Abstract
PurposeTo describe a novel method for quantitative measurement of area parameters in ocular anterior segment ultrasound biomicroscopy (UBM) images using Photoshop software and to assess its intraobserver and interobserver reproducibility.MethodsTwenty healthy volunteers with wide angles and twenty patients with narrow or closed angles were consecutively recruited. UBM images were obtained and analyzed using Photoshop software by two physicians with different-level training on two occasions. Borders of anterior segment structures including cornea, iris, lens, and zonules in the UBM image were semi-automatically defined by the Magnetic Lasso Tool in the Photoshop software according to the pixel contrast and modified by the observers. Anterior chamber area (ACA), posterior chamber area (PCA), iris cross-section area (ICA) and angle recess area (ARA) were drawn and measured. The intraobserver and interobserver reproducibilities of the anterior segment area parameters and scleral spur location were assessed by limits of agreement, coefficient of variation (CV), and intraclass correlation coefficient (ICC).ResultsAll of the parameters were successfully measured by Photoshop. The intraobserver and interobserver reproducibilities of ACA, PCA, and ICA were good, with no more than 5% CV and more than 0.95 ICC, while the CVs of ARA were within 20%. The intraobserver and interobserver reproducibilities for defining the spur location were more than 0.97 ICCs. Although the operating times for both observers were less than 3 minutes per image, there was significant difference in the measuring time between two observers with different levels of training (p<0.001).ConclusionMeasurements of ocular anterior segment areas on UBM images by Photoshop showed good intraobserver and interobserver reproducibilties. The methodology was easy to adopt and effective in measuring.
Highlights
Measurements of the anterior segment are important in the assessment of a variety of ocular diseases, especially in the diagnosis and follow up of angle closure
The intraobserver and interobserver reproducibilities of Anterior chamber area (ACA), posterior chamber area (PCA), and iris cross-section area (ICA) were good, with no more than 5% coefficient of variation (CV) and more than 0.95 intraclass correlation coefficient (ICC), while the CVs of ARA were within 20%
The intraobserver and interobserver reproducibilities for defining the spur location were more than 0.97 ICCs
Summary
Measurements of the anterior segment are important in the assessment of a variety of ocular diseases, especially in the diagnosis and follow up of angle closure. Ultrasound biomicroscopy (UBM) can provide high-definition cross-sectional images of the anterior chamber, iris and angle structures, retroiridial structures, and ciliary processes, allowing reliable and repeatable quantitative measurements on ocular anterior segment [1,2]. The built-in software of the UBM device provides limited linear measurements which only give partial information about the anterior segment. Due to the irregularity of the boundaries of the anterior segment, it is difficult to perform area measurements using images generated by UBM. Such study may provide important insight into the pathogenesis of anterior segment diseases
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