Everything About Pulse Oximetry-Part 1: History, Principles, Advantages, Limitations, Inaccuracies, Cost Analysis, the Level of Knowledge About Pulse Oximeter Among Clinicians, and Pulse Oximetry Versus Tissue Oximetry.

Purpose: Pulse oximetry is a noninvasive medical technique that measures the amount of oxygen in a person's blood by shining light through their skin. It is widely used in medical care and is considered as important as the 4 traditional vital signs. In this article, it was aimed to review all aspects of pulse oximetry in detail. Materials and Methods: The international and national reliable sources were used in the literature review for critical data analysis. A total of 13 articles including 9 reviews, 1 comparative clinical research, 1 cost-saving quality improvement project, 1 cross-sectional and multicenter descriptive study, and 1 questionnaire study were used for the preparation of this part of the review. Results: The history, principles, advantages, limitations inaccuracies, cost analysis, the level of knowledge about pulse oximeter among clinicians, and pulse oximetry versus tissue oximetry were all reviewed in detail. Conclusion: The device has a significant impact on modern medicine, allowing continuous monitoring of hemoglobin oxygen saturation in arterial blood. Oximeters are valuable in managing oxygen levels in respiratory and nonrespiratory diseases and have become an essential tool in hospital settings. Detecting low levels of oxygen saturation early can alert patients to seek medical attention promptly. It is crucial to comprehend the working and limitations of pulse oximetry technology to ensure patient safety.

Normative Data Assessment of Peripapillary and Macular Vessel Density and Foveal Avascular Zone Metrics Using Optical Coherence Tomography Angiography in Children.

PURPOSE: To quantify the vessel density of the macula and optic disc and foveal avascular zone (FAZ) in healthy children and to evaluate the effects of age, gender, axial length, body mass index (BMI), and refractive errors on vessel density and FAZ. METHODS: This study enrolled 92 eyes of 92 participants (42 boys and 50 girls). Optical coherence tomography angiography (OCTA) was performed using AngioVue (Avanti; Optivue). FAZ area, nonflow area, superficial and deep vessel density, FAZ perimeter, acircularity index of FAZ, foveal density, and radial peripapillary capillary vessel density were analyzed by gender. Correlations between the investigated OCTA parameters and age, axial length, and BMI were evaluated. RESULTS: Girls had significantly larger nonflow and FAZ area than boys (P = .01 and .02). Superficial and deep vessel density at the fovea was significantly higher in boys compared to girls (P = .01 and .03). Inferior temporal and superior temporal Radial peripapillary capillary vessel densities were significantly higher in girls than boys (P = .01 and .03). No significant difference was found in the macular and optic disc vessel density measurements within refractive groups (P > .05, for all). Regarding the correlation of age with FAZ and vessel density parameters, only nonflow area was positively correlated with age (r = 0.22, P = .03). CONCLUSIONS: This study provides normative data for children. Although boys had greater foveal vessel density, girls had greater FAZ area and nonflow area. Refractive status of the eye and BMI did not influence the OCTA parameters. Although nonflow area was positively correlated with age, other parameters were steady within the ages of 7 to 18 years. [J Pediatr Ophthalmol Strabismus. 2020;57(6):388-398.].

Assessment of corneal topographic, tomographic, densitometric, and biomechanical properties of Fabry patients with ocular manifestations.

PURPOSE: To investigate whether cornea verticillata affects corneal topography, tomography, densitometry, or biomechanics of Fabry patients with ocular manifestations and to compare these results with those obtained from healthy subjects. METHODS: This prospective, cross-sectional study included 23 Fabry patients (Fabry group) with cornea verticillata and the 37 age- and sex-matched healthy subjects (control group). After comprehensive ophthalmological examinations, corneal topography, tomography, and densitometry measurements were taken using Pentacam HR and corneal biomechanics were captured via Corvis ST for all participants. RESULTS: All the investigated topographic and tomographic values were similar in the eyes with Fabry disease (FD) and the controls (P > 0.05). The corneal densitometry values of patients with FD were statistically significantly higher in all the concentric zones and layers, except posterior 0-2 mm and posterior 2-6 mm zones, compared to the controls (P < 0.05). The mean values of A1 velocity, A2 velocity, deformation amplitude ratio, Corvis biomechanical index, tomographic and biomechanical index, and Stiffness parameter at the first applanation in the Fabry group were statistically significantly different compared to control group (P < 0.05). However, the mean values of A1 length, A2 length, and the biomechanically corrected intraocular pressure were similar between the groups (P = 0.317, P = 0.819, and P = 0.468; respectively). CONCLUSION: Although cornea verticillata associated with FD is not considered to affect vision, it is associated with increased light backscattering and reduced corneal transparency as well as altered corneal biomechanical properties.

Assessment of corneal backward light scattering in the healthy cornea and factors affecting corneal transparency.

PURPOSE: To quantify normative corneal optical density (COD) values of healthy individuals and to investigate alterations in the COD in relation to their ocular and demographic characteristics. STUDY DESIGN: Prospective, cross-sectional, and observational. METHODS: In total, 588 eyes from 588 healthy participants with clear corneas were consecutively enrolled. Corneal densitometry values expressed in standardized grayscale units (GSU) from different corneal layers and zones obtained using the rotating Pentacam Scheimpflug system were analyzed. RESULTS: The mean (SD) COD over the 12-mm diameter area was 14.4 ± 2.74 GSU. A significant positive correlation was found between the participants' age and the total COD (r = 0.756, P < .001). No significant differences were found between males and females with respect to COD (P = .51). No significant correlation was found between the COD measurements and refractive error, pachymetry, and keratometry (P > .05 for all comparisons). On the other hand, COD was negatively correlated with white-to-white (WTW) corneal diameter (r = - 0.415, P < .001). Moreover, the WTW corneal diameter was correlated with the COD in any zone and layer of the cornea (P < .05 for all comparisons). CONCLUSIONS: Wide variations in COD can be detected even in corneas deemed clinically clear. Age and corneal diameter that seem to influence corneal transparency should be taken into account when evaluating corneal backscatter.