What is the vitreous and posterior vitreous detachment?
The vitreous is a clear substance within the eye. It has a gel-like consistency. Vitreous gel is composed of 99% water by weight, and the other 1% is made up of special substances known as collagen and hyaluronic acid, which give the vitreous its gel-like consistency.
The vitreous is a vestige of development, necessary to the growth of the hyaloidal artery during growth in utero. Once we are born, this blood vessel atrophies or dissolves as it is no longer needed to carry blood from the back of the eye to the front of the eye.
Normally, the back surface of the vitreous, called the hyaloid, is in direct contact with the retina, which is the light-sensitive tissue that converts light into a chemical signal. However, as we age, the vitreous forms liquid pockets that cause surrounding vitreous to collapse centrally, providing space for the hyaloid to separate from its point of attachment at the back or posterior of the eye at the optic nerve.
This separation is called a posterior vitreous detachment (PVD). In the vast majority of patients, the process of separation has no symptoms and goes unrecognized. In a few people, however, this separation is noticeable immediately due to one or more of the following symptoms:
- Flashes of light called photopsia
- Showers of floaters
- Darkness of the peripheral visual field.
Why is a symptomatic PVD important?
A symptomatic PVD carries a 10% risk of retinal tear with half of these tears leading to retinal detachment. If a retinal tear does occur during a posterior vitreous detachment, it usually happens at the same time as one begins to experience symptoms of the PVD. Therefore, it is important to be examined shortly after these symptoms begin.