title: Quantification of heterophoria and phoria adaptation using an automated objective system compared to clinical methods.
abstract: OBJECTIVE
  To develop a system with which to quantify objectively the heterophoria to be measured throughout eye movement experiments. This study compared precision, resolution and accuracy characteristics of a limbus eye movement tracking system to the alternate cover test and the Maddox rod.
  
  
  METHODS
  Precision testing was performed using each technique with binocularly-normal subjects at different test sessions. Resolution was measured and compared between the three systems. The heterophoria or phoria was measured from 40 cm/16 inches objectively with the limbus eye movement system and the Maddox rod during a sustained convergence-induced phoria adaptation experiment using physical and haploscope visual targets to compare accuracy.
  
  
  RESULTS
  Precision testing quantified that the responses objectively recorded using the limbus tracking system exhibited similar standard deviations to the Maddox rod and the alternate cover test techniques. The limbus tracking method has the ability to quantify the response decay to phoria and has better resolution when compared to the clinical methods. When physical targets were used to induce phoria adaptation, the correlation was significant between the limbus eye movement tracking system and the Maddox rod after near and far adaptation, where the Maddox rod measurements were slightly more esophoric compared to those measured with the limbus tracking system.
  
  
  CONCLUSIONS
  This objective limbus tracking system offers a better means by which to study the phoria and its adaptation throughout an eye movement experiment. The broader aim of this research is to establish a tool that will further the basic science of oculomotor control and binocular dysfunctions.
authors.affiliation: Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, NJ, USA.
authors.forename: Sang J
authors.initials: SJ
authors.lastname: Han
authors.forename: Yi
authors.initials: Y
authors.lastname: Guo
authors.forename: Bérangère
authors.initials: B
authors.lastname: Granger-Donetti
authors.forename: Vincent R
authors.initials: VR
authors.lastname: Vicci
authors.forename: Tara L
authors.initials: TL
authors.lastname: Alvarez
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology*; D000328:Adult; D000368:Aged; D003290:Convergence, Ocular / Q000502:physiology; D053483:Eye Movement Measurements / Q000592:standards*; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009907:Optometry / Q000379:methods*; D013285:Strabismus / Q000175:diagnosis*; D055815:Young Adult