8 Original Artcle Acta Medica Anatolia Ahmet Akça 1 , Yonca Anık 2 , Özgül Altıntaş 3 , Ali Demirci 2 1 Dr. Lutfi Kirdar Kartal Education and Research Hospital, Department of Radiology, İstanbul 2 Kocaeli University School of Medicine, Department of Radiology, Kocaeli 3 Kocaeli University School of Medicine, Department of Eye Disorders, Kocaeli Volume 4 Issue 1 2016 Effects of Refractive Errors on Visual Functional Magnetic Resonance Imaging Introducton The most common use of fMRI is for the presurgical mapping within the rolandic tumor surgery (1). Compared with the motor fMRI studies, there are a few visual fMRI studies in patients with tumor in or near the visual cortex. The visual fMRI is used in clinical areas including visual pathway imaging, evaluation of cortical activation in patients with visual field defect or optic neuritis, amblyopia, evaluation of chiasma anomalies and presurgical mapping in patients who are candidates for brain surgery (2). These studies generally give information about the course of the disease, treatment of choice and plan of the surgery. However, there is a question that merits consideration: because of it is based on the activation created by vision, should we correct the refractive errors to achieve the accurate results, in visual fMRI studies. On review of the literature, we found only two studies that evaluated the effects of refractive errors on fMRI of visual cortex. In this study, we aimed to evaluate the requirement of correction of refractive errors and the effect of induced myopia on visual fMRI. Material and Methods The institutional ethics committee approved the study protocol and the written informed consent form was obtained from all patients before procedure. A prospective study including 13 patients with refractive errors (group 1, 10 men and 3 women) and 30 emetropic volunteers (group 2, 18 men and 12 women) was performed. All patients had undergone preprocedural ophthalmologic examination. This examination included measurement of visual acuity, refraction, biomicroscobic fundoscopy, slit-lamp examination and measurement of eye tension. Exclusion criteria were eye tension greater than 21 mm hg, visual acuity under 0,8, nerve loss, cup/disc ratio greater than 0,3, ocular operation history and claustrophobia. Group 1 and group 2 demographics are shown in table 1. Images were obtained using a 3-Tesla MRI scanner (Philips Achievea Intera Release, Einthoven, Netherlands) with 16 channel head coil system. In all patients, sponge backing was placed bilaterally in the coil to prevent motion artifacts. Inversion recovery doi: 10.5505/actamedica.2016.22448 Abstract Objective: The purpose of our study is to evaluate the effects of refractive errors on functional magnetic resonance imaging (fMRI) of visual cortex. Methods and Materials: We performed a prospective study. The study included 13 patients with refractive error (group 1) and 30 emetropic volunteers (group 2). Group 2 was also subgrouped as 20-32 years old (young) and over 45 years old (old) to analyse accommodation effect. fMRI data were acquired with a block design paradigm with 3 Tesla MR system. In both groups, images initially were acquired in normal refractive state. fMRI was performed again in both groups during refractive error. Activation areas on visual cortex were calculated as square centimeter. Total activated areas on visual cortex was compared between normal refractive state and induced/ uncorrected refractive error. Results: In group 1, activation areas of visual cortex during uncorrected refractive error revealed significantly decrease com- pared with activation areas during corrected refractive error (p=0.001). In group 2, induced myopia resulted significant de- crease in activation areas compared with normal refractive state. Decrease in activation areas were significant both in 2 and 4 diopters (D) of myopia compared with normal refractive state (p=0.003, p<0.001 respectively). Both in young and old subgroup, activation areas were significantly decreased during induced myopia. We revealed no difference between young and old subgroups. Conclusion: The refractive errors have a clear effect on fMRI of visual cortex. Thus, to achieve accurate results they should be corrected in patients that included in the visual fMRI study. Keywords: Refractive errors, Functional magnetic resonance imaging, Visual cortex Received: 03.01.2016 Accepted: 19.01.2016 Correspondence: Ahmet Akça, Dr. Lutfi Kirdar Kartal Education and Research Hospital, Department of Radiology, Istanbul Conflict of Interest: None E-mail: ahmtakca@yahoo.com