title: Does Retinal Neurodegeneration Seen in Diabetic Patients Begin in the Insulin Resistance Stage?
abstract: OBJECTIVE
  To investigate whether retinal neurodegeneration and impairment in contrast sensitivity (CS), which have been demonstrated to begin in diabetic patients before the presence of signs of diabetic retinal vasculopathy, also occur in the stage of insulin resistance.
  
  
  METHODS
  The average, minimum and sectoral (inferior, superior, inferonasal, superonasal, inferotemporal and superotemporal) thicknesses of the ganglion cell-inner plexiform layer (GCIPL) measured using optical coherence tomography were compared between an insulin-resistant group and control group in order to evaluate the presence of retinal neurodegeneration. The CS of the two groups was also compared according to the logarithmic values measured at spatial frequencies of 1.5, 3, 6, 12 and 18 cycles per degree in photopic light using functional acuity contrast test (FACT).
  
  
  RESULTS
  Twenty-five eyes of 25 patients with insulin resistance (insulin resistant group) and 25 eyes of 25 healthy subjects (control group) were included in this study. There were no statistically significant differences between the two groups in any of the spatial frequencies in the FACT. The mean average GCIPL thickness and mean GCIPL thickness in the inferotemporal sector were significantly less in the insulin-resistant group when compared with the control group (mean average GCIPL thicknesses in the insulin-resistant and control groups were 83.6±4.7 µm and 86.7±3.7 µm respectively, p=0.01; mean inferotemporal GCIPL thicknesses in the insulin-resistant and control groups were 83±6.0 µm and 86.7±4.6 µm respectively, p=0.02).
  
  
  CONCLUSIONS
  Although it may not lead to functional visual impairment such as CS loss, the retinal neurodegeneration seen in diabetic patients may begin in the insulin resistance stage.
authors.affiliation: Çanakkale Onsekiz Mart University Faculty of Medicine, Department of Ophthalmology, Çanakkale, Turkey.
authors.forename: Sedat
authors.initials: S
authors.lastname: Arıkan
authors.affiliation: Çanakkale Onsekiz Mart University Faculty of Medicine, Department of Ophthalmology, Çanakkale, Turkey.
authors.forename: İsmail
authors.initials: İ
authors.lastname: Erşan
authors.affiliation: Çanakkale Onsekiz Mart University Faculty of Medicine, Department of Endocrinology and Metabolism, Çanakkale, Turkey.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Eroğlu
authors.affiliation: Çanakkale Onsekiz Mart University Faculty of Medicine, Department of Ophthalmology, Çanakkale, Turkey.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Yılmaz
authors.affiliation: Çanakkale Onsekiz Mart University Faculty of Medicine, Department of Ophthalmology, Çanakkale, Turkey.
authors.forename: Hasan Ali
authors.initials: HA
authors.lastname: Tufan
authors.affiliation: Çanakkale Onsekiz Mart University Faculty of Medicine, Department of Ophthalmology, Çanakkale, Turkey.
authors.forename: Baran
authors.initials: B
authors.lastname: Gencer
authors.affiliation: Çanakkale Onsekiz Mart University Faculty of Medicine, Department of Ophthalmology, Çanakkale, Turkey.
authors.forename: Selçuk
authors.initials: S
authors.lastname: Kara
authors.affiliation: Çanakkale Onsekiz Mart University Faculty of Medicine, Department of Endocrinology and Metabolism, Çanakkale, Turkey.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Aşık
keywords: contrast sensitivity; insulin resistance; retinal ganglion cell layer