[Ultrastructural characteristics of glaucomatous trabecular meshwork]. / Características ultraestructurales de la malla trabecular glaucomatosa.

PURPOSE: To compare the normal and glaucomatous trabecular meshwork ultrastructure and to relate the observed changes with the intraocular pressure increase characteristic of the primary open angle glaucoma. METHODS: 21 non glaucomatous trabecular meshworks, aged 23 to 99 years, and 5 from patients diagnosed of primary open angle glaucoma, aged 40 to 65 years, were fixed by Karnovsky's solution and processed and observed by transmission electron microscopy and their morphological characteristics were qualitatively compared. RESULTS: Ultrastructural changes of glaucomatous trabecular meshworks are similar, but much more intense, than those observed in the aged normal trabecular meshworks. These changes are loss of endothelial cells, thickening of basal membranes and trabecular beam central nucleus changes such as an increase of electrodense plaques and collagen degenerative processes. CONCLUSIONS: Ultrastructural changes observed in glaucomatous trabecular meshworks are comparable to an early aging of them. These changes can be related with the mechanisms that increase the intraocular pressure in primary open-angle glaucoma.

[Morphological alterations of the trabecular meshwork in primary open angle glaucoma]. / Alteraciones morfológicas de la malla trabecular en el glaucoma primario de ángulo abierto.

PURPOSE: In the present essay we have compared the morphology and structure of normal trabecular meshworks and glaucomatous trabecular meshworks with the purpose of obtaining information about the etiopathogeny of primary open angle glaucoma. METHODS: We have observed by conventional light microscopy and scanning electron microscopy a total amount of 20 trabecular meshworks from non-glaucomatous patients and 35 trabecular meshworks from surgical pieces of trabeculectomy performed in patients diagnosed of primary open angle glaucoma. RESULTS: We have observed that glaucomatous trabecular meshworks show morphological and structural alterations of their trabecular beams, as their enlarging, collapse, the partial loss of endothelial cells and the existence of plenty of material accumulated on them, like pigment granules and calcium precipitates. CONCLUSIONS: Glaucomatous trabecular meshworks present morphological and structural alterations which can be related to etiopathogeny of primary open angle glaucoma since they modify the normal conditions of drainage of aqueous humour to Schlemm's channel.

Morphological study of cryopreserved human corneal endothelium.

The aim of the present paper is to describe the morphological changes that occur in human corneal endothelium as an immediate consequence of corneal cryopreservation. Therefore, 16 human donor corneas were cryopreserved with an original procedure at a 1 degrees C/min cooling rate in a freezing solution cryoprotected with 7% dimethylsulphoxide until a final temperature of -100 degrees C was reached. After storage of the corneas in liquid nitrogen for periods ranging from 1 to 96 days (mean: 34.31 days), the corneas were thawed in a water bath at +37 degrees C. Eight additional control corneas were processed without cryopreservation. Morphological assessment of the endothelial layer was performed by scanning electron microscopy and trypan blue and alizarin red S vital staining. Results showed cryoinduced damage at variable degrees in all cryopreserved corneas. They were classified into three groups according to the intensity and extension of the cryoinduced damage: group I (n = 10): corneas with minor endothelial alterations consisting in the presence of microholes in the posterior cell membrane; group II (n = 1): corneas with generalized disruption of endothelial intercellular junctions and intact cell membranes; group III (n = 5): corneas with severe endothelial damage consisting of massive cell necrosis and complete alteration of the morphological pattern of the endothelium. All control corneas had intact endothelial layers. Cryoinduced damage cannot be completely avoided with the cryopreservation protocol tested. The high interindividual variability of the results observed is not related to the storage time of the cornea in liquid nitrogen.

Rigid gas permeable contact lenses surface roughness examined by interferential shifting phase and scanning electron microscopies.

The anterior surface roughness of seven factory new rigid gas permeable (RGP) contact lenses has been studied by interferential shifting phase microscopy (ISPM) and scanning electron microscopy (SEM). Five lenses were fluorsilicone acrylate and two lenses were silicone acrylate. Their material Dk ranged from 14 to 210. ISPM is shown to be a reliable and non-destructive method to observe and measure the relief of the contact lens surface. Moreover, profile and contour data are easily stored for further quantitative studies. ISPM contour patterns of the studied lenses are qualitatively compared with those obtained by SEM for the same lenses. Results point out that ISPM gives similar accuracy but it is non-destructive and cheaper than SEM. Moreover, the quantitative study of surface roughness suggests that there is a relationship between surface roughness and Dk of the lens material: surface roughness increases with Dk and allows to distinguish between lenses with low, medium and high Dk.

Morphometrical features of the corneal epithelium in mammals.

The study has been conducted on 40 species of mammals included in different taxonomic orders: 10 carnivores (felines and canides), 13 primates and 17 herbivores (artiodactyles, perisodactyles and proboscideans). Domestic, experimental and wild animals have been included in the sample. The purpose of the study is to offer new data regarding morphometric aspects of the epithelium of the cornea of mammals. We also aim to establish the relationships and differences between the different epithelia studied and to determine the morphometric characteristics which best define the epithelium of the different species under study. The results obtained have demonstrated the existence of correlations between thicknesses, number of cellular layers and number of the epithelial cells in the different groups. It has also been established that the variants in thickness and number of layers define and characterize the epithelia. Finally, the study reveals that morphometric characteristics of the epithelium of primates and carnivores have more similarities than those of herbivores.

Observation of deposits on disposable contact lenses by bio-, light and scanning electron microscopy.

There has been little published on the presence of deposits on disposable hydrogel contact lenses. The purpose of the present study was to determine the possible existence of such deposits. Seventy-two disposable lenses (polymacon; FDA group 1; non-ionic, low water contact lenses) were fitted to six patients and replaced weekly in the course of a total follow-up period of six weeks. By means of biomicroscopy, light microscopy and scanning electron microscopy, different types of deposits were observed on all the lenses studied. Our results also indicate that the accumulation rate of these deposits expressed as a percentage of the total area of the lens which they covered increased after the third replacement of the lenses over the 4th, 5th and 6th weeks. Finally, we observed that the amount of deposits varies in the different patients studied in the course of a 6 week follow-up period.

Morphological and morphometric aspects of primate cornea: a comparative study with human cornea.

Morphological and morphometric features of the cornea of 13 species of primates have been studied in order to determine possible morphological differences between them. The existence of relationships between different morphometric corneal variables was also examined to establish which variables best defined and characterized the cornea. The present aim is to determine which primate cornea resembles that of the human being most with a view to possible future clinical and experimental studies. The results obtained revealed that all the cornea under study presented similar morphological features. The relationship between total corneal thickness and corneal epithelial thickness was determined as well as the relationship between epithelial thickness, the number of epithelial layers and the number of epithelial cells. However, the morphological pattern of Bowman's membrane and corneal endothelium differed in the species studied. Finally, the study indicates that the chimpanzee and the gorilla are the species with a corneal morphometry which is closest to that of the human cornea.

Long-term cryopreservation of human donor corneas.

The purpose of the present study was to develop an optimal freezing method for cryopreservation of human donor corneas for transplantation. Three groups of ten human donor corneas each were cryopreserved using cooling rates of 0.5 degree C/ min, 1 degree C/min and 9 degrees C/min. The freezing medium contained 10% fetal calf serum and 7% dimethylsulphoxide. Ten additional human donor corneas were used as controls. Endothelial cell survival after complete thawing was assessed by calculating the mean endothelial cell density and percentage of non-viable endothelial cells from vital staining and scanning electron micrographs. Significant differences in endothelial cell survival between all groups were detected by analysis of variance (p < 0.001), but paired contrast found no real differences between corneas frozen at 0.5 degree C/min or 1 degree C/min. Nevertheless, 60% of the corneas cryopreserved at 1 degree C/min but only 10% of those cryopreserved at 0.5 degree C/min fulfilled both requirements to be considered suitable for transplantation (endothelial cell density > 2000 cells/mm2 and less than 10% dead cells). None of the corneas frozen at 9 degrees C/min fulfilled these requirements. Mean endothelial cell density of corneas frozen at 1 degree C/min was 2084 cells/mm2 (range 2020 to 2630 cells/mm2). Except for isolated corneas frozen at 0.5 degree C/min, only corneas cryopreserved at a cooling rate of 1 degree C/min achieved satisfactory endothelial cell survival for their use in transplantation. However the significant interindividual variability among corneas frozen at 1 degree C/min (ANOVA: p < 0.001) prevents prediction of the condition of the cornea after the complete cryopreservation process. Until this high variability can be drastically reduced, systematic corneal cryopreservation in eye banking remains unattainable.

Scanning electron microscopy of the human zonule of the lens (Zonula ciliaris).

In the present study eight human eyeballs were specifically prepared for scanning-electron-microscopic observation of the zonule. The zonule consisted of two main layers of radial fibres, an anterior and a posterior one, that inserted on the anterior and the posterior lens capsules, respectively. Some fibres inserted on the equator of the lens. Posterior zonular fibres originated at the pars plana, entered the dorsal part of the ciliary valleys and then changed their direction towards the posterior face of the lens. Posterior fibres inserted on the posterior capsule of the lens by branched endings 1 mm behind the equator of the lens. Anterior zonular fibres originated mainly at the pars plana and occasionally at the ciliary valleys. After running completely through the ciliary valleys in close contact with the lateral walls of the ciliary processes, they changed their direction at the anterior endings of the pars plicata and reached the anterior lens capsule. Anterior zonular insertions were achieved by webbed endings that diffused into the anterior capsule 2 mm in front of the lens equator. The extraordinary distension capacity of the zonular fibres was demonstrated by pulling the anterior lens capsule after hydrodissection. As a consequence, the anterior fibres were stretched up to four times their original length without breaking or disinserting.