Choroid

Suprachoroid

Outermost choroidal layer containing long collagen fibers connecting choroid to sclera and melanocytes.

Choroidal stroma

Layer containing collagen elastin and melanocytes surrounding vessels.

Haller’s layer

Large choroidal blood vessel layer within the stroma.

Sattler’s layer

Medium and small choroidal blood vessel layer within the stroma.

Choroidal artery anastomoses

Functional arterial system

Choroidal vein anastomoses

Choroidal veins have anastomoses.

Choriocapillaris

Innermost vascular layer containing fenestrated choriocapillaries.

Choriocapillaris fenestrations

Fenestrated mainly on the retinal side.

Choriocapillaris density

Highest behind the fovea moderate at the equator lowest in the periphery.

Foveal blood supply

Fovea has highest arteriole-to-venule ratio for redundant supply to cones.

Bruch’s membrane

Innermost choroidal layer composed of five sublayers.

Bruch’s membrane sublayers

BM of choriocapillaris, outer collagenous zone, elastic layer, inner collagenous zone, BM of RPE.

Bruch’s membrane function

Acts as a barrier to nutrient diffusion.

Bruch’s membrane aging

Thickens from about 2 micrometers to 6 micrometers with age.

Choroidal arterial supply

Posterior ciliary arteries.

Short posterior ciliary arteries

Supplied posterior choroid and surround lamina cribosa.

Long posterior ciliary arteries

Supplied anterior choroid via lateral and medial LPCAs.

Choroidal venous drainage

Vortex veins.

Vortex veins count

Four to five vortex veins at least one per quadrant.

Choroid sympathetic supply

Long ciliary nerves causing vasoconstriction.

Choroid parasympathetic supply

Short ciliary nerves causing vasodilation.

Choroid sensory supply

Sensory innervation via long ciliary nerves.

Choroid function nourishment

Nourishes outer retina including RPE and photoreceptors.

Choroid oxygen supply

Nearly all oxygen delivered goes to photoreceptors.

Choroid thermoregulation

Choroidal blood flow regulates retinal temperature as heat source and sink.

Choroidal modulation of eye growth

Choroid changes thickness in response to defocus (choroidal accommodation).

Hyperopic defocus effect

Choroid decreases in thickness.

Myopic defocus effect

Choroid increases in thickness.

Choroid thickness speed

Thickness changes occur within minutes and are transient.

Choroid diurnal variation

Thickest mid-night thinnest mid-day.

Axial length relationship

Choroidal thickness variation opposes diurnal axial length variation.

Light scatter absorption

Melanin in choroid absorbs excess light.

Choroid cellular development

Cellular components derive from neural ectoderm.

Choroid vascular development

Vascular components derive from mesenchymal mesoderm of optic cup.

Choriocapillaris development

Begins at 3 weeks following RPE development.

Ciliary process capillaries

Develop independently and early; fed by LPCA bypassing choroid.

Haller’s and Sattler’s development

Large and medium vessels develop at 4–6 months.

Drusen

Deposits of lipid protein and debris between choroid and RPE associated with AMD.

Drusen location

Most commonly in macula due to high metabolism and blood supply.

Drusen effect

Pushes RPE and photoreceptors away from blood supply.