June 2015
Volume 56, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2015
Magnetic Resonance Imaging (MRI) Models of the Posterior Segment
Author Affiliations & Notes
  • James D Akula
    Ophthalmology, Boston Children's Hospital, Boston, MA
    Ophthalmology, Harvard Medical School, Boston, MA
  • Robert Munro
    Ophthalmology, Boston Children's Hospital, Boston, MA
  • Emily A Swanson
    Ophthalmology, Boston Children's Hospital, Boston, MA
  • Tara L Favazza
    Ophthalmology, Boston Children's Hospital, Boston, MA
  • Toco Yuen Ping Chui
    Ophthalmology, New York Eye & Ear Infirmary, New York, NY
  • Anne Moskowitz
    Ophthalmology, Boston Children's Hospital, Boston, MA
    Ophthalmology, Harvard Medical School, Boston, MA
  • Ramkumar Ramamirtham
    Ophthalmology, Boston Children's Hospital, Boston, MA
  • Sanjay Prabhu
    Radiology, Boston Children's Hospital, Boston, MA
    Radiology, Harvard Medical School, Boston, MA
  • Ronald M Hansen
    Ophthalmology, Boston Children's Hospital, Boston, MA
    Ophthalmology, Harvard Medical School, Boston, MA
  • Anne B Fulton
    Ophthalmology, Boston Children's Hospital, Boston, MA
    Ophthalmology, Harvard Medical School, Boston, MA
  • Footnotes
    Commercial Relationships James Akula, None; Robert Munro, None; Emily Swanson, None; Tara Favazza, None; Toco Chui, None; Anne Moskowitz, None; Ramkumar Ramamirtham, None; Sanjay Prabhu, None; Ronald Hansen, None; Anne Fulton, None
  • Footnotes
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Investigative Ophthalmology & Visual Science June 2015, Vol.56, 2778. doi:
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    • Get Citation

      James D Akula, Robert Munro, Emily A Swanson, Tara L Favazza, Toco Yuen Ping Chui, Anne Moskowitz, Ramkumar Ramamirtham, Sanjay Prabhu, Ronald M Hansen, Anne B Fulton; Magnetic Resonance Imaging (MRI) Models of the Posterior Segment. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2778.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: To evaluate high-resolution MRI sequences for utility in defining the 3D shape of eyes by comparing emmetropic and myopic eyes of subjects born full-term to those with a history of retinopathy of prematurity (ROP), a disease associated with both short axial length and myopia.

Methods: We use T1- and T2-weighted spin echo sequences to image both eyes of all subjects at 0.5×0.5×0.5 mm isotropic resolution. To date, we have imaged 17 subjects: eight emmetropes born full-term (ET), six myopes born full-term (MT), one emmetrope with a history of ROP (EROP), and two myopes with a history of ROP (MROP). We measured axial length (AxL, mm) with an IOLMaster (Carl Zeiss AG) and derived spherical equivalent refraction (SE, D) from autorefractions (Grand Seiko). In Voxar3D (Toshiba Medical Visualization Systems), by tilt, rotation and panning, we exported two 2D cross-sections from each eye: the transverse plane that included both the pupil and optic nerve, and the largest orthogonal (coronal) cross-section. We segmented the vitreo-retinal boundary in each image and fit it with both circular (diameter) and elliptical (long and short axes) shape descriptors. Finally, we used Mimics Innovation Suite (Materialise) to segment and register T1 and T2 images.

Results: We found that a T2 ‘Sampling Perfection with Application-optimized Contrasts using different flip angle Evolution’ (SPACE) sequence was excellent for vitreo-retinal boundary detection. A T1 ‘Multi-Echo Magnetization Prepared Rapid Acquisition Gradient Echo’ (MEMPRAGE) sequence clearly showed the insertion points of the extraocular muscles (which were invisible in the SPACE images) and sometimes offered superior lens segmentation in Mimics. None of the eyes had staphylomata. Consistent with the peculiar features of ROP myopia, mean AxL in our subjects, from highest, was: MT 25.6 (SE -5.41), MROP 24.9 (SE -5.66), ET 23.5 (SE -0.24), and EROP 22.3 (SE +0.19). Coronal diameters followed the same rank order; the most perfectly circular eye at the equator was the EROP eye. In the transverse sections, the rank order (from the highest) of the ratio of the long to short elliptical axes was ET, EROP, MT, MROP.

Conclusions: T1 and T2 sequences provide complementary information and, in combination, are suitable for modeling the shape of the eye. Myopic eyes are enlarged at the equator, not just axially enlarged. In this small sample, ROP eyes are shorter than is typical for their SE.

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