Is there evidence for a surgeon learning curve for endothelial keratoplasty in Australia?

IMPORTANCE: Expected outcomes from endokeratoplasty may vary with surgeon experience. BACKGROUND: It was explored whether a surgeon learning curve exists for Descemet stripping endothelial keratoplasties (manual or automated) performed in Australia. DESIGN: This is a prospective cohort study, with various clinical settings. PARTICIPANTS: There were 2139 recipients of 2615 endothelial grafts, registered by 85 surgeons between January 2006 and December 2013. METHODS: Kaplan-Meier survival analyses and Cox proportional hazards regression were used to examine longitudinal graft survival. Manual and automated Descemet stripping endothelial keratoplasties were analysed together. Pearson chi-squared analyses were performed to examine differences amongst groups. Continuity correction was used for 2 × 2 tests, and statistical significance was set at P < 0.05 (two-sided). MAIN OUTCOME MEASURE: The main parameter measured was endothelial graft survival. RESULTS: Survival of the first 56 registered grafts was significantly poorer than survival of subsequent grafts (χ2  = 8.83, df = 1, P = 0.003), when data were combined for all surgeons. Surgeon workload influenced graft survival significantly (P < 0.001). This variable was retained in multivariate analysis designed to investigate independent factors influencing graft survival. Primary non-functioning grafts were significantly less likely to be reported for endokeratoplasties performed by surgeons with more than 56 registered grafts, compared with those registering 56 or fewer grafts (4.3% vs. 8.5%; χ2  = 18.38, df = 1, P < 0.001). CONCLUSIONS AND RELEVANCE: Our findings suggest that for less experienced or low-volume surgeons, longitudinal graft survival improved once 56 or more endokeratoplasties had been performed, indicative of a learning curve. The learning curve was less apparent for surgeons with 57 or more Descemet stripping endothelial keratoplasties and/or Descemet stripping automated endothelial keratoplasties registered during the 8-year study period. Different learning curves may be anticipated for these two groups of surgeons.

A comparison of endothelial and penetrating keratoplasty outcomes following failed penetrating keratoplasty: a registry study.

PURPOSE: To compare graft survival and visual outcomes for endothelial keratoplasty (EK) after a first penetrating keratoplasty (PK), with outcomes of repeat PK after a first PK. METHODS: 400 eyes with a second graft (65 EKs, 335 PKs) performed after failure of a primary PK were identified through the Australian Corneal Graft Registry, a national prospectively followed cohort. Grafts were performed after January 2008 (follow-up of the second graft extending to 6.75 years maximum). Kaplan-Meier graft survival plots were constructed and Cox proportional hazards regression was used to identify independent risk factors for graft failure. Best-corrected Snellen visual acuity (BCVA) at last follow-up was compared with pregraft acuity. RESULTS: Poor Kaplan-Meier graft survival was observed for PK-EK compared with PK-PK (log-rank=29.66, p<0.001). Variables retained in multivariate analysis as significantly influencing survival of the second graft included graft type (PK-EK or PK-PK, p<0.001), length of survival of the previous PK (global p=0.011), graft era (global p=0.018), occurrence of rejection in the second graft (p=0.005) and a history of raised intraocular pressure at any time (p=0.048), but not indication for the first graft. BCVA improved in the majority of surviving grafts and attainment of 6/12 vision was similar for both PK-EK and PK-PK groups. CONCLUSIONS: Our registry findings suggest that repeat PK may deliver a better outcome in terms of graft survival than EK after a failed PK that was performed initially for keratoconus or pseudophakic bullous keratopathy. For surviving grafts, visual outcomes appeared equivalent across groups.

History of corneal transplantation in Australia.

Corneal transplantation is a triumph of modern ophthalmology. The possibility of corneal transplantation was first raised in 1797 but a century passed before Zirm achieved the first successful penetrating graft in 1905. Gibson reported the first corneal graft in Australia from Brisbane in 1940 and English established the first eye bank there a few years later. Corneal transplantation evolved steadily over the twentieth century. In the second half of the century, developments in microsurgery, including surgical materials such as monofilament nylon and strong topical steroid drops, accounted for improvements in outcomes. In 2013, approximately 1500 corneal transplants were done in Australia. Eye banking has evolved to cope with the rising demands for donor corneas. Australian corneal surgeons collaborated to establish and support the Australian Corneal Graft Registry in 1985. It follows the outcomes of their surgery and has become an important international resource for surgeons seeking further improvement with the procedure.

Deep anterior lamellar keratoplasty versus penetrating keratoplasty for treating keratoconus.

BACKGROUND: Keratoconus is an ectatic (weakening) disease of the cornea, which is the clear surface at the front of the eye. Approximately 10% to 15% of patients diagnosed with keratoconus require corneal transplantation. This may be full-thickness (penetrating) or partial-thickness (lamellar). OBJECTIVES: To compare visual outcomes after deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty for keratoconus, and to compare additional outcomes relating to factors which may contribute to poor visual outcomes (e.g. astigmatism, graft rejection and failure). SEARCH METHODS: We searched a number of electronic databases including CENTRAL, PubMed and EMBASE without using any date or language restrictions. We last searched the electronic databases on 31 October 2013. We also handsearched the proceedings of several international ophthalmic conferences. SELECTION CRITERIA: We included all randomised controlled trials (RCTs) comparing the outcomes of DALK and penetrating keratoplasty in the treatment of keratoconus. DATA COLLECTION AND ANALYSIS: Two authors assessed trial quality and extracted data independently. For dichotomous data (graft failure, rejection, achievement of functional vision) results were expressed as odds ratios (ORs) and 95% confidence intervals (CIs). For continuous data (postoperative best corrected visual acuity (BCVA), uncorrected visual acuity (UCVA), keratometric astigmatism and spherical equivalent) results were expressed as mean differences (MDs) and 95% CIs. MAIN RESULTS: We identified two completed studies, with a total of 111 participants (n = 30 and n = 81), both conducted in Iran, that met our inclusion criteria. Participants had moderate to severe keratoconus pre-operatively and were randomly allocated to receive either DALK or penetrating keratoplasty. Only one eye of each participant was treated as part of the trials. The smaller study had 12 month follow-up data for all participants. For the larger study, four DALK surgeries had to be abandoned due to technical failure and visual and refractive outcomes were not measured in these participants. Follow-up length for the remaining 77 participants ranged from 6.8 to 36.4 months, with all 77 followed for at least three months post-suture removal. Details of the randomisation procedure were unavailable for the smaller study and so sensitivity analyses were conducted to determine if the results from this study had affected the overall results of the review.Neither of the included studies reported a difference between groups on any of the measures of post-graft visual achievement, keratometric astigmatism or spherical equivalent. A single case of graft failure in a penetrating keratoplasty was reported. No postoperative graft failures were reported in the DALK group of either study.Instances of graft rejection were reported in both groups, in both studies. The majority of these cases were successfully treated with steroids. The data, which related to all cases in each study - given that the four cases that did not go ahead as planned had already technically failed without presence of rejection - showed that rejection was less likely to occur in DALK (odds ratio (OR): 0.33, 95% confidence interval (CI) 0.14 to 0.81, GRADE rating: moderate).Results of the sensitivity analysis indicated that inclusion of the Razmju 2011 study did not bias the results with regards to rejection episodes. While sensitivity analysis showed altered results with regards to failure rates, the data available from the Javadi 2010 study alone had a very wide 95% CI, suggesting an imprecise estimate. Therefore, even after removal of the Razmju 2011 data, it is still difficult to draw conclusions regarding superiority of one technique over another with regards to graft failure.DALK was unable to be completed as planned in four cases and in a further three cases, complications during dissection required further intervention. Other adverse events, of varying severity, were reported in both intervention groups with similar frequency. For both types of surgery, these included postoperative astigmatism, steroid induced ocular hypertension and persistent epithelial defects. In recipients of DALK, one participant had interface neovascularisation (a proliferation of blood vessels where the host and donor cornea come together) and one had wrinkling of Descemet's membrane, the basement membrane separating the corneal stroma from the corneal endothelium. In the penetrating keratoplasty groups, one participant required graft resuturing and one had an atonic pupil, a condition in which the pupil dilates and is non-reactive.Overall, the quality of the evidence was rated as very low to moderate, with methodological limitations, incomplete data analysis and imprecision of findings, as well as high risk of bias in several areas for both studies. AUTHORS' CONCLUSIONS: We found no evidence to support a difference in outcomes with regards to BCVA at three months post-graft or at any of the other time points analysed (GRADE rating: very low). We also found no evidence of a difference in outcomes with regards to graft survival, final UCVA or keratometric outcomes. We found some evidence that rejection is more likely to occur following penetrating keratoplasty than DALK (GRADE rating: moderate). The small number of studies included in the review and methodological issues relating to the two, mean that the overall quality of the evidence in this review is low. There is currently insufficient evidence to determine which technique may offer better overall outcomes - final visual acuity and time to attain this, keratometric stabilisation, risk of rejection or failure, or both, and risk of other adverse events - for patients with keratoconus. Large randomised trials comparing the outcomes of penetrating keratoplasty and DALK in the treatment of keratoconus are needed.

A comparison of lamellar and penetrating keratoplasty outcomes: a registry study.

OBJECTIVES: To investigate changing patterns of practice of keratoplasty in Australia, graft survival, visual outcomes, the influence of experience, and the surgeon learning curve for endothelial keratoplasty. DESIGN: Observational, prospective cohort study. PARTICIPANTS: From a long-standing national corneal transplantation register, 13 920 penetrating keratoplasties, 858 deep anterior lamellar keratoplasties (DALKs), and 2287 endokeratoplasties performed between January 1996 and February 2013 were identified. METHODS: Kaplan-Meier functions were used to assess graft survival and surgeon experience, the Pearson chi-square test was used to compare visual acuities, and linear regression was used to examine learning curves. MAIN OUTCOME MEASURES: Graft survival. RESULTS: The total number of corneal grafts performed annually is increasing steadily. More DALKs but fewer penetrating grafts are being performed for keratoconus, and more endokeratoplasties but fewer penetrating grafts are being performed for Fuchs' dystrophy and pseudophakic bullous keratopathy. In 2012, 1482 grafts were performed, compared with 955 in 2002, translating to a requirement for 264 extra corneal donors across the country in 2012. Comparing penetrating grafts and DALKs performed for keratoconus over the same era, both graft survival (P <0.001) and visual outcomes (P <0.001) were significantly better for penetrating grafts. Survival of endokeratoplasties performed for Fuchs' dystrophy or pseudophakic bullous keratopathy was poorer than survival of penetrating grafts for the same indications over the same era (P <0.001). Visual outcomes were significantly better for penetrating grafts than for endokeratoplasties performed for Fuchs' dystrophy (P <0.001), but endokeratoplasties achieved better visual outcomes than penetrating grafts for pseudophakic bullous keratopathy (P <0.001). Experienced surgeons (>100 registered keratoplasties) achieved significantly better survival of endokeratoplasties (P <0.001) than surgeons who had performed fewer grafts (<100 registered keratoplasties). In the hands of experienced, high-volume surgeons, endokeratoplasty failures occurred even after 100 grafts had been performed. CONCLUSIONS: More corneal transplants, especially DALKs and endokeratoplasties, are being performed in Australia than ever before. Survival of DALKs and endokeratoplasties is worse than the survival of penetrating grafts performed for the same indications over the same timeframe. Many endokeratoplasties fail early, but the evidence for a surgeon learning curve is unconvincing.

Comparative outcomes of penetrating and component endothelial cell corneal allografts in outbred sheep.

Lamellar (component cell) corneal transplantation is replacing penetrating keratoplasty for some corneal disorders in humans, but the relative risks of immunological graft rejection for the two procedures remain uncertain. A model of component endothelial cell keratoplasty (endokeratoplasty) was developed in outbred sheep. Clinical and histological graft outcomes after endokeratoplasty were then compared with contemporaneous penetrating corneal allografts. No topical or systemic immunosuppression was administered to any recipient sheep. Endothelial cell allografts (n = 10) took significantly longer to achieve perfect transparency following surgery than did penetrating corneal grafts (n = 7) (day 10 vs. day 4; p = 0.003; two-tailed Mann-Whitney U test). The median day to rejection of penetrating grafts was postoperative day 18; for endothelial cell grafts, it was day 48 (p = 0.04; two-tailed Mann-Whitney U test). The clinical courses of the two procedures were therefore quite different. Penetrating grafts gained clarity quickly but exhibited rapid graft neovascularization. Clinical rejection was preceded by inflammation in the anterior segment. Endothelial cell grafts exhibited a fluctuating, more indolent course of opacification, although all did eventually fail. Histological analysis confirmed immunological rejection in all failed grafts, but with different patterns of leukocytic infiltration in endokeratoplasties compared with penetrating keratoplasties. Inflammatory cells in endothelial cell grafts were generally fewer in number and were more often found in the posterior stroma. We conclude that, in the absence of immunosuppression, all endothelial cell allografts do undergo immunological rejection, albeit at a slower rate than penetrating grafts.

The influence of Australian eye banking practices on corneal graft survival.

OBJECTIVE: To identify eye banking practices that influence corneal graft survival. DESIGN, SETTING AND PARTICIPANTS: Prospective cohort study of records of 19,254 followed corneal grafts in 15160 patients, submitted to the Australian Corneal Graft Registry between May 1985 and July 2012. MAIN OUTCOME MEASURES: Influence of corneal preservation method (organ culture, moist pot, Optisol, other); death-to-enucleation, death-to-preservation and enucleation-to-graft times; transportation by air; graft era; and indication for graft on probability of graft survival at most recent follow-up. RESULTS: In multivariate analysis, 919 penetrating grafts performed using corneas transported interstate by air exhibited worse survival than 14,684 grafts performed using corneas retrieved and used locally (hazard ratio [HR], 1.44; 95% CI, 1.21-1.73; P = 0.001). This was also the case for traditional lamellar grafts (64 corneas transported by air and 813 used locally; HR, 1.69; 95% CI, 1.03-2.78; P = 0.038). Indication for graft influenced survival of penetrating grafts (4611 keratoconus, 727 emergency or high-risk, 10,265 other indication; global P < 0.001) and traditional lamellar grafts (65 keratoconus, 212 emergency or high-risk, 600 other indication; global P < 0.001). The preservation medium in which corneas used for traditional lamellar grafts were stored exerted a marginal influence on graft survival (global P = 0.047). CONCLUSIONS: Donor corneas transported interstate exhibited poorer survival after transplantation than those retrieved and grafted locally. Higher proportions of emergency procedures involving transported corneas did not account for this difference. Where possible, efforts to avoid transportation of corneal tissue by air freight within Australia may be warranted.

Replication and meta-analysis of candidate loci identified variation at RAB3GAP1 associated with keratoconus.

PURPOSE: Keratoconus is a common complex corneal ectasia that can lead to severe visual impairment. Although a genetic component is well recognized, the genetic risk factors for keratoconus are yet to be fully elucidated. A recent genome-wide association study (GWAS) by Li et al. identified 15 potentially associated single nucleotide polymorphisms (SNPs). Here, we aimed to replicate these associations, and conduct a meta-analysis of the current and previous studies. METHODS: We genotyped the 15 reported associated SNPs in 524 Australian Caucasian cases with keratoconus and 2761 controls. Association analysis was conducted in PLINK. A meta-analysis of this study with the adjusted P values of the previously published GWAS was conducted using the method of Fisher to combine P values. RESULTS: Our Australian cohort showed association (P < 0.003) at SNPs near RAB3GAP1, KCND3, IMMPL2, and in a gene desert on chromosome 13q33.3, providing evidence of replication of the published results. The meta-analysis showed SNP rs4954218 near RAB3GAP1 gene was associated significantly with keratoconus, with P = 9.26 × 10(-9) passing the genome-wide significance level. CONCLUSIONS: Although the mechanism of disease association is yet to be determined, SNP rs4954218 is associated consistently with keratoconus and likely tags a functional variant that contributes to disease susceptibility.

Expression of an anti-CD4 single-chain antibody fragment from the donor cornea can prolong corneal allograft survival in inbred rats.

AIM: To investigate whether expression of an anti-CD4 antibody fragment (scFv) by a lentivector-transduced donor cornea can prolong rat corneal allograft survival. METHODS: Inbred Fischer 344 rats received penetrating corneal allografts from Wistar-Furth donors after a 3 h transduction of the donor cornea with a lentivector carrying anti-CD4scFv cDNA (Lv-CD4scFv), a lentivector carrying the reporter gene-enhanced yellow fluorescence protein (LV-eYFP), or an adenoviral vector carrying anti-CD4 scFv cDNA (Ad-CD4scFv). Unmodified controls were also performed. Graft survival was assessed by corneal clarity, and rejection was confirmed histologically. RESULTS: In organ-cultured corneas, expression of anti-CD4 scFv was detected at 2 days post-transduction with the adenoviral vector, compared with 5 days post-transduction with the lentivector, and was 10-fold higher than the former. More inflammation was observed in Ad-CD4scFv-modified allografts than in Lv-CD4scFv-modified grafts at 15 days postsurgery (p=0.01). The median time to rejection for unmodified, LV-eYFP and Ad-CD4scFv grafts was day 17, compared with day 22 for Lv-CD4scFv grafts (p≤0.018). CONCLUSION: Donor corneas transduced with a lentiviral vector carrying anti-CD4scFv cDNA showed a modest but significant prolongation in graft survival compared with unmodified, Lv-eYFP and Ad-CD4scFv grafts. However, rejection still occurred in all Lv-CD4scFv grafts, indicating that sensitisation may have been delayed but was not prevented.

The influence of cervical and thoracic lymphadenectomy on corneal allograft rejection in inbred rats.

AIM: To investigate the site of alloantigen presentation in the rat following orthotopic corneal transplantation. METHODS: Adult inbred Fischer 344 rats received penetrating corneal allografts from inbred Wistar Furth donors (n=17), without lymphadenectomy. A second group (n=8) underwent bilateral removal of superficial cervical and facial lymph nodes 7 days before transplantation. A third group (n=9) underwent bilateral removal of superficial cervical, facial, internal jugular and posterior cervical nodes. Graft survival was assessed by corneal clarity and rejection was confirmed histologically. RESULTS: All allografts underwent rejection. The median time to rejection for unmodified allografts was day 15, compared with day 14.5 for minimally lymphadenectomised recipients and day 18 for more extensively lymphadenectomised recipients (p>0.05, all comparisons). The median day to rejection for the combined group of lymphadenectomised rats was day 17 (p>0.05 compared with unmodified grafts). The rejection process was similar in all recipients. CONCLUSIONS: Removal of multiple lymph nodes in the neck and thorax did not significantly influence the incidence, tempo or nature of the corneal allograft response. Sensitisation and clonal expansion of corneal alloantigen-reactive cells cannot occur only in superficial cervical, facial, internal jugular and posterior cervical lymph nodes in the rat.

Association of polymorphisms in the hepatocyte growth factor gene promoter with keratoconus.

PURPOSE: Keratoconus is a progressive disorder of the cornea that can lead to severe visual impairment or blindness. Although several genomic regions have been linked to rare familial forms of keratoconus, no genes have yet been definitively identified for common forms of the disease. METHODS: Two genome-wide association scans were undertaken in parallel. The first used pooled DNA from an Australian cohort, followed by typing of top-ranked single-nucleotide polymorphisms (SNPs) in individual DNA samples. The second was conducted in individually genotyped patients, and controls from the USA. Tag SNPs around the hepatocyte growth factor (HGF) gene were typed in three additional replication cohorts. Serum levels of HGF protein in normal individuals were assessed with ELISA and correlated with genotype. RESULTS: The only SNP observed to be associated in both the pooled discovery and primary replication cohort was rs1014091, located upstream of the HGF gene. The nearby SNP rs3735520 was found to be associated in the individually typed discovery cohort (P = 6.1 × 10(-7)). Genotyping of tag SNPs around HGF revealed association at rs3735520 and rs17501108/rs1014091 in four of the five cohorts. Meta-analysis of all five datasets together yielded suggestive P values for rs3735520 (P = 9.9 × 10(-7)) and rs17501108 (P = 9.9 × 10(-5)). In addition, SNP rs3735520 was found to be associated with serum HGF level in normal individuals (P = 0.036). CONCLUSIONS: Taken together, these results implicate genetic variation at the HGF locus with keratoconus susceptibility.

Repeat penetrating corneal transplantation in patients with keratoconus.

PURPOSE: To determine factors influencing penetrating corneal graft survival in patients receiving repeat grafts in the same eye after a failed first graft for keratoconus. DESIGN: Large cohort study from a national register of corneal grafts, in which data were recorded prospectively and analyzed retrospectively. Follow-up extended to 23 years. PARTICIPANTS: Follow-up was available for 229 regrafts performed in 177 eyes of 173 patients. Regrafts were performed more than once in 16 eyes. METHODS: Corneal graft survival was analyzed using Kaplan-Meier survival plots and Cox proportional hazards regression, clustered by patient. MAIN OUTCOME MEASURES: Graft survival. RESULTS: Graft survival was significantly worse (P<0.001) for second (n = 176) and third or greater grafts (n = 20), compared with first grafts for keratoconus (n = 4871). Kaplan-Meier survivals at 1, 5, and 15 years postgrafting were 88%, 69%, and 46% for second grafts, and 65%, 49%, and 33% for third and subsequent grafts, respectively (P<0.001). Risk factors associated with graft failure of repeat grafts in multivariate analysis were the geographic location of surgery ("center"; P = 0.04), failure of the previous graft within 10 years of surgery (P = 0.02), recipient age at graft ≥60 years (P = 0.04), occurrence of rejection episodes (P = 0.007), and corneal neovascularization postoperatively (P = 0.007). CONCLUSIONS: Repeat corneal grafts in eyes originally grafted for keratoconus showed better survival when the previous graft had survived ≥10 years, surgery was performed at a favorable location, the recipient was <60 years old at grafting, and graft rejection and neovascularization were circumvented. FINANCIAL DISCLOSURE(S): The authors have no proprietary or commercial interest in any of the materials discussed in this article.

Corneal transplantation for keratoconus: a registry study.

OBJECTIVE: To determine factors influencing long-term graft survival and visual acuity in 4834 eyes of 4060 patients receiving their first penetrating corneal graft for keratoconus. METHODS: A large cohort study was performed from a national register of corneal grafts in which data were recorded prospectively and analyzed retrospectively. Main outcome measures were graft survival and Snellen visual acuity. Follow-up extended up to 23 years. RESULTS: Kaplan-Meier survival rates of first grafts for keratoconus were 89%, 49%, and 17% at 10, 20, and 23 years, respectively. After 15 years, the graft survival rate was no better than that of all other penetrating grafts (P = .36). Multivariate risk factors influencing failure of first grafts for keratoconus included time to suture removal, postgraft uveitis or microbial keratitis, corneal vascularization prior to or after graft, geographic location of surgery and follow-up (center effect), recipient age at graft, occurrence of rejection episodes, graft size, and surgeon workload. The timing of bilateral grafts made no difference to the risk of rejection. A Snellen visual acuity of 20/40 or better at the most recent follow-up was recorded in 74% of grafts. CONCLUSIONS: Penetrating grafts performed for keratoconus exhibited better visual outcome and graft survival than grafts performed for other indications. However, the Kaplan-Meier survival rate of first penetrating grafts for keratoconus was 17% at 23 years after graft and had not plateaued at this time, indicating that young patients are likely to need 1 or more repeated grafts during their lifetime.

The outcome of corneal transplantation in infants, children, and adolescents.

OBJECTIVE: To examine factors affecting penetrating corneal graft survival and visual outcomes in patients aged less than 20 years. DESIGN: Large prospective, cohort study. PARTICIPANTS: Records of 14 865 followed penetrating corneal grafts in 11 929 patients were searched to identify 765 grafts in 640 patients aged younger than 20 years of age at the time of graft. METHODS: Records submitted to the Australian Corneal Graft Registry by 381 ophthalmic surgeons and 253 follow-up practitioners from May 1985 to June 2009 were analyzed using Kaplan-Meier survival plots and Cox proportional hazards regression analysis. MAIN OUTCOMES MEASURES: Probability of corneal graft survival and Snellen acuity at the time of most recent follow-up and at defined intervals post-graft. RESULTS: Infants (<5 years) exhibited poorer graft survival than children aged 5 to 12 years. Adolescents (13-19 years) exhibited better corneal graft survival than other age groups; 86% of grafts in adolescents were for keratoconus. Factors significantly affecting corneal graft survival in pediatric patients included indication for graft, graft inflammation, history of intraocular surgery, vascularization, rejection episodes, post-graft operative procedures, and refractive surgery. Fourteen percent of pediatric grafts failed, of which 65% failed within 2 years post-graft. Forty-four percent of failures were due to unknown causes (18) or irreversible rejection (30). CONCLUSIONS: Corneal grafts for keratoconus in adolescents show excellent survival. Infants exhibit poor graft survival and visual outcomes, especially those undergoing transplantation for Peters' anomaly. Corneal graft survival and visual outcomes vary more by indication for graft than recipient age. The major reason for graft failure is irreversible rejection. Corneal transplantation improves overall bilateral vision in pediatric patients.

Lentivirus-mediated gene transfer of interleukin 10 to the ovine and human cornea.

BACKGROUND: Gene transfer to a donor cornea ex vivo can modulate corneal graft failure in experimental animal models. We compared a lentiviral vector (LV) carrying the transgene ovine interleukin 10 (IL10) with a comparable adenoviral vector (Ad) for its ability to transduce ovine and human corneas and to modulate ovine corneal allograft survival. METHODS: The LV carrying the ovine IL10 gene was used to transduce ovine and human corneas in vitro. LV-mediated gene expression in corneal endothelium was assessed by real-time quantitative reverse-transcriptase polymerase chain reaction, at varying doses and duration of transduction. The effect of ex vivo transduction of the donor cornea with LV-SV40-IL10 was assessed following orthotopic corneal transplantation in outbred sheep. RESULTS: Expression of IL10 mRNA in Ad-CMV-IL10-transduced ovine corneas was 10(3)-fold higher than in LV-SV40-IL10-transduced corneas (P < 0.0001), and 10(7)-fold higher than in non-transduced controls. IL10 was secreted rapidly from Ad-CMV-IL10-transduced, organ-cultured corneas, peaking at 13-15 days. IL10 secreted from LV-SV40-IL10-transduced corneas increased 20-fold compared with controls, but had not reached a plateau at 15 days. Gene expression driven by LV-SV40-IL10 varied with vector dose and transduction time, but was less than with Ad-CMV-IL10 at both mRNA and protein levels. Gene expression driven by LV-SV40-IL10 was faster in the human cornea than the ovine cornea. Corneal allograft survival was prolonged by a median of 7 days in the LV-SV40-IL10-treated recipients, compared with the control group (P = 0.026). CONCLUSION: Although lentiviral vectors show some promise for corneal gene therapy, they are less efficient than adenoviral vectors.