How does optic disc edema can cause retinal and choridal folds and the
difference between the two types of folds?

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The term edema refers to an abnormal accumulation of fluid in the body
tissues or in the body cavities causing swelling or distention of the
affected parts.  The primary cause of optic disk edema is slowed
cellular conduction along the optic nerve, which occurs when swelling
of the prelaminar axons causes elevation and expansion of the optic
nerve head.  This swelling is caused by an accumulation of
intracellular fluids and metabolic by-products that dam up and
eventually results in swelling of the prelaminar axons.  When swelling
occurs, the normally distinct border of the optic disc becomes blurred
as swollen axons become elevated and less transparent.  The pressure
caused by this swelling can result in circumferential retinal
microfolds (Paton’s lines) and choroidal folds.

The basic difference between the two types of folds is that retinal
folds are concentric (rings) to the disk while choroidal folds are
radial (arranged like the spokes of a wheel) to the disk.  Details on
differences:

The retina is the inner layer at the back of the eye, where
light-sensitive rods and cones are located. Chemical changes in the
retina transmit electrical signals through the optic nerve to the
brain to produce sight.  When the retinal venules become engorged due
to optic disk edema, it can cause hemorrhages and/or cotton wool spots
to form in the peripapillary area.  An increase in the diameter of the
intraocular portion of the optic nerve from axonal swelling produces
concentric perpapillary chorioretinal folds, often called Paton’s
lines, in the region surrounding the disk.

The choroid is the middle membrane of the eye and is part of the uveal
tunic, between the retina and outer coating.  It supplies blood to the
eye.  Choroidal folds are caused when the optic sheath expands due to
optic disk edema, and protrudes into the posterior globe, creating
radial folds emanating from the center of the disk.


Additional links:

Handbook of Ocular Disease Management: 
( http://www.revoptom.com/handbook/sect6b.htm )

Optic Nerve Disorders (pgs. 5-6)
( http://www3.us.elsevierhealth.com/HS/reqoph/MartinCh04.pdf )

VisionWeb Glossary: (
http://www.visionweb.com/content/consumers/glossary.jsp )


Search  terms:

Optic disk edema

Choroidal folds

Paton’s lines

Ocular diseases

Optic nerve disorders

Great answer! Explained both types of folds in a way that was
understood easily. The sources are going to help us a lot.