scholarly journals Involvement of anterior and posterior corneal surface area imbalance in the pathological change of keratoconus

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Koji Kitazawa ◽  
Motohiro Itoi ◽  
Isao Yokota ◽  
Koichi Wakimasu ◽  
Yuko Cho ◽  
...  
Keyword(s):  
Surface Area ◽  
Pathological Change ◽  
Corneal Surface

scholarly journals Quantitative comparison of corneal surface areas in keratoconus and normal eyes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
François-Xavier Crahay ◽  
Guillaume Debellemanière ◽  
Stephan Tobalem ◽  
Wassim Ghazal ◽  
Sarah Moran ◽  
...  
Keyword(s):  
Surface Area ◽  
Quantitative Comparison ◽  
Corneal Surface ◽  
Surface Areas ◽  
Corneal Diameter ◽  
Irregular Astigmatism ◽  
Corneal Thinning ◽  
Corneal Disorder

AbstractKeratoconus is a highly prevalent corneal disorder characterized by progressive corneal thinning, steepening and irregular astigmatism. To date, pathophysiology of keratoconus development and progression remains debated. In this study, we retrospectively analysed topographic elevation maps from 3227 eyes of 3227 patients (969 keratoconus and 2258 normal eyes) to calculate anterior and posterior corneal surface area. We compared results from normal eyes and keratoconus eyes using the Mann–Whitney U test. The Kruskal–Wallis test was used to compare keratoconus stages according to the Amsler–Krumeich classification. Keratoconus eyes were shown to have statistically significantly larger corneal surface areas, measured at the central 4.0 mm and 8.0 mm, and total corneal diameter. However, no significant increase in corneal surface area was seen with increasing severity of keratoconus. We suggest that these results indicate redistribution, rather than increase, of the corneal surface area with keratoconus severity.

Corneal surface area: an index of anterior segment growth

2001 ◽  
Vol 21 (4) ◽  
pp. 286-295 ◽  
Author(s):  
Richard A. Stone ◽  
Ton Lin ◽  
Reiko Sugimoto ◽  
Cheryl Capehart ◽  
Maureen G. Maguire ◽  
...  
Keyword(s):  
Surface Area ◽  
Anterior Segment ◽  
Corneal Surface

scholarly journals Sexual Dimorphism in Eye Morphology in a Butterfly (Asterocampa leilia; Lepidoptera, Nymphalidae)

2000 ◽  
Vol 103 (1-2) ◽  
pp. 25-36 ◽  
Author(s):  
Kristine S. Ziemba ◽  
Ronald L. Rutowski
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Visual Field ◽  
Surface Area ◽  
Sexual Differences ◽  
Corneal Surface ◽  
Mate Searching ◽  
Eye Morphology ◽  
Eye Size ◽  
Males And Females

In the Empress Leilia butterfly,Asterocampa leilia, as in many insects, males have larger eyes than females. We explore the morphological causes and consequences of this dimorphism in eye size by comparing the corneal surface area, facet numbers, and patterns of variation in facet dimensions in males and females. We report that, with body size (measured by forewing length) controlled, male eyes are consistently larger than female eyes, and that, although males and females do not differ significantly in the number of facets per eye, males have significantly larger facets. Also, males have disproportionately larger facets both frontally and dorsally. As a result of these sexual differences in eye structure, males are expected to have a larger and more acute visual field than females which could be advantageous in the context of this species' mate searching tactic.

scholarly journals Post-embryonic development of the lateral eye of Cloeon sp. (Ephemeroptera: Baetidae) as revealed by scanning electron microscopy

2000 ◽  
Vol 11 (2) ◽  
pp. 89-96 ◽  
Author(s):  
Susmita Gupta ◽  
Abhik Gupta ◽  
V. Benno Meyer-Rochow
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Embryonic Development ◽  
Surface Area ◽  
Corneal Surface ◽  
Developmental Patterns ◽  
Male And Female ◽  
Lateral Eye ◽  
Males And Females ◽  
Scanning Electron

Post-embryonic developmental patterns of the lateral eyes of both male and female Cloeon sp. are described and compared with each other morphometrically on the basis of scanning electron microscopy. In the larvae number of ommatidia, ommatidial size, and total corneal surface area of the eye increase towards the subimaginal moult. It is then that clear differences between males and females begin to occur: while further increases in the number of ommatidia are recorded from the lateral eye of subimago and imago females (accompanied by decreasing facet sizes and interommatidial angles), males show decreasing numbers of ommatidia and total corneal areas in their lateral eyes as they prepare to leave the water. Consequently, the lateral eyes of a female are larger than those of a male imago. It appears that the enormous development of the dorsal eyes of the males has occurred at the expense of the lateral eyes. In male as well as female lateral eyes two major facet shapes are encountered: squares with rounded corners which are predominantly found in the central and upward looking areas, and hexagons which are dominating the lateral and ventral-facing regions. The different roles of the lateral eyes in male and female baetid mayflies is discussed in relation to their flights and the intriguing idea is presented that females might choose males with the largest dorsal eyes.

scholarly journals Quantitative Interocular Comparison of Total Corneal Surface Area and Corneal Diameter in Patients With Highly Asymmetric Keratoconus.

2021 ◽  
Author(s):  
François-Xavier CRAHAY ◽  
Guillaume DEBELLEMANIÈRE ◽  
Stephan TOBALEM ◽  
Wassim GHAZAL ◽  
Sarah MORAN ◽  
...  
Keyword(s):  
Surface Area ◽  
Anterior Chamber Depth ◽  
Strongly Correlated ◽  
Altman Analysis ◽  
Corneal Surface ◽  
Surface Areas ◽  
Elevation Data ◽  
Orbscan Ii ◽  
Corneal Diameter ◽  
Corneal Disorder

Abstract Keratoconus is a progressive corneal disorder which is frequently asymmetric. The aetiology of keratoconus remains unclear, and the concept of keratoconus as an ectatic disorder has been challenged recently. We carried out a retrospective study in 160 eyes of 80 patients, to evaluate and compare interocular differences in corneal diameter and surface area in patients with unilateral/highly asymmetric keratoconus (UHAKC). Calculations were performed using raw topographic elevation data derived from topographic measurements using Orbscan II, and we extrapolated surface areas up to measured corneal diameter. We also evaluated inter-eye correlation, and correlation between corneal surface area, corneal diameter and keratoconus severity. Our results showed a statistically significant but not clinically important greater corneal diameter (12.14mm and 12.17 mm; p=0.04), and corneal surface area (paired t-test, p<0.0001; p=0.0009 respectively) in more affected eyes. Inter-eye comparison revealed corneal diameter, anterior chamber depth, and corneal surface area were strongly correlated between eyes. Corneal surface area remained strongly correlated, and Bland-Altman analysis also showed strong inter-ocular agreement. Our results show that in patients with UHAKC the interocular difference in corneal diameter and corneal surface area is clinically insignificant, and are consistent with a redistribution, rather than increase, of corneal surface area with keratoconus progression.

scholarly journals The corneal surface of aquatic vertebrates: microstructures with optical and nutritional function?

2000 ◽  
Vol 355 (1401) ◽  
pp. 1171-1176 ◽  
Author(s):  
H. Barry Collin ◽  
Shaun P. Collin
Keyword(s):  
Surface Structure ◽  
Surface Area ◽  
Cell Density ◽  
Tear Film ◽  
Adaptive Plasticity ◽  
Aquatic Environments ◽  
Outer Cell ◽  
Corneal Surface ◽  
Phascolarctos Cinereus ◽  
Interspecific Differences

The anterior surface of the mammalian cornea plays an important role in maintaining a smooth optical interface and consequently a sharp retinal image. The smooth surface is produced by a tear film, which adheres to a variety of microprojections, which increase the cell surface area, improve the absorbance of oxygen and nutrients and aid in the movement of metabolic products across the outer cell membrane. However, little is known of the structural adaptations and tear film support provided in other vertebrates from different environments. Using field emission scanning electron microscopy, this study examines the density and surface structure of corneal epithelial cells in representative species of the classes Cephalaspidomorphi, Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves and Mammalia, including some Marsupialia. Variations in cell density and the structure and occurrence of microholes, microridges, microplicae and microvilli are described with respect to the demands placed upon the cornea in different aquatic environments such as marine and freshwater. A progressive decrease in epithelial cell density occurs from marine (e.g. 29348 cells mm −2 in the Dover sole Microstomius pacificus ) to estuarine or freshwater (e.g. 5999 cells mm −2 in the black bream Acanthopagrus butcheri ) to terrestrial (e.g. 2126 cells mm −2 in the Australian koala Phascolarctos cinereus ) vertebrates, indicating the reduction in osmotic stress across the corneal surface. The microholes found in the Southern Hemisphere lampreys, namely the pouched lamprey ( Geotria australis ) and the shorthead lamprey ( Mordacia mordax ) represent openings for the release of mucus, which may protect the cornea from abrasion during their burrowing phase. Characteristic of marine teleosts, fingerprint–like patterns of corneal microridges are a ubiquitous feature, covering many types of sensory epithelia (including the olfactory epithelium and the oral mucosa). Like microplicae and microvilli, microridges stabilize the tear film to maintain a smooth optical surface and increase the surface area of the epithelium, assisting in diffusion and active transport. The clear interspecific differences in corneal surface structure suggest an adaptive plasticity in the composition and stabilization of the corneal tear film in various aquatic environments.

Preparation and characterisation of vanadium pentoxide supported rhodium catalyst

1988 ◽  
Vol 46 ◽  
pp. 946-947
Author(s):  
A. Legrouri
Keyword(s):  
Aqueous Solution ◽  
Thermal Decomposition ◽  
Physicochemical Properties ◽  
Surface Area ◽  
Vanadium Pentoxide ◽  
High Purity ◽  
Gas Adsorption ◽  
Rhodium Catalyst ◽  
Optical Methods ◽  
Reducible Oxides

The industrial importance of metal catalysts supported on reducible oxides has stimulated considerable interest during the last few years. This presentation reports on the study of the physicochemical properties of metallic rhodium supported on vanadium pentoxide (Rh/V2O5). Electron optical methods, in conjunction with other techniques, were used to characterise the catalyst before its use in the hydrogenolysis of butane; a reaction for which Rh metal is known to be among the most active catalysts.V2O5 powder was prepared by thermal decomposition of high purity ammonium metavanadate in air at 400 °C for 2 hours. Previous studies of the microstructure of this compound, by HREM, SEM and gas adsorption, showed it to be non— porous with a very low surface area of 6m2/g3. The metal loading of the catalyst used was lwt%Rh on V2Q5. It was prepared by wet impregnating the support with an aqueous solution of RhCI3.3H2O.

Cell morphology, volume, and surface area determinations from multilevel contouring within HVEM micrographs of serial sections and whole-cell mounts

1987 ◽  
Vol 45 ◽  
pp. 588-589
Author(s):  
M. Marko ◽  
A. Leith ◽  
D. Parsons
Keyword(s):  
Surface Area ◽  
Electron Micrographs ◽  
Cell Morphology ◽  
Individual Variation ◽  
Serial Section ◽  
Stereo Pair ◽  
Complex Structures ◽  
Serial Sections ◽  
Surface Areas ◽  
Computer Based

The use of serial sections and computer-based 3-D reconstruction techniques affords an opportunity not only to visualize the shape and distribution of the structures being studied, but also to determine their volumes and surface areas. Up until now, this has been done using serial ultrathin sections.The serial-section approach differs from the stereo logical methods of Weibel in that it is based on the Information from a set of single, complete cells (or organelles) rather than on a random 2-dimensional sampling of a population of cells. Because of this, it can more easily provide absolute values of volume and surface area, especially for highly-complex structures. It also allows study of individual variation among the cells, and study of structures which occur only infrequently.We have developed a system for 3-D reconstruction of objects from stereo-pair electron micrographs of thick specimens.

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