What Happens to The Cornea?
The cornea is the transparent outermost part of your eye. It helps focus images by refracting light onto the eye’s neurosensory tissue. If your cornea is damaged, it can become swollen or scarred. This causes light that is entering the eye to scatter or distort, resulting in glare or blurred vision.
About the Cornea
The cornea is comprised of several layers. The epithelium is the external barrier. The stroma, which is 95% of the corneal thickness, provides the corneal structure and transparency. The inside of the cornea is lined by endothelial cells, which contain fluid pumps that keep the cornea in a relatively dehydrated state.
A corneal transplant is sometimes necessary for people who have cloudy or scarred corneas. This can be due to injury, infection, or stromal dystrophies, corneal swelling (Fuchs’ endothelial dystrophy or secondary corneal edema), or corneal thinning from keratoconus. An experienced corneal specialist should be consulted if you have severe corneal vision loss to determine the cause and the appropriate treatment.
More Complex Surgeries
Penetrating Keratoplasty (PK)
Transplantation of the full thickness cornea is penetrating keratoplasty. This procedure was first performed in 1905 and has been advanced over the past century to improve visual outcomes. Other innovations in corneal transplantation have focused on providing targeted replacement of the diseased or damaged corneal layers.
Endothelial Keratoplasty (DSAEK/DMEK)
The procedure known as endothelial keratoplasty replaces the patient’s damaged corneal endothelium with either a healthy new endothelium alone (DMEK) or in combination with a thin strip of donor stroma tissue (DSAEK). These procedures are appropriate when the inner layer of the cornea, the endothelium, is the only layer that needs repairing. These techniques eliminate the need for sutures and decrease the patient's recovery time.
Deep Anterior Lamellar Keratoplasty (DALK)
To help with diseases that exclusively affect the middle stromal layer, an approach known as deep anterior lamellar keratoplasty is used. In these diseases the stroma is sick, cloudy, or deformed, but the inner layers (Descemet’s membrane and endothelial cells) are healthy. Purely stromal diseases include keratoconus and some corneal dystrophies. The patient’s Descemet’s membrane and endothelium may be left intact which improves safety of the procedure, speeds visual recovery, and leads to longer graft survival.
Removal of the pterygium may be needed if it affects the vision or causes discomfort. This is an overgrowth of the conjunctiva, or mucus membrane lining of the eye, onto the corneal surface.
Irregularity or nodules under the epithelium (e.g. Salzmann’s nodules or anterior basement membrane dystrophy) that affect the smoothness of the cornea’s outer surface can distort the vision or cause discomfort of the eye surface. These can be removed and the surface of the eye smoothed with a procedure called superficial keratectomy.