What Is It?
Pigment Dispersion Syndrome is an uncommon condition. Most commonly effected are nearsighted males between the ages of 30 and 50. It is also more common in Europeans. The cause of pigment dispersion is a mechanical rubbing between two ocular structures: the IRIS and ZONULES. The iris is the colored part of the eye. It constricts and dilates to change the size of the pupil (depending upon the surrounding light). Behind the iris is the lens. The lens helps focus our vision.
The lens is supported by a multitude of fine fibers called zonules. These fibers move back and forth to allow the lens to focus.
Normally, the iris and zonules have a space between them. However, in pigment dispersion syndrome, the iris inserts further back than usual. Additionally, the iris “bows” back such that it is in contact with the zonules.
As the two ocular structures move there is a mechanical rubbing against each other. This rubbing releases pigment from the back of the iris. The fine pigment from the back of the iris. The fine pigment granules float in the fluid of the eye, and eventually will settle in various places within the eye. One such place is the back surface of the cornea. Here the pigment forms a harmless vertical deposit called a Krukenberg Spindle.
Signs and Symptoms
When a Krukenberg spindle is noticed during an eye exam, the doctor will look for other signs of pigment dispersion. One of the most important findings, are areas of the iris that have been rubbed thin. These are called transillumination defects and appear where the most mechanical contact takes place. This very subtle finding usually confirms the diagnosis of pigment dispersion syndrome.
Patients might be asked about fluctuating vision during reading or exercise. These activities can cause the iris and zonules to move quite a bit. Sometimes large amounts of pigment are released leading to a temporary blur in vision. Most patients do not have this syndrome.
The released pigment often makes its way to the drain of the eye. The eye is constantly making and draining fluid and a delicate balance. The drain for the fluid is located in the angle between the iris and cornea. It is made up of many fine channels or canals. The pigment can lodge in these channels and block the flow (like hair in the sink). It takes many years for enough pigment to accumulate such that the drainage is significantly effected. The drain can take a large amount of pigment before it actually begins to clog. However, when this does occur the pressure in the eye can begin to rise.
Glaucoma is a term used for eye damage caused by pressure within the eye that is too high. There are many causes and types of glaucoma. The common feature is that the Optic Nerve suffers over time by an eye pressure that essentially strangles it. The process is usually very slow, taking years for damage to be noticed. Also different people can tolerate different pressures, so it truly must be evaluated individually. However as a general rule, eye pressures about 22mm should be monitored.
10% of patients with pigment dispersion will develop elevated pressures that can cause glaucoma damage. Patients with this disease need to be monitored for this possibility.
If glaucoma develops, it can be treated with a variety of eye drops. These eye medications act either to slow the flow of fluid into the eye or decrease flow out. Patients on drops also need to be monitored intermittently to ensure that the therapy remains adequate. The pigment continues to be released and there is a tendency for the pressure to increase over time.
Laser For Pigment Dispersion Syndrome
Ophthalmologists have been using the laser to make a tiny hold in the iris for many years to treat angle closure glaucoma. Recently, it has been found promising for patients with pigment dispersion.
The procedure is done in the office in a matter of minutes. It is painless and has very few risks associated. A tiny hold is made in the mid or peripheral iris so that fluid can travel through it. This equalizes the pressures in the front and back of the eye. Interestingly, this equalization allows the iris to move forward, away from the zonules. Almost immediately the iris is much less “bowed-back”.
The hope is that this new position of the iris ill decrease the contact with the zonules, thus slowing or stopping the release of further pigment. It does not eliminate the pigment already released, or any damage that has already been caused.
To truly know the value of this procedure will take many years of monitoring patients-both the ones that had the laser and those that did not. Certainly, the theory and immediate effects of the procedure are quite promising. We do use this laser for select patients, particularly younger ones that are developing elevated pressure.
This disease can sometimes accelerate the formation of cataracts. Cataract surgery actually stops the process of pigment dispersion, but moving the zonules back away from the iris.