The New Zealand National Eye Bank study 1991-2003: a review of the source and management of corneal tissue.

PURPOSE: To evaluate donor demographics and source, donor tissue processing and storage, biologic contamination, and the utilization and distribution of corneal tissue procured by the New Zealand National Eye Bank. METHODS: As part of a prospective longitudinal study, the electronic records of the NZNEB for the 13-year period 1991-2003 were analyzed for each year with respect to donor demographics, donor source and cause of death, death-to-preservation interval, storage methods, endothelial assessment, biologic contamination, corneal tissue utilization, and distribution. RESULTS: During the study period, 3221 corneas were retrieved from 1628 donors (69.8% male, 30.2% female), with the mean age of donors 59.4 years (SD 18.3 years) and range 4 to 95 years. No significant correlation was identified between donor age group (using 10-year intervals) and the proportion of corneas suitable for transplantation. Donors were procured from the Coroner's service (67.6%), public hospitals, (23.5%) and multiorgan donors (7.1%). The most common causes of donor death were cardiovascular disease, trauma, and cerebrovascular disease. Average storage duration increased from 3.5 to 11.8 days when organ culture replaced hypothermic storage in 1992. Biologic contamination occurred in 5% of all donor corneas. The most common bacterial and fungal isolates were coagulase-negative staphylococci and Candida spp, respectively. A significant decrease in contamination rate over the years of the study was identified. Overall, 79.4% of corneal tissue procured was used for corneal transplantation (75.8% for penetrating keratoplasty, 2.1% for lamellar keratoplasty, and 1.5% for unspecified transplants), and 21.6% was discarded. Most common reasons for discarding tissue were biologic contamination, abnormal serology, and failed endothelial assessment. CONCLUSION: Analysis of the NZNEB database provides valuable information in relation to eye banking and corneal transplantation in New Zealand. Significant trends were identified in donor demographics, donor procurement source, improved donor tissue processing and storage, decreased biologic contamination, and increased utilization of corneal tissue.

A CACNA1F mutation identified in an X-linked retinal disorder shifts the voltage dependence of Cav1.4 channel activation.

Light stimuli produce graded hyperpolarizations of the photoreceptor plasma membrane and an associated decrease in a voltagegated calcium channel conductance that mediates release of glutamate neurotransmitter. The Ca(v)1.4 channel is thought to be involved in this process. The CACNA1F gene encodes the poreforming subunit of the Ca(v)1.4 channel and various mutations in CACNA1F cause X-linked incomplete congenital stationary night blindness (CSNB2). The molecular mechanism of the pathology underlying the CSNB2 phenotype remains to be established. Recent clinical investigations of a New Zealand family found a severe visual disorder that has some clinical similarities to, but is clearly distinct from, CSNB2. Here, we report investigations into the molecular mechanism of the pathology of this condition. Molecular genetic analyses identified a previously undescribed nucleotide substitution in CACNA1F that is predicted to encode an isoleucine to threonine substitution at CACNA1F residue 745. The I745T CACNA1F allele produced a remarkable approximately -30-mV shift in the voltage dependence of Ca(v)1.4 channel activation and significantly slower inactivation kinetics in an expression system. These findings imply that substitution of this wild-type residue in transmembrane segment IIS6 may have decreased the energy required to open the channel. Collectively, these findings suggest that a gain-of-function mechanism involving increased Ca(v)1.4 channel activity is likely to cause the unusual phenotype.

Clinical manifestations of a unique X-linked retinal disorder in a large New Zealand family with a novel mutation in CACNA1F, the gene responsible for CSNB2.

PURPOSE: To describe the phenotype in a New Zealand family with an unusual severe X-linked retinal disorder with a novel I745T mutation in CACNA1F, the gene responsible for incomplete congenital stationary night blindness (CSNB2). METHODS: Members of the family tree were invited for clinical, psychophysical and electrodiagnostic evaluation. RESULTS: Male family members had severe non-progressive visual impairment, abnormal colour vision, congenital nystagmus, hyperopia and normal fundi. Some were intellectually disabled. Female family members had congenital nystagmus and decreased visual acuity frequently associated with high myopia. Electroretinograms (ERG) identified reduced rod and cone responses with negative waveform in male and female family members, with atypical features for CSNB2. CONCLUSIONS: Although there were similarities to CSNB2, distinctive features in male family members included severity of phenotype, and association of intellectual disability. Moreover, all female heterozygotes had clinical and ERG abnormalities. CACNA1F encodes the Ca(v)1.4 alpha1 subunit of a voltage-gated calcium channel, which may mediate neurotransmitter release from photoreceptors. Molecular analyses, reported separately, identified a novel I745T CACNA1F mutation that was associated in vitro with major alterations in gating and kinetics of the Ca(v)1.4 channel. It is speculated that the unique phenotype described in this family may reflect similarly altered function of Ca(v)1.4 channel activity in vivo.

Confocal imaging of the human keratocyte network using the vital dye 5-chloromethylfluorescein diacetate.

BACKGROUND: The human corneal stroma consists of intercalated layers of collagen and keratocytes. These cells are known to maintain the stroma and aid in repair but it is likely they have other crucial roles throughout the cornea. The complexity of their anatomy is revealed in this study by ex vivo in situ images of the human keratocyte covering a range of ages. METHODS: Human donor corneas of different ages were stained with 5-chloromethylfluorescein diacetate (CMFDA), a dye that is anchored and retained within the cell cytoplasm. The tissue was fixed, sectioned, mounted, and then imaged using a confocal laser scanning microscope at various magnifications and tissue planes. The digital image sets were transferred to multifunction image processing software for analysis and production of 3-D stereo images of keratocyte networks throughout the stroma. RESULTS: High quality images of CMFDA-stained cells revealed differences in the structure and orientation of keratocytes in the anterior, central and posterior stroma, which did not differ throughout the age-range studied. This method reveals very fine cell process ramifications not previously visualized, orientated in lateral and antero-posterior directions, and it confirms the potential for multidirectional communication between keratocyte networks. CONCLUSIONS: This qualitative study found consistency of keratocyte morphology in the normal human cornea throughout life. It confirmed differences in keratocyte anatomy, and the potential for rapid cellular communication by multiple interconnecting processes supporting cohesive keratocyte activity. This high-resolution 3-D microscopic study should assist in identifying gross deviant cellular behaviour in post-surgical and disease states.

Indications for corneal transplantation in New Zealand: 1991-1999.

PURPOSE: To identify the indications for keratoplasty in patients supplied with donor tissue through the New Zealand National Eye Bank. METHODS: Analysis of penetrating and lamellar keratoplasty data collected by the New Zealand National Eye Bank, Auckland, from 1991 to 1999. RESULTS: In this 9-year period, donor material was supplied for 1370 corneal grafts; 1308 for penetrating keratoplasty, 26 for lamellar keratoplasty, and 36 for unspecified grafts. This accounts for a minimum of 85% of the penetrating keratoplasties performed in New Zealand from 1991 to 1999. The leading indications for penetrating keratoplasty were keratoconus (45.6%), pseudophakic or aphakic corneal edema (17.9%), regraft (8.7%), viral keratitis (7.3%), and trauma (5.5%). The average age of patients was 47.5 years (SD = 22.6) and age distribution was bimodal, with peaks in the 3rd and 8th decades. Keratoconus, regraft, and trauma were significantly more common as indicators for penetrating keratoplasty in male patients than female patients; however, pseudophakic or aphakic corneal edema was more common in female patients. CONCLUSION: The majority of transplantation surgery in New Zealand is performed using corneal tissue from the New Zealand National Eye Bank. In this representative study, keratoconus is the leading indicator for penetrating keratoplasty in New Zealand, accounting for a higher proportion than in any other published literature. The other indications, age distribution and gender differences correlate with previous reports. These findings suggest that keratoconus leading to transplantation may have increased prevalence in New Zealand.