Population-based associations between progression of normal-tension glaucoma and Yang-deficient constitution among Chinese persons

PURPOSE: To explore the association between constitution types as defined by traditional Chinese medicine (TCM) and risk for normal-tension glaucoma (NTG). DESIGN: Population-based cohort study. METHODS: Persons were identified in a population cohort aged ≥30 years with NTG, defined as having an untreated mean intraocular pressure measurement ≤21 mm Hg over six separate occasions, with no single reading >24 mm Hg (as in the Collaborative Normal Tension Glaucoma Study). The Body Constitution in Traditional Chinese Medicine Questionnaire was used to assess each participant’s TCM constitution types. The association between various constitutions and visual field progression according to Early Manifest Glaucoma Trial criteria was assessed using Cox regression HR models. RESULTS: Among 142 participants (245 eyes), 23 persons (17.6%) and 25 eyes (10.2%) progressed, over a mean (SD) follow-up duration of 3.49 (0.99) years. Progression rates were highest in participants with Yang-deficient constitution (n=19, 13.4%), among whom 7 (36.8%) exhibited worsening fields. After adjusting for sex, age, central corneal thickness, retinal nerve fibre layer thickness and mean deviation on visual field testing, Yang-deficient constitution (HR 4.63, 95% CI 1.77 to 12.1, p=0.002) and higher mean intraocular pressure during follow-up (HR 1.25, 95% CI 1.01 to 1.56, p=0.044) were associated with field progression. CONCLUSIONS: Yang-deficient constitution and higher intraocular pressure are risk factors for visual field progression in NTG patients. Yang deficiency is characterised by abnormal vasoregulation, and these results may be consistent with prior studies linking NTG progression to Raynaud’s phenomenon and migraine.