Effect of factors unrelated to tissue matching on corneal transplant endothelial rejection

Corneal Transplantation for Infectious Keratitis: A Prospective Dutch Registry Study

PURPOSE

The aim of this study was to analyze real-world practice patterns and graft survival after corneal transplantation for infectious keratitis in the Netherlands.

METHODS

All consecutive keratoplasties for infectious keratitis registered in the Netherlands Organ Transplant Registry were included. Graft survival was analyzed using Kaplan-Meier survival curves with Cox regression to compare the 3 most common pathogens with subgroup analysis for type and reason of transplantation, sex, and graft size. Multivariable analysis was performed using the same explanatory factors.

RESULTS

Between 2007 and 2017, 1111 keratoplasties for infectious keratitis were registered in the Netherlands Organ Transplant Registry. The most common pathogens were viruses (n = 437), bacteria (n = 271), and Acanthamoeba (n = 121). Human leukocyte antigen (HLA) matching did not provide a significant survival benefit, whereas emergency procedures showed worse graft survival [hazard ratio (HR) = 0.40, P = 0.120; HR = 2.73, P < 0.001, respectively]. Graft size >8.5 mm was significantly worse than graft size 8.5 mm (HR = 2.062, P = 0.010). In therapeutic keratoplasty, graft survival was significantly worse for Acanthamoeba than viral keratitis (HR = 2.36, P = 0.008). In the multivariable model, adjusting for graft size, type, and reason for transplantation, viral and bacterial keratitis did not differ significantly in graft survival, and Acanthamoeba showed a significantly worse prognosis (vs. viral keratitis, HR = 2.30, P < 0.001; bacterial keratitis, HR = 2.65, P < 0.001).

CONCLUSIONS

Viral keratitis was the most common indication for transplantation, followed by bacterial and Acanthamoeba keratitis. HLA matching did not offer protection over elective non-HLA-matched procedures, whereas emergency procedures and grafts sized >8.5 mm showed poor survival. In optical keratoplasty, survival is high for all pathogens, whereas in therapeutic keratoplasty Acanthamoeba shows poor outcome.

Risk factors for graft failure after penetrating keratoplasty

The objective of our study was to define principal risk factors for graft failure in patients who underwent penetrating keratoplasty (PK).Retrospective data obtained from a cohort of 895 penetrating keratoplasties performed between 2001 and 2006 were analysed. Recipient related factors, graft characteristics, and surgical technique were assessed in a univariate analysis and with a multivariate proportional hazard model to detect principal risk factors for definitive graft failure.Multivariate analysis showed clear significance for diagnosis and number of previous grafts and border line significance for the oldest donor age group. Patients with keratoconus had the best 10-year survival estimate (95%), followed by endothelial and stromal dystrophies (both 55%), infectious leukomas (49%), trauma (33%) and chemical burns (14%). Primary PK grafts had a survival rate of 81%, second grafts of 33% and third or more grafts of 16%. Overall 10-year survival estimate based on univariate analysis was found to be 65%.In conclusion, we found that primary diagnosis and previous graft failures in the recipient are the most important risk factors of graft failure after a PK.

Deep anterior lamellar keratoplasty: A surgeon's guide

Purpose

To review and highlight important practical aspects of deep anterior lamellar keratoplasty (DALK) surgery and provide some useful tips for surgeons wishing to convert to this procedure from the conventional penetrating keratoplasty (PK) technique.

Methods

In this narrative review, the procedure of DALK is described in detail. Important pre, intra, and postoperative considerations are discussed with illustrative examples for better understanding. A comprehensive literature review was conducted in PubMed/Medline from January 1995 to July 2017 to identify original studies in English language regarding DALK. The primary endpoint of this review was the narrative description of surgical steps for DALK, its pitfalls, and management of common intraoperative complications.

Results

A standard DALK procedure can be successfully performed taking into consideration factors such as age, ophthalmic co-morbidities, status of the crystalline lens, retina, and intraocular pressure. Careful trephination and dissection of the host cornea employing appropriate technique (such as big bubble technique, manual dissection, visco-dissection, etc.) suitable for the specific case is important to achieve good postoperative outcomes. Prompt identification of intraoperative complications such as double bubble, micro and macroperforations, etc. are vital to change the management strategies.

Conclusion

Although there is a steep learning curve for DALK procedure, considering details and having insight into the management of intraoperative issues facilitates learning and reduces complication rates.

Effect of Histocompatibility Y Antigen Matching on Graft Survival in Primary Penetrating Keratoplasty

PURPOSE

To investigate the influence of histocompatibility Y (H-Y) antigen matching on corneal graft survival in primary penetrating keratoplasty (PK).

METHODS

Medical records of patients who underwent primary PK at Seoul National University Bundang Hospital between June 2005 and October 2015 were retrospectively analyzed. The eyes were classified into 2 groups: H-Y-compatible (115 eyes) and H-Y-incompatible (23 eyes). The H-Y-compatible group included donor/recipient combinations of male/male (57 eyes), female/male (44 eyes), and female/female (14 eyes). The H-Y-incompatible group included the male/female (23 eyes) combination alone. A subgroup analysis of low- and high-risk patients according to preoperative diagnoses was also performed. Survival analysis was conducted using the Kaplan-Meier method; differences between groups were assessed with a log-rank test.

RESULTS

A total of 138 eyes from 136 patients (age: 58 ± 18 years) were enrolled. Rejection-free graft survival and graft survival were not significantly different between H-Y-compatible and H-Y-incompatible groups (χ = 0.4, P = 0.548; χ = 1.9; P = 0.17, respectively). Preoperative diagnoses of high-risk cases included those with corneal perforation or thinning (8.7%) and infectious keratitis (7.2%). Low-risk cases included corneal opacity (50.0%), bullous keratopathy (25.4%), keratoconus (5.8%), and corneal dystrophy (2.9%). In the high-risk group, rejection-free graft survival rate was significantly higher in the H-Y-compatible group (χ = 3.9, P = 0.049).

CONCLUSIONS

H-Y antigen matching does not influence graft rejection and failure in cases of primary PK. However, matching the H-Y antigen could help reduce graft rejection, especially in preoperatively high-risk patients.

Angiogenesis and lymphangiogenesis in corneal transplantation-A review

Corneal transplantation has been proven effective for returning the gift of sight to those affected by corneal disorders such as opacity, injury, and infections that are a leading cause of blindness. Immune privilege plays an important role in the success of corneal transplantation procedures; however, immune rejection reactions do occur, and they, in conjunction with a shortage of corneal donor tissue, continue to pose major challenges. Corneal immune privilege is important to the success of corneal transplantation and closely related to the avascular nature of the cornea. Corneal avascularity may be disrupted by the processes of angiogenesis and lymphangiogenesis, and for this reason, these phenomena have been a focus of research in recent years. Through this research, therapies addressing certain rejection reactions related to angiogenesis have been developed and implemented. Corneal donor tissue shortages also have been addressed by the development of new materials to replace the human donor cornea. These advancements, along with other improvements in the corneal transplantation procedure, have contributed to an improved success rate for corneal transplantation. We summarize recent developments and improvements in corneal transplantation, including the current understanding of angiogenesis mechanisms, the anti-angiogenic and anti-lymphangiogenic factors identified to date, and the new materials being used. Additionally, we discuss future directions for research in corneal transplantation.

MicroRNA-122 ameliorates corneal allograft rejection through the downregulation of its target CPEB1

Transplant rejection is a major cause of corneal transplantation failure. MicroRNAs (miRNAs) are a family of small RNAs that regulates gene expression in a sequence-specific manner. miRNAs have recently been shown to have important roles in human organ transplantation, but reports of miRNAs directly associated with corneal transplantation rejection remain limited. To investigate the role of miRNAs during corneal allograft rejection, we established a mouse penetrating keratoplasty model and used microarrays to screen for differentially expressed miRNAs. Our results revealed that the expression of miR-122 was significantly decreased in the allogeneic group. Consistent with this result, the expression of cytoplasmic polyadenylation element-binding protein-1 (CPEB1), a direct target of miR-122, was significantly increased. Further analysis demonstrated that miR-122 inhibited inflammatory cytokine-induced apoptosis in corneal keratocytes through the downregulation of its target CPEB1. We also found that increased miR-122 expression significantly reduced the risk of corneal transplantation rejection. Thus, our results indicate that miR-122 is an important miRNA associated with corneal graft rejection and can be used as a therapeutic target for the prevention of immune rejection after keratoplasty.

Penetrating Keratoplasty for Keratoconus With and Without Resolved Corneal Hydrops: Long-term Results

PURPOSE

To evaluate the long-term risk of endothelial rejection, graft survival, and associated factors following penetrating keratoplasty (PK) for keratoconus, with and without prior resolved corneal hydrops.

DESIGN

Retrospective cohort study.

METHODS

Primary outcome measures were endothelial rejection-free survival and failure-free survival. Secondary outcome measures were corneal neovascularization following hydrops and complications following PK.

RESULTS

A total of 245 eyes underwent PK for keratoconus with mean follow-up of 5.6 ± 3.6 years. Eyes with prior hydrops (n = 74) had lower endothelial rejection-free survival rates compared with eyes without prior hydrops: 86.5% ± 4.0% vs 86.5% ± 2.6% at 1 year, 61.0% ± 6.2% vs 76.9% ± 3.3% at 5 years, and 45.8% ± 10.1% vs 70.9% ± 4.3% at 10 years, respectively (P = .023). Multivariate analysis identified factors associated with endothelial rejection as age ≤25 years (P = .017), corneal neovascularization (P = .001), donor trephination size >8 mm (P = .017), and poor clinic attendance (P = .015). There was no difference in the failure-free survival rates with and without prior hydrops: 98.6% ± 1.3% vs 97.1% ± 1.3% at 1 year, 97.3% ± 1.9% vs 95.1% ± 1.9% at 5 years, and 97.3% ± 1.9% vs 92.2% ± 2.7% at 10 years, respectively (P = .42). Corneal neovascularization was present at the time of PK in 44.6% of eyes with prior hydrops and 7.6% without prior hydrops (P < .001).

CONCLUSIONS

Corneal neovascularization, a frequent complication of corneal hydrops, was associated with increased risk of endothelial rejection following PK. However, allograft survival was similar in eyes with and without prior hydrops.

Corneal graft rejection 10 years after penetrating keratoplasty in the cornea donor study

PURPOSE

The aim of this study was to assess the effect of donor and recipient factors on corneal allograft rejection and evaluate whether a rejection event was associated with graft failure.

METHODS

One thousand ninety subjects undergoing penetrating keratoplasty for a moderate risk condition (principally Fuchs dystrophy or pseudophakic corneal edema) were followed for up to 12 years. Associations of baseline recipient and donor factors with the occurrence of a rejection event were assessed in univariate and multivariate proportional hazards models.

RESULTS

Among 651 eyes with a surviving graft at 5 years, the 10-year graft failure (±99% confidence interval) rates were 12% ± 4% among eyes with no rejection events in the first 5 years, 17% ± 12% in eyes with at least 1 probable, but no definite rejection event, and 22% ± 20% in eyes with at least 1 definite rejection event. The only baseline factor significantly associated with a higher risk of definite graft rejection was a preoperative history of glaucoma, particularly when previous glaucoma surgery had been performed and glaucoma medications were being used at the time of transplant (10-year incidence 35% ± 23% compared with 14% ± 4% in eyes with no history of glaucoma/intraocular pressure treatment, P = 0.008).

CONCLUSIONS

Patients who experienced a definite rejection event frequently developed graft failure raising important questions as to how we might change acute and long-term corneal graft management. Multivariate analysis indicated that previous use of glaucoma medications and glaucoma filtering surgery was a significant risk factor related to a definite rejection event.

Outcome of "mushroom" pattern femtosecond laser-assisted keratoplasty versus conventional penetrating keratoplasty in patients with keratoconus

PURPOSE

The aim of this study was to compare the outcomes of "mushroom" femtosecond laser-enabled keratoplasty (M-FLEK) with those of conventional penetrating keratoplasty (PKP) in eyes with keratoconus. The femtosecond laser-enabled "mushroom" pattern keratoplasty technique results in less postoperative astigmatism and higher endothelial cell counts compared with conventional PKP in patients with keratoconus.

METHODS

This was a nonrandomized retrospective, single private center clinical study. Between March 2010 and April 2012, 26 eyes underwent M-FLEK and 33 eyes underwent conventional PKP. Data on preoperative and postoperative manifest refraction, uncorrected visual acuity and best-corrected visual acuity (BCVA), endothelial cell counts, vector analysis, and complications were retrieved and analyzed.

RESULTS

At 12 months of follow-up, the mean logMAR BCVA was 0.31 ± 0.55 in the M-FLEK group and 0.32 ± 0.21 in the PKP group (P = 0.91). The mean spherical equivalent was similar between the groups. The mean manifest cylinder was significantly lower in the M-FLEK group (-2.84 ± 1.08 diopters) than in the PKP group (-3.93 ± 2.26 diopters; P = 0.03). There was a smaller mean endothelial cell loss in the M-FLEK group compared with the PKP group (32.1% vs 38.7%, respectively, P = 0.17) 1 year postoperatively. The complication rates were similar for both groups.

CONCLUSIONS

M-FLEK appears to be a safe procedure that results in less astigmatism and a trend toward higher endothelial cell counts compared with conventional PKP, with similar postoperative BCVA.

Corneal allograft reaction associated with nonocular inflammation

Corneal allograft rejection is known to have many risk factors, including ocular infection and inflammation. Although not reported in the literature, local nonocular inflammation may also have the ability to incite a graft reaction. We report 2 cases, one with dental inflammation and the other with a facial abscess, with simultaneous corneal transplant rejection. Possible pathophysiology and a review of the literature are given.

Topical 0.03% tacrolimus preventing rejection in high-risk corneal transplantation: a cohort study

BACKGROUND/AIMS

The present study aims to identify the rate of rejection and safety of 0.03% tacrolimus eye drops associated with 1% prednisolone in a topical formulation, comparing them with the use of 1% prednisolone eye drops alone in patients with high-risk corneal transplantation.

METHODS

Retrospective cohort study with 72 patients (72 eyes) who underwent more than one penetrating keratoplasty (PK) in the same eye or had severe chemical burn between 2004 and 2011 in the department of cornea and external disease of the Clinical Hospital of Porto Alegre, Brazil. We compared the records of 36 patients that performed unilateral PK and received only 1% prednisolone eye drops between May 2004 and July 2008, with 36 patients that received 0.03% tacrolimus eye drops in addition to 1% prednisolone between August 2008 and August 2011.

RESULTS

The mean follow-up of the group exposed to tacrolimus was 23.1 months and 24.0 in the prednisolone alone group. The demographics, intraoperative and initial indications for first PK were similar between groups, as well as the number of regrafts performed. Intraocular pressure (IOP) was not statistically different among groups. Regarding irreversible rejections, topical tacrolimus showed greater protection: only seven grafts (19.4%) lost transparency against 16 (44.4%) in the 1% prednisolone alone group (p <0.05).

CONCLUSIONS

Topical 0.03% tacrolimus was effective in preventing irreversible rejection in patients with high-risk corneal transplantation without increasing IOP.

Indications and outcomes of corneal transplantation in geriatric patients

PURPOSE

To identify the most common corneal transplant procedures, indications, coexisting ocular diseases, and outcomes in elderly patients, and to compare younger geriatric patients with super-geriatric patients.

DESIGN

Retrospective case series.

METHODS

Data of all patients 65 years old and older who underwent corneal transplantation at Wills Eye Institute from April 2007 to January 2013, and were followed up for at least 1 year, were collected. Two hundred seventy-one eyes of 253 patients were divided into 2 groups according to the age of the patient.

RESULTS

Group I (65-79 years old) included 181 eyes and Group II (80 years and older) included 90 eyes. The most common indication was Fuchs endothelial dystrophy, with 78 eyes (43%) in Group I and 34 eyes (38%) in Group II. In Group I, 93 Descemet stripping endothelial keratoplasty (DSEK) (51%), 84 penetrating keratoplasty (PK) (46%), and 4 keratoprosthesis procedures(2%) were performed; in Group II, 37 DSEK (41%), 51 PK (57%), and 2 keratoprosthesis procedures (2%) were performed. Graft survival rate at last visit was 90% for Group I and 88% for Group II. Rejection occurred in 18 Group I eyes (10%) and 7 Group II eyes (8%) (P = .562).

CONCLUSION

Endothelial abnormalities were more common indications and keratoconus was a less common indication for surgery in the elderly. Fuchs dystrophy was the leading indication for surgery in both super-geriatric and younger geriatric patients. Graft survival rate was slightly higher in the younger geriatric age group but was not statistically significant. In the elderly, there is an increased prevalence of both glaucoma and retinal diseases that can affect the visual outcomes after corneal transplantation.

Long-term outcomes in patients who received a corneal graft for keratoconus between 1980 and 1986

PURPOSE

To estimate the probability of allograft rejection, graft failure, and recurrent keratoconus (KC) and to assess vision-specific quality of life 20 to 25 years after corneal transplantation for KC.

DESIGN

Retrospective case series.

METHODS

Two hundred nineteen eyes of 184 subjects were identified from the Michigan Corneal Transplantation Patient Registry as receiving corneal transplantation for KC from 1980 through 1986. Current ophthalmic examinations and the 25-item National Eye Institute Visual Function Questionnaire were obtained. Kaplan-Meier analyses were used to estimate the time-related probability of allograft rejection, graft failure, and KC recurrence. Cox regression was used to identify predictive factors of these outcomes. The 25-item National Eye Institute Visual Function Questionnaire scores were summarized with descriptive statistics.

RESULTS

Follow-up was available up to 27 years after surgery (median, 10 years). Rejection occurred in 98 of 219 grafts. Most rejections occurred in the first 2 years (probability, 41%; standard error, 3%). KC recurrence was noted in 6 grafts 9 to 20 years after surgery, with a 20-year probability of 10% (standard error, 4%). Eighteen grafts failed, with a 20-year probability of 12% (standard error, 3%). Larger host trephine size, male donor gender, and nonwhite donor race were associated with increased rejection hazard. Worse astigmatism and nonwhite recipient race were associated with increased failure hazard. Twenty-eight subjects completed the 25-item National Eye Institute Visual Function Questionnaire at an average of 23 years after surgery (range, 18 to 26 years). Their mean composite score was 84.5 (standard deviation, 12.1).

CONCLUSIONS

Allograft rejection is frequent in the 2 years after corneal graft for KC. However, the 20-year probabilities of graft failure and recurrent KC are low. Given the relative youth of KC graft recipients, these statistics should enhance the information they receive.

Corneal Allograft Rejection: Immunopathogenesis to Therapeutics

Corneal transplantation is among the most successful solid organ transplants. However, despite low rejection rates of grafts in the ‘low-risk’ setting, rejection can be as high as 70% when grafted into ‘high-risk’ recipient beds. Under normal homeostatic conditions, the avascular cornea provides a unique environment that facilitates immune and angiogenic privilege. An imbalance in pro-inflammatory, angiogenic and lymphangiogenic mediators leads to a breakdown in corneal immune privilege with a consequent host response against the donor graft. Recent developments in lamellar and endothelial keratoplasties have reduced the rates of graft rejection even more, while providing improved visual outcomes. The corneal layer against which an immune response is initiated, largely determines reversibility of the acute episode. While epithelial and stromal graft rejection may be treated with topical corticosteroids with higher success, acute endothelial rejection mandates a more aggressive approach to therapy due to the lack of regenerative capacity of this layer. However, current immunosuppressive regimens come with the caveat of ocular and systemic side effects, making prolonged aggressive treatment undesirable. With the advent of biologics, efficacious therapies with a superior side effect profile are on the horizon. In our review we discuss the mediators of ocular immune privilege, the roles of cellular and molecular immune players in graft rejection, with a focus on human leukocyte antigen and antigen presenting cells. Furthermore, we discuss the clinical risk factors for graft rejection and compare rates of rejection in lamellar and endothelial keratoplasties to traditional penetrating keratoplasty. Lastly, we present the current and upcoming measures of therapeutic strategies to manage and treat graft rejection, including an overview of biologics and small molecule therapy.

Clinical presentation, risk factors and treatment outcomes of first allograft rejection after penetrating keratoplasty in early and late postoperative period

PURPOSE

Corneal graft rejection is the most common reason for the failure of an allograft corneal transplant. We undertook this study to identify and compare risk factors and treatment outcomes for early and late corneal graft rejections after optical penetrating keratoplasty.

METHODS

A retrospective case file analysis of 880 primary penetrating keratoplasties was performed at a tertiary ophthalmic care centre. Patients were divided into early rejectors (rejection episode within 6 months postoperatively) and late rejectors (rejection episode after 6 months postoperatively). Main parameters evaluated were demographics, preoperative diagnosis and clinical signs, donor tissue details, surgical technique, details of rejection episode, treatment, and outcome information.

RESULTS

A total of 156 patients with rejection episodes were identified. Of these, 42 (26.9%) patients experienced early rejection episodes and 114 (73.1%) patients experienced late rejection episodes. Preoperative donor and recipient characteristics, surgical technique, and clinical presentation of graft rejection were found to be similar between both groups after a Bonferroni correction was applied (P>0.005). Treatment outcomes of graft rejections were not significantly different (P=0.46) between early and late rejectors, with 83% of patients responding to rejection treatment (80% early rejectors; 85% late rejectors).

CONCLUSION

Patients with early and late graft rejection have similar characteristics and both groups respond to treatment equally.

Factors influencing outcomes of the treatment of allograft corneal rejection

PURPOSE

To identify patient characteristics influencing treatment outcomes of allograft corneal rejection.

DESIGN

Retrospective case file review.

METHODS

Files containing details of first episode of corneal allograft rejections in patients who underwent penetrating keratoplasty at the Royal Victorian Eye and Ear Hospital, Melbourne, Australia from 1991 to 2006 were reviewed. Cases were divided into 2 groups based on the response to treatment for graft rejection: treatment responders and failures. Main parameters evaluated were demographic characteristics, preoperative clinical profile, donor characteristics, surgical technique, presentation, and treatment of rejection episode.

RESULTS

A total of 235 cases of graft rejection were identified, of which 195 cases (83%) were successfully treated and 40 (17%) failed to respond. Age (P = .08) and gender (P = .61) were comparable in both groups. On univariate analysis, primary diagnosis of keratoconus (P = .04) and phakic lens status at the time of surgery (P = .02) were more common in treatment responders whereas aphakic bullous keratopathy (P ≤ .01), history of glaucoma (P < .01), aphakia (P < .01), and previous grafts (P < .01) were more common among treatment failures. Multivariate analysis revealed that preoperative corneal neovascularization (adjusted odds ratio [aOR] 3.6, 95% CI: 1.3-9.7, P = .01), a larger (>9 mm) donor size (aOR 5.7, 95% CI: 1.3-24.9, P = .02), and corneal edema at presentation (aOR 4.7, 95% CI: 1.7-13.2, P < .01), were independently associated with failure of treatment of graft rejection.

CONCLUSIONS

Treatment failure in cases of corneal allograft rejection is more likely to occur among patients with corneal neovascularization, large donor graft buttons, and corneal edema at presentation.

Intracameral triamcinolone acetonide as treatment for endothelial allograft rejection after penetrating keratoplasty

PURPOSE

Intracameral injection of triamcinolone acetonide as treatment of therapy-resistant endothelial allograft rejection after penetrating keratoplasty is reported.

METHODS

A 32-year-old patient showed conventional therapy-resistant endothelial allograft rejection 2 months after penetrating keratoplasty. The patient received an intracameral injection of 4 mg in 0.1 mL of triamcinolone acetonide. Preinjection visual acuity was count fingers at 3 ft, and the graft showed diffuse haze and multiple endothelial rejection lines.

RESULTS

Within 2 weeks after injection, marked resolution of the microcystic edema and reversal of the endothelial rejection was noted. Fourteen months after injection, best-corrected visual acuity was 20/20, and intraocular pressure was 17 mm Hg without antiglaucoma therapy.

CONCLUSIONS

Intracameral injection of triamcinolone acetonide may be an additional treatment modality in the treatment of endothelial allograft rejection when traditional steroid therapies have failed.

Corneal Graft Rejection

Penetrating keratoplasty is the most widely practiced type of transplantation in humans. Irreversible immune rejection of the transplanted cornea is the major cause of human allograft failure in the intermediate and late postoperative period. This immunological process causes reversible or irreversible damage to the grafted cornea in several cases despite the use of intensive immunosuppressive therapy. Corneal graft rejection comprises a sequence of complex immune responses that involves the recognition of the foreign histocompatibility antigens of the corneal graft by the host's immune system, leading to the initiation of the immune response cascade. An efferent immune response is mounted by the host immune system against these foreign antigens culminating in rejection and graft decompensation in irreversible cases. A variety of donor- and host-related risk factors contribute to the corneal rejection episode. Epithelial rejection, chronic stromal rejection, hyperacute rejection, and endothelial rejection constitute the several different types of corneal graft rejection that might occur in isolation or in conjunction. Corneal graft failure subsequent to graft rejection remains an important cause of blindness and hence the need for developing new strategies for suppressing graft rejection is colossal. New systemic pharmacological interventions recommended in corneal transplantation need further evaluation and detailed guidelines. Two factors, prevention and management, are of significant importance among all aspects of immunological graft rejection. Preventive aspects begin with the recipient selection, spread through donor antigenic activity, and end with meticulous surgery. Prevention of corneal graft rejection lies with reduction of the donor antigenic tissue load, minimizing host and donor incompatibility by tissue matching and suppressing the host immune response. Management of corneal graft rejection consists of early detection and aggressive therapy with corticosteroids. Corticosteroid therapy, both topical and systemic, is the mainstay of management. Addition of immunosuppressive to the treatment regimen helps in quick and long term recovery. Knowledge of the immunopathogenesis of graft rejection may allow a better understanding of the immunological process thus helping in its prevention, early detection and management.

Penetrating keratoplasty in a California Brown Pelican

Fresh homologous penetrating keratoplasty (PK) was performed on the left cornea of a young adult female California Brown Pelican (Pelecanus occidentalis) for the treatment of vision-threatening corneal scarring and granulation tissue. The procedure appeared to be highly successful based on short-term clinical follow-up and histopathology results. However, the patient died from unrelated causes before long-term follow-up could be obtained.

Risk Factors for the First Episode of Corneal Graft Rejection in Keratoconus

PURPOSE

To evaluate the relationship between topical corticosteroids and other variables and the risk for rejection after penetrating keratoplasty for keratoconus.

METHODS

The records of all keratoconus patients who, after their first penetrating keratoplasty in that eye, experienced a first episode of corneal graft rejection during a specific 3-year period were retrospectively reviewed in a case-control fashion. Twenty-three cases were identified, and they were matched with 3 controls each, for a total of 69 controls and 92 total patients. Multiple variables including steroid potency, recent steroid tapering, and length of time on the current level of steroids were analyzed to see whether there were any significant relationships between postoperative changes in steroid management and rejection. In addition, other variables such as graft size, suture technique, recent suture removal, suture status at the time of the rejection episode, and prior grafting in the fellow eye were examined to determine if any of these factors were associated with a higher risk of graft rejection.

RESULTS

Most of the proposed risk factors, including steroid dose and tapering, differing suturing techniques, loose and/or broken sutures at the time of rejection, percentage of sutures remaining at the time of rejection, and prior grafting in the fellow eye, did not correlate with the risk of rejection. Only graft size had a correlation, with host trephination size > or = 8.25 mm having a nearly sixfold increased risk of rejection (P = 0.015). Most patients (70%) were diagnosed with rejection at a scheduled office visit rather than at an emergency visit, and correspondingly, nearly one half (43%) had no symptoms when rejection was identified. There was no significant difference in final best-corrected visual acuities between the cases and controls, and 91% of the corneas that underwent rejection did not progress to graft failure, remaining centrally clear at most recent follow-up.

CONCLUSION

In this study, the most important risk factor for rejection after corneal transplantation for keratoconus was the size of the graft. Physician detection of rejection is paramount, because a graft rejection episode is more often diagnosed at a scheduled office visit than at an emergency visit. Fortunately, progression to graft failure can usually be prevented if treatment is started promptly and intensively.

Tacrolimus immunosuppression in high-risk corneal grafts

BACKGROUND

Unlike the immune privilege enjoyed by low-risk corneal grafts, high-risk corneal grafts experience rejection rates comparable to liver and kidney transplants. Systemic immunosuppression reduces the risk of rejection in high-risk corneal grafts.

METHODS

Systemic tacrolimus, a specific T cell inhibitor, was used at a mean daily dose of 2.5 mg to immunosuppress 43 patients undergoing high-risk corneal transplantation. Immunosuppression was continued for a period of 18-24 months after the high-risk corneal graft.

RESULTS

During a mean follow-up period of 33.7 months, clarity of the graft was maintained in 65% of patients. Eight patients experienced rejection episodes while on tacrolimus, and this led to graft failure in five patients.

CONCLUSION

Tacrolimus is relatively safe and effective in reducing rejection and prolonging graft survival in patients with high-risk keratoplasty compared with other series where similar immunosuppression was not used.

Donor age as a predictor of cornea transplant success

BACKGROUND

The purpose of this study was to examine the association between donor age and cornea transplant success.

METHODS

This retrospective cohort study comprised 116 patients who had cornea transplants performed for the first time. The primary analysis was performed to evaluate the time to graft failure as a function of donor age. Donor age was divided into 3 categories: (1) continuous, (2) younger than 65 versus 65 years and older, and (3) younger than 60 versus older than 70 years. We controlled for other variables that may affect graft outcome by multivariate modeling. The primary outcome was graft failure.

RESULTS

No statistically significant association was found between time to failure and donor age [adjusted hazard ratio: 1.004 (p = 0.68) for continuous age, 1.18 (p = 0.68) for age < 65 vs. > or = 65 years, and 2.10 (p = 0.089) for age < 60 vs. > 70 years]. However, with all model-building strategies, our results demonstrated that all hazard ratios calculated were greater than 1.00 for the older versus the younger aged groups.

INTERPRETATION

The influence of donor age on success of cornea transplants remains unresolved. Large, multicentre prospective cohort studies and randomized trials are needed to decisively determine the impact of donor age on cornea transplant success.

Outcomes of repeat penetrating keratoplasty and risk factors for graft failure

PURPOSE

To compare repeat penetrating keratoplasty (PKP) with primary PKP with respect to patient characteristics, survival rates, and risk factors for graft failure.

METHODS

Retrospective, consecutive, noncomparative case series of 116 patients who underwent repeat PKP and who were identified from a cohort of 696 PKPs performed by one surgeon over a 7.5-year period.

RESULTS

Compared with patients who underwent primary PKP, regraft patients were 5 years older, had a higher rate of peripheral anterior synechiae (PAS), were more likely to require intraocular pressure (IOP)-lowering medications prior to surgery, were more likely to develop postoperative corneal neovascularization, were less likely to be phakic, and were more likely to undergo PKP in conjunction with a lens procedure. There was no difference between the two groups with respect to the distribution of original diagnoses leading to PKP and the rate of graft rejection. Two- and 5-year survival rates for repeat PKP were 63.9% and 45.6%, respectively. In a multivariate analysis, the original diagnosis leading to corneal transplantation, the presence of preoperative PAS, intraoperative anterior vitrectomy, and postoperative corneal neovascularization were identified as risk factors for graft failure in patients undergoing a regraft.

CONCLUSIONS

Patients undergoing PKP for the first and second time share common risk factors for graft failure, namely, the original diagnosis leading to corneal transplantation, the presence of preoperative PAS, and the occurrence of postoperative corneal neovascularization. The difference in graft survival rates between the two groups can be partially explained on the basis of higher rates of the latter two risk factors among regrafts.

The potential of antibody-based immunosuppressive agents for corneal transplantation

Corneal transplantation is a sight-restorative procedure but its success is limited by irreversible graft rejection, which accounts for up to 50 per cent of failures. The normal eye is an immune-privileged site. Multiple mechanisms maintain ocular privilege, including the blood-eye barrier, the lack of blood vessels and lymphatics in the normal cornea, the relative paucity of mature antigen-presenting cells in the central cornea, the presence of immunomodulatory factors in ocular fluids, and the constitutive expressive of CD95L (Fas ligand) within the eye. However, privilege can be eroded by the sequelae of inflammation and neovascularization. Corneal graft rejection in humans is currently suppressed with topical glucocorticosteroids, which are moderately effective. Systemically administered immunosuppressive therapy is of limited efficacy and may be accompanied by unacceptable morbidity. Alternative therapies are needed to improve outcomes. Corneal graft rejection is primarily a cell-mediated response controlled by the CD4+ T cell, and thus CD4 and costimulatory molecule blockade are appealing targets for new therapeutic interventions. A number of monoclonal antibodies have shown promise as immunosuppressants to prolong corneal graft survival in experimental animal models, and may eventually prove to be useful adjuncts to corticosteroids.

Randomised controlled trial of corticosteroid regimens in endothelial corneal allograft rejection

AIM

To determine whether the addition of systemic corticosteroid to local intensive corticosteroid therapy of endothelial corneal allograft rejection improves outcome.

METHODS

A prospective randomised treatment trial was carried out at a tertiary referral centre. 36 consecutive corneal graft recipients, presenting with a first episode of endothelial graft rejection, received either (i) one intravenous pulse of methylprednisolone 500 mg in addition to local corticosteroid treatment, or (ii) local treatment only. The regimen of local treatment standardised in all cases for the first 24 hours consisted of one subconjunctival betamethasone 2 mg injection and dexamethasone 0.1% drops in the affected eye every hour for 24 hours.

RESULTS

Failure to reverse the graft rejection episode was found in 3/36 (8%) patients. Each of these had been treated with local steroid only. Graft failure from any cause occurred in 9/36 (25%) within 2 years of follow up. No statistically significant difference was found between the two groups with regard to reversal of the graft rejection episode, later recurrence of graft rejection, or graft failure.

CONCLUSIONS

In treatment of graft rejection, additional systemic treatment with 500 mg methylprednisolone yields no significant benefit over intensive local corticosteroid alone. Graft survival following treatment of a rejection episode with local corticosteroid treatment alone is good in those patients without other risk factors for graft failure and much higher than reported previously.

Prolonged survival of corneal allografts incubated in alloantibody fragments

BACKGROUND

In this study, we determined the binding characteristics of F(ab')2 alloantibody fragments to corneal antigens and assessed the capacity of these antibody fragments to protect corneal allografts from immune attack.

METHODS

Goat anti-rabbit alloantibodies were pepsin-digested and labeled with 125I, and the time course of association and dissociation of the F(ab')2 fragments was determined. Corneal allografts were incubated in unlabeled F(ab')2 fragments and transplanted into allogeneic recipients, and the graft survival times were recorded.

RESULTS

Binding of radiolabeled F(ab')2 fragments to rabbit cornea cells reached a maximum at 12 hr. At 32 degrees C (rabbit corneal temperature), the radiolabel eluted rapidly from the cornea, reaching baseline at 72 hr. At 4 degrees C (corneal graft storage temperature), significant amounts remained associated with the cornea at 96 hr. Mean survival time for grafts incubated in F(ab')2 anti-rabbit fragments was significantly greater than that of grafts incubated in nonimmune F(ab')2 fragments. Three of the corneal allografts incubated in goat F(ab')2 anti-rabbit fragments survived for 100 days, whereas the longest surviving control allograft incubated in goat F(ab')2 nonimmune fragments was rejected on day 24. Preincubation of corneas in unlabeled, immune F(ab')2 fragments followed by incubation in radiolabeled, immune F(ab')2 fragments suggested that antigen masking was not a factor in the prolongation of graft survival.

CONCLUSION

Based on the binding and release kinetics and the graft survival times, it appears that the protective effect of immune F(ab')2 fragments extends well beyond the binding interval of the antibody fragments to corneal cell membranes.

The use of combined intravenous pulse methylprednisolone and oral cyclosporin A in the treatment of corneal graft rejection: a preliminary study

PURPOSE

Oral cyclosporin A used in addition to high-dose intravenous pulse methylprednisolone has been shown to have an adjunctive effect in reversing the rejection of liver and renal transplants. The aim of this prospective study was to evaluate the benefits and risks of this combined drug therapy in acute corneal graft rejection.

METHODS

Eleven patients with acute corneal graft rejection received the combined regimen of a single pulse of intravenous methylprednisolone (500 mg) and a low dose of oral cyclosporin A (to maintain a trough blood level of 100-200 micrograms/l).

RESULTS

At a mean follow-up of 16.5 months (range 8-22 months) from the presentation of the graft rejection, reversal of graft rejection was achieved in 10 of 11 cases (90.9%). No recurrence of graft rejection was encountered during the study period. One patient developed a duodenal ulcer, which healed after medical treatment. No other complications were encountered.

CONCLUSIONS

The high efficacy and low risk of the combined regimen demonstrated in this preliminary study call for a larger-scale prospective double-masked study to confirm the value of this treatment protocol.

Management of conjunctival cicatrizing diseases and severe ocular surface dysfunction

Physical or chemical injuries, infections, immunologic oculocutaneous disorders, drugs, and various systemic disorders may cause scarring of the conjunctiva and disturbances of the ocular surface. Trichiasis, lid margin malposition, and dry eye may result in persistent ocular irritation. The cornea may be primarily or secondarily involved. If severe, disturbances of the ocular surface may lead to significant visual impairment. Thorough evaluation of patients and of the underlying disease process is required for optimal management. Treatment may be challenging and should be comprehensive, combining medical measures and surgical correction of structural changes. Suppression of exogenous irritants, treatment of dry eye, antiinflammatory therapy, and immunosuppressants are paramount to control the underlying disease and allow optimal surgical results. Surgical correction of trichiasis and lid margin malposition, conjunctival grafting, mucous membrane transplantation, limbal stem cell transplantation, amniotic membrane transplantation, and penetrating keratoplasty help reestablish a physiologic ocular surface. Severe cases may require keratoprosthetics for visual rehabilitation. Corneal ulceration or perforation requires prompt attention to maintain ocular integrity. Special measures should be considered for patients who require cataract or glaucoma surgery.

The effects of donor age on the outcome of penetrating keratoplasty in adults

OBJECTIVE

The purpose of the study is to determine whether there is a higher incidence of complications in adult patients receiving corneas from pediatric donors compared to those receiving corneas from adult donors.

DESIGN

The design is a follow-up of two matched cohorts.

PARTICIPANTS

The outcome of penetrating keratoplasty in 29 adult patients (age 20 years of age and older) receiving pediatric donor corneas (range, 0-5 years) was compared to that of 29 control patients matched for recipient age and diagnosis who received adult donor corneas (range, 40-70 years).

INTERVENTION

Chart review was performed.

MAIN OUTCOME MEASURES

Graft rejection, postoperative keratometry, postoperative refractive cylinder, postoperative intraocular pressure, and graft failure due to rejection were measured.

RESULTS

One or more allograft reactions occurred in 11 (37.9%) of 29 patients who received pediatric donor corneas compared to 2 (6.9%) of 29 patients who received adult donor corneas (P = 0.005, chi-square). There were a total of 20 rejection episodes in patients receiving pediatric donor corneas compared to a total of 5 rejection episodes in patients receiving adult donor corneas. The average postoperative keratometry was 46.1 diopters for the pediatric donor group and 44.0 diopters for the adult donor group (P = 0.03). There was no statistically significant difference in average refractive cylinder (P = 1.0), intraocular pressure (P = 0.26), or the incidence of graft failure due to rejection (P = 1.0) between the two groups. The average follow-up time for clear grafts was 58.3 months in the pediatric donor group and 59.9 months in the adult donor group.

CONCLUSIONS

The incidence of allograft reactions and the postoperative corneal curvature is greater in adult eyes undergoing penetrating keratoplasty with young donor corneas compared to those undergoing penetrating keratoplasty with older donor corneas. There was no difference in the incidence of graft failure due to rejection between the two groups.

Graft survival and risk factors of penetrating keratoplasty for microbial keratitis

PURPOSE

To evaluate graft survival rates and prognostic factors in relation to penetrating keratoplasty for microbial keratitis.

METHODS

The records of 95 patients treated with penetrating keratoplasty for microbial keratitis during a twenty-year period were reviewed. Data were analysed by construction of survival curves using the Kaplan-Meier non parametric method.

RESULTS

The overall survival of a clear cornea was 72% after one year, 71% after two years and 52% after five years. A significantly lower survival rate (p<0.05) was found in the presence of preoperative local risk factors such as wear of contact lenses and trauma and in inflamed eyes. In contrast, systemic diseases like diabetes, cancer or rheumatoid arthritis did not affect survival and neither did recipient age nor the degree of vascularization of the eye. Male donor buttons showed superior survival compared to female ones (p < 0.05), while females seemed to constitute the best recipients. Recurrence rates of microbial keratitis postoperatively were 11%, 16% and 24% after one, two and five years, respectively. Corresponding graft rejection rates were 9%, 15% and 27%.

CONCLUSIONS

Patients suffering from microbial keratitis have a relatively high risk of graft failure. To improve the prognosis care should be taken to minimize local risk factors. Surgery should whenever possible be performed on quiet eyes. The unexpected finding of a better prognosis for male donor buttons might suggest the preferred use of male donors in patients suffering from microbial keratitis, but the observation needs further documentation.

Association between HLA-DPB1 matching and 1-year rejection-free graft survival in high-risk corneal transplantation

We analyzed the effect of matching for HLA class II alleles on corneal graft outcome in a single-center, retrospective study from January 1991 through April 1996. The study involved 81 transplant recipients at high and low risk of corneal graft rejection, who were typed by the polymerase chain reaction-restriction fragment length polymorphism method and who completed at least 1-year of follow-up. The DRB1, DQB1, and DPB1 alleles were analyzed together and transplant recipients were subdivided into groups with matching (one to four alleles matched in the high risk or one to five alleles matched in the low risk) and without matching (no allele matched) for HLA class II. A significantly higher rate of 1-year rejection-free graft survival was revealed in high-risk transplant recipients with matching, compared with those without matching (P=0.0238). We have shown that matching for at least one HLA class II allele was actually beneficial in high-risk transplants. An analysis of matching for each allele separately, detected that only HLA-DPB1 matching was significantly associated with a higher rate of 1-year rejection-free graft survival in high-risk transplant recipients with matching (one or two alleles matched) compared with those without matching (no allele matched) (P=0.0139). In particular, matching for one DPB1 allele was significantly beneficial compared with no matching (P=0.0140). There was no significant effect of HLA-DRB1 and -DQB1 matching (P=0.3177 and P=0.2878, respectively). Furthermore, a strong association between DPB1 matching and 1-year rejection-free graft survival was observed in DRB1-incompatible high-risk transplant recipients (P=0.0308). Nevertheless, no significant effect of DPB1 matching was detected in DQB1-incompatible transplant recipients. Our findings indicate that HLA class II DNA typing is clinically relevant for corneal transplant recipients and that especially HLA-DPB1 matching has a beneficial effect in high-risk corneal transplantation.