The Effect of Heterophoria on the Size of Distance and Near Fusion Vergence.

AIMS: To demonstrate changes in distance and near fusional vergence measured with prism bars, while compensating for present heterophoria using current ametropia correction. In addition, to determine the differences in values of the AC/A ratio determined by the heterophoric (calculation) and gradient methods. MATERIAL AND METHODS: The basic sample includes 19 subjects with a mean age of 21.5 ±3.0 years (min. 18, max. 27). We used the Von Graefe technique for examination of distance and near phoria, and prism bars for examination of fusion vergences measured in prism diopters. We divided the basic cohort into six research sets according to the size of distance and near heterophoria. This was a cohort of patients with distance (D OR) and near orthophoria (N OR), a cohort of patients with distance (D EX) and near exophoria (N EX) and a set of patients with distance (D ES) and near esophoria (N ES). RESULTS: In the case of both groups with exophoria (distance, near) we found a statistically significant result only for negative fusion vergence (NFV). There was a statistically significant increase in NFV in the sample with distance and near exophoria (D EX, p = 0.01 and B EX, p = 0.02, respectively). In our study, we also demonstrated a statistically significant difference (p < 0.001) in the values of the AC/A ratio measured by the gradient and heterophoric methods. The values determined by the gradient method are lower (3.0 ±1.1 pD/D versus 5.8 ±0.9 pD/D) than by the heterophoric method. CONCLUSION: By comparing fusion vergence values in patients with exophoria and orthophoria, we demonstrated that in the presence of distance or near exophoria there is an increase in ipsilateral fusion vergence. In the case of an increase in ipsilateral fusion vergence, the finding was statistically significant both distance and near (p = 0.01 and p = 0.02, respectively). By contrast, we were unable to prove this fact in the group of patients with esophoria. In our study, we also demonstrated a statistically significant difference (p < 0.001) in the values of the AC/A ratio measured by the gradient and heterophoric methods. The values determined by the gradient method are lower (3.0 ±1.1 pD/D versus 5.8 ±0.9 pD/D) than by the heterophoric method.

Importance of evaluation of bone invasion type in squamous cell carcinomas of the oral cavity and oropharynx.

AIMS: The objective of this study was to compare bone invasion type with histopathological, clinical and immunohistochemical prognostic factors. METHODS: The study included 49 patients who were treated for oral squamous cell carcinoma. Of which, 30 patients, with presence of bone invasion on histopathology, were divided according to the type of bone invasion (erosive, infiltrative, mixed). Each invasion type was compared to microvascular density using the CD34 marker. RESULTS: The bone invasion was observed in 30 out of 49 patients (61.22%). On McNemar's test, statistically significant association was observed between bone invasion types and histopathological grade. In contrast, no significant correlation was observed between bone invasion type, and tumour volume or nodal metastases. In tumours with bone invasion of the infiltrative type, higher frequency of locoregional relapses was observed. The 5-year survival, since diagnosis, was approximately 60% in the erosive group, 40% in the mixed group, and merely 15% in the infiltrative group. CONCLUSION: Peritumoural microvascular density was not significantly related to bone invasion types. Whereas, a significantly higher intratumoural microvascular density was observed in infiltrative type of the bone invasion, when compared to the erosive and mixed type.

A Method for Evaluation the Fatigue Microcrack Propagation in Human Cortical Bone Using Differential X-ray Computed Tomography.

Fatigue initiation and the propagation of microcracks in a cortical bone is an initial phase of damage development that may ultimately lead to the formation of macroscopic fractures and failure of the bone. In this work, a time-resolved high-resolution X-ray micro-computed tomography (CT) was performed to investigate the system of microcracks in a bone sample loaded by a simulated gait cycle. A low-cycle (1000 cycles) fatigue loading in compression with a 900 N peak amplitude and a 0.4 Hz frequency simulating the slow walk for the initialization of the internal damage of the bone was used. An in-house developed laboratory X-ray micro-CT imaging system coupled with a compact loading device were employed for the in situ uni-axial fatigue experiments reaching a µ2µm effective voxel size. To reach a comparable quality of the reconstructed 3D images with the SEM microscopy, projection-level corrections and focal spot drift correction were performed prior to the digital volume correlation and evaluation using differential tomography for the identification of the individual microcracks in the microstructure. The microcracks in the intact bone, the crack formation after loading, and the changes in the topology of the microcracks were identified on a volumetric basis in the microstructure of the bone.

In-situ X-ray Differential Micro-tomography for Investigation of Water-weakening in Quasi-brittle Materials Subjected to Four-point Bending.

Several methods, including X-ray radiography, have been developed for the investigation of the characteristics of water-saturated quasi-brittle materials. Here, the water content is one of the most important factors influencing their strength and fracture properties, in particular, as regards to porous building materials. However, the research concentrated on the three-dimensional fracture propagation characteristics is still significantly limited due to the problems encountered with the instrumentation requirements and the size effect. In this paper, we study the influence of the water content in a natural quasi-brittle material on its mechanical characteristics and fracture development during in-situ four-point bending by employing high-resolution X-ray differential micro-tomography. The cylindrical samples with a chevron notch were loaded using an in-house designed four-point bending loading device with the vertical orientation of the sample. The in-house designed modular micro-CT scanner was used for the visualisation of the specimen's behaviour during the loading experiments. Several tomographic scans were performed throughout the force-displacement diagrams of the samples. The reconstructed 3D images were processed using an in-house developed differential tomography and digital volume correlation algorithms. The apparent reduction in the ultimate strength was observed due to the moisture content. The crack growth process in the water-saturated specimens was identified to be different in comparison with the dry specimens.

Comparison of keratometric values and corneal eccentricity.

The aim of this work is to compare the findings of keratometric values and their differences at various refractive errors. The eccentricity of the cornea in the sense compared to the possible influence of refraction of the eye is topographically observed. Groups of myopia, hyperopia and emmetropia (as a control group) are always represented in total 600 eyes. The studied cohort in total of 300 clients enrolled. Autorefraktokeratometer with Placido disc was used to measure the steepest and the flattest meridian to determine the corneal eccentricity. Group I consisted of 100 myopes, 35 men and 65 women, average age 37.3 years. Objective refraction--sphere: -2.9 D, cylinder: -0.88 D. Keratometry in this group is in the steepest meridian 7.62 mm and the flattest meridian is 7.76 mm. The eccentricity was 0.37. Group II consisting of 100 hyperopic subjects, 40 men and 60 women, average age 61.6 years. Objective refraction--sphere: +2.71 D, cylinder: -1.0 D. Keratometric measurement looks as follows: the steepest meridian is 7.67 mm, the flattest meridian then is 7.81 mm. The value of the eccentricity is 0.37. The third group III consists of 100 emetropic subjects, then clients without refractive errors who achieve without corrective aids Vmin = 1.0. This group is composed of 42 men and 58 women, mean age 41.4 years. Objective refraction--sphere: +0.32 D, cylinder: -0.28 D. The steepest meridian is 7.72 mm the flattest meridian then 7.83 mm. The eccentricity is represented by the observed values of 0.36. Keratometry as well as topography are fundamental methods of corneal anterior surface measurement. Their proportions are essential for the proper parameters selection especially in case of contact lenses as one of the possible means intended to correct refractive errors.

Visual field.

This article is dedicated to main information about visual field, monocular and binocular ranges of visual field including their defects. Visual field loss may occur to disease of the eye, optic nerve or brain. Typical changes are present at glaucoma and macular degeneration. Visual pathway is also mentioned. The basic medical examinations of visual fields are Amsler grid, kinetic and static perimetry and the other. Newer method is microperimetry which detects the changes directly on the retina. The aim of this poster is importance and determination of visual field as a preventive ophthalmologic and optometric examination.

Corneal shape and eccentricity in population.

The human cornea is an important tissue involved in the mediation of visual perception. It is important to measure its shape especially in the case of correction of refractive errors. Suitable correction such as contact lenses is chosen based on the measured values of the refractive error. An inappropriately fitted contact lens can significantly affect the physiology of the cornea and the eye. Corneal eccentricity can be modeled on the sections of a conoid by which is possible to describe corneal surface. This article follows the keratometry values in a sample of a population as one of the factors affecting contact lenses fitting.