title: Deformation of Optic Nerve Head and Peripapillary Tissues by Horizontal Duction.
abstract: OBJECTIVE
  To ascertain deformation of the optic nerve head (ONH) and peripapillary tissues caused by horizontal duction.
  
  
  METHODS
  Prospective, experimental study.
  
  
  METHODS
  Optical coherence tomography of the ONH region was performed in 23 eyes of 12 normal volunteers in central gaze and increasing (10, 20, and 30 degrees) adduction and abduction. Main outcome measures were changes from central gaze in the configuration of the ONH and peripapillary tissues in eccentric gazes.
  
  
  RESULTS
  Adduction but not abduction was associated with significant, progressive relative posterior displacement of the temporal peripapillary retinal pigment epithelium (tRPE) from its position in central gaze reaching 49 ± 10 μm in 30-degree adduction (standard error of mean, P < .0001). Absolute (anterior or posterior) optic cup displacement (OCD) averaged 41 ± 7 μm in 30-degree adduction. Linear regression showed significant effect of adduction on absolute OCD (slope 1.09 ± 0.36 μm/degree, P = .0037). In 20-degree and 30-degree adduction, all eyes exhibited significant progressive temporal ONH tilting reaching 3.1 ± 0.4 degrees in 30-degree adduction (P < .0001). Abduction was not associated with significant peripapillary RPE displacement, OCD, or ONH tilt. Both nasal and temporal peripapillary choroid averaged 9-19 μm thinner in adduction and abduction than in central gaze (P < .02).
  
  
  CONCLUSIONS
  Adduction temporally tilts and displaces the prelaminar ONH and peripapillary tissues. Both adduction and abduction compress the peripapillary choroid. These effects support magnetic resonance imaging and biomechanical evidence that adduction imposes strain on the ONH and peripapillary tissues. Repetitive strain from eye movements over decades might in susceptible individuals lead to optic neuropathies such as normal tension glaucoma.
authors.affiliation: Department of Ophthalmology, David Geffen Medical School at University of California, Los Angeles, California; Stein Eye Institute, David Geffen Medical School at University of California, Los Angeles, California.
authors.forename: Melinda Y
authors.initials: MY
authors.lastname: Chang
authors.affiliation: Department of Ophthalmology, David Geffen Medical School at University of California, Los Angeles, California; Stein Eye Institute, David Geffen Medical School at University of California, Los Angeles, California.
authors.forename: Andrew
authors.initials: A
authors.lastname: Shin
authors.affiliation: Department of Ophthalmology, David Geffen Medical School at University of California, Los Angeles, California; Stein Eye Institute, David Geffen Medical School at University of California, Los Angeles, California.
authors.forename: Joseph
authors.initials: J
authors.lastname: Park
authors.affiliation: Department of Ophthalmology, David Geffen Medical School at University of California, Los Angeles, California; Stein Eye Institute, David Geffen Medical School at University of California, Los Angeles, California.
authors.forename: Aaron
authors.initials: A
authors.lastname: Nagiel
authors.affiliation: Department of Ophthalmology, David Geffen Medical School at University of California, Los Angeles, California; Stein Eye Institute, David Geffen Medical School at University of California, Los Angeles, California.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Lalane
authors.affiliation: Department of Ophthalmology, David Geffen Medical School at University of California, Los Angeles, California; Stein Eye Institute, David Geffen Medical School at University of California, Los Angeles, California.
authors.forename: Steven D
authors.initials: SD
authors.lastname: Schwartz
authors.affiliation: Department of Ophthalmology, David Geffen Medical School at University of California, Los Angeles, California; Stein Eye Institute, David Geffen Medical School at University of California, Los Angeles, California; Department of Neurology, David Geffen Medical School at University of California, Los Angeles, California; Neuroscience, David Geffen Medical School at University of California, Los Angeles, California; Bioengineering Interdepartmental Program, David Geffen Medical School at University of California, Los Angeles, California. Electronic address: jld@jsei.ucla.edu.
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Demer
mesh_terms: D002829:Choroid / Q000000981:diagnostic imaging*; D005133:Eye Movements; D005260:Female; D005500:Follow-Up Studies; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D009412:Nerve Fibers / Q000473:pathology; D009898:Optic Disk / Q000000981:diagnostic imaging*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D011446:Prospective Studies; D012165:Retinal Ganglion Cells / Q000473:pathology; D055213:Retinal Pigment Epithelium / Q000000981:diagnostic imaging*; D041623:Tomography, Optical Coherence / Q000379:methods*; D055815:Young Adult