Ocular Blood Supply and Circulation Overview

Common Carotid Artery

Supplies head and neck circulation.

Internal Carotid Artery

Supplies cranium, eye, and related structures.

External Carotid Artery

Supplies superficial head and neck areas.

Ophthalmic Artery

First major branch of internal carotid artery.

Central Retinal Artery

Smallest branch supplying inner retina.

Short Posterior Ciliary Arteries

Form 10-20 branches around optic nerve.

Long Posterior Ciliary Arteries

Supply blood to the eye, except inner retina.

Major Arterial Circle of the Iris

Source of radial vessels in the iris.

Anterior Ciliary Arteries

Supply blood to conjunctiva and ciliary body.

Ocular Adnexa

Structures associated with the eye.

Cavernous Sinus

Venous sinus where internal carotid artery enters.

Optic Canal

Passage for optic nerve and ophthalmic artery.

Lamina Cribosa

Structure where central retinal artery enters optic disc.

Choriocapillaris

Nourishes retina from equator forward.

Circle of Zinn

Arterial network encircling optic nerve.

Collateral Branches

Branches from central retinal artery to optic nerve.

Deep Capillary Network

One of two capillary networks from retinal arteries.

Superficial Capillary Network

Second capillary network from retinal arteries.

Optic Nerve Head

Point where optic nerve exits the eye.

Uveal Vessels

Blood vessels supplying the uveal tract.

Rectus Muscles

Muscles that anterior ciliary arteries branch from.

Episclera

Layer where anterior ciliary arteries form networks.

Sclera

Outer layer of the eye pierced by arteries.

Ciliary Body

Structure where anterior ciliary arteries anastomose.

Nasal Branches

Branches of central retinal artery supplying nasal retina.

Temporal Branches

Branches of central retinal artery supplying temporal retina.

Optic Nerve

Nerve transmitting visual information to the brain.

Pia Mater

Inner layer of meninges surrounding optic nerve.

Lateral Rectus

Extraocular muscle responsible for lateral eye movement.

Superior Rectus

Extraocular muscle elevating the eye upwards.

Superior Oblique

Extraocular muscle that rotates the eye downwards.

Medial Rectus

Extraocular muscle responsible for medial eye movement.

Inferior Rectus

Extraocular muscle that depresses the eye downwards.

Inferior Oblique

Extraocular muscle that elevates and laterally rotates the eye.

Angular Artery

Facial artery supplying the medial palpebral margin.

Dorsalis Nasi

Ophthalmic artery supplying the nasal region.

Lacrimal Artery

Ophthalmic artery supplying the lacrimal gland.

Transverse Facial Artery

Branch of superficial temporal artery supplying the orbit.

Posterior Ciliary Arteries

Supply the choroid and outer retina.

Muscular Branches

Arteries supplying extraocular muscles and anterior ciliary arteries.

Ophthalmic Veins

Veins draining blood from the eye orbit.

Superior Ophthalmic Vein

Larger vein formed by supraorbital and angular veins.

Inferior Ophthalmic Vein

Drains blood from lower eye structures.

Central Retinal Vein

Drains retinal tissue; exits near optic nerve.

Vortex Veins

Drain choroid; 4-7 veins exit posteriorly.

Anterior Ciliary Veins

Receive blood from anterior conjunctiva and limbal arcades.

Infraorbital Vein

Drains facial veins; enters infraorbital foramen.

Ocular Perfusion Pressure

Pressure driving blood through ocular vessels.

Hemodynamic Patterns

Blood flow influenced by pressure and resistance.

Mean Arterial Pressure

Average pressure in arteries entering the eye.

Perfusion Pressure

Difference between arterial and venous pressure.

Autoregulation

Maintains constant blood flow despite pressure changes.

Myogenic Theory

Vasodilation and vasoconstriction via smooth muscle communication.

Local Metabolite Theory

Metabolites alter blood flow in response to stress.

Vasoactive Substances

Agents regulating vascular tone and permeability.

Retinal Arterioles

Smaller arteries; systolic pressure 88 mmHg.

Intraocular Pressure (IOP)

Pressure within the eye; affects blood flow.

Critical Closing Pressure

Pressure at which a blood vessel collapses.

Central Retinal Artery Occlusion (CRAO)

Blockage causing retinal ischemia and vision loss.

Fenestrated Capillaries

Capillaries with pores for rapid solute exchange.

Neural Control of Ocular Circulation

Regulated by autonomic nervous system inputs.

Parasympathetic Innervation

Vasodilation effects primarily in anterior uvea.

Sympathetic Innervation

Vasoconstriction to maintain blood flow during hypertension.

Metabolic Activity

Influences blood flow based on oxygen levels.

Lymphatic Drainage

No lymphatics on the eye; present in conjunctiva.

Submandibular Lymph Nodes

Receive lymph from medial eyelids and canthal structures.

Parotid Lymph Nodes

Receive lymph from lateral eyelids and lacrimal gland.

Major Arterial Circle

Formed by ACA and LPCA supplying the iris.

Iris

Contains minor arterial circle for blood flow.

Cilioretinal Artery

Supplies macular area; present in 15-50% population.

Dual Blood Supply

Central retinal artery for inner retina; choriocapillaris for outer retina.

Blood Retinal Barrier

Tight junctions preventing toxic blood from retina.

Diabetic Retinopathy

Damage to blood-retinal barrier causing vision issues.

Transparent Vessel Walls

Allows visibility of blood column within vessels.

Arterio-Venous Nicking

Arterial wall thickening compresses adjacent vein.

Central Retinal Vein Occlusion

Thrombus formation due to tight anatomical position.

CRVO Symptoms

Variable visual loss, retinal hemorrhages, optic disc edema.

Branch Retinal Vein Occlusion

Artery crosses vein; may cause venous occlusion.

Branch Retinal Arterial Occlusion

Occlusion of CRA branch, often from embolus.

BRAO Commonality

90% involve temporal retinal vessels at bifurcations.

Ischemia Effects

Leads to intracellular edema and retinal whitening.

Anterior Ischemic Neuropathy

Nonperfusion of ciliary blood supply to optic nerve.

Conjunctivitis Symptoms

Bright-red conjunctiva with injected superficial vessels.

Uveitis Symptoms

Purplish circumlimbal area with deeper vessel injection.