Common Corneal Conditions
Due to its specialized nature and function, any abnormal condition of the corneaThe cornea is the clear, transparent 'front window' of the eye through which light enters the eye. It handles about two-thirds of the focusing power of the eye and is critical for good vision. See Info on Eyes – Anatomy. has a huge impact on the quality of vision a person perceives. The conditions that may lead to a corneal transplant may be placed in 3 broad categories:
- Corneal opacity - a cornea that was affected by inflammation or injury may develop scarring. Because of the resulting opacity, images are perceived as dull and blurred.
- Corneal thinning - a cornea that becomes progressively thinner, starts to develop an irregular shape. This leads to a steady increase in nearsightedness and/or astigmatism
- Failure to maintain corneal clarity - a cornea that is becoming increasingly swollen develops an opacity due to failure of the endothelial layer of cells. This causes images to become progressively dull and/or blurred, as well as the cornea becoming irritated.
An example of each of the above is listed below:
- Corneal scarring:
- Injuries to the central cornea may cause permanent scarring within the field of vision. Virus infectionsInfections may be caused by bacteria, viral or fungal agents that penetrate and affect any part of the body, including the eyes. Treatment of an infection depends on the source and nature of the agent that caused it. infections with agents such as Herpes Simplex and Herpes Zoster infections are leading causes for corneal scarring. Likewise, a corneal abscess secondary to contact lens wear may have the same impact on vision. Depending on the depth of such a scar, it might be possible to perform a transplant of the superficial layers only, leaving the deeper layers intact.
- KeratoconusKeratoconus is an eye condition that causes the cornea to spontaneously bulge outward, like the tip of a rugby ball. It causes very high levels of myopia and astigmatism.
See Eye Diseases – Keratoconus. and other ectatic corneal degenerations:
- This condition is discussed elsewhere on the website. A number of transplant techniques may be employed for this condition, including SALKSALK is the acronym for Superficial Anterior Lamellar Keratoplasty. It is one of the lamellar techniques used for cornea transplants. See Cornea Centre – Techniques., manual and microkeratomeA microkeratome is a high-precision motorised scalpel used to make the flap for a corrective lasik treatment. assisted DALKDALK is the acronym for Deep Anterior Lamellar Keratoplasty. It is one of the lamellar techniques used for cornea transplants. See Cornea Centre – Techniques., ‘Big Bubble DALK’, mushroom PKMushroom PK is an abbreviation for 'Mushroom Lamellar Keratoplasty'. It is one of the lamellar techniques used for cornea transplants. See Cornea Centre – Techniques. and PKPPKP is the acronym for Penetrating Keratoplasty. It is one of the techniques used for cornea transplants. See Cornea Centre – Techniques., depending on the level and severity of involvement.
- Corneal endothelial conditions:
- As mentioned elsewhere, the cornea has 5 layers, of which the epithelium is the most superficial layer and the endothelium the most internal layer. A dystrophy of the monolayer of endothelial cellsThe corneal endothelium is a single layer of specialized cells on the inner surface of the cornea and faces inward towards the iris. It actively maintains the cornea in a slightly dehydrated state, which is required to keep the cornea optically clear and transparent. or other pathology may cause corneal decompensation with severe impact on vision. The most frequent conditions affecting this layer of cells are Fuch’s endothelial dystrophy and pseudophakic bullous keratopathy. The latter condition is occasionally seen as a complication after cataractA cataract forms when the natural lens in the eye is, or is starting to become, opaque. If not treated, it can lead to blindness, which in most cases can be treated. See Cataract Centre – Understanding Cataracts. surgery. With the advent of modern technology, it is now possible to transplant the internal part of the cornea only through the DSAEKDSAEK is the acronym for Descemet's Stripping Automated Endothelial Keratoplasty. It is one of the modern lamellar techniques used to replace the corneal endothelium. See Cornea Centre – Techniques. and DMEKDMEK is the acronym for Descemet Membrane Endothelial Keratoplasty. It is the most recent and elegant technique to replace the corneal endothelium. See Cornea Centre – Techniques. procedures.