- sclera and cornea

Outer fibrous/supporting layer

- choroid, ciliary body, part of iris

Middle, vascular or uveal layer

- retina, ciliary body, part of iris ('non-visual retina')

Inner or retinal layer

- transparent gelatinous mass composed of loose collagen fibers and hyaluronic acid

- produced by hyalocytes (tissue macrophages)

- attached to retina posteriorly

- liquefy with age and detach from retina (increased retinal detachment risk)

Vitreous body

- part of inner (retinal) layer

- expanded inner processes of Muller's cells (modified astrocytes) and their basal lamina

inner limiting membrane

- part of inner (retinal) layer

- axons of ganglion cells

- superficial to inner limiting membrane

- deep to ganglion cell layer

nerve fiber layer

- part of inner (retinal) layer

- superficial nerve fiber layer

- deep to inner plexiform layer

ganglion cell layer

- part of inner (retinal) layer

- composed of bipolar cell axons, dendrites of ganglion cells, processes of amacrine cells and synapses

- superficial to ganglion cell layer

- deep to inner nuclear layer

inner plexiform layer

- part of inner (retinal) layer

- composed of nuclei of bipolar, horizontal amacrine, supporting (Muller's cells) and interneurons

- superficial to inner plexiform layer

- deep to outer plexiform layer

inner nuclear layer

- part of inner (retinal) layer

- composed of processes of rod and cone cells (spherules and pedicles), synaptic ribbons (controls release of neurotransmitters)

- superficial to inner nuclear layer

- deep to outer nuclear layer

outer plexiform layer

- part of inner (retinal) layer

- composed of rod and cone nuclei and cell bodies

- superfiical to outer plexiform layer

- deep to outer limiting membrane

outer nuclear layer

- part of inner (retinal) layer

- composed of junctional complexes of Muller's cells and photoreceptor cells

- superficial to outer nuclear layer

- deep to layer of rods and cones

outer limiting membrane

- part of inner (retinal) layer

- superficial to outer limiting membrane

- deep to retinal pigment epithelium

layer of rods and cones

- part of inner (retinal) layer

- composed of cells that contain melanin, phagocytose rod and cone membranes that are shed, and form the BBB (tight junctions)

- they also process vit A and pump ions

- superficial to layer of rods and cones

retinal pigment epithelium

- this occurs when rods and cones separate from the retinal pigment epithelium and are deprived of nourishment

Retinal detachment

- this part of the rod contains numerous mitochondria, rough ER, and glycogen

inner segment

- found at the constriction of the outer and inner rod segments

basal body

- the outer segment that extends from the basal body is considered this (although it lacks the central microtubular pair)

cilium

- the outer segmental membrane forms these

- they are formed at the base and old ones are sloughed at the tip where the retinal epithelium phagocytoses them

disks

- the distinguishing factor between rod and cone disks is that cone disks are attached on one side while the rod disks are this

free floating

- periphery of the retina consists only of these cells

rods

- sensitive to low light levels, contain rhodopsin

- 70-140 million/retina

Rods

- have three kinds (green, red, and blue)

- contain retinal plus each kind of opsin

Cones

- number of rods synapse with single bipolar neuron; number of bipolar neurons synapse with single ganglion cell

convergence

- "yellow spot"

- depressed center is fovea centralis (consists of cones)

- 1:1:1 cone:bipolar neuron:single ganglion cell

- avascular

Macula lutea

- optic nerve vessels supply the inner surface of this layer and penetrate only inner layer

- arterioles --> nerve fiber

- capillaries --> inner nuclear

- venules return from inner plexiform

- rods and cones by way of capillaries in the choroid (diffusion)

Retinal layer

- part of the Middle (vascular) layer

- highly elastic, contains melanocytes

- consists of Bruch's (glassy) membrane --> choriocapillary layer --> vessel layer --> suprachoroid

Choroid

- part of the Middle (vascular) layer

- includes the basal lamina of the pigment epithelium, as well as collagen and elastic fibers

Bruch's (glassy) membrane

- part of the Middle (vascular) layer

- flattened vascular channels lined with fenestrated endothelium

- nutrition source for outer retinal layers

- superficial to Bruch's membrane

- deep to vessel layer

choriocapillary layer

- part of the Middle (vascular) layer

- larger vessels found here

- superficial to choriocapillary layer

- deep to suprachoroid

vessel layer

- part of the Middle (vascular) layer

- contains elastic fibers and melanocytes

- superficial to vessel layer

- deep to sclera

Suprachoroid

- contributes smooth muscle (ciliary muscle)

- anchored to sclera, free to pull on choroid

- covered by a double layer of cuboidal epithelium

- continuous with the retinal layer ("non-sensory retina")

Ciliary body

- epithelium produces aqueous humor and the zonules fibers

- have plasma membrane infolding and Na/K- ATPase for fluid and ion transport

- tight junctions between epithelial cells from the blood-aqueous barrier

Ciliary process

- consist of stroma, spiraled blood vessels and variable numbers of melanocytes

- anterior surface lacks an epithelial covering but has stromal cells facing the anterior chamber

- provides the color in the eye

Iris

- dilator and sphincter muscles (symp/parasymp innervation) derived from pigment epithelium

- double layer of epithelium on posterior surface of iris is continuous with double layer of the ciliary body epithelium

- thin sheet of smooth muscle (myoepithelium)

- circular band at pupil margin

Retinal components of the iris

- ciliary muscle relaxes

- lens flattens by being pulled on by the fibers of the ciliary zonule (attached to choroid)

Accommodation for far vision

- ciliary muscle contracts and pulls on choroid

- takes tension of the ciliary zonule

- lens takes on globular shape

- sphincter of the iris contracts

Accommodation for near vision

- consists of collagen fibers arranged in irregular sheets

- average thickness is 0.5 mm

- continuous with the meninges covering the optic nerve

- covered by conjunctiva

Sclera

- transparent because it is relatively dehydrated

- contains no vessels, has only free nerve endings

- major bending of light takes place here

Cornea

- part of outer layer (cornea)

- non-keratinized stratified squamous epithelium

- regenerates readily when damaged

- "vermiform" ridges present on air contact surface to retain a layer of fluid

- superficial to Anterior limiting (Bowman's) membrane

Corneal epithelium

- part of outer layer (cornea)

- basement membrane of corneal epithelium

- forms a scar when damaged

- superficial to stroma

- deep to corneal epithelium

Bowman's membrane

- part of outer layer (cornea)

- made up of layers of collagen fibrils of uniform size, arranged uniformly at right angles

- contains a ground substance (proteoglycans) which maintain appropriate hydration and uniform collagen spacing

- corneal fibroblasts produce the stroma

- superficial Descemet's membrane, deep to Bowman's

Stroma or substantia propria

- part of outer layer (cornea)

- thick basement membrane of the inner epithelium

- tough layer, stops penetration

- does regenerate following injury

- deep to stroma, superficial corneal endothelium

Descemet's membrane

- part of outer layer (cornea)

- simple squamous epithelium

- provides for metabolic exchange between aqueous humor and cornea

- provides pumps that keep the stroma dehydrated

- damage can result in corneal edema with decreased vision

- deep to Descemet's membrane

Corneal endothelium

- consists of a capsule, anterior epithelium, and fibers

Lens

- part of lens

- very elastic physically

- anchors the zonule fibers

- thick basal lamina w/ collagen IV

Lens Capsule

- part of lens

- single layer of cuboidal cells

- form new lens fibers at lens equator

- slowly increases in size throughout life

Lens Anterior epithelium

- deeper fibers have lost their nuclei

- gap junctions present

- part of the lens

lens fibers

- fills the anterior/posterior chambers

- produced by the epithelium on the ciliary body

- absorbed into the venous blood by way of trabecular meshwork across endothelium into the canal of Schlemm

Aqueous humor

- made of axons of ganglion cells

- covered w/ meninges

- contains glial cells

- axons become myelinated after leaving the eye at the lamina propria

- has septa (different from peripheral nerve)

- no schwann cells

Optic Nerve