Issues of rehabilitation of the patients with symblepharon using oral mucosal autografts.

PURPOSE: To systematize clinical variants of symblepharon and to analyze rehabilitation availability boundaries in patients with different forms of symblepharons. METHODS: Retrospective analysis of clinical cases included 26 patients with local, subtotal, and total symblepharon (ankyloblepharon) with a normal or anophthalmic orbit. In all patients, symblepharon was operated using split- or full-thickness oral mucosal autografts and their fixation with U-shaped stitches and compression plates. Preoperatively and postoperatively, best-corrected visual acuity, IOP, extraocular motility, results of Schirmer I test, and tear break-up time with slit-lamp biomicroscopy were analyzed, as well as additional ultrasound and electrophysiological studies were performed in some cases. Follow-up period lasted from 1.5 to 6 years. RESULTS: The proposed surgical technique using mucosal autografts in all patients allowed complete anatomical restoration of conjunctival fornices and cavity. It resulted in improvement of visual function in patients with local symblepharon, full restoration of ocular motility in patients with a presence of the eye and provided an opportunity to wear artificial eye in patients with anophthalmia. Nonetheless, loss of conjunctival Krause's and Wolfring lacrimal glands, goblet cells, meibomian glands, and limbal stem cells prevents from further optic keratoplasty in patients with total or subtotal symblepharon on potentially sighted eye. CONCLUSION: The most difficult patients for visual rehabilitation were the ones with subtotal or total symblepharon (ankyloblepharon) on potentially sighted eye due to the loss of conjunctival goblet cells, meibomian glands, and limbal stem cells.

A Novel Method for Complex Diagnostics of Globes' Position.

Spiral computed tomography is a gold standard in diagnostics of intraorbital pathological changes. Modern software provides great opportunities at viewing and analyzing DICOM files. Earlier, the authors introduced a method of computed exophthalmometry for precise measurement of globes' position even in the cases of lateral orbital rim fracture. However, eye proptosis is known to be depending on the eye length (ocular component), retrobulbar volume (orbital component), as well as anatomy of neurocranium and brain (cerebral component). Nevertheless, conventional Hertel exophthalmometry and other proposed methods do not specify the component, involved in the pathogenesis of enophthalmos or exophthalmos, that is why additional examinations are required. In this article, the authors propose a novel approach, which can complement and/or substitute instrumental methods used for differential diagnostics of enophthalmos or exophthalmos.

Prediction and Experimental Evaluation of Mechanical Properties of SiC-Reinforced Ti-4.25Al-2V Matrix Composites Produced by Laser Direct Energy Deposition.

An important direction in the development of additive technologies is associated with the addition of ceramic particles (oxide, carbide, boride, and nitride ceramics) to metal powders. The prediction of the physical and mechanical characteristics of SiC-particle-reinforced composite materials (PRCMs) in comparison with experimental results was studied. A near-α Ti-4.25Al-2V titanium-alloy-based composite reinforced by 1 vol.% of SiC ceramic particles was produced using laser direct energy deposition. A multiscale modeling approach at the micro and macro levels was applied. At the micro level, the toughness and strength characteristics for a temperature interval of T = 20-450 °C were predicted using a representative volume element of PRCM with the nearly real shape of SiC particles. At the macro level, the features of plastic deformation and fracture of the PRCM were predicted by numerical modeling using the commercial software Digimat Student Edition ver. 2022.4 and Ansys Student 2023 R2. The addition of SiC particles was found to improve the physical and mechanical properties in the whole temperature range. The results of the numerical modeling were consistent with the experimental data (the deviation did not exceed 10%). The proposed approach for predicting the physical and mechanical properties of Ti-4.25Al-2V/SiC can also be used for other PRCMs obtained by laser direct energy deposition.

Features of Heat Treatment the Ti-6Al-4V GTD Blades Manufactured by DLD Additive Technology.

Additive manufacturing of titanium alloys is one of the fastest growing areas of 3D metal printing. The use of AM methods for parts production in the aviation industry is especially promising. During the deposition of products with differently sized cross-sections, the thermal history changes, which leads to non-uniformity of the structure and properties. Such heterogeneity can lead to failure of the product during operation. The structure of deposited parts, depending on the thermal cycle, may consist of α', α + α' + ß', and α + ß in different ratios. This problem can be solved by using heat treatment (HT). This paper presents research aimed towards the determination of optimal heat treatment parameters that allows the reception of the uniform formation of properties in the after-treatment state, regardless of the initial structure and properties, using the example of a deposited Ti-6Al-4V gas turbine blade.

Effect of Elevated Temperatures on the Mechanical Properties of a Direct Laser Deposited Ti-6Al-4V.

In the present work, the mechanical properties of the DLD-processed Ti-6Al-4V alloy were obtained by tensile tests performed at different temperatures, ranging from 20 °C to 800 °C. Thereby, the process conditions were close to the conditions used to produce large-sized structures using the DLD method, resulting in specimens having the same initial martensitic microstructure. According to the obtained stress curves, the yield strength decreases gradually by 40% when the temperature is increased to 500 °C. Similar behavior is observed for the tensile strength. However, further heating above 500 °C leads to a significant increase in the softening rate. It was found that the DLD-processed Ti-6Al-4V alloy had a Young's modulus with higher thermal stability than conventionally processed alloys. At 500 °C, the Young's modulus of the DLD alloy was 46% higher than that of the wrought alloy. The influence of the thermal history on the stress relaxation for the cases where 500 °C and 700 °C were the maximum temperatures was studied. It was revealed that stress relaxation processes are decisive for the formation of residual stresses at temperatures above 700 °C, which is especially important for small-sized parts produced by the DLD method. The coefficient of thermal expansion was investigated up to 1050 °C.

Computed exophthalmometry is an accurate and reproducible method for the measuring of eyeballs' protrusion.

PURPOSE: The aim of this study was to assess reproducibility of the repeated measurements from proposed computed exophthalmometry and to make a comparison with the Hertel exophthalmometer. METHODS: Computed tomography scans of patients with pathological (group 1) and intact orbits (group 2) were included in this retrospective study. In both groups, a single investigator measured a difference of eyeballs' protrusion using the proposed method of computed exophthalmometry. Briefly, the distances from the corneal apices of the left and right eyeballs to the line placed through the styloid processes of the temporal bones were measured and compared to each other three times independently. RESULTS: In some patients with intact lateral orbital rims the results of computed exophthalmometry correlated with the measurements from the Hetrel exophthalmometer. The analysis of the triple measurements with computed exophthalmometry revealed no significant difference in the value of standard deviation of the results in patients with intact and pathological orbits. In comparison with the Hertel-type exophthalmometry, the proposed method demonstrated very low variability and high repeatability of the measurements. The difference of 0.10-0.87 mm in the eyeballs protrusion should be considered as normal. Computed exophthalmometry is an accurate and reproducible method, which can be used for the measurements of eyeballs' protrusion.