Graft central thickness measurement by rotating Scheimpflug camera and ultrasound pachymetry after penetrating keratoplasty.

PURPOSE: To assess agreement between rotating Scheimpflug camera and ultrasound pachymetry in measuring graft central thickness, and compare reproducibility/repeatability of these methods in corneal grafts and normal corneas. DESIGN: Experimental study. PARTICIPANTS: Sixty-five patients with corneal grafts after penetrating keratoplasty and 20 controls with normal corneas (1 eye per patient). METHODS: In 45 eyes with clear grafts after penetrating keratoplasty, graft central thickness measurements were compared between the 2 methods (examiner 1). In another 20 eyes with clear grafts after penetrating keratoplasty and in 20 normal corneas, 2 independent examiners (1 and 2) each employed both methods in a first session to assess interexaminer reproducibility; measurements were then repeated by examiner 1 alone in a second session, and differences with his first session measurements used to assess intraexaminer repeatability. Paired t test, intraclass correlation coefficient (ICC) and 95% limits of agreement (95% LoA) were calculated to assess differences, correlation, and variability of methods, examiners, and first-second measurements. MAIN OUTCOME MEASURES: Graft central thickness measurements by 2 methods. Difference of measurements by 2 examiners; and difference of first-second measurements by 1 examiner, in corneal grafts and normal corneas with both methods. RESULTS: Mean graft central thickness measurement was 556.9+/-41.8 microm with the rotating Scheimpflug camera and 561.8+/-40.8 with ultrasound pachymetry (P = 0.012). There was a significant linear correlation in graft central thickness measurement between the 2 methods (r = 0.93; P<0.001) and 95% LoAs were -34 to +23.4 microm. Interexaminer and intraexaminer correlations were high with both methods: ICCs were > or = 0.94 in corneal grafts and > or = 0.98 in normal corneas. Interexaminer and intraexaminer variability was slightly higher with the rotating Scheimpflug camera than with ultrasound pachymetry, and in corneal grafts than in normal corneas. CONCLUSIONS: Measurements of graft central thickness with the rotating Scheimpflug camera, although slightly lower, were comparable to those with ultrasound pachymetry. The reproducibility and repeatability of these methods in corneal grafts are only slightly lower than in normal corneas.

Keratocyte density and recovery of subbasal nerves after penetrating keratoplasty and in late endothelial failure.

OBJECTIVE: To determine central keratocyte and subbasal nerve densities in clear and failed grafts after penetrating keratoplasty. METHODS: Clear grafts and grafts with late endothelial failure (LEF) were examined using confocal microscopy 1 to 31 years after penetrating keratoplasty. Keratocyte density, number of keratocytes in a full-thickness column of stroma, and subbasal nerve density were determined from images. Comparisons were made with normal corneas. RESULTS: The mean +/- SD keratocyte density in clear grafts (22 101 +/- 3799 cells/mm(3)) was lower than that in normal corneas (26 610 +/- 3683 cells/mm(3); P < .001) but did not differ from that in grafts with LEF (21 268 +/- 3298 cells/mm(3); P = .47). The mean +/- SD number of keratocytes in clear grafts (10 325 +/- 1708 cells) was lower than that in normal corneas (11 466 +/- 1503 cells; P < .001) but did not differ from that in grafts with LEF (10 778 +/- 1760 cells; P = .39). Median subbasal nerve density in clear grafts (150 microm/mm(2)) was lower than that in normal corneas (7025 microm/mm(2); P < .001), and nerve recovery correlated with time after surgery (r = 0.36; P < .001). CONCLUSIONS: Keratocyte density and number are decreased in penetrating grafts compared with normal corneas. Subbasal nerve density does not recover to normal through 3 decades.

Recurrence of keratoconus in two corneal grafts after penetrating keratoplasty.

PURPOSE: To report the recurrence of postkeratoplasty keratoconus in 2 corneal grafts harvested from the same donor. DESIGN: Interventional case reports. METHODS: A 21-year-old-man with advanced keratoconus in his right eye and a 28-year-old-woman with corneal leucoma in her right eye underwent penetrating keratoplasty with 2 grafts coming from the same donor. Approximately 1.5 years after grafting, corneal irregularity and astigmatism caused visual acuities of the patients to decrease to counting fingers. Clinical findings and corneal topography suggested the recurrence of keratoconus. A repeat keratoplasty was performed in both patients. RESULTS: Histopathology of the excised corneal grafts was consistent with keratoconus and confirmed the preoperative diagnosis. CONCLUSIONS: Recurrence of keratoconus in a patient who had no preexisting keratoconus and in 2 corneal grafts coming from the same donor suggested transmission of the disorder from the donor instead of true recurrence.

Comparison of optical low-coherence reflectometry and ultrasound pachymetry in measuring corneal graft thickness.

PURPOSE: To compare optical low-coherence reflectometry (OLCR) and ultrasound pachymetry in measuring corneal graft thickness in patients after keratoplasty. METHODS: We retrospectively measured the central graft thickness in 41 eyes of 41 patients with the OLCR pachymeter (Haag Streit, Koeniz, Switzerland) and the SP-2000 contact ultrasound pachymeter (Tomey, Nagoya, Japan). Five separate measurements were performed on each eye with both methods. Mean, SD, repeatability, and coefficient of variation of measurements were calculated, and the correlation between the 2 methods was studied with Spearman regression. RESULTS: Mean central graft thickness was 546 +/- 51 (SD) microm with the contact ultrasound pachymeter and 546 +/- 47 microm with the OLCR pachymeter. The correlation between both methods was strong (rs = 0.96). No significant differences in mean SD of measurements were observed between OLCR pachymetry (mean SD = 4.66 microm) and contact ultrasound pachymetry (mean SD = 4.88 microm). The repeatability of both methods was comparable (P = 0.06) and high (the average coefficient of variation of the central corneal graft thickness was 0.9% with both pachymeters). The postoperative time did not affect the correlation between both pachymeters (P > 0.05). CONCLUSIONS: Central corneal graft thickness values obtained with the OLCR pachymeter were similar to those obtained with a contact ultrasound pachymeter. In some cases of lamellar keratoplasty, the corneal refractive index could change at the interface level that could affect OLCR measurements.

In vivo confocal microscopy of corneal grafts shortly after penetrating keratoplasty.

PURPOSE: To describe the microstructural status of corneal grafts shortly after penetrating keratoplasty (PK) and to evaluate the efficacy and safety of confocal microscopy in examining corneal grafts at that time. METHODS: A confocal microscope with a 40 x front lens was used to examine corneal grafts in 32 patients (32 eyes) 4 days after PK. Images were analyzed, and endothelial cell density counts were compared with presurgical, eye bank values determined by specular microscopy. RESULTS: Microstructural alterations of the graft included epithelial and stromal edema, epithelial degeneration in both superficial and basal cell layers, dark stromal striae, activated keratocytes, and needle-like structures in the stroma. Descemet membrane folds were visible in 31 of 32 grafts; in 1 graft, the dense stromal edema did not allow imaging of posterior layers. Stromal nerve fibers were imaged in 28 grafts (88%). Endothelial cell density ranged from 1666 to 2548 cells/mm2 (mean+/-SD, 2125+/-283 cells/mm2); perioperative endothelial cell density loss varied from 0% to 29% (mean, 12%). No adverse reactions or signs of worsening of clinical condition were observed after the examination. CONCLUSIONS: White light scanning slit confocal microscopy permits imaging of a graft's microstructure (including epithelium and stromal layers), as well as calculation of endothelium cell density, as soon as 4 days after PK. The most frequently observed morphologic alterations of corneal grafts shortly after PK include epithelial and stromal edema, epithelial degeneration, stromal striae, and Descemet membrane folds. Stromal nerves can still be seen in the graft 4 days after PK.

A longitudinal case series investigating cellular changes to the transplanted cornea using confocal microscopy.

PURPOSE: To perform a longitudinal evaluation of subjects who had undergone penetrating keratoplasty, using slit scanning confocal microscopy. METHODS: In vivo confocal microscopy was used to evaluate the central cornea of four subjects who had recently undergone penetrating keratoplasty. Subjects were examined on four occasions over a 12-month period after surgery. Quantitative and qualitative aspects of corneal morphology were compared against data from normal control subjects. RESULTS: The epithelium varied in appearance between subjects and took at least 12 months to return to a similar arrangement to that seen in normal eyes. Bowman's layer was viewed as an acellular layer immediately after surgery with no evidence of nerve fibres, although nerve components were apparent 12 months after surgery. Stromal nerves were not visible immediately after surgery. One year following penetrating keratoplasty there was evidence of thin nerves running a straight course through the central stroma. Keratocyte density in the anterior and posterior stroma was lower in the transplanted cornea but appeared to remain constant over a period of 1 year. Activated keratocytes were seen in the anterior stroma of all subjects; they appeared to be responsible for significant levels of corneal haze. The time period within which this keratocyte activation occurred varied between individuals. Endothelial cell density decreased at an accelerated rate over the 12-month period. CONCLUSIONS: Confocal microscopy allows cellular changes to be monitored in vivo following penetrating keratoplasty and may assist clinicians in understanding postoperative recovery.

Promotion of murine orthotopic corneal allograft survival by systemic administration of anti-CD4 monoclonal antibody.

A mouse model of orthotopic corneal allograft rejection was used to examine the efficacy of anti-CD4 and anti-CD8 monoclonal antibodies in preventing immunologic rejection of corneal allografts. Although it is believed by many that corneal graft rejection is mediated, at least in part, by CD8-positive cytotoxic T-lymphocytes, systemic administration of anti-CD8 antibody did not reduce the rejection rate of corneal allografts that differed from the host at the entire major histocompatibility complex. By contrast, systemic administration of anti-CD4 monoclonal antibody reduced the rejection rate from 83% (untreated controls) to 33%. Fluorocytometric analysis of residual lymphoid populations showed that neither monoclonal antibody eliminated the inappropriate subset of T-cells in antibody-treated animals. In vitro cell-mediated cytotoxicity assays showed that both antibodies eliminated allospecific cytotoxic T-lymphocyte populations; however, only anti-CD4 antibody promoted graft survival. Thus, these results indicate that anti-CD4 monoclonal antibody is a powerful immunosuppressive agent for promoting corneal graft survival and that CD8-positive T-cells alone do not cause rejection of corneal allografts.

Keratocyte activation and apoptosis in transplanted human corneas in a xenograft model.

PURPOSE: To study keratocyte activation and cellular apoptosis in transplanted human corneas during the early postoperative period. METHODS: Ten human donor corneas preserved for 6 days at 4 degrees C were transplanted into the eyes of 10 adult cats. After confocal and specular microscopy in vivo 1 week after keratoplasty, the cats were killed, and the fixed corneas were examined by TUNEL assay and by scanning (SEM) and transmission electron microscopy (TEM). RESULTS: Abnormal keratocytes, in which portions of cell bodies and processes as well as nuclei were visible, were present in all corneas and occupied the anterior 16 to 562 microm of the stroma. By TEM in the same corneas, these abnormalities represented keratocytes that were activated to a repair phenotype. Only 0% to 1% of all corneal cells were apoptotic by TUNEL assay, except for the donor keratocytes near the wound, where 7% were apoptotic. The midstromal keratocyte density was decreased at 13,936 +/- 5,910 cells/mm(3) (mean +/- SD), and the endothelial cell density was 2,298 +/- 688 cells/mm(2), representing an endothelial cell loss of 7% +/- 16%. CONCLUSIONS: Substantial keratocyte activation and low levels of cellular apoptosis occur 1 week after human corneal transplantation. The human-to-cat xenograft model of corneal transplantation demonstrated endothelial cell loss and other clinical findings similar to human allografts. The model will be useful for preclinical testing of new methods of long-term corneal preservation and of donor endothelial cell augmentation, as well as the study of human corneal wound healing and keratocyte replacement during the early postoperative period.

Effect of alloantibodies on corneal allograft survival.

PURPOSE: The precise role of antibodies in corneal transplantation is ambiguous, with evidence to support as well as repudiate their involvement in graft rejection. Accordingly, this study was undertaken to investigate the direct contribution of donor-specific antibodies to corneal graft rejection. METHODS: Serum samples from CB6F1 rejecters of orthotopically grafted C3H/Hej corneas were tested by ELISA for elevated levels of donor-specific alloantibody. Orthotopic corneal allograft rejection was also examined in B-cell-deficient mice. In a prospective study, naïve BALB/c T-cell-deficient nude mice and complement-depleted nude mice were passively infused with immune donor-specific serum and grafted with fully allogeneic C57BL/6J corneas. The incidence and speed of graft rejection were observed in each case. The susceptibility of corneal cells to antibody-mediated lysis was tested in vitro. RESULTS: Seventy percent of the CB6F1 hosts that rejected the C3H/Hej corneal allografts possessed significantly elevated levels of alloantibody in serum. Although BALB/c corneal allografts were rejected by B-cell-deficient mice at the same incidence as wild-type control mice, their mean survival time (MST) was significantly longer than that of their wild-type counterparts. Serum of BALB/c mice immunized against C57BL/6J alloantigens produced complement-dependent cytolytic activity against C57BL/6J corneal cells in vitro. Passive transfer of this alloantiserum to T-cell-deficient BALB/c nude mice produced complement-dependent corneal lesions, resulting in significantly increased opacity of C57BL/6J corneal grafts, compared with the relatively clear grafts in control hosts. CONCLUSIONS: Alloantibody, although not necessary for corneal graft rejection, can produce extensive injury to corneal allografts in a complement-dependent manner.

Ultrastructural and molecular analysis of Bowman's layer corneal dystrophies: an epithelial origin?

PURPOSE: Two mutations (R555Q and R124L) in the BIGH3 gene have been described in anterior or Bowman's layer dystrophies (CDB). The clinical, molecular, and ultrastructural findings of five families with CDB was reviewed to determine whether there is a consistent genotype:phenotype correlation. METHODS: Keratoplasty tissue from each patient was examined by light and electron microscopy (LM and EM). DNA was obtained, and exons 4 and 12 of BIGH3 were analyzed by polymerase chain reaction and single-stranded conformation polymorphism/heteroduplex analysis. Abnormally migrating products were analyzed by direct sequencing. RESULTS: In two families with type I CDB (CDBI), the R124L mutation was defined. There were light and ultrastructural features of superficial granular dystrophy and atypical banding of the "rod-shaped bodies" ultrastructurally. Patients from three families with "honeycomb" dystrophy were found to carry the R555Q mutation and had characteristic features of Bowman's dystrophy type II (CDBII). CONCLUSIONS: There is a strong genotype:phenotype correlation among CBDI (R124L) and CDBII (R555Q). LM and EM findings suggest that epithelial abnormalities may underlie the pathology of both conditions. The findings clarify the confusion over classification of the Bowman's layer dystrophies.

Use of topical FK506 in a corneal graft rejection model in Lewis rats.

PURPOSE: To evaluate the immunosuppressive effect of topical FK506 on allograft corneal rejection in rats. METHODS: Lewis rats were used as recipients and Fisher rats as corneal graft donors. In Experiment 1, all rats received intraperitoneally FK506 (0.3 mg/kg per day) for 7 days to ensure equal baseline parameters. The rats then were assigned randomly to treatment with topical 0.3% FK506 or vehicle alone. In another set of experiments, rats were treated only with topical treatment. The grafts were inspected by clinical evaluation. Corneas obtained at the time of maximum rejection were used for histology and immunohistochemistry. RESULTS: The selected combination of rat strains caused 100% graft rejection in untreated animals within 2 weeks after the penetrating keratoplasty. In the treated animals, rejection was delayed until the end of topical therapy. One third of corneal grafts remained clear until day 30. Histologic and immunohistochemical studies confirmed the clinical evaluations. Untreated rat corneas had a large number of infiltrating helper-inducer T cells, macrophages, interleukin-2 receptor-expressing cells, and Ia-antigen-expressing cells. At the same timepoint, topically treated corneas showed a limited inflammatory response characterized by a 2/3 reduction in the number of infiltrating helper and cytotoxic cells, and a five-fold decrease in the expression of class I and class II major histocompatibility antigens. CONCLUSIONS: Topical FK506 treatment is an effective way of preventing corneal graft rejection in the Lewis rat corneal graft model. It shows promise as a drug to prevent corneal graft rejection in humans.

Effects of the immunosuppressant FK506 on a penetrating keratoplasty rejection model in the rat.

PURPOSE: The immunosuppressive effects of FK506 on allogeneic corneal transplantation were tested in a rat model. METHODS: Inbred-strain Lewis rats were used as recipients, and Fisher rats were used as donors. Intraperitoneal injection of FK506 (0.3, 1.0, and 3.0 mg/kg per day) was administered for 2 weeks, and the grafts were inspected by clinical evaluation. Mixed lymphocyte culture assay, using lymphocytes from recipients of penetrating keratoplasty as responder cells and irradiated splenocytes from naive Fisher or Brown Norway as stimulator cells, was used to identify allogeneic stimulation. The rejection process was studied by histology and immunohistochemistry. RESULTS: The rat strain combination developed 100% graft rejection in about 2 weeks after the penetrating keratoplasty. FK506 prolonged the graft survival in a dose-dependent manner, as observed by clinical evaluation. In mixed lymphocyte culture assay, Lewis rats that had been primed to allogeneic stimulation at the time of cornea transplantation presented significant proliferation to Fisher stimulator splenocytes. FK506 suppressed this primed lymphocyte proliferation. Immunohistochemical and histologic studies confirmed the clinical evaluations. Untreated rat corneas, at the second postoperative week, presented a large number of helper/inducer T cells, macrophages, IL-2 receptor-expressing cells, and Ia-antigen-expressing cells. In the same period, FK506-treated rats appeared normal and had no cellular infiltration. Corneas rejected after FK506 cessation had less intense cell infiltration than the control corneas. CONCLUSIONS: These data indicate that FK506 prolonged the corneal graft survival and can be a potentially useful drug in the immunotherapeutic arsenal to suppress corneal graft rejection.

Reassembly of corneal epithelial adhesion structures after excimer laser keratectomy in humans.

OBJECTIVE: To determine the pattern of long-term reformation of the adhesion structures after excimer laser phototherapeutic keratectomy. METHODS: Four corneal buttons were removed at penetrating keratoplasty 6 to 15 months after initial excimer laser phototherapeutic keratectomy. Morphometric analysis of electron micrographs of the wound bed was performed to determine the extent and pattern of reformation of hemidesmosomes, anchoring fibrils, and basal laminae. RESULTS: Eight percent of the basal epithelial cells had underlying normal anchoring fibrils at 6 months, compared with 35% at 15 months. The percentage of basal cell membrane occupied by hemidesmosomes remained fairly constant (35.2% to 37.7%). With the exception of a localized area of multilamination seen at 9 months, the cross-sectional area of basal lamina per 100 microns of basal cell membrane increased with the duration of wound healing (18.0 microns 2 at 6 months, 24.4 microns 2 at 15 months) but remained below normal levels (32 microns 2). CONCLUSIONS: These data suggest that after human excimer keratectomy, the anchoring fibrils and basal lamina do not completely normalize even after 15 months.

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.

Corneal endothelium five years after transplantation.

We asked the recipients of 500 consecutive corneal transplants to return for examination and endothelial photography at two months and at one, three, and five years postoperatively. Thirty-six regrafts and 70 fellow eyes of bilateral cases were excluded, leaving 394 eyes for analysis. We also recorded episodes of graft rejection and failure. In 129 grafts in patients who returned at each postoperative interval and had no rejection episodes, the mean endothelial cell density continued to decrease 7.8% per year from three years to five years after keratoplasty, compared with approximately 0.5% per year in unoperated-on normal corneas. The mean cell loss compared with the preoperative examination was 58.9% five years after keratoplasty. The percentage of hexagonal cells did not return to preoperative levels by five years after keratoplasty, suggesting that the endothelium continued to be unstable. The mean corneal thickness increased significantly with time. The Kaplan-Meier rates of rejection episodes and failure were 19% and 17%, respectively, five years after keratoplasty. Eyes with posterior chamber lens implants lost more endothelial cells by five years after keratoplasty than did eyes with open-looped anterior chamber lens implants. Low endothelial cell densities were statistically significantly associated with increased corneal thickness and with an increased risk of subsequent failure. The central endothelial cells of successful corneal transplants five years after keratoplasty form an unstable monolayer with continued accelerated loss of cells and abnormal cellular morphologic features. This process results in fewer endothelial cells remaining on the central graft with an associated increase in stromal swelling and graft failure.

Infection of the corneal endothelium in herpes simplex keratitis.

PURPOSE: To describe viral infection of the corneal endothelium in a patient with recurrent herpes simplex virus keratitis in the corneal graft. METHODS: Case report. A healthy 28-year-old man presented with necrotizing stromal keratitis and corneal perforation in the corneal graft. A second penetrating keratoplasty was performed. The corneal button was processed for histopathologic, immunohistochemical, and electron microscopic studies. RESULTS: Histopathologically, the corneal endothelium showed viral inclusion bodies. Herpes simplex virus antigens and viral particles were identified in stromal keratocytes and corneal endothelial cells. CONCLUSION: Productive herpes simplex virus infection of the corneal endothelial cells may contribute to corneal graft failure in recurrent herpes simplex virus infections.

Preliminary findings in corneal allograft rejection in patients with keratoconus.

PURPOSE: Classically, corneal allograft rejection is thought to be a T(H)1-mediated phenomenon. However, T(H)2-mediated allograft rejection has been reported in other transplanted organ systems, including the heart and kidney. We previously reported a form of T(H)2-mediated corneal allograft rejection in a murine model with a T(H)2 immune bias. In this study we sought to determine if there was any evidence for this form of corneal allograft rejection in humans. DESIGN: Experimental study with an interventional case series. METHODS: The clinical records of all keratoconus patients undergoing penetrating keratoplasty at the University of Texas, Southwestern Medical Center from 1994 to 1999 were reviewed. Careful attention was paid to a clinical history of atopy. Atopic patients were selected, because these patients have been shown to have a "T(H)2 immune bias." The corneal graft rejection rate in these patients and the number of repeat corneal transplants performed was determined. The experimental group consisted of patients with a clinical history of atopy and keratoconus who had at least one repeat penetrating keratoplasty for an immunologically rejected corneal transplant. Any patient with evidence of primary allograft failure was excluded from this study. Tissue specimens from these patients were embedded in paraffin, serially sectioned, stained with Giemsa stains, and examined histologically. The control group consisted of patients without a clinical history of allergy (and therefore no T(H)2 immune bias) who underwent corneal transplantation for Fuch corneal endothelial dystrophy, or aphakic/pseudophakic bullous keratopathy. Failed grafts from these control patients were also paraffin embedded, serially sectioned, stained, and examined histologically. The human experimental and control corneal specimens were compared with data obtained in a murine model of T(H)2-mediated corneal allograft rejection. Briefly, full-thickness penetrating C57BL/6ByJ corneal allografts were transplanted onto Balb/cByJ and Balb/c-IFN-gamma(tm1Ts) (Balb/c-IFN-gamma knockout) mice. Additionally, full-thickness Balb/cByJ corneal allografts were transplanted onto C57BL/6ByJ and C57BL/6ByJ-IFN-gamma(tm1Ts) mice. Corneal allograft rejection rates and mean rejection times were calculated and compared between wild-type and interferon gamma (IFN-gamma) knockout hosts. The rejected allografts were examined histologically by the same methods used in the human tissue. RESULTS: There were 84 penetrating keratoplasties performed from 1994 to 1999 for keratoconus. Seven of these 84 patients rejected their corneal grafts. Of the 7 patients who rejected their corneal allografts, 4 had repeat penetrating keratoplasty. Of these 4 repeat corneal allografts, 3 showed eosinophilia when compared with rejected grafts in control patients. Atopic keratoconus patients had a mixed inflammatory cellular infiltrate in the rejected corneal tissue specimen with a significantly greater density of eosinophils (P =.001) compared with patients who did not have a pre-existing T(H)2 bias. The inflammatory infiltrate in these patients without a T(H)2 immune bias was mononuclear. In the murine model, corneal allograft rejection did occur in the absence of IFN-gamma, a critical T(H)1 cytokine in both fully allogeneic donor-host combinations. Histologically, rejection in these ("T(H)2 mice") was characterized by a predominant eosinophilic infiltrate in the rejected graft bed when compared with wild-type animals ("T(H)1 mice") that had a predominantly mononuclear infiltrate in the rejected corneal graft bed. CONCLUSIONS: Preliminary findings show that corneal allograft rejection in patients with a pre-existing T(H)2 phenotype is similar to what is seen in the murine model of T(H)2-mediated corneal allograft rejection. Based on this small sample, it appears that eosinophils may play a role in corneal allograft rejection in this group of patients. However, further study is necessary to determine the importance of these cells in allograft rejection.

Effects of posterior chamber lens implantation on the endothelium of transplanted corneas.

AIMS: The morphological changes of the corneal endothelium after posterior chamber lens implantation in the transplanted corneas were investigated. METHODS: 36 patients underwent extracapsular cataract extraction with posterior chamber lens implantation. Among these, penetrating keratoplasty had been performed in 18 patients before cataract surgery. The indications for penetrating keratoplasty in these cases included keratoconus, herpetic keratitis, and macula cornea. 18 cataract patients with normal corneas were also studied as controls. The central corneal endothelium in each subject was examined with a wide field specular microscope at a few days before and 3 months after cataract surgery. RESULTS: Although the transplanted corneas showed lower endothelial cell densities, marked polymegethism, and pleomorphism in the baseline variables, the endothelial morphological changes in the transplanted corneas after posterior chamber lens implantation were comparable with those in the normal corneas. Also, there was no clinical evidence, especially, of corneal epithelial and/or endothelial rejections and corneal decompensation in all corneas. CONCLUSION: Even though the transplanted corneas have a lower endothelial cell density and marked polymegethism, it is believed that cataract surgery does not induce corneal decompensation in cases where the peripheral recipient endothelium can be considered to have normal morphology.

Corneal epithelium following penetrating keratoplasty.

AIMS: This study was designed to observe any changes to the corneal epithelium after penetrating keratoplasty. METHODS: The corneal epithelia of 26 patients were observed by specular microscopy 1 week, 1 month, 3 months, and 6 months following penetrating keratoplasty. RESULTS: After re-epithelialisation was confirmed by biomicroscopy 1 week after surgery, specular microscopy revealed many abnormal cells, including spindle shaped cells, nucleated cells, large cells, as well as irregular cell configurations. Although these abnormal findings tended to decrease with time, they were still present in some cases as much as 6 months postoperatively. Computerised morphometric analysis yielded mean cell areas of 1121 (SD 168) microns 2, 1139 (675) microns 2, 1712 (496) microns 2, and 1400 (377) microns 2 at 1 week, 1 month, 3 months, and 6 months respectively, all significantly greater than that of age matched controls (710 (151) microns 2). The shape factor decreased with time, but was still greater than the control level at 6 months. CONCLUSIONS: This study demonstrates that epithelial abnormalities persist longer than expected after penetrating keratoplasty, and that these subtle changes can be detected by specular microscopic observation, potentially allowing for modification and enhancement of the wound healing process.

Penetrating keratoplasty for keratoconus: a long-term review of results and complications.

PURPOSE: To study the long-term complications of penetrating keratoplasty (PKP) to evaluate current recommendations to patients with keratoconus. SETTING: John Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. METHODS: Retrospective study of all PKP procedures for keratoconus performed by 4 surgeons during a 312 year period. Follow-up was 1 day and 1, 3, 6, 12, and 24 months post-PKP. Data from 93 eyes were reviewed for allograft reaction, astigmatism, visual acuity, reasons for decreased visual acuity, and other complications. RESULTS: Allograft reaction was seen in 31% of cases but no graft failure due to allograft reaction. Mean astigmatism was 2.76 diopters (D) +/- 1.99 (SD) at 24 months, with only 15% > 5.00 D. Last best corrected visual acuity was 20/25 or better in 77% of cases (87% had 20/25 or better at some time during follow-up). Complications that did not cause decreased visual acuity were noted. Punctate keratitis was noted in 20% of patients 180 days or more after surgery. CONCLUSIONS: Penetrating keratoplasty is a good treatment option for patients with keratoconus but should be reserved for those who do not tolerate contact lenses or do not get needed visual acuity with contact lenses because of complications. This procedure has become a second-line treatment for keratoconus patients and has generally good results.