia, or opacified by traumatic or infectious scars, but there is a healthy endothelial layer only the altered superficial layers are replaced. What are the advantages of lamellar corneal transplantation techniques? The main advantages of lamellar transplantation techniques over penetrating transplantation are: Faster vision recovery; Better refractive result, that is, less degree of astigmatism, myopia, hyperopia and other refractive problems; Significant decrease in the risk of eye infection or immune graft rejection. So, whenever the corneal disease permits, the ophthalmologist will decide on a lamellar transplantation technique. However, in the most severe cases , such as very advanced keratoconus or deep healing or ulcerative lesions, penetrating transplantation remains the only therapeutic solution, capable of allowing patients with severe visual impairment to recover functional levels of vision. Meet the Ophthalmology team of Hospital da Luz network. The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
