Vitreomacular traction (VMT)

In other subheadings within this internet site, we discuss specific macular diseases that can arise because of vitreomacular traction (see macular hole, macular pucker).

If we think on the eye as a soccer ball, where air is present in the ball, we find a gel in the eye, which we call the vitreous gel. The vitreous is a transparent substance that fills the eye and is in contact with the retina; in fact it sticks to the retina when we are young. As we age, the gel liquefies and its attachment to the retina weakens leading to a posterior vitreous detachment (PVD). As this happens it is common to observe floating bodies in the field of vision (See floaters for more details).

The junction between the vitreous and the retina can be stronger in some parts of the eye. Indeed it is normal for the junction to be stronger in the center of vision called the macula. The macular is the central area of the retina, where you are able to see with great detail. It is what is used for example to read, drive or recognize faces. If the adhesion between the vitreous and the retina is particularly strong, it will lead to an area of persistent adhesion surrounded by areas where the vitreous is detached from the retina. When this happens, with the movement of the eye, the gel moves inside pulling wherever there is a persistent area of adhesion. This pulling action is called vitreomacular traction (VMT) when it is located in the macula. Constant traction on the macula can lead to water accumulating in the retina (macular edema) or to the development of a macular hole. Other changes are also possible.

What do you see? What are the symptoms?

Patients with VMT usually complain of decreased vision or distortion (a warped image). A very sensitive test to identify the distortion is the Amsler grid. If you see on an amsler grid an area, in which the lines appear distorted or does not look right, contact your eye doctor for a complete evaluation. However, be aware that the test should be carried out with only one eye open.

The vision loss is usually progressive but since we do not routinely close one eye to see with the other, you may suddenly notice a decrease in vision. Other complaints are the presence of a dark or grey spot occupying the center of vision or just blocking out a few letters on printed material.

What investigations will be done during the consultation?

In your first consultation we will check your current level of vision. We will also check the front part of your eye including the lens to make sure that there is no other cause or reason for a vision drop (even partial).

The inside of your eye will be examined after your pupil is dilated. At your first visit, we always dilate both pupils. Your eye will be examined by the Eye MD, looking at the macula but also the peripheral retina for any areas of thinning or damage. The exam is often completed with additional tests such as the OCT and microperimetry. These tests give us a better idea of how well your retina functions or how extensive is the damage due to traction. Occasionaly other tests may be necessary.

What can be done?

Not all vitreomacular traction is necessarily bad. In some cases it will resolve on its own, and you only need to be followed periodically to make sure that the vision is not getting worse, and that the appearance of the retina on the OCT remains normal.

If there is structural damage to the retina or the EyeMD estimates that one damage may occur soon then the EyeMD will need to release the traction around the macula. There are two possible solutions for this:

• In some cases we can use especial enzymes that, when injected into the eye are able to release the vitreous from its insertion onto the retina. The recently approved drug Jetrea (ocriplasmin) is one of such enzymes. Within one to two weeks after the injection, the vitreous usually separates and surgery is not required to cause this release. If vision had started to decrease it recovers in most cases fully.
• There are cases where a surgical intervention is required. For these we use fine microinstruments of 25G (0.46 mm) or 27G (0.36mm) diameter that we insert into the eye to remove the vitreous and release the traction around the macula. Your EyeMD will explain the procedure in detail if he feels that it is required.