title: Prevalence of Split Nerve Fiber Layer Bundles in Healthy People Imaged with Spectral Domain Optical Coherence Tomography.
abstract: OBJECTIVE
  The presence of retinal nerve fiber layer (RNFL) split bundles was recently described in normal eyes scanned using scanning laser polarimetry and by histologic studies. Split bundles may resemble RNFL loss in healthy eyes. The aim of our study was to determine the prevalence of nerve fiber layer split bundles in healthy people.
  
  
  METHODS
  We imaged 718 eyes of 359 healthy persons with the spectral domain optical coherence tomography in this cross-sectional study. All eyes had intraocular pressure of 21 mmHg or less, normal appearance of the optic nerve head, and normal visual fields (Humphrey Field Analyzer 24-2 full threshold program). In our study, a bundle was defined as 'split' when there is localized defect not resembling a wedge defect in the RNFL deviation map with a symmetrically divided RNFL appearance on the RNFL thickness map. The classification was performed by two independent observers who used an identical set of reference examples to standardize the classification.
  
  
  RESULTS
  Inter-observer consensus was reached in all cases. Bilateral superior split bundles were seen in 19 cases (5.29%) and unilateral superior split was observed in 15 cases (4.16%). In 325 cases (90.52%) there was no split bundle.
  
  
  CONCLUSIONS
  Split nerve fiber layer bundles, in contrast to single nerve fiber layer bundles, are not common findings in healthy eyes. In eyes with normal optic disc appearance, especially when a superior RNFL defect is observed in RNFL deviation map, the RNLF thickness map and graphs should also be examined for split nerve fiber layer bundles.
authors.affiliation: Başkent University Faculty of Medicine, Department of Ophthalmology, Ankara, Turkey.
authors.forename: Sirel
authors.initials: S
authors.lastname: Gür Güngör
authors.affiliation: Başkent University Faculty of Medicine, Department of Ophthalmology, Ankara, Turkey.
authors.forename: Ahmet
authors.initials: A
authors.lastname: Akman
authors.affiliation: Başkent University Faculty of Medicine, Department of Ophthalmology, Ankara, Turkey.
authors.forename: Almila
authors.initials: A
authors.lastname: Sarıgül Sezenöz
authors.affiliation: Başkent University Faculty of Medicine, Department of Ophthalmology, Ankara, Turkey.
authors.forename: Gülşah
authors.initials: G
authors.lastname: Tanrıaşıkı
keywords: Retinal nerve fiber layer; optical coherence tomography; split nerve fiber layer bundles