Anterior Chamber Depth and Lens Thickness Measurements in Pediatric Eyes: Ultrasound Biomicroscopy Versus Immersion A-Scan Ultrasonography.

OBJECTIVE: To compare anterior chamber depth (ACD) and lens thickness (LT) measurements by ultrasound biomicroscopy (UBM), A-scan cross vector (CV) overlay with UBM, and immersion A-scan technique in pediatric eyes. METHODS: This prospective comparative cohort study comprised 43 eyes of 25 pediatric participants (mean age: 2.3±2.2 y). UBM and immersion A-scan biometry were performed prior to dilation and intraocular surgery. ACD and LT were measured by UBM image analysis, A-scan CV UBM overlay, and immersion A-scan technique. RESULTS: ACD and LT measurements obtained using immersion A-scan were significantly greater than with UBM image analysis with mean differences of 0.52 mm and 0.62 mm, respectively (p < 0.001). Immersion A-scan and UBM measurements were moderately correlated (r = 0.70 and 0.64, p < 0.001). ACD and LT measurements obtained using CV overlay were not significantly different than UBM measurements and the values were strongly positively correlated (r = 0.95 and 0.93, p < 0.001). CONCLUSION: Immersion A-scan may overestimate ACD and LT compared to UBM in pediatric patients due to oblique placement of the A-scan probe relative to the optical axis. Supplemental use of UBM and/or CV overlay is indicated to improve measurement accuracy in pediatric patients who cannot reliably fixate due to the ability to confirm proper alignment of the probe with the pupil by visualizing the anterior segment.

High-Resolution Ultrasound to Quantify Sub-Surface Wrinkles in a Woven CFRP Laminate.

Carbon fiber reinforced polymer (CFRP) composites are popular materials in the aerospace and automotive industries because of their low weight, high strength, and corrosion resistance. However, wrinkles or geometric distortions in the composite layers significantly reduce their mechanical performance and structural integrity. This paper presents a method for non-destructively extracting the three-dimensional geometry, lamina by lamina, of a laminated composite. A method is introduced for fabricating consistent out-of-plane wrinkled CFRP laminate panels, simulating the in-service wrinkle observed in industries that utilize thick structure composites such as the vertical lift or wind power industries. The individual lamina geometries are extracted from the fabricated coupon with an embedded wrinkle from captured ultrasonic waveforms generated from single-element conventional ultrasonic (UT) scan data. From the extracted waveforms, a method is presented to characterize the wrinkle features within each individual lamina, specifically the spatially varying wrinkle height and intensity for the wrinkle. Parts were fabricated with visibly undetectable wrinkles using a wet layup process and a hot press for curing. Scans were performed in a conventional immersion tank scanning system, and the scan data were analyzed for wrinkle detection and characterization. Extraction of the layers was performed based on tracking the voltage peaks from A-scans in the time domain. Spatial Gaussian averaging was performed to smooth the A-scans, from which the surfaces were extracted for each individual lamina. The extracted winkle surface aligned with the anticipated wrinkle geometry, and a single parameter for quantification of the wrinkle intensity for each lamina is presented.

Ultrasound in ocular oncology: Technical advances, clinical applications, and limitations.

Due to its accessibility and ability for real-time image acquisition of ocular structures, ultrasound has high utility in the visualization of the eye, especially in ocular oncology. In this minireview, we summarize the technical rationale and applications of ultrasound modalities, A-scan, B-scan, high-frequency ultrasound biomicroscopy (UBM), and Doppler measurement. A-scan ultrasound uses a transducer of 7-11 MHz, making it useful for determining the echogenicity of ocular tumors (7-8 MHz) and measuring the axial length of the eye (10-11 MHz). B-scan ultrasound operates at 10-20 MHz, which can be used for measuring posterior ocular tumors while UBM operates at 40-100 MHz to evaluate anterior ocular structures. Doppler ultrasonography allows for the detection of tumor vascularization. While ultrasonography has numerous clinical applications due to its favorable penetration compared with optical coherence tomography, it is still limited by its relatively lower resolution. Ultrasound also requires an experienced sonographer due to the need for accurate probe localization to areas of interest.

Quantitative and Qualitative Assessments of Retinal Structure with Variable A-Scan Rate Spectralis OCT: Insights into IPL Multilaminarity.

The aim of this study was to evaluate the qualitative and quantitative differences between 20 and 85 kHz A-scan rate optical coherence tomography (OCT) images acquired by spectral domain OCT. The study included 60 healthy subjects analyzed with horizontal linear scans with a variable A-scan rate (SHIFT technology, Heidelberg Engineering, Heidelberg, Germany). The retinal thickness measurement of each retinal layer was performed in three different positions (subfoveal, nasal, and temporal). The qualitative assessment was performed by two independent observers who rated every image with a score ranging from 1 ("sufficient") to 3 ("excellent") on the basis of three parameters: visualization of the vitreo-retinal interface, characterization of the retinal layers, and visualization of the sclero-choroidal interface. No statistically significant differences in terms of retinal layer thickness between the two A-scan rate scans were observed (p > 0.05). The coefficient of variation of the retinal thickness values was lower in the 20 kHz group (25.8% versus 30.1% with the 85 kHz). The 20 kHz images showed a higher quality index for both observers. An inner plexiform layer (IPL) multilaminarity was detected in 78.3% of patients from the 20 kHz group and in 40% of patients from the 85 kHz group (p < 0.05).

Large ciliary body melanocytoma with pseudocysts: a case report.

BACKGROUND: To describe the correlation between standardized A-scan echography and histopathology in a ciliary body melanocytoma. CASE PRESENTATION: We present a case of a large ciliary body melanocytoma with significant growth, vision loss, and elevated intraocular pressure that was diagnosed clinically as a melanoma, but the standardized A-scan findings correlated to the histopathological description of a melanocytoma with multiple pseudocysts. CONCLUSIONS: The reflectivity of this melanocytoma by standardized A-scan was consistent with multiple pseudocysts on pathological evaluation. This echographic pattern guided the differential diagnosis. Standardized A-scan is an important diagnostic tool in the differentiation of ciliary body melanocytomas from melanomas.

Multicenter Observational Study to Evaluate the Diagnostic Value of Sonography in Patients with Chronic Rhinosinusitis.

(1) Background: Computed tomography (CT) is considered mandatory for assessing the extent of pathologies in the paranasal sinuses (PNS) in chronic rhinosinusitis (CRS). However, there are few evidence-based data on the value of ultrasound (US) in CRS. This multicenter approach aimed to compare diagnostic imaging modalities in relation to findings during surgery. (2) Methods: 127 patients with CRS were included in this prospective multicenter study. Patients received preoperative US and CT scans. The sensitivity and specificity of CT and US were extrapolated from intraoperative data. (3) Results: CT scans showed the highest sensitivity (97%) and specificity (67%) in assessing CRS. Sensitivities of B-scan US were significantly lower regarding the maxillary sinus (88%), the ethmoid sinus (53%), and the frontal sinus (45%). The highest overall sensitivity was observed for assessing the pathology of the maxillary sinus. (4) Conclusions: We observed high accuracy with CT, confirming its importance in preoperative imaging in CRS. Despite the high US expertise of all investigators and a standardized examination protocol, the validity of CT was significantly higher than US. Ultrasound of the PNS sinuses is applicable in everyday clinical practice but lacks diagnostic accuracy. Nevertheless, it might serve as a complementary hands-on screening tool to directly correlate the clinical findings in patients with PNS disease.

Effect of Percutaneous Tracheostomy on Optic Nerve Sheath Diameter (TONS Trial).

How to cite this article: Di Paola I, Graziano M, Cornetta P. Effect of Percutaneous Tracheostomy on Optic Nerve Sheath Diameter (TONS Trial). Indian J Crit Care Med 2022;26(5):653.

Correlation between the optic nerve pial diameter and radial peripapillary vascular changes in primary open-angle glaucoma.

PURPOSE: To assess the optic nerve pial diameter (ONPD) in patients with primary open-angle glaucoma (POAG) using standardized A-scan ultrasound and to evaluate the correlation between the ONPD and structural, vascular optic nerve head features and visual field parameters in glaucomatous eyes. METHODS: In this prospective study, we enrolled 126 eyes of 63 POAG patients and 124 eyes of 62 healthy controls. In all subjects, the ONPD was evaluated by means of A-scan ultrasound. Spectral domain (SD)-OCT was used to assess ganglion cell complex (GCC), retinal nerve fiber layer (RNFL), thicknesses, and the optic nerve head (ONH) morphology. OCTA measured the vessel density (VD) of radial peripapillary capillary (RPC) plexus. RESULTS: The ONPD showed a statistically significant reduction in POAG group with respect to controls (p < 0.001). SD-OCT and OCTA parameters showed a significant impairment in patient group with respect to controls (p < 0.001). The ONH analysis revealed significantly lower values in rim area (p = 0.009) and an increased cup-to-disc area ratio (p = 0.013) and cup volume (p < 0.001) in patients with respect to controls. Significant correlations were shown in POAG group between ONPD and RPC plexus (p = 0.006). Moreover, significant correlation was also found between ONPD and structural SD-OCT parameters (p = 0.001) and between ONPD and visual field parameters (p = 0.001). CONCLUSIONS: The standardized A-scan ultrasound measurements of the ONPD showed a significant correlation with structural and vascular glaucomatous changes measured by means of SD-OCT and OCTA. These results confirm the diagnostic reliability of the ultrasound evaluation in glaucoma optic neuropathy.

Comparison of the accuracy of axial length measurement by different imaging methods in Sprague Dawley rats.

Background: Obtaining accurate axial length (AL) is very important for the establishment of animal models of myopia. The purpose of this study is to compare the accuracy of Quantel A-B scan, OD-1 A scan, and vernier caliper in measuring AL in Sprague Dawley (SD) rats. Methods: In total, 60 5-week-old SD rats were divided into female rat group (n = 30) and male rat group (n = 30). Quantel A-B scan and OD-1 A scan were, respectively, used to measure the AL of both eyes of each living rat, and vernier caliper was used to measure the anterior-posterior diameter of each rat's eyeball. Besides, the correlation between refractive error (RE) and AL measured by different instruments was evaluated, and the accuracy of the three measurement methods was compared according to gender and left/right eyes. Results: There were significant differences in AL and diopter of SD rats at the same age (p < 0.05). the AL of male rats was greater than that of female rats, while diopter (D) was the opposite; There was no significant difference in AL and D between left and right eyes in the same SD rats (p > 0.05); There were statistical differences among the three measurement methods (p < 0.05), AL measured by vernier caliper was the largest, followed by Quantel A-B scan, OD-1 A scan; Difference in AL between male and female was not statistically significant between the results obtained by Quantel A-B scan and vernier caliper (p > 0.05), but there were statistically significant differences between the other two measurement methods (p < 0.05). Conclusion: Sex is the influencing factor of AL and RE. Imaging measurement can accurately measure the AL in living small rodents. Compared with OD-1 A scan, Quantel A-B scan may be more accurate.

Comparative study on the axial length measurement with A-scan on different postures for difficult measuring eyes / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To provide guidance for more accurate measurement of axial length(AL)of difficult measuring eyes by comparing the differences in the AL of the patient's difficult measuring eye with three methods of the sitting position, supine position A-scan and Lenstar 900(Lenstar, LS900). METHODS: Clinical case-control study. We selected 102 cases(102 eyes)including cataract patients with combined silicone oil filled, vitreous hemorrhage or retinal detachment and patients with dislocation of the lens or IOL in Zhengzhou Second Hospital from May 2019 to September 2020. AL were measured using LS900 and A-scan on sitting position and supine position respectively, and the results of the three methods were statistically analyzed.RESULTS: The detection rates of LS900 and A-scan axial measurement were 83% and 100% respectively. Three methods of A scan in sitting position, supine position and LS900 to measure the overall AL, silicone oil group, lens dislocation group and vitreous hemorrhage group, the differences were statistically significant(P&#x003C;0.001), The mean values of AL measured by overall A-scan, supine positions of silicone oil group, supine position of lens dislocation group and vitreous hemorrhage group were statistically significant differences with LS900 measurement(all P&#x003C;0.05), while there was no statistical difference between the results of the overall sitting position and the difficult measuring eye groups' sitting position compared with the LS900 measurement of AL. The three measurements showed good consistency within the 95% consistency range, but the result of A-scan on sitting position was closer to LS900.CONCLUSION: Changing the conventional decubitus position to the sitting position can improve the accuracy of the measurement results and provide clinicians with more reliable guidance for the treatment of patients with difficult measuring eyes of A-scan axial measurement, especially in diseases with altered ocular structure.

A-scan ultrasound in ophthalmology: A simulation tool.

In the present study, we developed a computational tool for simulating the ophthalmological applications of A-scan ultrasound, including cataract characterisation and biometry. A-scan biometry is used to measure the axial length (AL) of the eye before cataract surgery to calculate the refractive power of the intraocular lens to be implanted. Errors in the measurement of the AL lead to post-surgical refractive errors. The simulation tool was developed using the k-Wave Matlab toolbox, together with a user-friendly interface developed in Matlab. Diverse error sources were evaluated. Constant ultrasound speed assumptions may introduce refractive errors of up to 0.6 D; by contrast, probe positioning errors had a lower impact, of up to 0.11 D. The correct identification of the Bruch's membrane is limited not only by axial resolution constraints but also by the low reflection coefficient at the retina/choroid interface. Regarding cataract characterisation, the amplitudes of the echoes reflected at the lens interfaces are sensitive to diverse cataract types and severities, and a more realistic representation could be obtained by using a higher resolution in the eye grid; however, the required computational times would make simulations impracticable when using personal computers. The simulation tool shows good versatility for evaluating diverse aspects of A-scan biometry.

Comparative analysis of measurements of the anterior segment and the axial length parameters of the eyeball obtained with optical and ultrasound technique.

PURPOSE: To compare anterior chamber depth (ACD), keratometry (K1, K2), central corneal thickness (CCT), and axial length (AL) measured by four different devices. MATERIAL AND METHODS: 150 eyes qualified for cataract surgery were included in the study. Four devices: IOL Master 500, OCT CASIA2, Dual Scheimpflug Analyzer Galilei G6, and Quantel Compact Touch ultrasound biometer, were compared. The agreement of measurements between the devices was evaluated by the Bland-Altman method. RESULTS: ACD was significantly different for Ultrasound and IOL Master 3 ± 0.33 3.12 ± 0.42 respectively Interclass correlation ecoefficiency (ICC):0.69 (95% confidence interval (CI): 0.62; 0.76) p < 0.001. A significant difference was observed between Casia and IOL while measuring K1, 43.5 ± 1.7 vs. 43.61 ± 1.56 ICC:0.84 (95%CI: 0.79; 0.87) and ACD parameters 2.65 ± 0.45 vs. 3.12 ± 0.42 ICC 0.68 (95%: 0.6; 0.75) and K2 42.51 ± 1.62 vs. 44.57 ± 1.59 ICC; 0.83 (95%CI:0.78; 0.87) p < 0.001. Similarly, measurements obtained by Casia, and Galilei were also different K1 43.5 ± 1.7 ICC:0.7 (95%CI:0.62; 0.76), CCT 546.35 ± 34.75 vs. 566.73 ± 37.92 ICC:0.88 (95%CI:0.84; 0.9) p < 0.001. Differences between Galilei and IOL master were not significant p values from 0.175 to 0.999 ICC 0.8 (95%CI:0.75; 0.85) to ICC 0.94 (95%CI:0.92; 0.95). CONCLUSIONS: The measurements obtained from Casia, and Ultrasound were significantly different and not interchangeable except for IOL master and Galilei.

Comparison of A-Scan ultrasonography and the Lenstar optical biometer in Guinea pig eyes.

OBJECTIVE: To compare the biometric parameters provided by A-scan ultrasonography and the Lenstar optical biometer in guinea pig eyes, including anterior segment depth (ASD), lens thickness (LT), vitreous chamber depth (VCD), and axial length (AL), and differences of them between treated form deprivation (FD) eyes and untreated fellow eyes after 4 weeks of FD. METHODS: Three-week-old guinea pigs (N = 41) were subjected to biometric measurements before monocular FD (baseline) and after a 4-week FD. Statistical analyses including within-subject standard deviation (SDwithin), coefficient of variation (CV), and intraclass correlation coefficient (ICC), used to evaluate repeatability for both the A-scan ultrasonography and the Lenstar individually, and correlation and Bland-Altman analyses were used to assess agreement between the two methods. The absolute values of ASD, LT, VCD and AL as measured by the two devices were compared, and the differences of them between treated (T) and untreated fellow (F) eyes (ΔASD, ΔLT, ΔVCD and ΔAL) (Δ = T-F) were compared between the two devices after 4 weeks of FD. RESULTS: Measurements by the Lenstar (ICC: 0.923-0.994) were more repeatable than A-scan ultrasonography (ICC: 0.825-0.870). There was a high correlation for AL (r = 0.851, P < 0.001), a moderate correlation for VCD (r = 0.571, P < 0.001) and LT (r = 0.423, P < 0.001), and a low correlation for ASD (r = 0.230, P < 0.01) between the two devices. The values for ASD, VCD and AL measured by A-scan ultrasonography were larger than those measured by the Lenstar (all, P < 0.001), while LT provided by A-scan ultrasonography was much smaller than that of the Lenstar (P < 0.001). Bland-Altman plots showed poor agreement of absolute values of the four parameters between the two devices. Moreover, there was a high correlation between both methods for ΔAL (r = 0.704, P < 0.001), a moderate correlation for ΔVCD (r = 0.534, P < 0.001) and ΔASD (r = 0.574, P < 0.001), and no correlation for ΔLT (r = 0.303, P = 0.054). The ΔASD, ΔLT, and ΔAL measurements obtained by A-scan ultrasonography were greater than those obtained by the Lenstar (all, P < 0.001), while ΔVCD was mildly smaller using A-scan ultrasonography (P < 0.05). Bland-Altman plots illustrated there is good agreement of ΔAL, ΔVCD, ΔASD, and ΔLT between the two devices. CONCLUSIONS: The Lenstar exhibited better repeatability and provided smaller measurements for AL, VCD and ASD than A-scan ultrasonography. Furthermore, a high correlation and a good agreement for the ΔAL was observed between the two devices after a period of FD. In summary, the two devices cannot replace each other directly to obtain absolute values of ASD, LT, VCD and AL, but the Lenstar still can serve as an option in measuring ΔAL between eyes in guinea pig myopia model.

Preoperative measurements for cataract surgery: a comparison of ultrasound and optical biometric devices.

PURPOSE: To evaluate differences in preoperative measurements and refractive outcomes between ultrasound and optical biometry when using the Barrett Universal II intraocular lens (IOL) power formula. METHODS: In this consecutive case series, cataract extraction and IOL implantation cases from two surgical centers in Toronto, Canada, were recruited between January 2015 and July 2017. Differences between ultrasound (applanation or immersion A-scan) and optical biometry (IOLMaster 500) were compared for axial length (AL), anterior chamber depth and refractive outcomes. The primary outcome was the percentage of cases in each cohort within ± 0.50D of refractive error. RESULTS: In total, 527 cataract cases underwent IOLMaster testing. Of these, 329 eyes (62.4%) were also measured by applanation A-scan, and the other 198 eyes (37.6%) received immersion A-scan testing. Applanation ultrasound led to 5.8%, 16.0% and 46.4% of eyes within ± 0.25D, ± 0.50D and ± 1.00D of refractive error, respectively, whereas the IOLMaster 500 led to 48.5%, 77.1% and 94.9%, respectively (n = 293, ± 0.50D: p < 0.001). Immersion ultrasound led to 31.2%, 57.6% and 91.2% of eyes within ± 0.25D, ± 0.50D and ± 1.00D of refractive error, respectively, whereas the IOLMaster 500 led to 42.4%, 72.0% and 92.0%, respectively (n = 125, ± 0.50D: p = 0.001). Applanation (n = 329, A-scan AL: 23.64 ± 1.67 mm, IOLMaster AL: 24.20 ± 1.70 mm, p < 0.001) and immersion ultrasound (n = 198, A-scan AL: 25.01 ± 2.06 mm, IOLMaster AL: 25.08 ± 2.13 mm, p = 0.002) yielded significantly lower AL values compared to optical biometry measurements. CONCLUSIONS: Optical biometry yielded a significantly larger percentage of cases within ± 0.50D of refractive error compared to ultrasound biometry when using the Barrett Universal II IOL power formula.

Comparison of anterior chamber depth measurements using three methods and the influence factors in age-related cataract patients / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To compare the measurement results of anterior chamber depth(ACD)by Pentacam, IOL Master and Contact Ultrasonic A-scan, and analyze the difference, correlation, consistency and influencing factors of the three measurement methods.<p>METHODS: In this study of 307 eyes of 250 cataract patients with preoperative, ACD estimation was done by Pentacam, IOL Master and Contact Ultrasonic A-scan. The independent sample <i>t</i>-test, Analysis of Variance(ANOVA), Pearson's correlation test and multiple linear regressions were used to analyze the results.<p>RESULTS: The mean of ACD measured by Pentacam(ACDp), IOL Master(ACDi)and A-scan(ACDa)were 2.42±0.45mm, 2.96±0.43mm, 2.58±0.36mm, the difference was statistically significant(<i>F</i>=136.694, <i>P</i><0.05). The three methods were sequentially compared in pairs, and the differences within the groups were statistically significant(<i>P</i><0.05). Pearson's correlation test was performed on the three methods in pairs, and there was a linear positive correlation within each group. When the ACDp and the central corneal thickness(CCT)were added, the sum(ACDp2)was no statistically significant compared with the ACDi(<i>P</i>=0.93). When the ACDp was less than 1.85mm(ACDi was about 2.40mm), the ACDa increases significantly and the fluctuation increases. Among the many possible influencing factors, axial length, lens thickness and age have the highest relative importance for ACD measurement.ACD was positively correlated with axial length(<i>r</i>Pentacam=0.602, <i>r</i>IOL Master=0.603, <i>r</i>A-scan=0.483), and negatively correlated with the lens thickness(<i>r</i>Pentacam= -0.382, <i>r</i>IOL Master= -0.350, <i>r</i>A-scan= -0.582), negatively correlated with age(<i>r</i>Pentacam= -0.328, <i>r</i>IOL Master= -0.414, <i>r</i>A-scan= -0.265). Three factors were included in the multiple linear regression model, and the age factor of Contact Ultrasonic A-scan was eliminated due to the low influence weight.<p>CONCLUSION: ACDp2 and ACDi may be closer to the true value of the anterior chamber depth. The Contact Ultrasonic A-scan may increase the measurement error when measuring shallow anterior chamber. Axial length, lens thickness and age have the greatest influence on ACD measurement, which are the influencing factors of Pentacam and IOL Master, but age is not the influencing factor of Contact Ultrasonic A-scan.

[Possibilities of ultrasound methods in diagnostics of eyelid tumors]. / Vozmozhnosti ul'trazvukovykh metodov issledovaniya v diagnostike novoobrazovanii vek.

PURPOSE: To determine the informative value of ultrasound biomicroscopy (UBM) with A-scan for assessment of qualitative and quantitative characteristics of eyelid tumors less than 5 mm in size. MATERIAL AND METHODS: The study included 25 patients (25 eyes) with eyelid tumors less than 5 mm in size. In addition to standard ophthalmic examination, complex ultrasound diagnostics including B-scan, Color Doppler imaging and UBM with A-scan were performed. The localization, size, structure of eyelid tumors and the state of perifocal tissues were evaluated. All patients underwent surgical treatment with following histological examinations of dissected tissues. Due to qualitative analysis of the studied formations and small number of included patients, there was no need in statistical analysis of the data. RESULTS: Complex application of UBM and A-scan allowed specifying the localization, size, structure of the small-sized tumors and detecting typical echographic signs of benign or malignant properties of the pathological process. Ultrasound data (UBM and A-scan) of eyelid tumors was highly correlated to histological features. CONCLUSION: UBM with A-scan can be recommended for differential diagnostics of small-sized tumors and optimizing their management.

Safety Assessment of an A-Scan Ultrasonic System for Ophthalmic Use.

OBJECTIVES: This study describes the safety assessment of an A-scan ultrasonic system for ophthalmic use. The system is an investigational medical device for automatic cataract detection and classification. METHODS: The risk management was based on the International Organization for Standardization (ISO) standard DIN EN ISO 14971:2009-10 and International Electrotechnical Commission (IEC) standard IEC 60601-2-37. The calibration of the ultrasonic field was conducted according to the standards IEC 62127-1:2007 and IEC 62359:2010. The uncertainty on measurements was delineated in agreement with the guide JCGM 100:2008. RESULTS: After risk management, all risks were qualitatively classified as acceptable. The mechanical index (0.08 ± 0.05), soft tissue thermal index (0.08 ± 0.08) and spatial-peak temporal-average intensity (0.56 ± 0.59 mW/cm2 ) were under the maximum index values indicated by the US Food and Drug Administration guidance, Marketing Clearance of Diagnostic Ultrasound Systems and Transducers (0.23, 1, and 17 mW/cm2 , respectively). CONCLUSIONS: This study presents a practical approach for the safety assessment of A-scan ultrasonic systems for ophthalmic use. The safety evaluation of a medical device is mandatory before its use in clinical practice. However, the safety monitoring throughout its life cycle should also be considered, since many device components may deteriorate over time and use.