IV. Miscellaneous subjects
1. Causes of corneal opacities
1. Scars either nebula, leukoma non adherent or leukoma adherent.
2. Edema due to either:-
- Disruption of endothelial barrier in cases of buphthalmos, acute hydrops of keratoconus and blunt trauma.
- Endothelial pump failure due to iridocyclitis or acute glaucoma.
- Inflammatory edema min cases of keratitis and corneal ulcers
3. Corneal vascularization (mention the causes).
4. Degenerations as arcus senilis.
In this operation we remove an abnormal part of the cornea of a patient and replace it by a similar part of healthy donor's cornea. The donor may be:
- The cornea of the other eye if it is blind (autograft). There is no incidence of rejection in this case.
- The cornea of dead person taken maximally 6 - 10 hours post-mortem (homograft).
Types of keratoplasty:
1. Penetrating, i.e; transplantation of the whole corneal layers.
2. Lamellar: We dissect and transplant the superficial layers only. It is more difficult, but carries a less incidence of rejection.
Indications of keratoplasty:-
1. Optical: in cases of central corneal opacification and keratoconus.
2. Therapeutic in cases of resistant corneal ulcers and corneal fistula.
3. Structural and cases of perforated corneal ulcers and after multiple pterygium excision.
4. Cosmetic in cases of leukoma.
Contraindications of keratoplasty:-
1. Dryness and exposure because they lead to graft ulceration.
2. Corneal anaesthesia because loss of the nerve growth factor prevents healing of the graft.
3. Diseases as glaucoma and iridocyclitis should be treated at first.
NB. Corneal graft rejection is less common than other organs because the cornea is avascular and has a low cellular content. On the other hand, corneal vascularization will increase the risk of graft rejection.
3. Corneal vascularization
It means invasion of cornea by abnormal vessels. It may be superficial or deep