Corneal Diseases

Corneal ulcer

Cornea refers to the clear, transparent covering of the eyeball. When this part gets scarred or becomes cloudy that it interferes with vision, surgery is performed. Several corneal diseases, such as herpes zoster, keratoconus or thinning of the cornea corneal infections and corneal dystrophies can cause permanent damage to the cells of the cornea.

Corneal endothelial disease affects the innermost layer of the cornea, the endothelium. It primarily functions to maintain normal balance of fluid inside the cornea. However, endothelial cells do not have the capacity to regenerate. Corneal edema ensues due to permanent damage of the endothelium. If this happens, the only option is corneal transplant.

Corneal disease is not the only cause for surgery. Surgery is also performed to correct vision problems. Refractive surgery is performed if the patient has severe astigmatism, nearsightedness or farsightedness. Corneal surgery can be done using traditional surgical tools or it may be done using laser surgery.

Corneal transplant surgery uses either local or general anesthesia. The traumatized area of the cornea is removed using an instrument called trephine, which functions like a cookie cutter. Under a specialized, high-powered microscope, the donor cornea is put into place and securely sewn with a very fine thread. Chances of success depend upon the type of corneal disease present. Common causes of surgical failure include primary transplant failure, graft rejection, wound separation, post-operative astigmatism, loose suture and macular edema.

Alternative procedures to corneal transplant include Phototherapeutic Keratectomy (PTK), which uses a device called an Excimer laser controlled using a computer. It is performed for treatment of corneal scars, infections and dystrophies. A laser beam emitting ultraviolet light is used to etch away irregularities in the cornea’s surface. The main purpose of this procedure is to produce a clearer and smoother cornea. Best candidates for PTK are those with inherited corneal disorders, corneal scarring and corneal clouding resulting to image blocking. PTK is favorable than corneal transplant because it produces little trauma to surrounding tissues, encourages re-growth of new tissues on the smooth surface, recovery time happens after a few days rather than months, rapid return of normal vision and high success rate.

A basic laser surgery procedure starts with cleaning of area around the affected eye followed by sterile draping and administration of anesthetic eye drops to numb the affected eye. To prevent blinking during the procedure, an eyelid holder keeps the eye wide open. The specific procedure ids then administered while patient looks directly at target light. Laser reshapes the cornea in a minute or two. After the procedure expect some blurred or hazy vision for up to five-day and mild eye discomfort. Pain medication, eye drops and protective lens may be given while resumption of normal activities usually happens after three days.

Photo-Refractive Keratectomy (PRK) is a corrective surgical procedure involving the removal of the epithelium or the outermost layer of the cornea followed by the laser applied to the surface. It corrects astigmatism by making the cornea more spherical. Farsightedness is corrected by making the cornea steeper while the cornea is made flatter in treating nearsightedness. Those age 18 years and above, has stable eye prescription for at least one year, large pupils, corneas too thin for LASIK, those who want to eliminate dependence on glasses and contacts and no health issues affecting the eyes are good candidates for PRK.

LASIK or Laser In-situ Keratomileusis is one of the most popular corrective laser eye surgery treatment today. It works very similar to PRK except that a corneal flap is created using an instrument called microkeratome. The laser is then applied to the inner tissue of the cornea. To qualify for a LASIK procedure patient needs to be at least 21 years old, has stable eye prescription for a year or more, no health issues concerning the eye, no glaucoma or cataracts and is willing to eliminate the use of contacts or glasses.

LASEK or Laser Epithelial Keratomileusis is the newest procedure which combines the advantages of PRK and LASIK. Epithelium is just loosened using a diluted alcohol solution and set aside while inner tissues are treated. The epithelium is then returned to its original position so there is lesser trauma to the eye. Best Candidates for LASEK include those at least 18 years old, has large pupils, stable eye prescription for at least a year, cornea too thin for LASIK and those who do not want to undergo LASIK due to usage of microkeratome.

The following links are recommended for additional reading on corneal diseases and corneal procedures:

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