Cornea and its Importance:

Cornea is a spherical concavo-convex transparent tissue in the anterior most part of the eye. It is made up of:

• Epithelial cells
• Bowman’s membrane
• Stroma of linearly arranged transparent collagen fibrils
• Descemet’s membrane
• Endothelium

The most fascinating aspect of cornea is it does not have any blood supply which is one of the factors contributing to transparency of cornea. Cornea gets its nutrition from oxygen of atmosphere dissolved in the tear film and partly from the aqueous humour circulating inside the eye. But It has very rich nerve supply. The nerves of the cornea have open nerve endings which makes cornea very sensitive to external stimuli.

Corneal Transplantation:

Corneal transplantation is otherwise called Penetrating Keratoplasty. It was first performed by Kissam in 1844 using pigs cornea in human eye. The graft remained clear for 2 weeks. First human to human corneal transplantation was done by Austrian surgeon Zirm in 1906.

OPTICAL: Where the graft is done for Visual rehabilitation
TECTONIC: For restoring the altered corneal structure
THERAPEUTIC: Tissue substitution for refractory corneal diseases

Indications For Corneal Transplant:

• Keratoconus
• Corneal Edema
• Failed Graft
• Corneal Infections
• Herpes Simplex Keratitis
• Corneal dystrophies
• Corneal trauma
• Corneal decompensation after eye surgery
• Corneal scaring

Corneal Donor:

A person is not eligible for corneal donation under the following circumstances:

• Death from unknown cause
• CNS diseases from unknown etiology
• Slow virus diseases
• HIV /Rabies / Syphilis
• Malignancies / Disseminated cancer

Donor cornea should be harvested less than 6 hours from the time of death for better outcome. Donor cornea is subjected to Specular microscopy to assess cell density, cell shape, cell size, uniformity, pleomorphism, polymegathism and to rule out evidence of old intraocular inflammation and endothelial insult.

The harvested cornea is preserved in MK medium (McCarey and Kaufman medium) / Chondroitin Sulfate enriched media(K-Sol medium) for short term preservation or storage. The long term storage is done by Cryopreservation where the corneal tissue is frozen at a controlled rate up to -80 C and subsequently stored at -160 C indefinitely.

Eye Banks:

 Harvested cornea is stored in authorised eye banks. It is a multi-tier organisation which specialises in:

• Creating public awareness on corneal donation
• Retrieval of donor cornea
• Processing and storage
• Distribution of cornea for transplant

Transplantation Complications

Early Complications:

• Primary graft failure
• Glaucoma
• Epithelial defect

Intermediate Complications:

• Graft Rejection
• Graft infection
• Wound dehiscence

Late Complications:

• Recurrence of Diseases(Dystrophies / Herpes simplex keratitis)
• Graft failure of unknown ethology
• Post keratoplasty astigmatism

Dr. Sudha Bhuvaneshwari
Associate Consultant in Ophthalmology
Kauvery Hospital