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.

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.

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.

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.

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.

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.

Hereditary influences in oxygen-induced retinopathy in the rat.

Rodent models of oxygen-induced retinopathy (OIR) provide important insights into the pathogenesis of human retinopathy of prematurity. Herein, we present an overview of our work with rat OIR to date. We have identified marked and consistent variations in susceptibility to OIR amongst different inbred rat strains and provide strong evidence for a genetic determinant of susceptibility to OIR. Furthermore, we have characterised differences in retinal angiogenic factor gene expression amongst different inbred rat strains exposed to cyclic hyperoxia. A key determinant of susceptibility to OIR appears to be the extent to which pro-angiogenic factor genes, such as vascular endothelial growth factor and erythropoietin, are expressed during the period of hyperoxic exposure. Those strains in which expression is relatively well maintained are less susceptible to retinopathy than are those in which expression is reduced. In addition, we identify an association between ocular pigmentation and OIR susceptibility.

Gene therapy for diseases of the cornea - a review.

The cornea is particularly suited to gene therapy. The cornea is readily accessible, normally transparent, and is somewhat sequestrated from the general circulation and the systemic immune system. The principle of genetic therapy for the cornea is to use an appropriate vector system to transfer a gene to the cornea itself, or to the ocular environs, or systemically, so that a transgenic protein will be expressed that will modulate congenital or acquired disease. The protein may be structural such as a collagen, or functionally active such as an enzyme, cytokine or growth factor that may modulate a pathological process. Alternatively, gene expression may be silenced by the use of modalities such as antisense oligonucleotides. Interestingly, despite a very considerable amount of work in animal models, clinical translation directed to gene therapy of the human cornea has been minimal. This is in contrast to gene therapy for monogenic inherited diseases of the retina, where promising early results of clinical trials for Leber's congenital amaurosis have already been published and a number of other trials are ongoing.

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.

The potential of viral vector-mediated gene transfer to prolong corneal allograft survival.

The cornea is a particularly attractive target for gene therapy designed to improve the outcome of corneal transplantation. First, there is a clear and well-defined clinical need. Second, because donor corneas can be preserved for days if not weeks within an eye bank, ex vivo transduction of a donor cornea can be carried out without the urgency associated with many other forms of transplantation. Finally, the partial sequestration of the eye from the systemic circulation decreases the likelihood of spillover of vector and transgene, and the immune privileged nature of the cornea and anterior segment affords a degree of protection from immune responses directed against the vector. A wide range of vectors has been investigated for gene transfer to the cornea. A number of viral vectors, in particular, have proved to be efficient at transducing the cornea and in association with a variety of transgenes, have been used successfully to prolong corneal allograft survival significantly in animal models. The most suitable such vector for future clinical studies in corneal transplantation has yet to be determined, but the most likely include recombinant adenoviral, adeno-associated viral and lentiviral vectors. In this review, we examine the ability of these viral vectors to transduce the cornea, and summarise those studies in which gene therapy has been used to prolong experimental corneal allograft survival.

Ancient Egypt to modern ophthalmology: via Otago, New Zealand.

The purpose of this report is to document the contribution of two New Zealanders, Barrie Jones and Rowland Wilson, to the development of modern ophthalmology. Their related contribution was made over a period of 80 years; it began in Egypt with Wilson, developed when they worked together in Dunedin and where they created the foundations for the brilliant career that Jones was to go on to in London. Their story emphasizes the impact of teaching and mentorship. It highlights the extended reach of teaching and the power of continuity in research.

Pythium insidiosum keratitis in an Australian child.

A 3-year-old girl from the Northern Territory developed suppurative keratitis after swimming in pools. A mycelial organism suspected to be Pythium insidiosum was cultured. Treatment with polyhexamethylene biguanide and voriconazole for 5 days was unsuccessful, and a corneal graft was performed. The infection was cleared and when last seen 14 months after surgery the patient had a stable graft and useful vision. The identification of the organism was confirmed by rRNA gene sequencing. P. insidiosum is an oomycete, an organism more closely related to kelp than to fungi. Masses of hyphae were seen in sections and, for the first time, the ultrastructure of P. insidiosum in human tissue is described. The staining characteristics of cultured hyphae were assessed; lactofuchsin and acridine orange were found to be the most useful methods. Although the diagnosis of P. insidiosum keratitis is not difficult, and the organism is susceptible in vitro to a number of antimicrobial agents, early corneal transplantation remains the treatment of choice.

Rejection and acceptance of corneal allografts.

PURPOSE OF REVIEW: Corneal transplantation is successful in the short-term, but the long-term prognosis has not improved over the past 20 years. Here, we review recent findings that may contribute to improved corneal allograft survival. RECENT FINDINGS: A better understanding of the molecular pathways affecting corneal graft survival has led to more targeted approaches to immune modulation. Costimulatory molecule blockade, inhibition of chemokine-chemokine receptor interactions, modulation of apoptotic pathways, and reduction of corneal neovascularization and lymphangiogenesis have been shown to prolong corneal graft survival in animal models. Conventional immunosuppressive drugs have been tested in new combinations and formulations with some success. Two randomized prospective clinical trials in clinical penetrating corneal transplantation have been reported, but there remains little evidence on the long-term outcomes of the newer lamellar corneal graft procedures. SUMMARY: New approaches to reducing the impact of rejection on corneal graft survival have focussed on topical rather than systemic therapies, and on component corneal transplantation. The most successful experimental strategies have been those in which more than one pathway has been targeted; it now seems likely that to improve clinical allograft survival, simultaneous modulation of multiple axes of the rejection process will be necessary.

Apparent autosomal dominant keratoconus in a large Australian pedigree accounted for by digenic inheritance of two novel loci.

Keratoconus is a debilitating ocular disease characterised by progressive asymmetrical thinning of the cornea, the clear covering at the front of the eye. The resulting protrusion of the cornea results in severe refractive error, in the most severe cases requiring corneal grafting. It is a complex disease with a genetic component. Despite several reports of linked loci, major gene identification has been elusive. A genome-wide linkage scan in a large Australian pedigree with apparent autosomal dominant keratoconus was conducted using the Affymetrix 10K SNP chip and two regions of linkage identified. Functional candidate genes from within both linkage peaks were assessed for corneal expression and screened for mutations in affected family members. Equal evidence of linkage was detected to both 1p36.23-36.21 and 8q13.1-q21.11 with LOD scores of 1.9. Analysis of both loci concurrently suggests digenic linkage with two-locus LOD score of 3.4. All affected individuals carry identical haplotypes at both loci. Carriers of either linked haplotype without the other do not have keratoconus. No mutations were identified in the following candidate genes expressed in the cornea: ENO1, CTNNBIP1, PLOD1, UBIAD1, SPSB1 or TCEB1. Although the pedigree appears to demonstrate simple autosomal dominant inheritance, the disorder is actually genetically complex. This pedigree may provide a link between inherited forms of keratoconus and sporadic cases.

PCR amplification of the functional immunoglobulin heavy chain variable gene from a hybridoma in the presence of two aberrant transcripts.

Single chain antibody fragment genes are commonly created by splicing together the immunoglobulin light chain (VL) and heavy chain variable (VH) genes of a monoclonal antibody produced by a hybridoma. Selective PCR amplification of the functional immunoglobulin variable gene rearrangements can be complicated by the existence of other unproductive immunoglobulin gene rearrangements in the hybridoma. Here we report the detection and preferential amplification of aberrant transcripts from two unproductive VH gene rearrangements derived from the fusion partner of a hybridoma. The functional VH gene of the monoclonal antibody was successfully amplified by selective use of primers to individual JH segments.

The immunobiology of corneal transplantation.

Corneal allotransplantation is highly successful in the short term, but much less successful in the longer term. Many corneal grafts in recipients with corneal neovascularization or the sequelae of ocular inflammation undergo irreversible rejection, despite topical immunosuppression with glucocorticosteroids. Sensitization to cornea-derived alloantigen proceeds by both direct and indirect routes, but the anatomic location of sensitization remains unclear. Multiple and redundant mechanisms operate in the effector phase of corneal graft rejection, which is largely cell-mediated rather than antibody-mediated. Human leukocyte antigen matching may improve outcomes in high-risk patients but systemic immunosuppression is frequently ineffective and is seldom used.