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Stanley Darma, Pauline Kok, Michael Abramoff, Thomas Van Den Berg, Frank Verbraak; The Effect of Media Opacities on Retinal Nerve Fiber Layer and Macular Inner Retinal Layer Measurements with Spectral Domain Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1437.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the effect of media opacities on thickness measurements of the peripapillary retinal nerve fibre layer (pRNFL), macular retinal nerve fiber layer (mRNFL) and macular inner retinal layers (mIRL) measured with spectral domain optical coherence tomography (SD-OCT) (Topcon, Marck II), by using a set of filters with known optical density (OD).
SD-OCT 3D volume scans of the optic disc and the macular area were performed in 16 healthy volunteers, using Topcon 3D OCT-1000 (Topcon Medical Systems). A set of five artificial filters with a known OD ranging from 0.04-0.69 was used. The correlation was calculated between the change in thickness measurements (Δ pRNFL and Δ mIRL) and the change in OD (Δ OD). All measurements were done in duplo by one operator.
Sixteen right eyes of sixteen healthy volunteers were included in this study. 378 OCT-scans were used for analyses. There was a significant correlation between ΔOD and ΔpRNFL (r=0,79, p<0,001). The ΔpRNFL caused by ΔOD was best described by a curvilinear relationship. The mIRL thickness only decreased significantly after a threshold OD of 0,26. Total macular retinal thickness also decreased after this threshold OD value. As well as ΔpRNFL, ΔmRNFL also showed a curvilinear relationship with ΔOD. Repeat measurements of all layer thickness measurements were well correlated (r > 0,95, p<0,001).
Both pRNFL and mIRL are influenced by media opacities. This leads to a significant underestimation of the layer thickness. The relationships between ΔOD and ΔpRNFL as well as between ΔOD and ΔmRNFL are best described as a curvilinear. The mIRL decreases significantly after a threshold OD of 0,26, which equals a quality factor of 59. We observed that the underestimation of layer thickness is caused by a shift of retinal layer boundary placement, due to image quality loss caused by media opacities.
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