CHOROID

 

• Posterior most part 
• Extension- optic disc to ora Serrata 
• Inner surface- smooth, brown, and in contact with RPE 
• Outer surface-rough and in contact with sclera 
• Thickness- posteriorly 0.22mm anteriorly 0.10mm

1. MICROSCOPIC STRUCTURE:
2. 1) Suprachoroidal lamina- lamina fusca: Thin layer, continues anteriorly with the supraciliary lamina of ciliary body

• Suprachoroidal space- contains long and short posterior ciliary arteries and nerves 

2) Stroma – plenty of pigmented cells, macrophages, mast and plasma cells

• Vessels- form the bulk 
• Arranged in two layers- outer consisting of large vessels(hallers layer) , inner of medium vessels ( sattlers layer) 
• Contains vessels, nerves, cells & connective tissue -Stromal cells include: a. Melanocytes b. Fibrocytes c. Macrophages d. Mast cells e. Plasma cells.

3) choriocapillaris- rich capillary network

• Supplies pigment epithelium and outer layers of the sensory retina 
• Few anastomosis with CRA

4)Basal lamina- 

• Bruch's membrane/lamina vitrae 
• Innermost layer • Between choriocapillaris and RPE 
• Electron microscopy- basement membrane of RPE, inner collagen, middle elastic and outer collagen and basement membrane choriocapillaris 
• With increasing age- produces hyaline excresences known as druscens

 FUNCTIONS OF CHOROID:

• BLOOD SUPPLY TO OUTER FOUR LAYERS OF RETINA 
• MODULATION OF VASCULARISATION 
• REGULATE RETINAL HEAT 
• ASSIST IN THE CONTROL OF INTRAOCULAR PRESSURE 
• PIGMENT ABSORBS EXCESS LIGHT SO AVOIDING REFLECTION