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Editors Selection IGR 22-3

Miscellaneous: Is a Yang-deficient constitution a risk factor for NTG?

Fei Li
Xiulan Zhang

Comment by Fei Li & Xiulan Zhang on:

96110 Population-based associations between progression of normal-tension glaucoma and Yang-deficient constitution among Chinese persons, Tang L; Chen L; Ye C et al., British Journal of Ophthalmology, 2021; 0:

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The study by Tang et al. demonstrated a strong correlation between visual field (VF) worsening in NTG patients and body constitution defined by Traditional Chinese Medicine (TCM). The patients with Yang-deficient constitution had a higher chance of VF progression during follow-up.

The results are interesting since it leads us to a novel perspective and provide us with a convenient way of clinical evaluation of NTG eyes. First, body constitution refers to the body's metabolism, functioning organs, and organ structure, which in turn affects how resistant we are to external pathogens. That means it is an overall evaluation of the human body but not only focusing on our eyes. The results support that optic nerve damage is associated with systemic status. Second, body constitution can be easily obtained by observing the tongue and the pulse, although its accuracy relies on the accumulation of clinical experience.

The findings are somehow explainable based on our current understanding of glaucoma pathogenesis. Yang deficiency is characterized by coldness and clamminess of the skin, which is related to the insufficient blood supply. This is consistent with the theory that glaucoma may be caused by retinal ischemia. However, in the current study, the authors didn't summarize the imaging characteristics of the Yang-deficient participants. It is important to know if Yang-deficient eyes differ from non-Yang deficient eyes in retinal anatomical (e.g. layer thickness) or microvasculature characteristics (e.g. capillary density). Furthermore, it would be useful if we could find some objective clues or evidence to diagnose Yang-deficiency instead of observing the tongue and pulse.

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