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PURPOSE: To determine whether the incidence of and susceptibility to climatic droplet keratopathy (CDK), an acquired, often bilateral degenerative corneal disease, is influenced by the genetic background of the individuals who exhibit the disorder. METHODS: To determine whether the disease expression was influenced by the genetic ancestry of CDK cases in native Mapuche of the northwest area of Patagonia in Argentina, we examined mitochondrial DNA and Y-chromosome variation in 53 unrelated individuals. Twenty-nine of them were part of the CDK (patient) population, while 24 were part of the control group. The analysis revealed the maternal and paternal lineages that were present in the two study groups. RESULTS: This analysis demonstrated that nearly all persons had a Native American mtDNA background, whereas 50% of the CDK group and 37% of the control group had Native American paternal ancestry, respectively. There was no significant difference in the frequencies of mtDNA haplogroups between the CDK patient and control groups. Although the Y-chromosome data revealed differences in specific haplogroup frequencies between these two groups, there was no statistically significant relationship between individual paternal genetic backgrounds and the incidence or stage of disease. CONCLUSIONS: These results indicate a lack of correlation between genetic ancestry as represented by haploid genetic systems and the incidence of CDK in Mapuche populations. In addition, the mtDNA appears to play less of a role in CDK expression than for other complex diseases linked to bioenergetic processes. However, further analysis of the mtDNA genome sequence and other genes involved in corneal function may reveal the more precise role that mitochondria play in the expression of CDK.

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PURPOSE: To determine levels of Peptidyl arginine deiminase 2 (PAD2) and its product protein-bound citrulline in cadaver eyes that suffered from normal tension glaucoma (NTG) compared to primary open angle glaucoma (POAG), and controls. METHODS: Western analysis, ELISA, and immunohistochemical analysis were performed with human tissues. RESULTS: We report over expression of PAD2 and higher levels of its product protein-bound citrulline in the optic nerve of normal tension glaucoma patients (NTG). CONCLUSIONS: This is the first report demonstrating that like in POAG, NTG also possesses elevated levels of both PAD2 and protein-bound citrulline.

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OBJECTIVE: To describe the functional and structural characteristics of the cornea in healthy Guinea pigs. ANIMALS STUDIED: Healthy male and female pigmented and albino Guinea pigs (Caviaporcellus) aged 3-5 months old were used. PROCEDURES: The animals' corneas underwent different in vivo studies including: slit-lamp biomicroscopy, fluorescein staining (FS), break-up time test (BUT), confocal microscopy and pachymetry. The corneas were also studied histopathologically with light microscopy, immunohistochemistry and transmission electron microscopy. RESULTS: No significant differences were found between pigmented and albino animals, male and female, OD and OS in any study performed. The differences on corneal thickness values were not significant among central (227.85 +/- 14.09 microm) and upper and temporal peripheral regions (226.60 +/- 12.50 and 225.70 +/- 14.40 microm, respectively). All histological studies performed permitted identification and precise description of the different corneal structures in Guinea pigs: the stratified epithelium (45.52 +/- 5.26 microm), Bowman's layer (2.23 +/- 0.38 microm), stroma (163.69 +/- 4.90 microm), Descemet's membrane (3.96 +/- 0.46 microm) and the endothelium (5.09 +/- 0.71 microm). Combining results from all eyes mean and SD from corneal BUT values was 4.98 +/- 1.67 s. Corneas often showed discrete superficial erosions being the FS positive in both eyes from all the animals. CONCLUSION: This study provides a detailed in vivo and postfixed histological description of the Guinea pig's cornea and information about the physiological tests.

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La Vitamina C o ácido L-ascórbico (AA), es una vitamina esencial y un importante agente antioxidante hidrosoluble, que se sintetiza químicamente a partir de la glucosa, mediante una serie de reacciones enzimáticas, siendo la L-gulono-g-lactona oxidasa (GLO) la última enzima involucrada. La incapacidad de sintetizar AA por ausencia de GLO ocurrió hace cientos de millones de años y se manifiesta sólo en algunas especies. La degradación del AA se lleva a cabo mediante procesos oxidativos que involucran la hidrólisis del anillo lactona para producir ácido 2,3-dicetogulónico (DCG), que posteriormente se degrada por decarboxilación, generando productos coloreados, encontrados en algunas patologías oculares. Entre las diferentes propiedades del AA cabe mencionar su capacidad de absorber radiación ultravioleta (RUV) y evitar el daño fotoquímico en órganos expuestos. En humanos, y en algunos animales (cobayos, ciertos primates, etc.) el humor acuoso tiene mayor concentración de AA que el plasma. Esto responde a un mecanismo de transporte activo especializado en el cuerpo ciliar que se encarga de transportar el AA desde la sangre hacia el humor acuoso y desde allí al epitelio corneal, transformando a la córnea en la estructura del ojo responsable de la mayor absorción de RUV.

Vitamin C or L-ascorbic acid (AA) is an essential vitamin and a water soluble important antioxidant agent, chemically synthesized from glucose, by enzymatic reactions, being the L-gulono-g-lactone oxidase (GLO) the last enzyme involved. The inability to synthesize AA by some species, due to the absence of GLO seems to have happened hundreds of millions years ago. The degradation of the AA is carried out by oxidative processes which involve the hydrolysis of the lactona ring to produce 2,3-diketogulonic acid (DCG) that is later degraded by decarboxilation, generating colored products, found in some ocular pathologies. Among the different properties of the AA, it is worth mentioning its capacity to absorb ultraviolet radiation (RUV) and to avoid the photochemical damage of exposed tissues. In humans and in some animals (guinea pigs, primates, etc) the aqueous humor has bigger concentrations of AA than plasma. This responds to a mechanism of specialized active transport in the ciliary body that transfers AA from the blood towards the aqueous humor and from there to the corneal epithelium, transforming the cornea into the structure of the eye responsible for the biggest absorption of RUV.

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PURPOSE: To present external eye findings and the observation of iris atrophy in patients with climatic droplet keratopathy (CDK). METHODS: Twenty-three patients with CDK and 13 controls living in a semideserted plain of the Argentine Patagonia were studied. Besides a comprehensive eye examination, Cochet-Bonnet aesthesiometry, Schirmer II test, breakup time (BUT), and surface staining were performed. According to corneal findings, eyes were grouped as grade 1 (confluent translucent microdroplets localized in the limbic region of the horizontal quadrants); grade 2 (band-shaped subepithelial haziness compromising the central cornea); and grade 3 (previously described lesions with yellow subepithelial droplets). Results were analyzed with the Fisher, Mann-Whitney, and Spearman tests, which were considered significant at P < 0.05. RESULTS: Nineteen of 23 patients with CDK had bilateral disease, which was asymmetric in 2 of them. Sixteen eyes had grade 1, 21 eyes had grade 2, and 5 eyes had grade 3 disease. Aesthesiometry showed that the more advanced the disease, the more profound the corneal hypoesthesia (P = 0.0008). BUT and ocular surface staining significantly differed between eyes with grade 3 and grade 1, grade 3 and grade 2, and grade 3 and controls. In 38.09% of eyes with CDK and in none of the controls, sectorial depigmentation and atrophy of the inferior iris were observed. CONCLUSIONS: A severe decrease of corneal sensitivity was observed in advanced stages of CDK. Some degree of dry eye was present in most patients, but severe disease was infrequent at any stage of CDK. Inferior iris depigmentation and atrophy was frequently observed among patients with CDK.

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