Javier Martínez

Mechanical Evolution of Lime Mortars during the Carbonation Process

Lime mortar is one of the most ancient and durable building materials. It is characterized by a slow carbonation during which Ca(OH)2 reacts with CO2 present in air and forms calcite, giving rise to a stronger and more compact material. This process takes place from the surface to the interior of the material and it is strongly affected by the reaction conditions. The aim of this study is to quantify the increase in strength and elasticity of different lime mortars according to their carbonation degree. For that, six types of mortars were elaborated, with different lime/aggregate proportions and aggregate mineralogy and grading. Mineralogical and textural studies were carried out to follow the carbonation process. Each mortar was tested in a uniaxial compression press after 15, 28, 60 days from the elaboration. In order to differentiate the mechanical behaviour of the external and internal parts of the mortars, two micro-samples (10×10×10 mm) were obtained from the first 10 mm and from the core of each prism. Results show that an increase in strength and especially in the elastic modulus is associated to the carbonation process, but it is different depending on the composition and compactness of the mortars.

Short-term outcomes of small-incision lenticule extraction (SMILE) for low, medium, and high myopia.

Purpose To determine the safety, efficacy, and predictability of small-incision lenticule extraction at 6-month follow-up, depending on the level of the myopic refractive error. The surgeries were performed by a surgeon new to this technique. Methods Seventy-one subjects with a mean age of 31.86 ± 5.57 years were included in this retrospective observational study. Subjects were divided into 3 groups depending on the preoperative spherical equivalent (SE): low group from -1.00 D to -3.00 D, medium from -3.25 D to -5.00 D, and high from -5.25 D to -7.00 D. Manifest refraction, corrected distance visual acuity (CDVA), and uncorrected distance visual acuity (UDVA) were measured before surgery and at 6 months after the treatment. Results In total, 1.4% of the eyes lost 1 line of CDVA after the procedure, whereas 95.8% remained unchanged and 2.8% gained 1 line. A significant undercorrection (p = 0.031) was found in the high myopia group (median -0.50 D), whereas the low and medium groups remained near to emmetropia. In terms of efficacy, no statistically significant intergroup differences for postoperative UDVA (p = 0.282) were found. The vector analysis also showed undercorrection of the preoperative cylinder, even though the standard deviations decreased from 0.9 D in the x axis and 0.7 D in the y axis to 0.24 D and 0.27 D, respectively. Conclusions Small-incision lenticule extraction might be a safe, effective, and predictable procedure even for inexperienced surgeons. No differences in efficacy were found among myopia levels even though undercorrections were found for SE and cylinder in high myopia.

Corneal Thickness After SMILE Affects Scheimpflug-based Dynamic Tonometry.

PURPOSE To evaluate the corneal biomechanical changes due to small incision lenticule extraction (SMILE) measured by Scheimpflug-based dynamic tonometry and to assess the impact of the corneal thickness. METHODS Sixty-eight patients measured with the Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany) preoperatively and 1 month after SMILE were included in this retrospective observational study. Patients were divided into three groups depending on the preoperative spherical equivalent: low from -1.00 to -3.00 diopters (D), medium from -3.25 to -5.00 D, and high from -5.25 to -7.25 D. Changes in Corvis ST parameters due to the surgery were analyzed and new indexes for correcting the impact of corneal thickness were proposed. RESULTS First and second applanation times changed after SMILE (P < .0001) but no differences were found in the comparison between these relative changes (P = .31). First applanation time was correlated with central corneal thickness (r = 0.368, P = .002) but not second applanation time (r = -0.149, P = .23). The change in first applanation time due to SMILE was different among myopic groups (P = .007) but equal when a new index that considers the removed central corneal thickness was used for comparison (P = .31). Deformation amplitude was also increased after SMILE (P < .0001), but after subtracting the removed corneal thickness from the postoperative deformation amplitude the result was equal to the preoperative deformation amplitude (P = .26). CONCLUSIONS SMILE produces significant changes in the Corvis ST parameters of time and deformation amplitude, but these changes are mainly explained by the confounding variable of corneal thickness. [J Refract Surg. 2016;32(12):821-828.].

Mechanical Characterisation of Ancient Egyptian Mortars

Several samples of ancient mortars were studied in the context of the archaeological excavations at Djehuty (Luxor, Egypt). The studied mortars had two different applications: to render external walls and as structural elements (adobe walls, contact between stone blocks, etc). An understanding of the mechanical stability of these materials is necessary in order to guarantee correct preservation of the remains. However, their mechanical characterisation using standard tests would require large samples (over 50 mm in cubic/cylinder form), which archaeological excavations are unlikely to be able to provide. The aim of this research was to analyse the mechanical behaviour of different gypsum mortars by means of the uniaxial micro-compression test and relate this to their microstructure. The microstructure is described in terms of the mineralogical composition (XRD), texture (SEM) and pore structure (MIP). Results showed that the studied gypsum mortars presented a very low strength and elastic modulus (0.25-1.60 MPa and 97.56-260.97 MPa, respectively). These mechanical characteristics are closely related to the mortar microstructure, since they presented a highly porous texture (57.93-68.35%), a polymodal pore size distribution in the 0.1-10 m range, and low contact between crystals (very open texture). Micro-compression characterisation of ancient mortars and building rocks was compared to meso-compression results found in the literature and confirmed the effectiveness of the micro-compression test as a low-invasive technique for characterising materials from architectural heritage.

From Presbyopia to Cataracts: A Critical Review on Dysfunctional Lens Syndrome

Dysfunctional lens syndrome (DLS) is a term coined to describe the natural aging changes in the crystalline lens. Different alterations in the refractive properties and transparency of the lens are produced during the development of presbyopia and cataract, such as changes in internal high order aberrations or an increase in ocular forward scattering, with a potentially significant impact on clinical measures, including visual acuity and contrast sensitivity. Objective technologies have emerged to solve the limits of current methods for the grading of the lens aging, which have been linked to the DLS term. However, there is still not a gold standard or evidence-based clinical guidelines around these new technologies despite multiple research studies have correlated their results with conventional methods such as visual acuity or the lens opacification system (LOCS), with more scientific background around the ocular scattering index (OSI) and Scheimpflug densitometry. In either case, DLS is not a new evidence-based concept that leads to new knowledge about crystalline lens aging but it is a nomenclature change of two existing terms, presbyopia and cataracts. Therefore, this term should be used with caution in the scientific peer-reviewed literature.

Corneal biomechanics after laser refractive surgery: Unmasking differences between techniques

The hypothesis that small-incision lenticule extraction provides better preservation of corneal biomechanics than previous laser refractive techniques has led to a growth in the interest in clinical and experimental research in this field. This hypothesis is based on the fact that corneal layers with greater stiffness are preserved with this new technique. However, this hypothesis is controversial because clinical research has shown a great disparity in the outcomes. In this review, we performed an in-depth analysis of the factors that might affect corneal biomechanics in laser refractive surgery procedures from a macrostructural to a microstructural viewpoint. New advances in algorithms with current devices or the introduction of new devices might help unmask the possible advantages of small-incision lenticule extraction in corneal biomechanics.

Prediction of surgically induced astigmatism in manual and femtosecond laser-assisted clear corneal incisions

Purpose: To assess the surgically induced astigmatism with femtosecond laser-assisted and manual temporal clear corneal incisions and to evaluate the performance of a model for prediction of the surgically induced astigmatism based on the preoperative corneal astigmatism. Methods: Clinical data of 104 right eyes and 104 left eyes undergoing cataract surgery, 52 with manual incisions and 52 with femtosecond laser-assisted incisions in each eye group, were extracted and revised retrospectively. In all cases, manual incisions were 2.2 mm width and femtosecond incisions were 2.5 mm width, both at temporal location. A predictive model of the surgically induced astigmatism was obtained by means of simple linear regression analyses. Results: Mean surgically induced astigmatisms for right eyes were 0.14D@65° (manual) and 0.24D@92° (femtosecond) (p > 0.05) and for left eyes, 0.15D@101° (manual) and 0.19D@104° (femtosecond) (p > 0.05). The orthogonal components of the surgically induced astigmatism (XSIA, YSIA) were significantly correlated (p < 0.05) with the preoperative orthogonal components of corneal astigmatism (Xpreop, Ypreop) (r = −0.29 for X and r = −0.1 for Y). The preoperative astigmatism explained 8% of the variability of the XSIA and 3% of the variability of YSIA. The postoperative corneal astigmatism prediction was not improved by the surgically induced astigmatism obtained from the model in comparison with the simple vector subtraction of the mean surgically induced astigmatism. Conclusion: Temporal incisions induce similar astigmatism either for manual or for femtosecond procedures. This can be clinically negligible for being considered for toric intraocular lens calculation due to the great standard deviation in comparison with the mean. The usefulness of the prediction model should be confirmed in patients with high preoperative corneal astigmatism.

Biometric Factors Associated with the Visual Performance of a High Addition Multifocal Intraocular Lens

ABSTRACT Purpose/Aim: To evaluate the impact of ocular parameters on the visual performance achieved with the multifocal intraocular lens (IOL) Bi-Flex M 677MY. Materials and Methods: About 26 subjects were included in the current study. Several physiological variables were retrieved from the 3-month follow-up visit, including pupil diameter and distance from pupil center to the vertex normal of the anterior cornea (µ). These variables were also obtained in the preoperative visit. Binocular and monocular visual acuity defocus curves were measured at 1 and 3 months after surgery, respectively. The monocular Area Under the Curve (AUC) was computed along the total range (Total Area Under the Curve (TAUC), +1.00 to −4.00 D) and for the ranges of Far (Far Area Under the Curve (FAUC), +0.50 to −0.50 D), (Intermediate Area Under the Curve (IAUC), −1.00 to −1.50 D) and Near vision (Near Area Under the Curve (NAUC), −2.00 to −4.00 D). Correlations between these areas and the postoperative physiological variables were assessed. Results: The mean µ was reduced from 0.21 to 0.10 mm after surgery, as well as pupil diameters, either photopic (−7.4%) or mesopic (−8.1%) (p < 0.05). The mean AUCs were 2.08 ± 0.74 for TAUC, 0.57 ± 0.17 for FAUC, 0.16 ± 0.09 for IAUC, and 0.81 ± 0.29 for NAUC. Significant correlations were found between NAUC and corneal power (r = −0.39, p = 0.05) as well as between IAUC and temporal decentration of the lens from vertex normal (ρ = −0.41, p = 0.04). Conclusions: The visual performance at near distance with the IOL evaluated improved in eyes with less corneal power. On the other hand, a slight temporal IOL decentration from vertex normal also improved intermediate visual acuity. The binocular defocus curve was similar to other trifocal IOLs.

Above-average defocus curves in photopic and mesopic vision with multifocal intraocular lenses after laser assisted in situ keratomileusis

Department of Ophthalmology (Qvision), Vithas Virgen del Mar Hospital, Almería 04120, Spain Department of Ophthalmology, Torrecárdenas Hospital Complex, Almería 04009, Spain Department of Optics, Pharmacology and Anatomy, University of Alicante, San Vicente del Raspeig, Alicante 03690, Spain Department of Ophthalmology (Oftalmar), Vithas Medimar International Hospital, Alicante 03016, Spain Correspondence to: David P. Piñero. Department of Optics, Pharmacology and Anatomy, University of Alicante, Crta San Vicente del Raspeig s/n, San Vicente del Raspeig, Alicante 03690, Spain. david.pinyero@ua.es Received: 2016-03-18 Accepted: 2016-04-25

Mechanical Analysis of Multi-Textural Rocks (Brecciated Dolostones and Limestones): A New Micro-Compression Test for Rocks

Both strength and elastic modulus of rocks are usually determined by compression testing at the mesoscopic scale (UNE-EN 1926; ASTMD 3148-96), and the values obtained are representative of homogeneous rocks. However, heterogeneous and texturally complex rocks show a broad dispersion range and their strength and elastic modulus depend on the presence of different textures and their mechanical properties. The aim of this study was to quantify the mechanical behaviour of these textures individually in order to understand the strength and elasticity of the whole rock. Four varieties of brecciated carbonates (limestones and dolostones) were studied. These rocks have a very complex fabric, presenting a dense network of fractures and clasts between fractures (mm-cm size). The fractures are completely filled with calcite cement, and clasts can have one or two different textures, each presenting differences in crystal size, mineralogy and porosity percentage and type. Samples measuring 4x4x4 mm were obtained in order to test each texture individually. These micro-samples were tested in a uniaxial compression press and the stress-strain curve was recorded. In addition, mean strength and Young’s moduli were calculated for each texture. Results show that textures with a larger crystal size, lower porosity and intercrystalline porosity had the lowest strength and were the least elastic.