**4. Time of rejection of the corneal implant**

According to the evidence of rejection time after surgery the rejection must be classified in hyperacute, acute or chronic rejection. The hyperacute rejection occurs within days after transplantation of the graft. This type of rejection has become rare, affecting less than 1% of transplant recipients due to improved pre-transplant projections. Hyperacute rejection occurs when the host antibodies recognize and bind to antigens of the graft (such as ABO blood group proteins or proteins of major histocompatibility complex). The binding of these antibodies lead to the initiation of the complement cascade, neutrophil recruitment, platelet activation, endothelial cell damage of the graft, and stimulation of coagulation reactions, which in turn lead to rapid thrombosis, loss of vascular integrity, heart tissue, and loss of graft function.

The acute rejection occurs in approximately fifty percent of transplant recipients experience acute rejection (with only 10% progressing to graft loss), which can occur several hours or days (even weeks) after transplantation. The incidence of acute rejection has decreased significantly with the successful use of immunosuppressants such as cyclosporine and azathioprine. The incidence of graft loss was reduced by the latest anti-rejection treatments. Acute rejection occurs when alloantigen-reactive T cells from the host to infiltrate the graft and become activated by contact with foreign proteins, related to the graft presented to

The Complications After Keratoplasty 115

make up for esthetical reasons around the eye, perhaps it can interfere the microbial equilibrium of normal flora and let the opportunistic flora to colonize the eye and cause infections. Among some aftercare corneal transplant recommendations after this finding

Prevention of rejection (immunological exams before surgery donor and receptor)

10-0. And the use of an antibiotic ointment administered at the end of surgery.

restriction recommended by American Ophthalmology Association:

glasses during the waking day, for 1 month.

slightly backwards for 2 weeks.

8. No swimming for 3 weeks.

10. Walking is permitted.

6. No heavy exercise of any kind for 3 weeks 7. No sexual intercourse for 3 days after surgery.

Other important recommendations to verify are:

9. Not read for more than 10 minutes at a time for 2 weeks.

5. May watch TV

To prevent post surgical infections the disinfection protocols are the main factor to consider for minimize complications: before starting the surgical procedures, all of the recipient eyes (including eyelids and conjunctiva) can be rinsed with povidone iodine solution, 5%, that was allowed to act for 3 to 5 minutes. After drying the periocular surface, the operation field was covered with sterile drapes and PK can be performed as follows: rinsed with sterile solution (balanced salt solution, it is recommended to introduce acetylcholine chloride (like Miochol-E) into the anterior chamber. Prior to donor trephination and the graft's sutural fixation, the donor's endothelium was covered by sodium hyaluronate, 1% (Healon ophthalmic viscosurgical device). To fix the grafts, a double-running cross-stitch suture with

It is important also instruct patients avoid restrictions and talk about postsurgical care to prevent fails. Some of these are: To take de prescription of antibiotics and drugs, and the

1. Use metal shield nightly or when taking a nap during the day and a cloth pad under

Recruitment of donor tissue : de donor must be removed within six hour after death, the viable storage period of the removed cornea-scleral button is two weeks, grafts donors < 12 months or > 70 years are preferably not to be used and for more security it is also important not use corneas from death of unknown causes, certain infectious diseases like Jacob-Creutzfeld, SSPE, progressive multifocal, leuko-encephalopathy (CNS), certain systemic infection (AIDS, septicemia, syphilis, viral hepatitis), leukemia and disseminated lymphoma, intrinsic eye diseases (tumors, active inflammations, previous intra-ocular surgery), with respect to the recipient cornea : absence of corneal sensations, stromal vascularization, corneal thinning at the expected recipient-donor margin, active inflammation) and also it is so important to verify the surgical procedure : decide about graft size, usually graft size is no bigger than 8,5 mm in diameter to avoid post-keratoplasty increase in intra-ocular pressure, anterior synechiae and

2. Not bend at the waist for more than 10 minutes at a time, but may squat at the knees. 3. Not lift or push anything heavier than 15 pounds, including grandchildren, for 2 weeks. 4. Hair may be gently shampooed by a friend or a beauty shop with the head leaning

around the world it should look the next factors:

More research for therapy protocols

 Integrity of sutures Ephitelization

Non-filtration.

them by antigen presenting cells. These T cells can lead to tissue damage of the graft by the direct elimination of graft cells (killer T cells) or the production of proinflammatory cytokines such as tumor necrosis factor, interleukin-1, and interferon. These cytokines are vasoactive and perpetuate the inflammatory cell recruitment and infiltration. As a result, graft inflammation progresses, leading to tissue distortion, vascular insufficiency, and cell destruction - all of which may eventually compromise graft function.

By the other hand, the chronic rejection occurs in 50% of transplant patients within 10 years after transplantation. This form of rejection is characterized by the development of occlusion of blood vessels luminal progressive thickening of the intima of medium and large artery walls. Chronic rejection is a pathological response of the tissue remodeling that takes place at a variable rate after graft endothelial cells are traumatized by mechanical damage, ischemia, and immune system during and after the transplant. Damaged vascular endothelial cells produce cytokines and tissue growth factors that initiate vascular repair, causing the underlying smooth muscle cells to begin proliferating. Large amounts of intimal matrix occur, leading to vascular wall thickening stop growing. Slowly progressive reduction in blood flow, results in regional tissue ischemia, cell death and tissue fibrosis.
