Interlamellar cohesive strength in the vertical meridian of human eye bank corneas.
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PURPOSE: Previously, human corneal stromal interlamellar cohesive strength in the horizontal meridian was shown to be twice as strong peripherally as centrally (approximately 2.90 x 10(-1) versus 1.40 x 10(-1) N/mm). In the current study, stromal samples excised from the vertical meridian were studied to determine if meridional differences also exist. Precise knowledge about corneal stromal structure is warranted, because anisotropy can influence postoperative healing strength and corneal shape. METHODS: Limbus-to-limbus stromal strips with a constant 2.2-mm width were obtained from the vertical meridians of 52 eyebank corneas (8 single, 22 pairs). Cohesive strength was recorded as samples were split at a constant 1.6 mm/s at 50% stromal depth. RESULTS: The mean cohesive strength in the inferior periphery was found to be only two thirds the strength observed in the nasal or temporal periphery (1.96 x 10(-1) N/mm versus approximately 2.94 x 10(-1) N/mm @ 5 mm). The mean cohesive strength in the inferior periphery was also significantly less than the strength of the superior periphery (1.85 x 10(-1) N/mm +/- 8.83 x 10(-3) SEM versus 2.34 x 10(-1) +/- 1.37 x 10(-2) @ 4 mm from the central cornea; P = 0.0027). Unlike the samples from the horizontal meridian, which could be described by a profile symmetric about the central cornea, force profiles for the vertical data could be characterized with distinct, classifiable patterns that were generally asymmetric. Fellow corneas from a single donor tended to have strength profiles belonging to the same class (P = 0.035; chi-square), although some paired eyes exhibited profiles from distinctly different classes. CONCLUSIONS: These data strongly support the concept of an anisotropic collagen macrostructure that is more complex than previously believed. This inherent structural anisotropy may become a significant determinant of corneal shape during ectatic disease and some forms of keratorefractive surgery. (+info)
Non-invasive assessment of the donor corneal endothelium using ocular redox fluorometry.
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AIMS: To investigate the usefulness of ocular redox fluorometry for evaluating donor corneal endothelial viability. METHODS: Corneas from 42 recipients of penetrating keratoplasty and four donor corneas were examined by ocular redox fluorometry. Autofluorescence from reduced pyridine nucleotides (PN) and oxidised flavoproteins (Fp) of the human corneal endothelium were measured non-invasively, and the PN/Fp ratio was used as a tissue metabolic indicator. Specular microscopy and electron microscopy were also performed. RESULTS: Both the quality of specular microscopic image and the PN/Fp ratio were significantly correlated with the degree of corneal endothelial damage determined by histological examination. Corneas with poor specular microscopic image showed significantly decreased PN/Fp ratio compared with corneas with good or fair specular images (p = 0.041 and 0.027, respectively). The PN/Fp ratio increased in corneas with mildly damaged endothelium but decreased in corneas with severely damaged endothelium determined by histological examination. Evaluation of corneal endothelium by combination of specular microscopy and ocular redox fluorometry showed excellent association with that of histopathological examination (p < 0.0001). CONCLUSION: Ocular redox fluorometry is useful for assessing donor corneal endothelial viability. Combination of ocular redox fluorometry and specular microscopy may increase the ability of donor cornea selection. (+info)
Three dimensional analysis of the retinal vasculature using immunofluorescent staining and confocal laser scanning microscopy.
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AIM: To undertake a qualitative and quantitative analysis in three dimensions of the human retinal vasculature. METHOD: Fixed and excised whole retinas were permeabilised and subjected to immunofluorescent staining for blood vessel components followed by confocal laser scanning microscopy. Single projection and stereoimages were constructed using computer software. XZ sections through the retina were constructed and the vasculature analysed using appropriate software. RESULTS: Immunofluorescent staining with no discontinuities was present in vessels of all sizes, the confocal images of the capillary network being free of out of focus blur at all depths. Quantitative analysis of XZ sections confirmed the qualitative impression of sharp delineation of the deep retinal capillary plexus, an absence of laminar arrangement of capillaries within the inner retina, and a truncated cone of capillaries around the foveal avascular zone (FAZ) wherein the superficial capillaries approached the FAZ more closely than those in the deeper retina. CONCLUSION: Immunofluorescent staining of the retina and confocal laser scanning microscopy were shown to be useful in analysing accurate three dimensional reconstructions of the normal retinal vasculature without affecting overall tissue architecture. (+info)
Eye bank's success due to vision of its founders.
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In 1955, the Eye Bank of Canada introduced Canadians to the idea of postmortem tissue donation. The long-time administrator of the bank's Ontario Division, Anne Wolf, recalls the organization's early days and how the management of donated corneas became a family affair. (+info)
Frequency of ocular metastases in patients dying of cancer in eye bank populations.
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AIMS: To examine the frequency of intraocular metastases in patients who had died of cancer, in an eye bank and necropsy population sample. METHODS: The first group included 302 cancer cases received from the Wisconsin Eye Bank between 1988 and 1993. In the second group, ocular pathology records at the Wilmer Institute from 1976 to 1980 were analysed for ocular metastases in necropsy subjects dying of cancer. Nonocular cancer was the cause of death in 741 cases; among these, 510 were attributed to carcinomas. RESULTS: In the Wisconsin Eye Bank group, three cases (1%) had gross metastases. Out of 255 carcinoma cases, one (0.4%) had gross metastases. In the Wilmer Institute group, gross metastases were observed in 35 (4.7%) cases. Of the 510 patients dying of carcinomas, six (1.2%) had macroscopic metastases. Ocular metastases were detected histopathologically in 93 of 741 (12.6%) of cases. CONCLUSION: Even though it is difficult to assess the true frequency of ocular metastases in patients dying of cancer, the answer to this question was attempted by determining the frequency of ocular metastasis in patients who died of cancer and who donated their eyes to the Wisconsin Eye Bank or had postmortem examination at the Johns Hopkins Hospital. Microscopic metastases were found in 12.6% of cases. The frequency of gross metastases has decreased over the past 12 years from 4.7% to 1% (p value = 0.005) owing to improved treatment of leukaemia; however, the frequency of macroscopic metastases due to carcinomas has not changed (p value = 0.38). (+info)
Donor corneal tissue evaluation.
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Proper evaluation of donor cornea is critical to the success of corneal transplantation. Attention must be paid to the cause of death and ocular condition as several general and ocular diseases constitute contraindications for donor corneal usage. Death to enucleation time should be noted. Gross examination and slit lamp biomicroscopy are mandatory for the evaluation of the donor eye while specular microscopy adds another useful dimension to information regarding donor cornea. This article provides a comprehensive review of all the aspects of donor corneal evaluation as practised today worldwide. (+info)
Changes in the corneal Na-K ATPase levels in eyes stored in moist chamber at 4 degrees C.
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This report deals with a chronological measurement of Na-K ATPase enzyme activity in human and bovine corneas stored in a moist chamber at 4 degrees C. Paired human and bovine eyes were sterilized by the standard eye bank procedure and stored up to 6 days. At the desired time, the corneal endothelium was assayed for Na-K ATPase activity. The protein content of each tissue sample was also determined. In a parallel set of experiments, the viability of identical stored corneas was determined by trypan blue and alizarin red staining technique, and morphometric analysis was done to quantify the extent of the corneal endothelial damage. The human corneas showed that there was a significant progressive decrease in the Na-K ATPase activity as the storage time increased. The decrease was related to morphological endothelial damage. (+info)
First cornea transplants meant blind WW I veterans saw first sights in 40 years.
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Eddie Baker, who was blinded during WW I, played a key role in the founding of the Canadian National Institute for the Blind and Canada's first Eye Bank. The latter development meant that some soldiers blinded between 1914 and 1918 had their sight restored in 1956, when the bank opened. (+info)