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G. Janzen, J. Ho, L. Smithen, Y. Chen, J. Liu, J. G. Fujimoto, J. S. Schuman, J. S. Duker; Analysis of Time and Spectral / Fourier Domain Optical Coherence Tomography Imaging of Patients With High Axial Myopia. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3262.
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© ARVO (1962-2015); The Authors (2016-present)
To analyze time and spectral / Fourier domain Optical Coherence Tomography (OCT) imaging in patients with high axial myopia via signal strength (SS) measurements and OCT image quality scores (IQS) assigned by two trained blinded observers.
Seven patients with high axial myopia (> -6 diopters) were recruited after receiving informed consents. The higher myopia eye was selected in each patient; the eye giving a higher SS was chosen if both eyes had equal levels. Imaging was conducted via the Stratus OCT macular thickness protocol (Carl Zeiss Meditec, Dublin, CA) and the Cirrus HD-OCT 5-line raster protocol (Carl Zeiss Meditec, Dublin, CA). One scan with the highest SS was selected from each protocol performed. Two blinded trained observers independently evaluated all 7 Cirrus images and then separately evaluated Stratus images to assign an IQS for each. SS and IQS were plotted against myopia level. SS were plotted against corresponding IQS for each device. Correlation coefficients were determined for all plots. Bland-Altman plots assessed agreeability between SS and IQS.
Patients had average myopia of -10.21±2.2 diopters (3 OD, 4 OS). Average SS for the Cirrus and Stratus OCT (both out of 10) was 6.57±1.72 and 8.57±0.98, respectively. SS was negatively correlated with the degree of myopia for Cirrus (R2= 0.399) and Stratus OCT (R2= 0.500). IQS also negatively correlated with myopia level (Cirrus R2= 0.076, Stratus R2= 0.449). SS was positively correlated with IQS (Cirrus R2= 0.616, Stratus R2= 0.488). Bland-Altman limits of agreeability (95% confidence interval) was 0.367 to 3.633 for Cirrus (range= 3.266) and -0.389 to -3.183 (range= 2.795) for Stratus OCT.
High myopia may have small effects on OCT image quality via decreased SS or IQS. IQS had weaker negative correlation with the level of myopia compared to corresponding values obtained from SS. The large range in the Bland-Altman limits of agreeability revealed that high SS from commercial OCT devices may not translate into observer perception of high image quality, and vice versa.
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