title: [Changes in retinal nerve fiber layer thickness after spinal surgery in the prone position: a prospective study].
abstract: OBJECTIVE
  Changes in ocular perfusion play an important role in the pathogenesis of ischemic optic neuropathy. Ocular perfusion pressure is equal to mean arterial pressure minus intraocular pressure. The aim of this study was to evaluate the changes in the intraocular pressure and the retinal nerve fiber layer thickness in patients undergoing spinal surgery in the prone position.
  
  
  METHODS
  This prospective study included 30 patients undergoing spinal surgery. Retinal nerve fiber layer thickness were measured one day before and after the surgery by using optical coherence tomography. Intraocular pressure was measured by tonopen six times at different position and time-duration: supine position (baseline); 10min after intubation (Supine 1); 10 (Prone 1), 60 (Prone 2), 120 (Prone 3)min after prone position; and just after postoperative supine position (Supine 2).
  
  
  RESULTS
  Our study involved 10 male and 20 female patients with the median age of 57 years. When postoperative retinal nerve fiber layer thickness measurements were compared with preoperative values, a statistically significant thinning was observed in inferior and nasal quadrants (p=0.009 and p=0.003, respectively). We observed a statistically significant intraocular pressure decrease in Supine 1 and an increase in both Prone 2 and Prone 3 when compared to the baseline. Mean arterial pressure and ocular perfusion pressure were found to be significantly lower in Prone 1, Prone 2 and Prone 3, when compared with the baseline.
  
  
  CONCLUSIONS
  Our study has shown increase in intraocular pressure during spinal surgery in prone position. A statistically significant retinal nerve fiber layer thickness thinning was seen in inferior and nasal quadrants one day after the spinal surgery.
authors.affiliation: Departamento de Oftalmologia, Canakkale Onsekiz Mart University, Canakkale, Turquia. Electronic address: barangencer@gmail.com.
authors.forename: Baran
authors.initials: B
authors.lastname: Gencer
authors.affiliation: Departamento de Neurocirurgia, Canakkale Onsekiz Mart University, Canakkale, Turquia.
authors.forename: Murat
authors.initials: M
authors.lastname: Coşar
authors.affiliation: Departamento de Oftalmologia, Canakkale Onsekiz Mart University, Canakkale, Turquia.
authors.forename: Hasan Ali
authors.initials: HA
authors.lastname: Tufan
authors.affiliation: Departamento de Oftalmologia, Canakkale Onsekiz Mart University, Canakkale, Turquia.
authors.forename: Selcuk
authors.initials: S
authors.lastname: Kara
authors.affiliation: Departamento de Oftalmologia, Canakkale Onsekiz Mart University, Canakkale, Turquia.
authors.forename: Sedat
authors.initials: S
authors.lastname: Arikan
authors.affiliation: Departamento de Neurocirurgia, Canakkale Onsekiz Mart University, Canakkale, Turquia.
authors.forename: Tarik
authors.initials: T
authors.lastname: Akman
authors.affiliation: Departamento de Anestesiologia e Reanimação, Canakkale Onsekiz Mart University, Canakkale, Turquia.
authors.forename: Hasan Ali
authors.initials: HA
authors.lastname: Kiraz
authors.affiliation: Departamento de Oftalmologia, Canakkale Onsekiz Mart University, Canakkale, Turquia.
authors.forename: Arzu Taskiran
authors.initials: AT
authors.lastname: Comez
authors.affiliation: Departamento de Anestesiologia e Reanimação, Dokuz Eylül University, Izmir, Turquia.
authors.forename: Volkan
authors.initials: V
authors.lastname: Hanci
keywords: Cirurgia da coluna vertebral; Espessura da camada de fibras nervosas da retina; Intraocular pressure; Pressão Intraocular; Pronação; Prone position; Retinal nerve fiber layer thickness; Spinal surgery