What is Pigment Dispersion Glaucoma?

Glaucoma is a condition that affects the eyes, leading to high pressure inside the eye that can cause damage to the optic nerve and loss of vision. Fluid, known as aqueous humor, is made in the back of the eye and moves to the front of the eye. Usually, this fluid drains out at the angle where the clear outer cover of the eye and the iris meet. If anything blocks this fluid from draining, it can cause glaucoma.

There are two main kinds of glaucoma. Closed-angle glaucoma occurs when the fluid cannot drain because the angle that it needs to pass through is blocked. Open-angle glaucoma is when the fluid can’t drain even though the angle is clear.

Pigment Dispersion Glaucoma (PG) is a type of open-angle glaucoma. This condition, along with a related one known as Pigment Dispersion Syndrome (PDS), share similar characteristics and are considered different stages of the same disease. If someone with PDS develops high eye pressure and vision loss, they are considered to have progressed to PG.

In 1899, Friedrich E. Krukenberg described a particular symptom associated with these conditions, known as Krukenberg’s spindle.

Three symptoms of PG were identified in 1949 by Sugar and his team. They noticed that there were pigment deposits on the back of the cornea, gaps in the pigmented area of the iris, and a lot of pigmentation in the drainage area of the eye.

In PG, pigment loss happens because of the constant rubbing between the backside of the iris and the lens parts during eye movement, especially in eyes that are nearsighted and have a large iris. All these pigment particles can cause harm to the drainage cells over time, impacting their function and efficiency.

As a result, the fluid builds up leading to high eye pressure in PG. This may cause vision loss associated with chronic nerve damage over time. This disease usually affects both eyes, occurs commonly in males who are nearsighted, and is usually identified between the age of 30 to 50.

What Causes Pigment Dispersion Glaucoma?

PDS (Pigment Dispersion Syndrome) and PG (Pigmentary Glaucoma) are typically caused by pigment being released into the front part of the eye. This happens when the colored part of the eye rubs against the structures that help the eye focus, generating friction.

Eyes with PDS and PG are more likely to have certain structural features that make this rubbing more possible. In some cases, the back of the iris (colored part) of the eye may bow backwards, which can be caused by certain factors like nearsightedness (also known as myopia) and a deep anterior chamber, which is the space in the eye in front of the iris.

Movements or positions of the eye or head can sometimes cause the iris to block the flow of a liquid (known as the aqueous) within the eye. This can lead to pressure building up within the eye, which pushes the iris against the lens and can lead to an increase in the eye’s internal pressure.

This build-up can cause the iris to bow outwards, and its back surface can rub against the structures that help focus the eye, causing pigment dispersion. This means that the colored cells of the iris can be more easily shed into the eye’s fluid.

The symptoms of PDS and PG are often due to the pigment being released within the eye. This pigment can build up on the inner side of the cornea (the clear front surface of the eye), causing dark, spindle-shaped patterns.

While PDS and PG can affect the thickness and shape of the cornea, they do not usually impair the functioning of the eye. The pigment can also build up within the fluid drainage system of the eye, which could affect how the fluid drains and increase the internal pressure of the eye.

PDS is often seen in nearsighted people, and the higher the degree of nearsightedness, the more severe the PG may be. Studies suggest that PG could run in families, showing that genes might play a role in the condition. However, it’s not just inherited features but also environmental factors that may contribute to PG.

If the pressure in the eye rises above a certain level without causing damage to the optic nerve (the nerve that connects the eye to the brain) or affecting vision, it is called POHT (Pigmentary Ocular Hypertension). This is more common in men, and if the pressure is very high when first measured, it could indicate a higher risk of developing PG.

Potential risk factors for PDS becoming PG include a family history of the condition, being white, being male, showing certain signs on the cornea, having a high internal eye pressure, or having PDS for more than five years.

Risk Factors and Frequency for Pigment Dispersion Glaucoma

Glaucoma is a disease impacting over 70 million people around the world. The most common type of this disease is known as Primary Open-Angle Glaucoma (POAG), but another type, pseudoglaucoma (PG), affects about 1-1.5% of people in Western countries.

  • PG and PDS (pigment dispersion syndrome) most often affect people of white race who are nearsighted. The distribution is similar between genders, but PG is more common in men.
  • The ratio of men to women with PG is about 3 to 1.
  • People of non-white race have a lower rate of these conditions, possibly due to differences in the iris’s behavior and structure – the part of your eye that controls the diameter of the pupil. White individuals usually have a thinner stroma (the supportive tissue of the iris), which makes the iris more likely to bend backwards (posterior bowing).
  • PG is typically diagnosed at a younger age than POAG, usually between the ages of 30 and 50 years.
  • PDS is a significant risk factor for PG. Research has shown that 10% of patients with PDS develop PG after five years, and 15% do so after 15 years. Other studies suggest that the lifetime risk of PDS patients developing PG could be as high as 35 to 50%.
  • In the Black population, PDS is associated with farsightedness, older age, and being more frequent in females.
Zentmayer line (Schie line) in an eye with pigment dispersion syndrome
Zentmayer line (Schie line) in an eye with pigment dispersion syndrome

Signs and Symptoms of Pigment Dispersion Glaucoma

Open-angle glaucoma can often go unnoticed in the early stages because there may be no symptoms. Pigmentary Glaucoma (PG) is a specific type of glaucoma where increased eye pressure (IOP) eventually damages the nerve fibers in the eye, resulting in cell death and loss of vision. This form of glaucoma typically affects central vision only at an advanced stage. When pigment is released in the eye, in cases of Pigment Dispersion Syndrome (PDS) or PG, it can cause temporary symptoms like sporadic blurry vision, eye pain, redness, light sensitivity, colored halos, and headaches, which may be especially frequent during physical activity, head movements, blinking, and prolonged reading.

PDS and PG mainly result from friction in the eye that releases pigment. This pigment can accumulate in the anterior chamber of the eye (the area between the cornea and the iris), leading to various symptoms and visual disturbances. The distinguishing signs of PG include pigment deposits on the cornea, radial iris transillumination defects, and pigment deposition in the trabecular meshwork (a group of tiny drainage channels located within the eye). These symptoms are typically only detected during a clinical eye examination.

During an eye examination, clinicians may also identify the Krukenberg spindle, a pattern of pigment deposits on the cornea that take a vertical spindle-like shape. Although this finding is not exclusive to PDS and PG, it’s often seen in these conditions. Certain factors, such as hormonal changes and blinking, can influence its formation. In some cases, abnormalities in the shape or size of corneal endothelial cells are noticeable. Additional disorders, including pseudoexfoliation syndrome, trauma, uveitis, peripheral iridotomy, and more can also cause pigment dispersion.

Clinicians can also note specific features in the iris, such as heterochromia (discoloration due to asymmetric involvement), pigmentation due to pigment deposits, and a dilator muscle that appears larger under microscopic examination. In addition to this, pigments might be seen on the inferior iris, and the shape of the pupil could differ in some cases. This is due to physical irritation caused by contact within the eye, leading to uneven pupil dilation.

The examination can also detect pigment dispersion in the trabecular meshwork, which can cause structural alterations, cell death, and contribute to increased eye pressure in PG. Over time, the pigmentation may decrease or disappear, causing the eye pressure to normalize. Lastly, it’s important to carry out a detailed inspection of the optic nerve head for signs of glaucoma-related damage, which can sometimes be uneven.

Testing for Pigment Dispersion Glaucoma

In order to diagnose and manage PDS/PG (Pigment Dispersion Syndrome/Pigmentary Glaucoma), it’s important to carry out several examinations consistently. This allows doctors to prevent the development and progression of glaucoma, a condition that damages the optic nerve and can lead to vision loss.

A slit-lamp examination, which is a type of eye exam where the doctor uses a microscope and a bright light to look at the structures at the front of the eye, includes a test called tonometry. Tonometry measures the pressure inside your eye, which is essential in monitoring glaucoma. Patients with PDS are at risk of developing PG, a form of glaucoma characterized by high eye pressure, along with visual field defects, damage to the optic nerve, and defects in the retinal nerve fibers.

Another exam the doctor may perform is gonioscopy. This is used to confirm if the angles of your eye are open and intensely pigmented, which is important in the management of glaucoma.

Looking at the back part of your eye (the fundus) is also very important. This examination can reveal typical signs of glaucoma such as changes in the optic nerve. Patients with PDS/PG can also have retinal tears and degenerations, especially if they are nearsighted. There’s usually no need for genetic testing for the clinical diagnosis of PDS/PG.

Consistent visual field testing is required to both diagnose glaucoma and manage the disease over time. Another procedure, Optical Coherence Tomography (OCT), can provide useful information about the structure of your eye, such as the thinning of the nerve fiber layer at the back of the eye, which is a sign of glaucoma damage.

Other tests like Ultrasound Biomicroscopy (UBM) and anterior segment OCT are used to document specific characteristics of the eye. Features examined can include the shape and features of the iris (the colored part of the eye) and the lens. They also look at the space between the front part of the eye (anterior chamber).

A phenylephrine provocative test is also sometimes used. This involves putting a drop of 10% phenylephrine into the eye every 5 minutes three times, then assessing the release of pigment in the front part of your eye, which can indicate a high risk of developing high eye pressure. After the drop is put in, the eye pressure is checked over the course of a couple of hours to see if it goes up, and if so, treatment for high eye pressure can be started if needed. This management can help prevent further issues that could potentially lead to glaucoma.

Treatment Options for Pigment Dispersion Glaucoma

In Pigmentary Glaucoma (PG), certain cells in the eye absorb pigment particles, leading to an increase in eye pressure as fluid can’t drain properly. This happens due to the continuous contact and friction between the color part of the eye, the iris, and the lens. The rubbing action causes pigment particles to be released and eventually clog the eye’s drain, increasing eye pressure.

Some studies in the 90s proposed a laser procedure, called Laser Peripheral Iridotomy (LPI), to reduce this contact and friction in the eye. LPI works by creating a small hole in the iris to balance pressure in the eye and reduce eye strain. LPI also helps to flatten the iris and reduce its curve, limiting further pigment release. However, LPI’s effectiveness is disputed, as research showed no significant differences in eye pressure or disease progression between eyes treated with LPI and those not treated. Therefore, LPI may not be a reliable treatment for patients with high eye pressure caused by PG.

However, for individuals below 40 years with normal eye pressure and certain signs seen on an ultrasound imaging of the eyes, LPI could still be an option. Either way, more research is needed to identify which patient groups can truly benefit from LPI.

People at risk of transitioning from Pigment Dispersion Syndrome to Pigmentary Glaucoma should have regular eye exams to monitor their eye pressure and the condition of their optic nerve. If they have high eye pressure accompanied by signs of nerve damage, they should receive treatment similar to other types of glaucoma. Medical treatment, which could include eye drops, is the first line of therapy. While some treatments offer theoretical benefits, such as reducing eye movement and further pigment release, they may cause side effects like blurred vision, eye pain, headache and even retinal detachment. Therefore, the choice of treatment is often personalized and depends on the specific patient’s condition.

Another treatment option for PG is Argon Laser Trabeculoplasty (ALT), which has been found to be particularly useful for younger patients. ALT involves using a laser to create tiny burns in the eye’s drain to help fluid flow out of the eye. However, its effectiveness tends to decrease over time, and it may also cause tissue scarring. In some cases, older patients or those with a long history of PG may experience an increase in eye pressure after ALT due to tissue damage or other changes in the eye’s drain.

An alternate laser procedure, Selective Laser Trabeculoplasty (SLT), causes less damage and can be repeated over time. It may be more effective in lessening eye pressure in people with PG, although in some cases, it can lead to a rise in eye pressure in people who have heavily pigmented eyes or are taking several glaucoma medications.

For people whose glaucoma can’t be controlled with medication or laser treatment, surgery could be an option. One common procedure, Trabeculectomy, has been shown to be successful in treating PG. However, certain patients, particularly young males with myopia, might be at higher risk of complications following this surgery. Hence, alternative surgical techniques with less risk, including minimally invasive glaucoma surgeries, might be considered.

Certain eye conditions can have similar features such as pigment showers, small dark deposits in different parts of the eye and increased eye pressure. These can be confusion with:

  • Eye injury or surgery
  • Pseudoexfoliation syndrome (PEX), a condition in which extra material is produced and not properly discarded by the eye
  • Eye cancer, such as anterior uveal melanomas
  • Inflammation of the eye (Uveitis)
  • Horner syndrome, a condition that affects the nerves to the eye and face
  • Other conditions, like a specific type of retinal detachment, cataract surgery, diabetes, prolonged pupil dilation, Posner Schlossman syndrome, or just natural aging

These conditions may appear similar initially as they can cause pigment changes in the eye and increased eye pressure. However, upon closer examination with an eye test, unique characteristics can differentiate each of these conditions. For example, in Pseudoexfoliation syndrome (PEX), the deposits in the eyes tend to appear as white flakes rather than dark pigments, and their pattern is usually not as dense. Correct diagnosis requires careful medical history taking and comprehensive eye examinations.

What to expect with Pigment Dispersion Glaucoma

Pigment dispersion syndrome (PDS) is the initial phase and a significant risk factor (accounting for 35 to 50%) in the development of pigmentary glaucoma (PG). Pigmentary glaucoma tends to occur more often in Caucasian males with short sightedness between the ages of 20 and 50 years. Interestingly, unlike many other diseases, the prognosis of pigmentary glaucoma tends to improve as patients age. As individuals get older, a phase referred to as ‘burn-out’ occurs leading to a reduction in the dispersion of pigment, clearer pigmentation in the angle structures of the eye, improved fluid drainage and a normalisation of intraocular pressure (pressure within the eye), which requires less glaucoma medication.

However, due to the reduction in pigmentary signs and a return to normal eye pressures, older individuals can sometimes be misdiagnosed with primary open-angle glaucoma (chronic condition with slow loss of vision) or normal-tension glaucoma (damage to the optic nerve without high eye pressure). It’s essential to note that people with pigmentary glaucoma may respond better to steroid treatments.

As we age, the symptoms of pigment dispersion syndrome may decrease due to the enlargement of the crystalline lens (the natural lens inside our eyes), which causes a physical obstruction to fluid flow and a forward movement of the iris. Also, the darkening of the trabecular meshwork (drainage system of the eye), the inner layer of the cornea, and the iris may dim with time, and the ability to adjust focus may be impacted.

Possible Complications When Diagnosed with Pigment Dispersion Glaucoma

Eyes that have Pigment Dispersion Syndrome (PDS) are more prone to developing Pigmentary Glaucoma (PG), especially if they have increased intraocular pressure. This type of pressure can cause damage to the eye, similar to other forms of open-angle glaucoma. Therefore, these patients should be treated in the same way as those with other types of open-angle glaucoma, to prevent further damage or worsening of the condition.

Potential Risks and Complications:

  • Pigment Dispersion Syndrome (PDS) having the potential to develop into Pigmentary Glaucoma (PG)
  • Increased intraocular pressure causing damage to the eye
  • Similar to other forms of open-angle glaucoma
  • Need for similar management methods to avoid the progression of the condition or additional complications

Preventing Pigment Dispersion Glaucoma

It’s essential for everyone to have regular eye checks, but it’s particularly important for those who are at risk of developing high eye pressure and eye conditions such as glaucoma. Two key tests in diagnosing and managing eye health are Visual Field Testing, which measures your side (peripheral) vision, and optical coherence tomography (OCT), a scan that provides images of your eye’s tissues.

Patients who are initially diagnosed with PDS (Pigment Dispersion Syndrome) and PG (Pigmentary Glaucoma), conditions that increase eye pressure and can lead to glaucoma, need to be monitored very closely to ensure healthy eye pressure. Teaching these patients about their treatment and the importance of sticking to it is crucial to help slow down or even prevent further damage from glaucoma.

For some patients who have not been able to manage their eye pressure even with regular medication or are seeing their glaucoma progress, there are other treatment options. This could include Laser treatment or surgical procedures after careful consideration.

Frequently asked questions

The prognosis for Pigment Dispersion Glaucoma tends to improve as patients age. As individuals get older, a phase referred to as 'burn-out' occurs leading to a reduction in the dispersion of pigment, clearer pigmentation in the angle structures of the eye, improved fluid drainage, and a normalization of intraocular pressure (pressure within the eye), which requires less glaucoma medication. However, older individuals with Pigment Dispersion Glaucoma may sometimes be misdiagnosed with other types of glaucoma or normal-tension glaucoma.

Pigment Dispersion Glaucoma (PG) is typically caused by pigment being released into the front part of the eye when the colored part of the eye rubs against the structures that help the eye focus, generating friction. This rubbing can occur due to certain structural features of the eye, such as a bowing of the back of the iris, nearsightedness, and a deep anterior chamber. Movements or positions of the eye or head can also cause the iris to block the flow of a liquid within the eye, leading to pressure build-up and the iris rubbing against the lens.

The signs and symptoms of Pigment Dispersion Glaucoma (PG) include: - Sporadic blurry vision - Eye pain - Redness - Light sensitivity - Colored halos - Headaches - Symptoms may be especially frequent during physical activity, head movements, blinking, and prolonged reading During a clinical eye examination, clinicians may identify the following distinguishing signs of PG: - Pigment deposits on the cornea - Radial iris transillumination defects - Pigment deposition in the trabecular meshwork (tiny drainage channels within the eye) - The presence of the Krukenberg spindle, a pattern of pigment deposits on the cornea that takes a vertical spindle-like shape - Abnormalities in the shape or size of corneal endothelial cells - Specific features in the iris, such as heterochromia (discoloration due to asymmetric involvement), pigmentation due to pigment deposits, and a dilator muscle that appears larger under microscopic examination - Pigments seen on the inferior iris - Differences in the shape of the pupil due to physical irritation caused by contact within the eye, leading to uneven pupil dilation It is important to note that these symptoms and signs are typically only detected during a clinical eye examination.

The types of tests needed for Pigment Dispersion Glaucoma include: 1. Slit-lamp examination with tonometry to measure the pressure inside the eye. 2. Gonioscopy to confirm if the angles of the eye are open and intensely pigmented. 3. Examination of the back part of the eye (fundus) to look for signs of glaucoma, such as changes in the optic nerve. 4. Consistent visual field testing to diagnose and manage glaucoma over time. 5. Optical Coherence Tomography (OCT) to provide information about the structure of the eye, including the thinning of the nerve fiber layer. 6. Ultrasound Biomicroscopy (UBM) and anterior segment OCT to document specific characteristics of the eye, such as the shape and features of the iris and the lens. 7. Phenylephrine provocative test to assess the release of pigment in the front part of the eye and determine the risk of developing high eye pressure. It's important to note that genetic testing is usually not necessary for the clinical diagnosis of Pigment Dispersion Glaucoma.

The doctor needs to rule out the following conditions when diagnosing Pigment Dispersion Glaucoma: - Eye injury or surgery - Pseudoexfoliation syndrome (PEX) - Eye cancer, such as anterior uveal melanomas - Inflammation of the eye (Uveitis) - Horner syndrome - Other conditions, like a specific type of retinal detachment, cataract surgery, diabetes, prolonged pupil dilation, Posner Schlossman syndrome, or just natural aging

When treating Pigment Dispersion Glaucoma, there are potential side effects that can occur. These side effects may include blurred vision, eye pain, headache, and even retinal detachment. The choice of treatment for Pigment Dispersion Glaucoma is often personalized and depends on the specific patient's condition.

You should see an ophthalmologist for Pigment Dispersion Glaucoma.

Pigment Dispersion Glaucoma affects about 1-1.5% of people in Western countries.

People with Pigment Dispersion Glaucoma are typically treated with medical treatment as the first line of therapy. This can include the use of eye drops. Other treatment options include laser procedures such as Laser Peripheral Iridotomy (LPI), Argon Laser Trabeculoplasty (ALT), and Selective Laser Trabeculoplasty (SLT). In some cases, surgery, such as Trabeculectomy, may be necessary if medication or laser treatment is not effective. The choice of treatment depends on the specific patient's condition and may be personalized.

Pigment Dispersion Glaucoma (PG) is a type of open-angle glaucoma where the fluid in the eye cannot drain properly, leading to high eye pressure and potential vision loss. It is characterized by pigment deposits on the back of the cornea, gaps in the pigmented area of the iris, and pigmentation in the drainage area of the eye.

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