What is Pigment Dispersion Syndrome?
Pigment dispersion syndrome, or PDS, happens when pigments from part of the eye called the iris separate and gather at the back of the eye’s cornea. This was first officially recognized by Friedrich E. Krukenberg back in 1899. Initially, people thought PDS was a birth defect. However, research later showed that it is related to a type of vision-threatening condition called glaucoma. That’s why we sometimes refer to it as pigmentary glaucoma (PG). People with PDS might experience higher eye pressure or PG. Meanwhile, others might not notice any symptoms or maybe get eye pain, redness, and sensitivity to light.
Early detection and careful management are so important for PDS to prevent vision loss. Clinical signs of this condition might include certain types of pigment lines or deposits in the eye, a concave iris, or other specific changes in the iris and eye structures.
Diagnosis usually involves standard assessments for glaucoma, like measuring eye pressure, checking the eye’s drainage angle, and examining the visual field and eye structures. Treatments can range from medications, laser therapy to surgery. One study that involved 799 patients found that people with normal eye pressure had better outcomes, and men were slightly more affected than women. The most common sign noted was pigmentation in the eye’s drainage meshwork, noticed in about 85% of patients. Also, 66% of PDS patients responded well to medications. For those who did not respond to medications, surgery was the next step.
What Causes Pigment Dispersion Syndrome?
Pigment Dispersion Syndrome (PDS) is thought to be caused by the iris’s specific shape, which curves inwards. This shape can cause the iris to rub against the fibers that hold our eye’s lens in place as our pupils widen and narrow. This rubbing can cause the iris’s pigment particles to break off and disperse. These released particles then settle in the front part of the eye, and can block the tiny channels that normally allow fluid to drain out of the eye. This blockage can lead to an increase in eyeball pressure (like water pressure in a water hose). Over time, this pressure can damage the cells and strands in the drainage channels, further increasing eye pressure and possibly leading to a type of glaucoma.
Research shows that patients with PDS or Pigmentary Glaucoma (PG), have 15 times more dispersed pigments in the front part of their eye compared to those without these conditions. These pigments are further released with the movement of pupils which typically happens often during blinking. Studies also suggest that intense exercises or workouts can cause the release of pigments, raising your eye pressure.
Certain factors increase the chance of having PDS. These include being male (men are more likely to have it than women), being young (men in their 30s and women in their 40s are particularly prone), having a specific type of eyesight error (a condition called myopia), having African American ancestry, having a flat cornea (the clear front surface of your eye), or having a specific shape and configuration of the iris. In some cases, PDS can be genetic and run in the family.
The progression from PDS to PG is more likely in patients with more pigmentation in the drainage channels, those with more contact between their iris and lens, or those with an intraocular pressure higher than 21 mmHg (a measurement of eye pressure).
Risk Factors and Frequency for Pigment Dispersion Syndrome
PDS, a disease often not showing symptoms, varies greatly in how commonly it occurs. Most people affected by PDS are between the ages of 20 and 40, making up 2-4% of patients. About 15% of PDS patients develop PG starting from 15 years of age. In people of African descent, there are 15 cases per 10,000 reported. Reflective surgery clinics see PDS quite often, especially among patients with nearsightedness, with a reported prevalence of 25.9%.
Significant prevalence of PG, 37.5% to be exact, has been noted among Latin American patients. Among white Americans, PDS has a recorded prevalence of 2.45%. Speakman’s study revealed that 20% of PDS patients have high eye pressure, and 25.6% have PG. Studies have shown a significant risk of glaucoma among PDS patients, ranging between 35-50%.
A retrospective study showed that 20% of PDS patients developed PG, and shockingly, 85% of them transitioned to PG within the first ten years. Furthermore, a conversion rate from PDS to PG nearing 50% has been reported by various major studies.
Signs and Symptoms of Pigment Dispersion Syndrome
Pigment dispersion syndrome (PDS) is a condition that might not show any symptoms, or it could cause pain, eye redness, light sensitivity, glare, and seeing halos around lights. This condition often appears in nearsighted patients during standard eye exams. When diagnosing PDS, doctors should check if the patient has any history of eye injuries, excessive physical activity, or complicated cataract surgery.
PDS can affect both eyes, that’s why a thorough examination of each eye is necessary. Symptoms might include loss of peripheral vision or general vision problems due to glaucoma and corneal swelling. To make a definitive diagnosis, doctors perform a detailed eye exam, measure eye pressure, examine the drainage angle in the eye, and test the patient’s visual field. They also rule out other factors, such as excessive eye blinking or hormonal changes.
The characteristics of PDS differ depending on the parts of the eye affected:
- Cornea: In PDS, pigment deposits might appear on the lower part of the cornea’s inner layer. These pigment deposits, known as Krukenberg spindle, are not exclusively associated with PDS. In the early stages, pigment can be diffusely deposited at the back of the cornea.
- Anterior Chamber: Patients with PDS typically have a deep anterior chamber (the front part of the eye between the cornea and the iris). Pigment can be mixed with the fluid in this chamber, and melanin granules may also be seen here.
- Anterior Chamber Angle: Pigment is often found more in the lower section of the anterior chamber angle during an examination. The quadrants can be densely pigmented with a band of pigment seen on the back of the eye’s meshwork. A line of pigmentation called Sampaolesi’s line, may form ahead of Schwalbe’s line, which is the boundary between the cornea and sclera. Pigmentation in the eye’s angle tends to decrease with age.
- Iris: The iris may exhibit specific signs of PDS, such as bright spot defects, spoke-like defects, and melanin depositing on the iris surface. Other signs can include patches or loss of the ruffled border of the iris. The iris color can vary, with the pigmented iris appearing darker. Additionally, the iris may appear concave or bowed backward in the middle section when examined.
- Lens: Pigment can also deposit on the front part of the lens in a specific pattern, forming a line (Scheie stripe) or a pigment ring (Zentmayer ring) around the middle part of the lens surface and the structures supporting the lens.
- Fundus: The back part of the eye should be examined for signs like peripheral retinal depigmentation (loss of pigmentation), myopic disc (changes related to nearsightedness), myopic macular degeneration (nearsighted changes to the central part of the retina), lattice degeneration (weakening of the retina), holes, tears, and retinal detachment. Glaucoma can cause optic nerve damage, with one eye showing severe glaucoma changes and mild changes in the other.
Testing for Pigment Dispersion Syndrome
Diagnosing PDS and PG, two conditions that affect the eye, involves both a clinical examination and the use of special imaging techniques.
A key part of the examination is testing visual acuity, which simply means how well you can see. Doctors use two measurements for this: uncorrected visual acuity and best-corrected visual acuity. Your vision might be impaired due to swelling in the cornea, cataracts, or a detached retina.
During the examination, your doctor will also measure the pressure inside your eye, known as intraocular pressure. They will do this using a noncontact tonometry test and then confirm the results with gold standard applanation tonometry. These tests can help detect any ocular hypertension (high pressure) and also PG (Pigmentary Glaucoma). The pressure can vary significantly in people with these disorders and it might even return to normal for some patients.
Another important part of diagnosing PDS (Pigment Dispersion Syndrome) involves a test called gonioscopy. This allows the doctor to check whether the angle where the iris meets the cornea is open or closed. It can reveal a backward-bowed iris, pigmentation in the angles, and other signs indicative of PDS.
Further diagnostic insight is obtained through visual field analysis, which uses automated perimetry. This test helps to establish the extent of any damage caused by PDS and PG, such as less temporal field damage compared to primary open-angle glaucoma.
Next, Anterior Segment Optical Coherence Tomography (AS-OCT) is used. This advanced imaging technique allows doctors to precisely measure the size and depth of the anterior chamber (the front part of the eye), the iris, and any iris concavity.
In addition to AS-OCT, Optic Nerve Head Optical Coherence Tomography is used to inspect the optic nerve head, the retinal nerve fiber layer, and the ganglion cell complex. It can help to differentiate between PDS and PG and it’s also key in monitoring the progression of the glaucoma.
Another form of Optical Coherence Tomography, known as OCT angiography or OCTA, assesses blood flow in the optic nerve and retina. Its advantage lies in being non-invasive while providing a sensitive assessment to help diagnose and monitor glaucoma.
The final technique employed is Ultrasound Biomicroscopy (UBM), which offers a detailed look at the eye’s angle structures that helps to identify any abnormal anatomy.
All these tests, along with your doctor’s clinical evaluation, can contribute to a complete diagnosis and help guide effective treatment.
Treatment Options for Pigment Dispersion Syndrome
Pigment Dispersion Syndrome (PDS) and Pigmentary Glaucoma (PG) management depends on the stage of the disease, pigment dispersion amount, intraocular pressure (IOP, the fluid pressure inside the eye) level, and presence or absence of damage to the optic nerve due to glaucoma.
PDS begins with widespread pigment dispersion usually between the ages of 20-30 and generally has no symptoms. Over time, these pigments can block part of the eye called the ‘trabecular meshwork’, leading to increased IOP and Ocular Hypertension (OHT, condition with higher than normal eye pressure). This can potentially harm the optic nerve and leads to PG. In later stages, the buildup of pigment reduces, and eye pressure becomes normal, but could include symptoms like a change in iris color. Therefore, patients with PDS should have yearly check-ups to prevent the development of OHT and damage to the optic nerve. Patients with advanced glaucoma should have check-ups every 4 to 6 months.
Since intense physical activity can worsen PDS, patients should receive advice concerning their exercise habits.
Medications used in managing PDS are similar to those used for primary open-angle glaucoma. Some of these, like pilocarpine, can limit pigment dispersion and can be used three times a day, but long-term use can lead to side effects like short-sightedness, ocular surface disease, and retinal detachment. Other drugs, including prostaglandin analogs, beta-adrenergic blockers, and alpha agonists are considered safe.
Laser procedures like Laser trabeculoplasty and Laser Peripheral Iridotomy (LPI) can be used to treat eyes with heavy pigment dispersion or to reduce pigment release respectively. However, LPI may not prevent the development of glaucoma.
More invasive procedures, like filtration surgery and the use of Glaucoma Drainage Devices, are considered when IOP cannot be controlled despite medical treatment and there is continued vision loss. Minimally Invasive Glaucoma Surgery (MIGS), like Trabectome, Goniotomy, and iStent, are currently used to ease fluid drainage in the eye, reducing IOP and therefore the risk of glaucoma.
Canaloplasty is another surgical procedure that aims to restore normal fluid drainage in the eye. This method could be used effectively to treat young patients with pigmentary glaucoma who have mild to moderate vision loss and require a lower target eye pressure.
What else can Pigment Dispersion Syndrome be?
Here are the different medical conditions similar to uveitis (inflammation of the eye’s middle layer), which doctors consider when diagnosing:
- Pseudoexfoliation syndrome
- Bilateral acute iris transillumination (BAIT)
- Bilateral acute depigmentation of the iris (BADI)
- Vogt-Koyanagi-Harada syndrome
- Sympathetic ophthalmia
- Acute autoimmune uveitis
- Posner-Schlossman syndrome
- Viral uveitis (herpetic)
- Fuch uveitic syndrome
- Traumatic uveitis
- Horner syndrome
- Acute angle-closure glaucoma
- Iris melanoma
What to expect with Pigment Dispersion Syndrome
The outcome for people with PDS and PG, two eye conditions that can increase the pressure in your eye, depends on certain risk factors. These include nearsightedness and damage to the optic nerve, which is the “cable” that carries visuals from the eye to the brain. If this pressure, or IOP, is well managed, most people have a good outcome. Permanent blindness is rare in such cases.
It also depends on how fast the disease progresses. About 10% of people with PDS develop PG within five years of PDS starting, and 15% within ten years of the disease starting. However, PDS patients with normal eye pressure and normal flow of eye fluid usually have a low risk of developing PG. This means they have a good prognosis, or likelihood of recovery.
Possible Complications When Diagnosed with Pigment Dispersion Syndrome
Medical problems can occur in the eyes which can have serious effects. These include:
- Swelling of the cornea (Corneal edema)
- Inflammation of the middle layer of the eye that doesn’t heal (Non-resolving uveitis)
- Sudden increase in eye pressure causing damage (Angle-closure glaucoma)
- Damage to the iris (Iris atrophy)
- Paralysis of the iris (Iridoplegia)
- Unequal pupils (Relative afferent pupillary defect)
- Difficult to control eye pressure (Intractable glaucoma)
- Increase in eye pressure after laser treatment (Post SLT IOP elevation)
Following eye surgery, some complications that can occur are:
- Leak from the wound (Wound leak)
- Late leak from the surgical spot (Late bleb leak)
- Inflammation of the surgical spot (Blebitis)
- Sudden increase in eye pressure (IOP spike)
- Blockage in the pupil (Pupillary block)
- A severe type of glaucoma (Malignant glaucoma)
- Excessive filtration of fluid in the eye (Over filtration)
- Flat surgical spot (Flat bleb)
- A hardened, blood-vessel filled surgical spot (Vascularized bleb / episcleral fibrosis)
- An enclosed surgical spot, like a cyst (Encapsulated bleb or Tenon cyst)
- Very low eye pressure (Hypotony)
- Nerve damage leading to loss of vision (Macular snuff out)
- Serious infection inside the eye (Endophthalmitis)
- Severe inflammation of all layers of the eye (Panophthalmitis)
- Complete loss of sight (Blindness)
Recovery from Pigment Dispersion Syndrome
After undergoing filtration surgery, patients usually start taking steroids like 1% prednisolone or 0.1% dexamethasone. Sometimes, a combination of steroids and antibiotics (like 1% prednisolone plus 0.5% moxifloxacin or gatifloxacin) may be required. These medications are taken in decreasing amounts (starting at 8, then 7, 6, 5, 4, 3, 2, and finally 1) for a week each.
Additionally, patients may need to take anti-glaucoma medicines based on whether their intraocular pressure (the fluid pressure inside the eye) increases after the surgery. It’s important for patients to have regular check-ups to identify and manage any possible issues that arise after the surgery.
Preventing Pigment Dispersion Syndrome
It’s important for patients with PDS (which refers to “pigment dispersion syndrome”, an eye condition that might cause glaucoma) to fully understand their eye condition. This includes understanding potential complications, as well as the potential future need for glaucoma treatment. Likewise, patients with PG, or “pigmentary glaucoma”, should understand why it’s important to keep their intraocular pressure (IOP – the fluid pressure inside the eye) under control, and why using their antiglaucoma medicine regularly and on time is so crucial.
Another key element is understanding that glaucoma is often a silent disease – meaning it doesn’t show obvious symptoms until damage has already occurred. This makes it even more vital for patients to be aware that they may need glaucoma surgery at any point in the future. They must also understand the importance of regular follow-up appointments and glaucoma assessments with an eye specialist.
Being informed about the potential side effects of antiglaucoma drugs, and about possible complications from procedures like laser iridoplasty (a treatment that alters the shape of the colored part of your eye) and filtration surgery (a procedure to relieve eye pressure), is also crucial.
However, patients should also be encouraged by knowing that with the right treatment and their own dedication to managing their condition, glaucoma can be kept under control. Their cooperation is a vital asset in ensuring successful treatment.
