We thank Dr Grzybowski for his interest in our paper. The description of the work on vitreous structure by Johann Gottfried Zinn included in this study was cited from the book that compiles the historical background of the research. As pointed out by Dr Grzybowski, we could not find the comparison of the vitreous structure to an onion in the original article written by Zinn. Unfortunately, we could not access the original article by Pappenheim. However, several books that associate the work of Pappenheim with the word “onion” or that did not associate the work of Zinn with onion were found. An article in the London Journal of Medicine: A Monthly Record of the Medical Sciences (1852) mentioned: “ Pappenheim, however, in 1842, announced that the vitreous body, when treated with a solution of carbonate of potass, exhibited a series of layers, like those of an onion ”; an article in the System of Diseases of the Eye (1900) stated: “ Pappenheim and Brucke, from consideration ∼. Two rival views — the concentric or ‘onion’ and the radial or ‘orange’ theory∼ ” ; an article in The American Journal of the Medical Sciences (1849) stated: “ The opinion of Pappenheim (who, having hardened the vitreous humour of an ox and a man, by treating it with carbonate of potash), that this body was composed of concentric layers, like those of an onion. ” A similar statement appeared in A Manual of Histology (1872) (“ Pappenheim was the first∼which are enveloped one within the other like the layers of an onion ”) and in The Collected Papers of Sir W. Bowman (1892), as pointed out by Dr Grzybowski. This suggests that information from earlier studies compiled and presented in articles or books should be verified by referring to multiple books and original articles, and each manuscript has the responsibility to disseminate historical evidence accurately. Again, we thank Dr Grzybowski for bringing this issue to our attention.