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Vitreous & Retinal Detachment
Most of the serious retinal problems which require
surgery are caused by problems with the vitreous, the clear jelly-like
substance which fills the space in the eye.
Posterior Vitreous Detachment
With age, the vitreous becomes more fluid, and
less jelly-like. As the eyeball moves, small pockets of liquid vitreous
can move around inside the vitreous cavity. This movement causes
the vitreous to pull on the retina, and, with time, the vitreous
can separate from the retina. This is called posterior vitreous
detatchment (PVD), because it usually happens at the back (posterior)
of the eye. PVD happens in most people eventually, and is rarely
a problem.
Flashes and Floaters
When PVD occurs, the detached vitreous can tug
on the retina. The brain interprets these tugs as flashes or large
spots in the vision. The vitreous can also become stringy, and form
visible strands which appear in the field of vision as floating
threads or small spots and circles. A patient with these floaters
should be examined, to check for other retinal damage. If there
are no problems, the patient can fairly easily learn to ignore the
floaters.
Retinal Tear and Vitreous Hemorrhage
Where the vitreous is securely attached to the
retina, vitreous detachment may cause the retina to tear. If the
retina tears across a blood vessel, there will be bleeding into
the vitreous - this is called vitreous hemorrhage. Small amounts
of bleeding cloud the vision, leading to the sensation of walking
through a swarm of insects - more severe bleeding leads to a mass
of red or black lines, and vision may become very dark. A retinal
tear is a serious problem; vitreous hemorrhage is even more serious.
Retinal tears may be sealed with lasers or cryotherapy,
or both, to prevent retinal detachment. Both these treatments seal
the retina to the wall of the eye, repairing the tear and preventing
detachment.
Retinal Detachment
A retinal tear is considered so serious because
the vitreous liquid may leak through the tear, and collect under
the retina. Gradually, the build up of liquid separates the retina
from the wall of the eye, a condition called retinal detachment.
The two major treatments for retinal detachment are scleral buckling
- where a sponge or length of silicon plastic is placed on the outside
of the eye and sewn in place, pushing the sclera toward the tear
in the retina - and pneumatic retinopexy, a less severe treatment
where the surgeon injects a gas bubble inside the vitreous cavity.
The bubble pushes the retina against the wall of the eye, allowing
the tear to seal against the eye wall.
Vitreous Surgery
If the retinal detachment is too severe for scleral
buckling or pneumatic retinopexy, surgery to reattach the retina
may be necessary. Under general anesthetic, the surgeon removes
the vitreous entirely, replacing it with air or a fluid compatible
with the eye. Over time, the fluid (or air) is absorbed, and replace
with the eye's own fluid. Lack of vitreous does not affect the patient's
vision.
Additional sites pertaining to Retinal Diseases:
- Understanding Diabetic
Retinopathy - RNIB (UK)
- Hereditary
Retinal Detachment - University of Iowa (US)
- Retinal
Detachment and Vitreous Surgery - RNIB (UK)
- The
Retinal Implant Project - MIT (US)
- About Retinitis
Pigmentosa - Molecular Ophthalmology Lab., University of Iowa
(US)
- Retina
Reference - University of Pennsylvania (US)
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