What is Pars Planitis?
Pars planitis is a long-term type of uveitis, which is eye inflammation, where no related illness or infection can be found. Uveitis primarily affects the vitreous, a gel-like substance that fills the space between the front and back of the eyeball. In this type of uveitis, inflammation can be found in the front part of the vitreous or just above the peripheral retina, the side region of the light-sensitive layer at the back of the eye.
This condition is recognized by clumps of inflammatory matter (known as “snowballs”) in the vitreous, and white deposits (called “snowbanking”) on the lower part of the pars plana, the flat part of the ciliary body in the eye. Intermediate uveitis encompasses posterior cyclitis, pars planitis, and hyalitis. Posterior cyclitis is inflammation of the back part of the eye; pars planitis is a type of intermediate uveitis; and hyalitis is inflammation of the vitreous.
The term ‘Pars planitis’ is used to describe a specific type of intermediate uveitis. This condition is distinguished by the existence of “snowball” or “snowbank” formations, without a related infectious or systemic disease.
What Causes Pars Planitis?
The exact cause of pars planitis, a condition that affects the eye, is still unknown. The most common theory is that it is an autoimmune disorder. An autoimmune disorder is when your immune system accidentally attacks your body.
The belief is that the condition starts when an unknown substance, called an antigen, triggers the immune system. The exact nature of this antigen is still not known. This exposure to the antigen activates the immune system, which in turn leads to the symptoms of pars planitis.
Several studies suggest a link between pars planitis and certain genetic markers called HLA-B51, HLA-DR2, HLA-DR15, and HLA-DRB1*0802. However, more research is needed to fully understand these connections.
Risk Factors and Frequency for Pars Planitis
Uveitis is a condition that has been studied around the world. According to a detailed study in France, there was a finding of 1.4 cases for every 100,000 people. The same study showed that 5.9 out of every 100,000 people are living with the condition. A similar study was conducted in the United States, and that study found that 1.5 out of every 100,000 people are diagnosed with uveitis every year, and 4 out of every 100,000 people are living with the condition.
- Uveitis commonly affects children and adults up to their early forties.
- In most cases, 70-90% of the time, both eyes are affected, though usually one eye shows more symptoms than the other.
- Lastly, anyone can get uveitis, regardless of their gender or racial background, as there’s no specific predisposition found in terms of sex or race.
Signs and Symptoms of Pars Planitis
Pars planitis is a condition that usually shows minimal symptoms, but is primarily associated with blurry vision or seeing floaters. Pain and light sensitivity are generally absent. However, patients might sometimes experience sudden vision loss, which could be due to a retinal detachment or serious bleeding in the vitreous.
The clinical signs of this condition can include mild inflammation in the front part of the eye. A key attribute of pars planitis is the presence of cells in the vitreous, ranging from a slight to heavy amount. In some cases, the cell infiltration can be so heavy that it blocks the view of the retina. Some patients may also have yellowish-white clusters in the lower part of the vitreous, which is a known feature of this condition. About 10% to 32% of patients may exhibit inflammation of the blood vessels in the periphery that can lead to clogging and, in rare cases, the formation of new blood vessels in the retina. Central retinal swelling, known as cystoid macular edema, may also occur and is usually the main cause of vision decline. In some cases, a specific type of cataract may also form.
In the early stages of the disease, white deposits are present. However, as the disease progresses, these are replaced by collagen which result in the formation of structures called snowbanks. These are typically located in the lower part of the retina, but occasionally they may surround the entire peripheral retina.
Testing for Pars Planitis
If your doctor suspects you may have pars planitis, an inflammation condition of the eye, they will run a series of tests. Pars planitis is signaled by more cells in the jelly-like substance behind your eye (the vitreous) than in the anterior chamber, the front part of the eye. Other signs include the presence of clumps of inflammatory cells floating in the vitreous (known as vitreous snowballs), and inflammations near the point where the colored part of your eye and the white part meet (pars plana exudates).
Your eye doctor, or ophthalmologist, will perform a clinical evaluation comprising tests to measure how clearly you see (visual acuity), what your eye pressure is (intraocular pressure), and a close-up examination of your eye using a specialist instrument (slit lamp examination). They will take a comprehensive look at the edges of your retina, the light-sensitive layer at the back of your eye, with a technique called scleral depression.
They may also want to check for related conditions such as sarcoidosis, an inflammatory disease affecting multiple organs, and tuberculosis. This would involve additional diagnostic imaging like a chest X-ray or contrast-enhanced CT scan of your chest. Additionally, they may conduct a blood test for an enzyme called ACE which may be higher in people with sarcoidosis.
Other tests may include a complete blood count, a test to see how long it takes your red blood cells to settle to the bottom of a test tube (erythrocyte sedimentation rate), and specific tests for sexually transmitted infections or HIV.
Before starting with anti-inflammatory medication (steroids), your doctor will further ensure that these symptoms are not due to infections or conditions like toxoplasmosis, acute retinal necrosis, and endophthalmitis. If an older patient presents these symptoms coupled with a cloudy vitreous but without swollen macula (the part of the eye responsible for detailed vision), they will rule out intraocular lymphoma, a rare form of eye cancer.
Your doctors may then perform a fluorescein angiography to better understand the extent of any blood vessel inflammation (vasculitis) and to identify areas with lack of blood flow or abnormal blood vessels. An optical coherence tomography test can also help check for swollen macular, the formation of an additional cellular layer on the retina (epiretinal membrane), and traction between the retina and the vitreous.
In some severe cases where it is challenging to rule out certain issues like retinitis, endophthalmitis, or tumors, the doctor might suggest a vitrectomy, a surgery to remove the vitreous from your eye, for diagnosis purpose.
Treatment Options for Pars Planitis
Treatment options for harmful inflammation in the eye (pars planitis) depend on various factors like how far the inflammation has spread, the presence of blood vessel inflammation (vasculitis), and whether there’s swelling in part of the retina (macular edema).
Historically, Dr. Kaplan suggested a four-step treatment plan for pars planitis which started with injections of corticosteroids or steroid medicines into the affected region, followed by oral medications if the injections didn’t work. If this failed, either freezing (cryotherapy) or lasers (photocoagulation) would be used on the peripheral retina. In the next step, surgeons would perform a vitrectomy – a surgery to remove the eye’s vitreous gel. And if all else fails, doctors would resort to immunosuppressive medications that sparingly use steroids.
However, nowadays, eye inflammation specialists commonly use either steroid injections into or around the eye, or oral steroids. If a patient’s eyes are unevenly affected, or if their inflammation is causing swelling in the macula, then doctors might consider steroid implants. For bilateral cases, doctors may treat one eye first to avoid systemic side effects of steroids. Before using steroids, it’s important that the patient is made aware of potential risks such as glaucoma and cataracts. Steroids are only used if significant anterior chamber cells are present.
For cases where either one eye doesn’t respond to the initial treatment or both eyes are severely affected, oral steroids are used. In cases requiring prolonged immunosuppression, immunomodulatory therapy (treatments that can modify or regulate the functioning of the immune system) may be considered. This includes medications like methotrexate, mycophenolate mofetil, azathioprine, and cyclosporine.
If traditional immunomodulatory therapies fail, doctors might consider using biological therapies – medicines that target specific parts of the immune system. One such biological treatment is Adalimumab which has been approved to be used for noninfectious uveitis. However, these treatments may increase the risk of damaging nerve fibers in the brain and spinal cord, and thus, utmost caution is required before administering these treatments.
Vitrectomy might be considered amidst severe conditions like vitreous hemorrhage, retinal detachment, or severe clouding of the vitreous. Committing to vitrectomy has its benefits, like removing inflammation-inducing substances in the vitreous and dealing with factors causing macular swelling. However, its rare risks include retinal detachment and recurrence of pars planitis.
Use of lasers or freezing to deal with blood vessels growing out of control (neovascularization) in the peripheral part of the retina are available options. However, using freezing treatment (cryotherapy) can be painful and may lead to retinal detachment.
Treating cataracts, a common complication of pars planitis, safely involves a surgical process if the inflammation inside the eye is controlled for at least three months before surgery using steroids or immunosuppressives.
What else can Pars Planitis be?
When dealing with certain medical conditions, there can be acute complications that arise. Conditions with such risks can include:
- Sarcoidosis
- Cat scratch disease
- Hepatitis C
- HLA-B27 syndromes
- Inflammatory bowel disease
- Interstitial keratitis
- Lyme disease
- Multiple sclerosis
- Toxocariasis
- Toxoplasmosis
Possible Complications When Diagnosed with Pars Planitis
Pars planitis is one of the milder forms of uveitis. Despite its benign nature, complications may arise from chronic inflammation.
One key eye complication from pars planitis is the formation of epiretinal membrane, or a thin film over the retina, which occurs in 7% to 36% cases and can take roughly 6.5 to 7.9 years to form. The disease is also associated with cataracts, affecting 14% to 30% of patients. It’s challenging to determine if these cataracts are due to the disease or the corticosteroid treatment. The most frequently diagnosed cataract type is the posterior subcapsular cataract. A condition called cystoid macular edema crops up as the primary cause of vision loss. Additional complications involve retinal vasculitis, retinal neovascularization, peripheral vitreous traction, and vitreous hemorrhage.
One study highlights several complications from pars planitis, including:
- Macular edema (47.7%)
- Vitreous opacities (38.6%)
- Papillitis (38.6%)
- Vasculitis (36.4%)
- Cataract (20.5%)
