Response to: 'Comment on: "Incidence of optic nerve kinking in a cohort of patients with Normal tension glaucoma"'.

Response to: ‘Comment on: “Incidence of optic nerve kinking in a cohort of patients with Normal tension glaucoma”’ - PMC Skip to main content An official website of the United States government Here's how you know Here's how you know Search Log in Primary site navigation Search Log in Search PMC Full-Text Archive Search in PMC Journal List User Guide As a library, NLM provides access to scientific literature. Inclusion in an NLM database does not imply endorsement of, or agreement with, the contents by NLM or the National Institutes of Health. Learn more: PMC Disclaimer | PMC Copyright Notice letter Eye (Lond) . 2025 May 5;39(9):1872. doi: 10.1038/s41433-025-03822-1 Response to: ‘Comment on: “Incidence of optic nerve kinking in a cohort of patients with Normal tension glaucoma”’ Hanspeter E Killer 1, ✉ , Jatta Berberat 2 , Luca Remonda 2 , Cynthia J Roberts 3 , Albert Neutzner 1 , Achmed Pircher 4 Author information Article notes Copyright and License information 1 Department of Biomedicine, University of Basel, Basel, Switzerland 2 Cantonal Hospital, Institute of Neuroradiology, Aarau, AG Switzerland 3 Departments of Ophthalmology & Visual Sciences; and Biomedical Engineering, The Ohio State University, Columbus, OH USA 4 Department of Neuroscience/Ophthalmology, Uppsala University, Uppsala, Sweden ✉ Corresponding author. Received 2025 Apr 4; Revised 2025 Apr 11; Accepted 2025 Apr 24; Issue date 2025 Jun. Subject terms: Outcomes research, Nervous system © The Author(s), under exclusive licence to The Royal College of Ophthalmologists 2025 PMC Copyright notice PMCID: PMC12130445  PMID: 40325168 Dear Editor, We appreciate the thoughtful comment by Yuwan Gao concerning our paper on optic nerve kinking [ 1 ]. We agree the 57 normal tension glaucoma (NTG) patients do not represent a large cohort of NTG patients. Nevertheless, it represents the largest radiological study ever performed in this condition. Concerning the variability between radiological methods, there is data that demonstrates a high congruence between computed tomography (CT) and magnetic resonance imaging ( MRI), whereas ultrasound, which we did not use in our study, is less reproducible [ 2 ]. We don’t agree that we did not describe explicit criteria for the definition of kinking as we used the following criteria: optic nerve kink: 0 = straight or slightly curved optic nerve, 1 = visible kink of the optic nerve in axial images (1.1 = 1 kink, 1.2 = two kinks), 2 = visible kink of the optic nerve in sagittal images (2.1 = 1 kink, 2.2 = two kinks), 3 = visible kink of the optic nerve in both, axial and sagittal, images. In addition, to mitigate bias in retrospective data collection, all radiological images were reviewed by two experienced neuro-radiologists and one experienced neuro-ophthalmologist blinded to whether the subject was NTG or control. It should be noted that kinking in the vertical plane was virtually absent in the control group. Further, we did not discuss whether kinking is an anatomical predisposition or the result of NTG. This question was not the subject of this study and will be the subject of a future paper. Our suggestion that kinking alters fluid dynamics has already been established in a review on twisted blood vessels [ 3 ]. We consciously did not include multivariant analysis, since such analysis only answers the question concerning correlation and never the question for causation [ 4 ] but we fully support that larger studies should be performed and would gladly offer our cooperation. The purpose of our current study was to demonstrate a radiological feature and not to elaborate on its origin. Competing interests The authors declare no competing interests. Footnotes Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. References 1. Pircher A, Berberat J, Remonda L, Roberts CJ, Neutzner A, Killer HE. Incidence of optic nerve kinking in a cohort of patients with Normal tension glaucoma. Eye. 2025;39:1270–5. [ DOI ] [ PMC free article ] [ PubMed ] 2. Giger-Tobler C, Eisenack J, Holzmann D, Pangalu A, Sturm V, Killer HE, et al. Measurement of Optic Nerve Sheath Diameter: Differences between Methods? A Pilot Study. Klin Monbl Augenheilkd. 2015;232:467–70. [ DOI ] [ PubMed ] [ Google Scholar ] 3. Han HC. Twisted blood vessels: symptoms, etiology and biomechanical mechanisms. J Vasc Res. 2012;49:185–97. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ] 4. Fleischmann D, Killer HE. Studies Utilizing Current Estimated CSF Pressure Equations Should Not Be Conducted and Published [Letter]. Eye Brain. 2021;13:239–40. 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