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Sasan Moghimi, Kouros Nouri-Mahdavi, Laurie Rahardjanoto, Gina Lee, Elena Bitrian, Jay Riddle, Naveed Nilforushan, Josepe Caprioli; Spectral-Domain OCT Underestimates Disc and Rim Areas Compared to Confocal Laser Ophthalmoscopy. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3062.
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© ARVO (1962-2015); The Authors (2016-present)
To compare optic disc parameters measured with confocal laser ophthalmoscopy (HRT) to those from a spectral-domain optical coherence tomography (SD-OCT).
Sixty-six eyes of 37 glaucoma patients and glaucoma suspects from the UCLA Imaging Study were included. Eyes with reliable fields (MD >-15.0 dB), spherical refractive error <8 D and astigmatism <3 D, and no prior glaucoma surgery were prospectively enrolled. Eligible patients had a full eye exam including biometry with IOLMaster, and disc and retinal nerve fiber layer (RNFL) SD-OCT imaging (Optic disc Cube 200x200, Cirrus OCT) and imaging with Heidelberg Retina Tomograph (HRT, software version 3.01). HRT global stereometric parameters and rim area measurements for twelve 30-degree sectors were exported after correcting for corneal base curve. Disc parameters and rim area in matching 30-degree sectors were also obtained for SD-OCT with the Cirrus research browser version 18.104.22.1686. Disc area, rim area, cup to disc area ratio, vertical cup to disc ratio, cup volume, and the 12 rim-area sectors were compared between the two devices.
The average (± SD) age and mean deviation for the study eyes were 65.2 (± 8.1) years and -3.1 (± 3.3) dB, respectively. Average disc size and rim area from SD-OCT were significantly lower compared to HRT (1.88 ± 0.55 vs. 2.08 ± 0.62 mm and 0.78 ± 0.24 vs. 1.06 ± 0.40 mm, respectively, p <0.001 for both). Conversely, the cup-related parameters from SD-OCT were significantly larger (p <0.001). The highest correlations between the two devices were observed for disc area (r2 = 0.64, p <0.001) and cup volume (r2 = 0.65, p <0.001). The correlations for vertical cup to disc ratio, cup to disc area ratio, and rim area were weaker (r2 = 0.388, 0.375, and 0.28, respectively, p <0.001 for all). The correlation between rim-area sectors was highest in sectors 5, 6, 7, and 8 (nasal and inferonasal regions; r2 = 0.26-0.30). Bland-Altman plots demonstrated no significant trend (p = 0.09) for the difference in the disc area as a function of disc size, whereas the difference in the rim area increased with increasing rim area (p <0.001).
SD-OCT underestimates optic disc size and rim area and overestimates cup parameters compared with HRT. Disc parameters from the two devices are not interchangeable.
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