Anatomy and Physiology of the Retina

Associate Professor Trevor SherwinDepartment of Ophthalmology

University of Auckland

Light entering the Eye

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Eye Exam

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The retina

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Function of the retina

-Transmit electrical impulse to the brain via ganglion cells

- To absorb photons of light

- Translate light into a biochemical message

- Translate biochemical message into electrical impulse

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Sagittal section of the retina

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Cellular detail of the retina

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Octopus Retina

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Octopus Retina

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Layers of the retina

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Cell bodies and synapses

All vertebrate retinas are composed of three layers of cell bodies and two layers of synapses

Cell bodies of rods/cones

Cell bodies of bipolar cells

Cell bodies of ganglion cells

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Neuropil layers

Photoreceptor -bipolar synapse

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Neuropil layers

Bipolar – ganglion synapse

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Photoreceptors

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Photoreceptors

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Photoreceptors

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Rhodopsin and photoreceptor cells

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Rhodopsin

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Central and peripheral retina

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Central and peripheral retina

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Optic Nerve

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Optic Nerve

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Blood supply to the Retina

Choroid supplies 85%Mainly outer retinaPhotoreceptors

Central retinal artery supplies 15%Inner retinal layer

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IV Fluorescein Angiogram

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IV Fluorescein Angiogram

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IV Fluorescein Angiogram

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IV Fluorescein Angiogram

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The foveaFoveal pit + foveal slope + parafovea + perifovea

= Macula

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Eagle Vision

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Photoreceptor cell diameter

Rods (IS) – 2 microns

Cones (IS) – 6 microns

However, in the foveaCones (IS) – 1.5 microns

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Photoreceptor cell diameter

Rods (IS) – 2 microns

Cones (IS) – 6 microns

However, in the foveaCones (IS) – 1.5 microns

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Photoreceptor density

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Acuity of the retina

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The Macula Lutea

Xanthophyll caratenoids –zeaxanthin & luteinTapetum

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Colour Absorbancy

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Colour Blindness

Red/green colour blindness - X linked

Males only have a single X chromosome

Almost all genes on the X have no counterpart on the Y

Any gene on X, even if recessive in females will be expressed in males

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Summary of photoreceptors

Rods - Low light levels (scotopic)Peripheral visionSlow response

Cones - Visual acuityColour visionFast response

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Clinical examination of photoreceptors

Form & spatial vision, measured by visual acuityReflects rod & cone distribution

Colour vision testing is indicative of cone function and associated processing of the signal

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Vision and Movement

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