Evaluation and transplantation of corneas from pseudophakic donor eyes.

PURPOSE: To evaluate the quality of corneal donor tissue from pseudophakic eyes for transplantation. METHODS: Only capsular-supported posterior chamber pseudophakia was studied. Forty-five pairs of donor eyes were assessed and evaluated by standard Minnesota Lions Eye Bank (MLEB) protocol. Thirty-three pairs were unilaterally pseudophakic with the unoperated phakic eye used as a control eye. Twelve donors were bilaterally pseudophakic. All corneas were rated for corneal clarity, epithelial defects, stromal edema, Descemet's membrane folding, endothelial cell density (ECD), and cell damage by slit-lamp examination and specular microscopy. If the corneas were not transplanted, the endothelium was vital stained with trypan blue and counterstained with alizarin red S for quantitation, localization, and visualization of cell morphology and damage. RESULTS: Sixty-eight of the 90 corneas in this study did not meet transplantation criteria. A significant difference in ECD (>22%) and in overall corneal rating was found in seven (21%) of 33 pairs of unilateral pseudophakic donors. Fourteen corneal transplants were performed using corneas from the donors in this study. Nine corneas from pseudophakic donor eyes were transplanted, resulting in one primary graft failure reported. CONCLUSION: Corneas from pseudophakic donor eyes may need more extensive evaluation for endothelial viability than is currently required by eye bank standards.

Effect of topically administered platelet-derived growth factor on corneal wound strength.

Since the cornea is an avascular tissue, the wound healing process is lengthy, with a need for sutures to stabilize the wound for a long time. Platelet-derived growth factor (PDGF) has been shown to accelerate wound healing in rat dermal models. Accelerated healing, if unaccompanied by side effects may reduce suture related complications such as astigmatism and infectious keratitis. This study evaluated the effect of PDGF on wound strength in corneal laceration and penetrating keratoplasty models using New Zealand white albino rabbits. Twenty-two rabbits were used in the corneal laceration model and sixteen rabbits in the penetrating keratoplasty model. The treated rabbits received 385 picomoles/drop of PDGF-BB dissolved in balanced salt solution six times on day 1 and three times a day for the remainder of the study. The control rabbits received balanced salt solution in the same dosing schedule. The pressure required to rupture the wound was measured using a pressure transducer. In the laceration model the PDGF treated group had mean (+/- standard deviation) average pressures on day 7 of 360 +/- 102 mm Hg for wound rupture compared to 210 +/- 102 mm Hg in the control group. (p = 0.005). The average pressures in the penetrating keratoplasty model on day 17 were 707 +/- 201 mm Hg for the controls and 1042 +/- 292 mm Hg for the PDGF treated group (p = 0.026). Histopathological evaluation of eyes not subjected to bursting showed increased fibroblasts at the wound junction with an increase in types III and type IV collagen production.(ABSTRACT TRUNCATED AT 250 WORDS)

Rapamycin inhibits corneal allograft rejection and neovascularization.

OBJECTIVE: To investigate the immunosuppressive effect of rapamycin in prolonging allograft survival in the rat model of orthotopic allogeneic penetrating keratoplasty. DESIGN: Thirty inbred Lewis rats received corneal allografts from Brown Norway donors. Animals were divided into two rapamycin treatment groups and one allogeneic control group. RESULTS: By the second week after surgery, all of the control animals had experienced allograft failure due to allograft rejection. However, allografts in seven of 10 animals in the low-dose treatment group and allografts in seven of nine animals in the high-dose treatment group remained clear. In addition, corneal neovascularization was markedly reduced in the treated animals. CONCLUSIONS: The systemic administration of rapamycin prolongs corneal allograft survival and significantly inhibits the neovascular component of rejection in the rat model of orthotopic allogeneic penetrating keratoplasty.

Whole globe enucleation versus in situ corneal excision: a study of tissue trauma and contamination.

Twenty-four pair of eyes donated to the Minnesota Lions Eye Bank were studied to determine the effect of corneal procurement methods on tissue quality. Eyes studied were ineligible for transplantation because of a preexisting medical condition other than sepsis or age of > 75 years. The procurement technique was randomized for each donor. One cornea was procured in situ (IS), whereas the fellow eye was enucleated and processed in the laboratory (EN). Procurement protocols were standard Eye Bank Association of America methods. Tissue characteristics were scored according to standard eye bank protocols. Cultures were performed at the time of tissue procurement and following storage for 7 days in Dexol media. With the exception of endothelial striae, no statistical difference was found between groups for any tissue characteristics. The average score for endothelial striae in the IS group was greater than twice that of the EN group. Initial cultures were positive in 10 of 24 in the IS group and four of 24 in the EN group. Each group had three positive end-storage cultures. These results demonstrate superior tissue decontamination after initial processing and less endothelial cell trauma with standard enucleation when compared to in situ corneal excisions.

Suppression of graft rejection using 15-deoxyspergualin in the allogeneic rat penetrating keratoplasty model.

We tested the ability of 15-deoxyspergualin (DSG), a new immunosuppressant, to inhibit corneal allograft rejection in the rat penetrating keratoplasty model. Fifty-six inbred Lewis rats were recipients of orthotopic corneal allografts from Brown Norway rats. Allogeneic groups received daily intramuscular injections of DSG 2, 3, 4, or 10 mg/kg/day. The animals treated with 2 mg/kg/day had four out of 10 grafts rejected; in the 3 mg/kg/day group none of the six grafts rejected; whereas in the 4 mg/kg/day group one out of 15 grafts rejected. The animals treated with 10 mg/kg/day became emaciated and died during the second and third postoperative weeks with relatively clear grafts. All corneas rejected following discontinuation of the drug. We conclude that the systemic administration of DSG at 3 or 4 mg/kg/day results in effective suppression of corneal allograft rejection in the rat penetrating keratoplasty model.

Betadine decontamination of donor globes.

Between May 1983 and December 1989, 2,921 donor eyes received by the Minnesota Lions Eye Bank underwent a decontamination protocol using 10% Betadine (1% povidone-iodine) solution. Positive pretreatment limbal cultures were obtained on 52.1% of donor eyes. Posttreatment limbal cultures demonstrated a 76.1% reduction in microbial growth, including an 85.7% reduction in Candida species. Streptococcus species were reduced by 76.7% and coagulase-negative Staphylococcus were reduced by 76.1%. In addition, of 250 donor rims obtained at the time of surgery, two had coagulase-negative. Staphylococcus present that were also present after the decontamination procedure. In no cases did endophthalmitis occur during this study. This study demonstrates that this protocol using 10% Betadine solution is extremely effective in decontaminating donor globes of aerobic bacteria and fungi. However, gentamicin-resistant organisms survived this protocol, emphasizing the need to develop storage media containing a broader-spectrum antibiotic agent then gentamicin.

Eye banking: the Minnesota experience.

We present a brief report on the activities of the Minnesota Lions Eye Bank. This eye bank receives and supplies tissue to several midwestern states. In addition, it plays a vital role in providing tissue for research and training at the University of Minnesota. In association with the Department of Ophthalmology, the eye bank is also actively involved in the research and development of various corneal preservation systems. Included below is information relative to procedures used in the eye bank for the selection and collection of donor material; the decontamination, preparation, and storage of corneas; cost of eye bank services; and staff coverage. Also included is some data on the number of eyes received and processed and the eventual uses of the tissues, during the last ten years.

Polysulfone corneal lenses.

Polysulfone is a thermoplastic compound first synthesized in 1965. A unique characteristic of polysulfone is its high refractive index (1.633), which allows very thin optical lenses to be manufactured. Over the last five years, D. Peter Choyce has surgically implanted over 40 polysulfone lenses into eyes of his patients. Analysis of his data indicates that polysulfone intraocular lenses are capable of correcting large refractive errors. Based on his work, a multicenter study was undertaken to evaluate the safety and efficacy of polysulfone as an intracorneal lens material in laboratory models. Four monkeys, eight baboons, and 24 cats were used as laboratory models; 5.0-mm to 6.0-mm diameter hyperopic (+28.5 diopter) and myopic (-17.0 and -25.5 diopter) lenses were surgically implanted within the corneal stroma in one eye of each of the laboratory models while a sham lamellar dissection was performed in the other eye. One hundred percent (4/4) of monkey eyes, 12.5% (1/8) of baboon eyes, and 70.0% (18/24) of cat eyes maintained clear media by ophthalmoscopic examination at follow-ups ranging from three to six months. Complications included both visually and nonvisually significant interface opacities, lens extrusion, anterior corneal necrosis, refractile particles, and epithelial thinning.

Minnesota system corneal preservation.

The clinical and laboratory results with a modified Minnesota system of organ culture corneal preservation are presented. A refinement of our preservation technique using a closed system, as well as the addition of chondroitin sulphate to the medium is presented. Laboratory results show preservation of corneal endothelial integrity for at least 21 days with maintenance of normal corneal thickness. In addition, a 10-day quarantine system reduces the risk of donor contamination and secondary endophthalmitis. Preliminary results of the 34 degrees C and 4 degrees C closed Minnesota corneal preservation system using chondroitin sulphate show that it is safe and efficacious and allows intermediate to long-term maintenance of sterile thin tissue prior to corneal transplantation.

Fungal contamination in organ culture.

Fungal contamination of organ-cultured corneas was studied retrospectively. Over a 3 1/2-year period, 5.2% of 696 corneas became contaminated by fungi in organ culture. The average length of time for fungal contamination to occur in organ culture was 11 days. The most frequent contaminating fungi were those of the Candida species. In addition to previously identified risk factors for donor cornea contamination, those corneas from donors given mechanical respiratory assistance at the time of death, those corneas with long postmortem times, and those corneas with positive postwash cultures were identified as being at higher risk for fungal contamination in organ culture.

The fate of experimental organ-cultured corneal xenografts.

Human, chicken, and guineapig corneas organ cultured (O.C.) from 1 to 4 weeks were transplanted intralamellarly into rabbits. Chicken and guinea pid corneal xenografts O.C 3 to 4 weeks had statistically significant delayed rejection times reject. Histologically, O.C. xenografts with delayed rejection or nonrejection were hypocellular. Chicken xenografts O.C. 4 weeks in which recipient (autochthonous) rabbit serum replaced the calf serum routinely used in the media also had a significant delay in rejection time when compared to fresh controls or chicken xenografts stored in pooled (allogeneic) rabbit serum. The rejection time of human corneal xenografts O.C. FOR PERIODS UP TO 4 WEEKS WAS NOt delayed. These data suggest that in this model, prolonged survival of xenografts after O.C. is species specific and represents a form of immunological modification, possibly reduced antigenicity sedondary to donor hypocellularity.