Ocular lymphoma is a rare form of cancer that affects the eye and can cause serious vision problems if not diagnosed and treated promptly. This disease develops when abnormal white blood cells, called lymphocytes, grow uncontrollably in various parts of the eye, including the retina, the gel-like fluid inside the eyeball, and even the optic nerve.

Understanding Ocular Lymphoma

Ocular lymphoma is a type of cancer that originates in the white blood cells called lymphatic cells or lymphocytes, which are part of the body’s immune system. These cells normally help fight infections, but in ocular lymphoma, they become cancerous and can affect any portion of the eye and surrounding tissues. The disease is particularly challenging because it often mimics other, more common eye conditions, which can delay proper diagnosis and treatment.^[1]

There are several distinct types of ocular lymphoma, and understanding these differences is important because they behave differently and require different approaches to treatment. The most common form is primary intraocular lymphoma (PIOL), also called vitreoretinal lymphoma (VRL). This type develops in the retina, which is the light-sensitive tissue that lines the back of the eye, in the vitreous, which is the jelly-like fluid inside the eye, or in the optic nerve at the back of the eye. Most cases of primary intraocular lymphoma are a type of non-Hodgkin’s lymphoma called Diffuse Large B cell lymphoma.^[1][3]

Another form is primary uveal lymphoma, which affects the choroid layer in the eye. This type is different from primary intraocular lymphoma and generally has a better outlook. There is also secondary intraocular lymphoma, which is seen in patients who already have lymphoma elsewhere in the body. This secondary form usually involves the choroid, iris, and rarely the retina.^[3][16]

Epidemiology

Ocular lymphoma is considered a very rare condition, though the exact number of people affected is difficult to determine because there is no central database specifically tracking this disease. Intraocular lymphoma makes up less than 1 percent of all non-Hodgkin lymphoma cases. In 2020, approximately 3,400 adults in the United States were diagnosed with ocular cancers, which includes lymphoma, melanoma, and other types of eye cancer.^[5][13]

Primary intraocular lymphoma is actually a subset of a larger group called primary central nervous system lymphoma (PCNSL). This larger group accounts for 1 to 2 percent of all extranodal lymphomas and 3 to 5 percent of primary tumors that develop in the central nervous system. The incidence of primary central nervous system lymphoma has increased over the past several decades, rising from 0.027 per 100,000 people in 1973 to 1 per 100,000 in the early 1990s. This increase has been observed in both people with weakened immune systems and those with normal immune function, though the reasons for this rise in immunocompetent patients remain unclear.^[2][9]

Ocular lymphoma typically affects middle-aged and older adults, though younger patients can occasionally develop the disease. There does not appear to be a clear preference for one gender or racial group over another.^[3]

Causes

The exact cause of ocular lymphoma remains not well understood, and researchers continue to investigate what triggers the development of this disease. However, several theories have been proposed to explain how this cancer develops. One theory involves chemical signals in the body. Certain proteins called chemokines, such as B-lymphocyte chemoattractant (BLC) and stromal cell-derived factor-1 (SDF-1), are present in the retinal pigment epithelium, which is a layer of cells at the back of the eye. These proteins may attract lymphoma cells from the blood vessels in the choroid to the retinal pigment epithelium, allowing the cancer to take hold in the eye.^[2]

Another theory focuses on infections as potential triggers. Certain infectious agents are known to cause white blood cells to multiply rapidly, and in some cases, this multiplication can become abnormal and turn into cancer. For example, the Epstein-Barr virus (EBV) infects B lymphocytes and can cause them to proliferate uncontrollably, especially when the immune system’s regulatory cells are weakened or absent, such as in people with AIDS. This connection is supported by the fact that EBV is consistently found in AIDS patients who develop primary central nervous system lymphoma. However, this same association has not been consistently observed in people with normal immune function who develop primary intraocular lymphoma.^[2]

Similarly, DNA from Toxoplasma gondii, a parasite that can infect the eye, has been detected in B cell lymphoma cells from patients with primary intraocular lymphoma, suggesting another possible infectious trigger.^[2]

Genetics may also play a role in the development of ocular lymphoma. Some people may inherit a gene from a parent that increases their chance of developing this type of cancer, though this connection is still being studied.^[3]

Risk Factors

While anyone can potentially develop ocular lymphoma, certain groups of people face a higher risk. Advanced age is one of the most significant risk factors. Most people who develop this disease are elderly or middle-aged, though younger individuals can occasionally be affected.^[1][3]

Having a weakened immune system substantially increases the risk of developing primary intraocular lymphoma. This includes people with AIDS (acquired immunodeficiency syndrome), a condition that severely compromises the body’s ability to fight infections and cancer. People with certain autoimmune diseases, such as rheumatoid arthritis, also face elevated risk. Rheumatoid arthritis is a condition in which the immune system mistakenly attacks the body’s own joints, and the chronic inflammation associated with this disease may contribute to cancer development.^[1][3]

People who take medications that suppress the immune system are also at higher risk. This includes individuals who have received organ transplants and must take anti-rejection drugs to prevent their body from attacking the transplanted organ. These immunosuppressive medications are necessary to keep the transplanted organ functioning, but they also reduce the body’s natural defenses against cancer.^[1][3]

Symptoms

The symptoms of ocular lymphoma can vary widely from person to person, which makes diagnosis particularly challenging. In fact, this variability is one reason why the disease is often misdiagnosed initially as a more common eye condition such as uveitis, which is inflammation of the eye. The most common symptoms that people with primary intraocular lymphoma experience include blurry vision, which can range from mild to severe and may affect one or both eyes. Many patients also notice a decrease or complete loss of vision in the affected eye.^[1][3]

Floaters are another frequent complaint. These appear as small dots or lines that seem to float across the field of vision, and they occur because the lymphoma cells and inflammation in the vitreous gel cast shadows on the retina. Some people also experience redness or swelling in the eye, and increased sensitivity to light, a condition called photophobia. Eye pain is possible but relatively rare.^[1][3][13]

While ocular lymphoma usually affects both eyes eventually, symptoms may be more obvious or severe in one eye than the other, at least initially. This can lead people to think the problem is minor or limited to just one eye. A common sign that doctors look for is vitreitis, which is inflammation of the vitreous fluid inside the eye. This occurs in about 75 percent of cases. The eye examination may also reveal changes in the retinal pigment epithelium, with yellow deposits under the retina.^[1][5][13]

If the lymphoma has spread to or developed in the central nervous system, additional symptoms can occur. These may include behavioral and cognitive changes, where a person’s personality, memory, or thinking abilities seem different. Seizures can also occur, as can various neurological problems that impair normal function.^[5][13]

Prevention

Because the exact causes of ocular lymphoma are not fully understood, there are no specific prevention strategies that can guarantee someone will not develop this disease. However, understanding the risk factors can help people and their doctors remain vigilant. People with weakened immune systems, whether from HIV/AIDS, autoimmune diseases, or immunosuppressive medications, should be particularly aware of any changes in their vision and report them promptly to their healthcare providers.^[1][3]

For individuals taking medications that suppress the immune system, such as those who have received organ transplants, regular monitoring by healthcare professionals is essential. While these medications are necessary and life-saving, being aware of the increased cancer risk allows for earlier detection if problems develop. Early detection is crucial because ocular lymphoma is more treatable when caught in its earlier stages, before it has spread extensively within the eye or to the brain.^[1]

Maintaining overall health and a well-functioning immune system through healthy lifestyle choices may help reduce cancer risk in general, though this has not been specifically studied for ocular lymphoma. These measures include eating a balanced diet, getting regular exercise, avoiding tobacco, limiting alcohol consumption, and managing chronic health conditions effectively.

Pathophysiology

The development of ocular lymphoma involves complex changes in how the body’s immune cells normally function. Lymphocytes, which are white blood cells, play a crucial role in the immune system by recognizing and fighting infections. During their normal development, the genes responsible for recognizing foreign substances undergo rearrangements, insertions, and deletions. This process creates an enormous variety of immune cells, each capable of recognizing different threats. When B cells, a type of lymphocyte, encounter a foreign substance, they undergo rapid multiplication and additional genetic changes to produce highly specific antibodies that can target and eliminate the invader.^[14]

During this rapid growth and genetic modification, normal cellular safeguards against harmful mutations are temporarily reduced. This necessary but risky process allows the immune system to adapt quickly to threats, but it also places lymphocytes at higher risk for developing cancer-causing mutations. Chromosomal translocations and other genetic errors can occur, potentially leading to uncontrolled cell growth and lymphoma.^[14]

In primary intraocular lymphoma, malignant B cells infiltrate the eye through mechanisms that are still being investigated. The chemokine theory suggests that specific chemical signals in the retinal pigment epithelium attract these cancerous cells from the bloodstream. Once in the eye, these malignant cells continue to multiply uncontrollably. They can infiltrate the retina, causing damage to this light-sensitive tissue. They also accumulate in the vitreous fluid, creating the floaters and haze that patients often experience. The cancer cells can form deposits beneath the retina, leading to the characteristic yellow subretinal infiltrates that doctors observe during examination.^[2]

The inflammatory response triggered by the cancer cells contributes to many of the symptoms patients experience. This inflammation can mimic or occur alongside true uveitis, making clinical diagnosis difficult. Changes in the retinal pigment epithelium occur as the cancer progresses, and these changes can be detected through various imaging techniques. In some cases, the cancer cells form solid masses that can be seen on examination, while in others, the infiltration is more diffuse and subtle.^[1]

Because primary intraocular lymphoma is a subset of primary central nervous system lymphoma, there is a strong connection between the eye and the brain in this disease. The eye and brain are both part of the central nervous system, and they share certain immune characteristics. This connection explains why most people with primary intraocular lymphoma either already have or will develop central nervous system involvement, with cancer spreading to or arising in the brain within approximately two years of the eye diagnosis in about 90 percent of cases.^[5][13]