The Eye

Outer Tunic

• Sclera.

• Tough connective tissue layer. covers most of eyeball and forms visible white part of eye.

• Protective

• Cornea.

• Anterior transparent portion of sclera.
• Window which helps focus light
• Most blindness from cloudy cornea

Middle Tunic

• Choroid

• Ciliary body

• Iris

• Lens

Choroid

• Highly pigmented layer which contains many blood vessels to nourish retina.

• Posterior 5/6 of eyeball

• Anterior portion becomes specialized into ciliary body and iris.

Ciliary body

• Rings eye forward from choroid.

• Controls lens shape for accommodation.

• Produces aqueous humor (fluid which nourishes non-vascular tissues of cornea and lens).

Iris

• Anterior to ciliary body.

• Gives eye its color.

• Controls size of pupil and how much light enters eye.

Lens

• For focusing light on retina.

• Separates interior of eye into 2 compartments.

• Anterior cavity has aqueous humor

• Larger posterior cavity between lens and retina has vitreous humor.

Posterior Cavity

• Vitreous humor in posterior cavity is semifluid, jellylike substance.

• Enables eye to retain its spherical shape.

• Failure to drain will --> increased pressure inside of eye = glaucoma. Pushes lens backward into vitreous humor, which is, in turn, pushed into retina. Can cause damage and blindness if not treated.

Inner Tunic

• Consists of retina.

• Retina has 4 layers

• Pigmented epithelium
• Receptor cells (rods and cones)
• Layer of bipolar neurons. Horizontal and amacrine neurons here too.
• Layer of ganglion cells.

Category: Anatomy Notes , Ophthalmology Notes