1. Vision

2. Accessory Structures of the Eye
Only about 17% of the eye is visible
About 2.5 cm in diameter
Accessories / external features of the eye:
Palpebrae - eyelids; evenly distribute tears across the surface of the eye to keep it moist
Palpebral fissure – cleft between upper/lower eyelid
Lacrimal caruncle – contains sebaceous/sweat glands
Lateral / medial canthus – 2 points where the upper/lower eyelid meet
Eyelashes
Tarsal glands – secretes oily substance that keeps eyelids from sticking together
Conjunctiva – thin mucous membrane that covers the eye / lubricates eye and contains vessels

4. Lacrimal Apparatus Produces, distributes, and removes tears
Lacrimal gland – tear gland
Provide most of the volume of tears that cover surfaces / supply nutrients and oxygen / contain antibacterial lysozyme
Lacrimal canaliculi – where tears drain  lacrimal sac  nasolacrimal duct
Lacrimal fluid contains lysozyme  fluid moves across eyeball surface and enters two openings in medial canthus  superior / inferior lacrimal puncta  lacrimal canals  lacrimal sac  nasolacrimal tract drains the tears into the nasal cavity

5. INTERNAL EYE Fibrous tunic – dense connective outer layer tissue
Sclera – white part of the tunic that covers the eye
Corneal lambus – the border between sclera and cornea; contain canal of Schlemm,
Cornea – NOT covered by sclera, transparent tissue where light enters the eye
Vascular tunic (uvea)
Iris (anterior)
Lens (posterior to iris) – focuses light
Ciliary body – where iris attaches
Pupil
Choroid (posterior) – melanin that absorbs light and prevents against reflection
Neural tunic (aka retina)
Pigemented part (outer layer)
Neural part – contains light-sensitive photoreceptors
Aqueous humor – maintains intraocular eyepressue and supplies nutritents to lens/ cornea
Vitreous body – holds retina against choroid and prevents collapse

7. How does the pupil change size?
Pupillary sphincter muscles / pupillary dilator muscles
Parasympathetic vs Sympathetic innervation

8. Cellular Organization of the Retina
Neural part of the retina contains the photoreceptors
And 2 types of sensory neurons  bipolar cells and ganglion cells
Photoreceptors
Rods – motion detection
Cones – visual acuity
Light  pigemented area  neural part  photoreceptors  bipolar cells  ganglion cells axons converge at optic disc
Amacrine cells – communication between bipolar and ganglion cells
Horizontal cells – inhibit or facilitate communication b/w photoreceptors and bipolar cells
Macula lutea – contains many cones
Fovea (center of ML) – sharpest vision at this point / no rods here

9. Diseases of the Eye Glaucoma Diabetic Retinopathy Conjunctivitis
Macular Degeneration
Sty

10. Refractive Problems

11. Visual Pathways
Begin with photoreceptors  visual cortex of cerebral hemispheres
130 million photo receptors and 6 million bipolar cells / 1 million ganglion cells
Convergence – increases effeciency of information transmitting but you lose specificity
M cells monitor rods  provide information about general form of an object and motion
P cells monitor cones  provide information about shape, form, color  cones provide more precise information

12. Visual Pathway
Bipolar cells and ganglion converge at optic disc  optic nerve  optic tract  lateral genicular nucleus Projection fibers  visual cortex