title: Diagnostic potential of iris cross-sectional imaging in albinism using optical coherence tomography.
abstract: OBJECTIVE
  To characterize in vivo anatomic abnormalities of the iris in albinism compared with healthy controls using anterior segment optical coherence tomography (AS-OCT) and to explore the diagnostic potential of this technique for albinism. We also investigated the relationship between iris abnormalities and other phenotypical features of albinism.
  
  
  METHODS
  Prospective cross-sectional study.
  
  
  METHODS
  A total of 55 individuals with albinism and 45 healthy controls.
  
  
  METHODS
  We acquired 4.37×4.37-mm volumetric scans (743 A-scans, 50 B-scans) of the nasal and temporal iris in both eyes using AS-OCT (3-μm axial resolution). Iris layers were segmented and thicknesses were measured using ImageJ software. Iris transillumination grading was graded using Summers and colleagues' classification. Retinal OCT, eye movement recordings, best-corrected visual acuity (BCVA), visual evoked potential (VEP), and grading of skin and hair pigmentation were used to quantify other phenotypical features associated with albinism.
  
  
  METHODS
  Iris AS-OCT measurements included (1) total iris thickness, (2) stroma/anterior border (SAB) layer thickness, and (3) posterior epithelial layer (PEL) thickness. Correlation with other phenotypical measurements, including (1) iris transillumination grading, (2) retinal layer measurements at the fovea, (3) nystagmus intensity, (4) BCVA, (5) VEP asymmetry, (6) skin pigmentation, and (7) hair pigmentation (of head hair, lashes, and brows).
  
  
  RESULTS
  The mean iris thickness was 10.7% thicker in controls (379.3 ± 44.0 μm) compared with the albinism group (342.5 ± 52.6 μm; P>0.001), SAB layers were 5.8% thicker in controls (315.1 ± 43.8 μm) compared with the albinism group (297.7 ± 50.0 μm; P=0.044), and PEL was 44.0% thicker in controls (64.1 ± 11.7 μm) compared with the albinism group (44.5 ± 13.9 μm; P<0.0001). The most ciliary quartile of the PEL yielded a sensitivity of 85% and specificity of 78% for detecting albinism. Phenotypic features of albinism, such as skin and hair pigmentation, BCVA, and nystagmus intensity, were significantly correlated to AS-OCT iris thickness measurements.
  
  
  CONCLUSIONS
  We have characterized in vivo abnormalities of the iris associated with albinism for the first time and show that PEL thickness is particularly affected. We demonstrate that PEL thickness has diagnostic potential for detecting iris abnormalities in albinism. Anterior segment OCT iris measurements are significantly correlated to BCVA and nystagmus intensity in contrast to iris transillumination grading measurements that were not.
  
  
  BACKGROUND
  The author(s) have no proprietary or commercial interest in any materials discussed in this article.
authors.affiliation: Ophthalmology Group, University of Leicester, Faculty of Medicine & Biological Sciences, Leicester Royal Infirmary, Leicester, United Kingdom.
authors.forename: Viral
authors.initials: V
authors.lastname: Sheth
authors.forename: Irene
authors.initials: I
authors.lastname: Gottlob
authors.forename: Sarim
authors.initials: S
authors.lastname: Mohammad
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: McLean
authors.forename: Gail D E
authors.initials: GD
authors.lastname: Maconachie
authors.forename: Anil
authors.initials: A
authors.lastname: Kumar
authors.forename: Christopher
authors.initials: C
authors.lastname: Degg
authors.forename: Frank A
authors.initials: FA
authors.lastname: Proudlock
mesh_terms: D000328:Adult; D016117:Albinism, Ocular / Q000473:pathology* / Q000503:physiopathology; D003430:Cross-Sectional Studies; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D006801:Humans; D007498:Iris / Q000002:abnormalities*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012044:Regression Analysis; D041623:Tomography, Optical Coherence; D014792:Visual Acuity / Q000502:physiology