title: Fourier domain optical coherence tomography to assess the iridocorneal angle and correlation study in a large Caucasian population.
abstract: BACKGROUND
  Recently, novel anatomic parameters that can be measured by optical coherence tomography (OCT), have been identified as a more objective and accurate method of defining the iridocorneal angle. The aim of the present study is to measure the iridocorneal angle by Fourier domain (FD) OCT and to identify correlations between angle measurements and subject factors in a large healthy Caucasian population.
  
  
  METHODS
  A cross sectional study was performed in 989 left eyes of 989 healthy subjects. The iridocorneal angle measurements: trabecular-iris angle (TIA), angle opening distance (AOD500) and trabecular-iris space area (TISA500) 500 μm from the scleral spur, were made using the FD-OCT RTVue®. Iris thickness was also measured. Correlations were examined between angle measurements and demographic and ocular factors. The main determinants of angle width were identified by multivariate linear regression.
  
  
  RESULTS
  TIA could be measured in 94% of the eyes, and AOD500 and TISA500 in 92%. The means recorded were TIA 35.8 ± 12.2 degrees (range 1.5 to 76.1), AOD500 542.6 ± 285.4 μm (range 15 to 1755), and TISA500 0.195 ± 0.104 mm(2) (range 0.02 to 0.62). The correlation between the temporal and nasal quadrant was R = 0.902 for TIA. The reproducibility of measurements was excellent (intraclass correlation coefficient >0.947). Mean angle width measurements were smaller in women (p = 0.02). Correlation was detected between angle means and anterior chamber volume (ACV; R = 0.848), anterior chamber depth (ACD; R = 0.818), spherical error (R = -0.619) and age (R = -0.487), while no correlation was observed with Intraocular pressure (R = -0.052). ACV emerged as the main determinant of TIA (R(2) = 0.705; p < 0.001).
  
  
  CONCLUSIONS
  In this Caucasian population, strong correlation was detected between FD-OCT anterior angle measurements and ACV, ACD, spherical refractive error and sex, emerging the ACV as the main determinant of TIA.
authors.affiliation: Department of Ophthalmology, Hospital Universitario Clínico San Carlos, Instituto de Investigación sanitaria San Carlos (IdISSC), c/Profesor Martín Lagos s/n, 28100, Madrid, Spain. jfvigo@hotmail.com.|Centro Internacional de Oftalmología Avanzada, Madrid, Spain. jfvigo@hotmail.com.
authors.forename: José Ignacio
authors.initials: JI
authors.lastname: Fernández-Vigo
authors.affiliation: Department of Ophthalmology, Hospital Universitario Clínico San Carlos, Instituto de Investigación sanitaria San Carlos (IdISSC), c/Profesor Martín Lagos s/n, 28100, Madrid, Spain.
authors.forename: Julián
authors.initials: J
authors.lastname: García-Feijóo
authors.affiliation: Department of Ophthalmology, Hospital Universitario Clínico San Carlos, Instituto de Investigación sanitaria San Carlos (IdISSC), c/Profesor Martín Lagos s/n, 28100, Madrid, Spain.
authors.forename: José María
authors.initials: JM
authors.lastname: Martínez-de-la-Casa
authors.affiliation: Department of Ophthalmology, Hospital Universitario Clínico San Carlos, Instituto de Investigación sanitaria San Carlos (IdISSC), c/Profesor Martín Lagos s/n, 28100, Madrid, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: García-Bella
authors.affiliation: Department of Ophthalmology, Hospital Universitario Clínico San Carlos, Instituto de Investigación sanitaria San Carlos (IdISSC), c/Profesor Martín Lagos s/n, 28100, Madrid, Spain.
authors.forename: Pedro
authors.initials: P
authors.lastname: Arriola-Villalobos
authors.affiliation: Department of Preventive Medicine, Hospital Universitario Clínico San Carlos, Instituto de Investigación sanitaria San Carlos (IdISSC), Madrid, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Fernández-Pérez
authors.affiliation: Centro Internacional de Oftalmología Avanzada, Madrid, Spain.|Department of Ophthalmology, Universidad de Extremadura, Badajoz, Spain.
authors.forename: José Ángel
authors.initials: JÁ
authors.lastname: Fernández-Vigo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003315:Cornea / Q000033:anatomy & histology*; D003430:Cross-Sectional Studies; D005260:Female; D005583:Fourier Analysis; D064368:Healthy Volunteers; D006801:Humans; D007498:Iris / Q000033:anatomy & histology*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D013223:Statistics as Topic; D041623:Tomography, Optical Coherence; D014129:Trabecular Meshwork / Q000033:anatomy & histology*; D044465:White People; D055815:Young Adult
keywords: Anterior chamber; Glaucoma; Iridocorneal angle; Optical coherence tomography