CORTICAL ADAPTATION TO VISUAL BLURRING: A 3T FUNCTIONAL MRI COMPARISON BETWEEN CORRECTED MYOPIA AND EMMETROPIA Nguyen T.H. 1, Stiévenart J.L. 1, Istoc A. 1, Girmens J.F. 2, Yoshida M. 3, Baranton K. 4, Habas C. 1, Abanou A Department of Neuro-Imaging, C.H.N.O. des 15-20, Paris, France 2 - Centre d’Investigations Cliniques (CIC), C.H.N.O. des 15-20, Paris, France 3 - Department of Ophthalmology, Jikei university School of Medicine, Tokyo, Japan 4 – Vision Science Department, R&D Optics, Essilor, Paris, France XIX Symposium Neuroradiologicum The World Congress of Diagnostic & Therapeutic Neuroradiology Bologna, Italy, 5 October 2010

Purpose To investigate a difference of the visual cortex response in corrected myopic patients and normal subjects, when submitted to blurred and unblurred images

Materials and methods (1) We explored 15 subjects from 18 to 35 years of age – 9 subjects with emmetropia (within – 0.75 and + 1 diopters) – 6 subjects with corrected myopia (from – 6 to – 1 diopters) Initial ophthalmological examination (C.I.C.) – Anisometropia below 1 diopter – No other ophthalmological pathology – Visual correction reaching 20/20 in ETDRS Chart "R"

Materials and methods (2) Functional exploration using a 3T MRI device (G.E.H.C., Milwaukee, U.S.A.) Spatial resolution alteration: image unblurring– blurring Cortical retinotopic locations

FLOU – NET : scènes Unblurring : Scenes

FLOU – NET : lettres Blurring : Optotypes

Materials and methods (3) Cortical response through statistical evaluation : individual and group analysis – Statistical Parametric Mapping (SPM 8) ® – BrainVoyager ® Time response at image resolution change

Individual analysis - Emmetropia UnblurringBlurring S O

Individual analysis - Corrected myopia UnblurringBlurring S O

Individual analysis - Emmetropia Unblurring Blurring

Individual analysis - Corrected myopia UnblurringBlurring

Group analysis - Unblurring EmmetropiaCorrected myopia

Group analysis - Blurring EmmetropiaCorrected myopia

Group analysis - Emmetropia vs myopia UnblurringBlurring

Time response at resolution alteration BlurringUnblurringBlurringUnblurring

Discussion (1) Extension in cortical response Comparable response in V1 and V2 Different extent in secondary and associative areas in emmetropia and corrected myopia – Frontal Eye Field - Supplementary Eye Field - Parietal Eye Field – The dorsal occipital – parietal pathway +++ – The ventral occipital – temporal pathway + – The insula (right hemisphere ++)

Discussion (2) Statistical values of the cortical reponse – V1, V2 and the ventral pathway : positive in-phase response – Associative areas and the dorsal pathway: negative in- phase response Variable amplitude in vascular response to natural scenes or to optotypes, to be confirmed in populations including at least 20 subjects

Discussion (3) Extended cortical response recruiting associative areas: for a better reconstruction of blurred images? Secondary and associative visual areas: – Attentional phenomenon, visuo-spatial location, working memory Cortical response in the insula – Decisional implication in image alteration analysis?

Discussion (4) Main difference in emmetropia and corrected myopia: – Unblurring: Earlier response in corrected myopia while images remain blurred in emmetropia – Blurring: Delayed response in corrected myopia In correspondance with a larger tolerance in corrected myopia to blurred images, at equal corrected visual acuity

Conclusion Preliminary results in 15 subjects, prior to a final exploration of 20 emmetropic and 20 myopic subjects Larger tolerance in corrected myopia for blurred images suggesting a long term cortical adaptation to progressive impaired vision  Next steps:  Comparison between E/M responses to scenes vs optotypes  Displaying an in-phase or out-phase connectivity in dorsal and ventral visual pathways

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