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Topic

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Retina

The retina is a thin, transparent, light-sensitive layer of neural tissue that lines the inner surface of the posterior segment of the eye. It plays a critical role in visual perception by converting incoming light into neural signals, which are then transmitted to the brain via the optic nerve. The retina contains photoreceptor cells (rods and cones) and various interneurons that process and integrate visual information, making it an essential structure for sight.

Synonyms

  • Neural layer of the eye

  • Sensory layer of the eye

  • Retinal membrane

Function

  • Converts light into electrical signals (phototransduction)

  • Houses photoreceptors: rods (dim light, peripheral vision) and cones (color, detail, central vision)

  • Processes visual information before transmission to the brain via the optic nerve

  • Plays a role in image formation, color detection, and adaptation to light and darkness

MRI Appearance

  • T1-Weighted Images (T1WI):

    • Retina is isointense to slightly hyperintense compared to vitreous humor

    • Appears as a thin, linear structure along the inner wall of the globe

    • Differentiation from adjacent choroid and sclera may be challenging without contrast

  • T2-Weighted Images (T2WI):

    • Retina appears hypointense (dark) relative to the hyperintense (bright) vitreous humor

    • Remains as a thin, distinct, hypointense line along the posterior globe

    • Layered structure of the retina is generally not resolved

  • STIR (Short Tau Inversion Recovery):

    • Retina remains hypointense against the bright vitreous signal

    • STIR is primarily useful for detecting edema or pathology (e.g., retinal detachment appears as a hyperintense line)

    • Normal retina is less conspicuous unless pathological fluid is present

CT Appearance

  • Retina is not individually visualized on routine CT due to limited spatial resolution

MRI images

Retina mri t2 sagittal image