Urgent need for normalization of corneal graft quality controls in French eye banks.
ABSTRACT Assessment of corneal tissue quality before graft is mainly based upon the determination of endothelial cell density (ECD) by eye banks. These cells are responsible for corneal transparency, and ECD correlates with graft survival. In France and often elsewhere in Europe, ECD is measured using a "naked-eye" procedure under a light microscope. To measure objectively the reliability of ECD determination in France, we developed four test corneas with a known ECD.
The test corneas consisted of 1 mm2 of human corneal endothelium with stained cell borders. The 64 technicians of the 21 French eye banks counted according to the protocol applied in their respective centers.
More than half of the 256 counts (152, 59%) deviated by more than 10% from actual ECD. Of the counts, 85 (33%) were over-estimated, and 67 (26%) were under-estimated. Deviation ranged between 42% under-estimation and 82% over-estimation. Eight banks (38%) constantly over-estimated, and nine (43%) under-estimated ECD. Half of the inter-technician gaps within an eye bank were more than 10%, with a maximum of 51%.
This audit highlights the unacceptable lack of reliability of manual ECD assessment in French eye banks. This surely indicates the delivery of poor quality corneas for graft in certain centers and wastage in others. We urgently advocate normalization of French counting methods. This may require upgrading to a computer-aided method.
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ABSTRACT: To determine when corneal transplants develop the decreased endothelial cell density that predisposes to late endothelial failure (LEF). Noted cohort study within a prospective case series. The authors compared 21 grafts that developed LEF with the remaining transplants (controls) in a longitudinal cohort study of 500 consecutive penetrating keratoplasties by 1 surgeon. Eyes regrafted during the study, fellow eyes of bilateral cases, and patients who did not want their data used for research purposes were excluded, leaving 389 grafts in 389 patients for analysis. Penetrating keratoplasty. Endothelial cell density before surgery and at 2 months and 1, 3, 5, and 10 years after surgery. Grafts with LEF had lower median endothelial cell densities than other grafts, both before surgery (2710 cells/mm2 vs. 2991 cells/mm2; P = 0.02) and 2 months after surgery (1895 cells/mm2 vs. 2501 cells/mm2; P < 0.001), a difference that was maintained through 5 postoperative years. Despite having lower preoperative cell densities, the grafts with LEF had larger median endothelial cell losses 2 months after keratoplasty (31% vs. 16%, P = 0.002). The endothelial cell loss subsequent to the 2-month examination, however, was not increased in the grafts with LEF. Risk factors for developing LEF included a low endothelial cell density before surgery (P = 0.007) and 2 months after surgery (P = 0.002), aphakia or pseudophakia (P = 0.04), older recipient age (P = 0.002) and older donor age (P = 0.03), and occurrence of an endothelial rejection episode (P = 0.03). Corneal grafts with LEF, the major cause of graft failure after 5 postoperative years, fail from low initial endothelial cell density rather than an increased rate of chronic postoperative cell loss. Improved techniques of corneal preservation should decrease the rate of LEF. In addition to low preoperative and 2-month postoperative endothelial cell density, a higher risk of LEF is also seen in patients with aphakia or pseudophakia, older recipient age, older donor age, and occurrence of an endothelial rejection episode.Ophthalmology 11/1999; 106(10):1962-5. · 5.56 Impact Factor
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ABSTRACT: Endothelial examination of organ culture stored corneas is usually done manually and on several mosaic zones. Some banks use an image analyser that takes account of only one zone. This method is restricted by image quality, and may be inaccurate if endothelial cell density (ECD) within the mosaic is not homogeneous. The authors have developed an analyser that has tools for automatic error detection and correction, and can measure ECD and perform morphometry on multiple zones of three images of the endothelial mosaic. 60 human corneas were divided into two equal groups: group 1 with homogeneous mosaics, group 2 with heterogeneous ones. Three standard microscopy video images of the endothelium, graded by quality, were analysed either in isolation (so called mono-image analysis) or simultaneously (so called tri-image analysis), with 50 or 300 endothelial cells (ECs) counted. The automated analysis was compared with the manual analysis, which concerned 10 non-adjacent zones and about 300 cells. For each analysis method, failures and durations were studied according to image quality. All corneas were able to undergo analysis, in about 2 or 7.5 minutes for 50 and 300 ECs respectively. The tri-image analysis did not increase analysis time and never failed, even with mediocre images. The tri-image analysis of 300 ECs was always most highly correlated with the manual count, particularly in the heterogeneous cornea group (r=0.94, p<0.001) and prevented serious count errors. This analyser allows reliable and rapid analysis of ECD, even for heterogeneous endothelia mosaics and mediocre images.British Journal of Ophthalmology 07/2002; 86(7):801-8. · 2.73 Impact Factor
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ABSTRACT: Keratoplasty is the oldest and one of the most successful forms of solid tissue transplantation. In the United States, over 33,000 corneal transplants are performed each year. Unlike other forms of tissue transplantation, keratoplasties are routinely performed without the aid of tissue typing or systemic immunosuppressive drugs. In spite of this, 90% of the first-time corneal transplants will succeed-a condition that demonstrates the immune privilege of keratoplasties. The avascular nature of the corneal allograft bed led many to suspect that corneal grafts were sequestered from the immune apparatus. Although pleasing in its simplicity, this explanation has given way to a more comprehensive hypothesis that embodies multiple, interdependent mechanisms, which promote the long-term survival of corneal allografts. These mechanisms conspire to interrupt the transmission of immunogenic stimuli to peripheral lymphoid tissues; induce the generation of a deviated immune response; and neutralize immune effector elements at the host-graft interface. This paradigm is analogous to a three-legged stool. Disassembly of any one of the three components results in the collapse of immune privilege. Strategies to re-establish corneal immune privilege may have clinical application for high-risk hosts who have rejected previous corneal allografts.Journal of Leukocyte Biology 09/2003; 74(2):167-71. · 4.57 Impact Factor