Sir,
We read with interest the excellent work of Loh and Wong1 in describing an earlier stage of myopic foveoschisis documented by optical coherence tomography. We noted that it was reported the central retinal thickness (CRT) was initially documented to be 159 μm, and more than 3 years later, to be 303 μm. Following the diagrams provided, the CRT/central foveal thickness appears to be similar, with splitting of the layers around it. We would like to enquire if these documented measurements were taken from automatic derived measurements or manually from the images obtained. Although it may not have any bearing on the excellent case reported by Loh and Wong, we wish to point out that automatic measurements tend to differ from manually measured thickness, especially if the software is unable to distinguish the contour of the layers in the retina. It has been reported that the difference between automated measurements and manual measurements is 7.9±90.8 μm, with a maximum difference of 455 μm.2 This is an important aspect to acknowledge, especially when documenting OCT findings for patients.
References
Loh B-K, Wong D . Myopic pre-foveoschisis: an earlier stage of myopic foveoschisis documented by optical coherence tomography. Eye 2010; 24: 1107–1109.
Keane PA, Jivrajka RV, Alasil T, Walsh AC, Liakopoulos S, Chang KT et al. Evaluation of optical coherence tomography retinal thickness parameters for use in clinical trials for neovascular age-related macular degeneration. Invest Ophthalmol Vis Sci 2009; 50 (7): 3378–3385.
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Nicholson, L., Shankar, J. Reply to Loh and Wong. Eye 25, 392 (2011). https://doi.org/10.1038/eye.2010.198
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DOI: https://doi.org/10.1038/eye.2010.198