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Bernadete Ayres, Ma?ra Martins, Elizabeth Parrish, Hakan Demirci; How to Measure the Largest Basal Diameter of the Choroidal Melanoma: A Mathematical Study. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3637.
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© ARVO (1962-2015); The Authors (2016-present)
Accurate assessment of largest basal dimension (LBD) is crucial in the treatment of choroidal melanoma. We evaluated ultrasonography techniques and mathematical formulas to more accurately characterize the length of the arc defining the LBD of choroidal melanomas.
Retrospective observational study reviewing the B-scan ultrasound images in 99 eyes of 99 choroidal melanoma patients. Two ophthalmic sonographers independently measured the LBD on the B-scan and using one, two, and three-chord measurements along the inner sclera. Those measurements were compared to the theoretical arc length estimated with trigonometry formulas based on the spherical model with the axial length as the globe diameter.
For chord measurements, the lowest error found using two-chord measurements that were similar to the theoretical arc (P=0.118). One-chord and three-chord techniques were less accurate and differences were found to be statistically significant (P <0.001 in both cases). The three-chord technique should provide more accurate results; however, in practical terms, the need to make three measurements introduced errors in estimation of the arc length. For tumors with LBD smaller than 12mm, the absolute error compared to the theoretical arc length using one-chord technique was smaller than 1mm. A user-friendly and practical software tool was developed to more accurately estimate the arc length based on one-chord measurements.
When using ultrasound to estimate LBD of ocular tumors, two-chord measurements should be used when LBD is larger than 12mm measured with the one-chord technique. For tumors with LBD smaller than 12mm, using one-chord measurements will result in satisfactory estimates of the arc length.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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