Uveal tract

Question 1

Sections of ON

Answer 1

Intraocular : within eye
Intraorbital : exits globe at posterior scleral foramen to apex of orbit
Intracanalicular : ON passing via optic foramen
Intracranial: optic canal to chiasm

Question 2

Lamina cribrosa

Answer 2

Opening in sclera (posterior scleral foramen) for ON where connective tissue forms mesh for axons to pass.
Most scleral fibers do not form this mesh and instead turn and run parallel with ON

Question 3

Optic nerve head

Answer 3

Seen in fundus. Optic cup in center, neuro-retinal rim in periphery.
Lamina cribrosa divides ONH into 3 regions from back to front (prelaminar, laminar, retrolaminar)

Question 4

Vascular supply to ON

Answer 4

Intra cranial/canalicular ON: Ophthalmic artery
Orbital ON: Central retinal artery
Postlaminar ON: central retinal artery branches
Laminar / Pre-laminar ON: Circle of Zinn-Haller / Choroid
Venous return via Central retinal vein

Question 5

Ganglion axon map on fundus

Answer 5

Nerve fiber layer forms lines towards ON
Majority of axons come from macula, immediately entering ON.
Other axons enter ON around macula axons, rearrange within ON before chiasm.

Question 6

Uveal tract

Answer 6

Vascular layer between sclera / retina.
Anterior = iris
Middle = ciliary
Posterior = choroid

Question 7

Uveal tract functions

Answer 7

Retinal illumination control at iris
Nourishment (CB, choroid)
Aqueous humor production (CB)
Accommodation (CB)

Question 8

Choroid structure

Answer 8

Posterior part of uvea (Ora serrata to ON)
Peri choroidal space (filled with suprachoroidal lamina tissue) separates it from inner sclera
4 layers, surpachoroid, stroma, choriocapillaris, bruchs membrane

Question 9

Choroid function of its layers

Answer 9

Suprachoroid (lamina): outermost connective tissue with nerve fiber
Stroma: elastic fibers with blood vessels (outer are large)
Choriocapillaris: smallest vessels, dense in macula
Bruch’s membrane: innermost membrane

Question 10

Bruch’s membrane and issues that can occur

Answer 10

Acellular sheet, thick at ON.
Drusen appears here forming atrophic or neovasc AMD
5 layers allowing blood retinal barrier

Question 11

Pigmentation of fundus

Answer 11

Melaninocytes present in choroid/RPE absorb stray light from rods/cones.
Accumulation of pigment = fundus color, makes it so we cant see vessels clearly

Question 12

Choroid vascular supply

Answer 12

Short posterior ciliary arteries
Long posterior ciliary arteries
Anterior ciliary arteries
Has high blood flow, cholinergic / adrenergic receptors = dilation / constriction

Question 13

Choroid venous supply

Answer 13

Vortex veins drain choroid, and join sup./Inf. ophthalmic vein, then into cavernous sinus / pterygoid venous plexus respectively

Question 14

Choroid innervation

Answer 14

Nerve plexus in perichoroidal space.
Long ciliary nerves: sensory (nasociliary of CN V), sympathetic (superior cervical ganglion)
Short ciliary nerves: sensory (nasociliary), sympathetic (superior cervical ganglion), parasympathetic
Can be seen in fundus as straight whiteish lines

Question 15

Ciliary body

Answer 15

Middle part of uveal tract

Anterior border of sclera, intermediate border of iris, posterior border of retina (ora serrata)

Question 16

Ciliary body function

Answer 16

Secretes aqueous humor, lens nourishment, accommodation muscle, aquesous humor outflow assistance, viterous hyaluronic acid contribution

Question 17

Ciliary body landmarks

Answer 17

Secretes aqueous humor, lens nourishment, accommodation muscle, aquesous humor outflow assistance, viterous hyaluronic acid contribution

Question 18

Pars plana:

Answer 18

Forms Ora Serrata to Pars Plicata
Retina becomes ciliary epithelium, RPE becomes pigmented ciliary epithelium
Looks scalloped, give rise to Ant. Zonules

Question 19

Pars Plicata

Answer 19

From Pars Plana to iris
Has ciliary processes (seen on microscope) for aqueous humor secretion into Pos. chamber, and zonule attachment
Thickest part of ciliary with underlying muscle.

Question 20

Ciliary stroma:

Answer 20

Loose connective tissue with vessels / nerves, and supraciliaris (layer connecting it to sclera)
Contains ciliary muscle

Question 21

Ciliary muscle:

Answer 21

smooth muscle in ciliary stroma.
Outer = longitudinal fiber
Intermediate = oblique fibers
Innermost (close to lens) = circular fibers
Ciliary muscle tendons anchor CB to sclera

Question 22

Ciliary epithelium:

Answer 22

2 single layer cuboidal epithelium.
Inner non pigmented: secretes aqueous humor, have tight junctions for blood aqueous barrier
Outer pigmented: continuous with Iris, have gap junctions for ion passage

Question 23

Innervation of ciliary body

Answer 23

Parasympathetic: short ciliary nerves, inferior division of CN III.
Sympathetic: long ciliary nerves from superior cervical ganglion.
Sensory: long ciliary nerves, nasociliary branch of ON (CN V)

Question 24

Zonule accommodation

Answer 24

3 insertion bands:
Anterior zonule = pars plana to pre-equator
Posterior zonules = pars plicata to post-equator
Equatorial conules = pars plicata to equator

Question 25

Process of accommodation

Answer 25

Distance: ciliary muscle relaxes, zonules taught, lens is thin
Near: CN III parasympathetic innervation. ciliary muscle contracts, moves towards lens. Zonules relax, lens thickens, anterior chamber becomes shallower. (convergence and pupil constriction occur)

Question 26

Ciliary body change with age

Answer 26

Morphology leads to increased connective tissue, loss of fibers, increases circular fibers. Less movement towards lens on contraction, less accommodation.

Question 27

Vascular supply to ciliary body

Answer 27

2 Long ciliary arteries = ant./int. CB, join forming major arterial circle
7 anterior ciliary arteries = pos./out. CB, join forming intramuscular circle.
Vortex veins drain blood

Question 28

Iris

Answer 28

Part of uveal tract. Connects to cornea at anterior chamber drainage angle.
Seperates ant./pos. chambers
Bathed in aqueous humor.

Question 29

Iris function

Answer 29

Retinal illumination regulator via pigments, contributes to blood-aqueous barrier, depth focus

Question 30

Iris landmarks

Answer 30

Pupil, pupil ruff (adjacent to pupil), collarete (next to ruff), ciliary zone (periphery).

Question 31

Iris structure and issues relating to lens.

Answer 31

Thick at collarette, thin at root (CB junction). Rests on lens for aqueous circulation, may become stuck (pupil block) causing iris bowing forward.
Ant. Has holes
Middle has vessels
Pos. has muscle, pigment and folds

Question 32

Iris zones

Answer 32

Ant. Border: connective tissue around crypts forming texture. Radial furrows allow folding during dilation
Stroma: includes sphincter (smooth) pupillae muscle innervated by post ganglionic parasympathetic fibers (CN III)
Ant. epithelium: cont. with outer epithelium of CB. includes dilator pupillae muscle innervated by post-ganglionic fivers of superior cervical ganglion (sympathetic NS)
Pos. pigmented epithelium: cont. with inner epithelium of CB

Question 33

Iris vascular supply

Answer 33

2 long posterior ciliary arteries
7 anterior ciliary arteries
Major arterial circle run via ciliary zone to collarette
Minor arterial circle branches in pupillary zone
Vortex veins drain blood Sup./Inf.

Question 34

Blood aqueous barrier

Answer 34

Iris BV / Ciliary epithelium have tight junctions, ensures no passive material transport.
Inflammation allows immune cell passage
Trauma allows erythrocyte passage (blood filling ant. Chamber)

Question 35

Iris innervation

Answer 35

Parasympathetic: short ciliary nerves = sphincter pupillae muscle
Sympathetic = long cilary nerves = dilator pupillae muscle
Sensory = nasociliary branch of CN V1 (ophthalmic), nerves terminate as non-myelinated filaments in stroma