PHED-2506EL Lecture Notes - Lecture 19: Visual Processing, Optic Chiasm, Depth Perception
25 Jun 2018
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Vision
List the accessory structures of the eye and give functions for each
Eyebrow: help shade eye from sunlight and prevent perspiration trickling down the
forehead from reaching the eyes
Eyelids: Protect and lubricate the eyes by reflex blinking.
Conjunctiva: lines the eyelids and covers the anterior eyeball surface, its mucus
lubricates the eyeball surface and prevents the eye from drying up.
Lacrimal apparatus: consists of lacrimal gland which produces lacrimal secretion also
knows as tears (mucus, antibodies and lysosomes which destroys bacteria). It cleans and
protects the eye surface as it moistens and lubricates it.
6 Extrinsic Eye muscles (Lateral rectus, Medial rectus, superior rectus, inferior rectus,
inferior oblique, superior oblique): these muscles help in the movement of the eyeballs.
List and describe the 3layers of the eye.
Outer layer or Fibrous Tunic: consists of sclera and cornea
Sclera: is the white of the eye, tough, tendon-like. It protects and shapes the eyeball and
provides a sturdy anchoring site for the extrinsic eye muscles. Sclera is continuous of the
dura mater of the brain.
Cornea: crystal clear cornea forms a window that lets light enter the eye, and it’s a
major part of the light-bending apparatus of the eye. Cornea is cover with epithelial
sheets which protects the cornea from abrasion.
Vascular Tunic or the Uvea: forms middle coat of the eyeball. Consists of choroid, ciliary body
and iris.
Choroid: Dark brown membrane and it forms posterior region of the uvea. It supplies
blood to all eye layers.
Ciliary body: anteriorly the choroid becomes the ciliary body which is a thickened ring of
tissue that encircles the lens. It consists of smooth muscles bundles called ciliary
muscles which acts to control lens shape. Consists of ciliary processes and suspensory
ligament. Ciliary processes secrete the fluid that fills the cavity of the anterior segment
of the eyeball. The suspensory ligaments hold the lens in its upright position.
Iris: Colored part of the eye, shaped like a flattened doughnut. Lies between the cornea
and lens and continuous with the ciliary body. Its round central opening is the pupil
which allows and regulates the amount of light entering the eye. Close vision and bright
light – pupils constrict, Distant vision and dim light – pupils dilate, Changes in emotional
state – pupils dilate when the subject matter is appealing or requires problem-solving
skills
Inner Layer or sensory Tunic consist of the Retina. 2 layers of the retina
Outer Pigmented Layer: absorbs light and prevent its scattering. Acts as phagocytes
participating in photoreceptor cell renewal and store vitamin A needed by
photoreceptor cells.
Inner Neural Layer: consists of 3main types of neurons from posterior to anterior.
Photoreceptors transduce light energy which is then spread to the bipolar cells and then
to the innermost ganglion cells (run along the inner surface of the retina, leave the eye
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Document Summary
List the accessory structures of the eye and give functions for each. Eyebrow: help shade eye from sunlight and prevent perspiration trickling down the forehead from reaching the eyes. Eyelids: protect and lubricate the eyes by reflex blinking. Conjunctiva: lines the eyelids and covers the anterior eyeball surface, its mucus lubricates the eyeball surface and prevents the eye from drying up. Lacrimal apparatus: consists of lacrimal gland which produces lacrimal secretion also knows as tears (mucus, antibodies and lysosomes which destroys bacteria). It cleans and protects the eye surface as it moistens and lubricates it. 6 extrinsic eye muscles (lateral rectus, medial rectus, superior rectus, inferior rectus, inferior oblique, superior oblique): these muscles help in the movement of the eyeballs. List and describe the 3layers of the eye. Outer layer or fibrous tunic: consists of sclera and cornea. Sclera: is the white of the eye, tough, tendon-like.
