title: Iris Crypts Influence Dynamic Changes of Iris Volume.
abstract: To determine the association of iris surface features with iris volume change after physiologic pupil dilation in adults.
  
  
  
  Cross-sectional observational study.
  
  
  
  Chinese adults aged ≥ 50 years without ocular diseases.
  
  
  
  Digital iris photographs were taken from eyes of each participant and graded for crypts (by number and size) and furrows (by number and circumferential extent) following a standardized grading scheme. Iris color was measured objectively, using the Commission Internationale de l'Eclairage (CIE) L* color parameter (higher value denoting lighter iris). The anterior segment was imaged by swept-source optical coherence tomography (SS-OCT) (Casia; Tomey, Nagoya, Japan) under bright light and dark room conditions. Iris volumes in light and dark conditions were measured with custom semiautomated software, and the change in iris volume was quantified. Associations of the change in iris volume after pupil dilation with underlying iris surface features in right eyes were assessed using linear regression analysis.
  
  
  
  Iris volume change after physiologic pupil dilation from light to dark condition.
  
  
  
  A total of 65 Chinese participants (mean age, 59.8±5.7 years) had gradable data for iris surface features. In light condition, higher iris crypt grade was associated independently with smaller iris volume (β [change in iris volume in millimeters per crypt grade increment] = -1.43, 95% confidence interval [CI], -2.26 to -0.59; P = 0.001) and greater reduction of iris volume on pupil dilation (β [change in iris volume in millimeters per crypt grade increment] = 0.23, 95% CI, 0.06-0.40; P = 0.010), adjusting for age, gender, presence of corneal arcus, and change in pupil size. Iris furrows and iris color were not associated with iris volume in light condition or change in iris volume (all P > 0.05).
  
  
  
  Although few Chinese persons have multiple crypts on their irides, irides with more crypts were significantly thinner and lost more volume on pupil dilation. In view that the latter feature is known to be protective for acute angle-closure attack, it is likely that the macroscopic and microscopic composition of the iris is a contributing feature to angle-closure disease.
authors: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore; Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore.
authors: Jacqueline
authors: J
authors: Chua
authors: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore.
authors: Sri Gowtham
authors: SG
authors: Thakku
authors: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore.
authors: Tin A
authors: TA
authors: Tun
authors: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore; Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore.
authors: Monisha E
authors: ME
authors: Nongpiur
authors: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore.
authors: Marcus Chiang Lee
authors: MC
authors: Tan
authors: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore; Department of Biomedical Engineering, National University of Singapore, Singapore.
authors: Michael J A
authors: MJ
authors: Girard
authors: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore; Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore; Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore.
authors: Tien Yin
authors: TY
authors: Wong
authors: SingHealth Polyclinics, Outram, Singapore.
authors: Joanne Hui Min
authors: JH
authors: Quah
authors: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore; Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore; Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore.
authors: Tin
authors: T
authors: Aung
authors: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore; Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore; Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore. Electronic address: chingyu.cheng@duke-nus.edu.sg.
authors: Ching-Yu
authors: CY
authors: Cheng
mesh_terms: D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D006068:Gonioscopy; D006801:Humans; D021621:Imaging, Three-Dimensional; D007429:Intraocular Pressure / Q000502:physiology*; D007498:Iris / Q000033:anatomy & histology*; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D010865:Pilot Projects; D011680:Pupil / Q000502:physiology*; D012016:Reference Values; D012189:Retrospective Studies; D041623:Tomography, Optical Coherence / Q000379:methods*