Intraocular Lymphoma: A Review

Intraocular lymphoma (IOL) is a rare form of non-Hodgkin lymphoma that primarily presents in two distinct types. The first type, known as primary intraocular lymphoma (PIOL), is mainly recognized as a subtype of primary central nervous system lymphoma (PCNSL). Recent classifications have emphasized the primary ocular sites affected, with vitreoretinal lymphoma emerging as the most common variant linked to PCNSL. Despite its rarity, the incidence of PIOL is rising among both immunocompromised and immunocompetent populations. Most cases of PIOL are identified as diffuse large B-cell lymphoma, although rare T-cell variants have also been reported. Secondary intraocular lymphoma (SIOL) originates from metastatic spread of non-CNS lymphomas to the ocular structures, including the retina, uvea, vitreous body, Bruch's membrane, and optic nerve. Diagnosis of IOL is challenging for ophthalmologists and pathologists, as it can easily mimic other ocular conditions. Advancements in laboratory diagnostics, such as immunocytochemistry, flow cytometry, and the evaluation of interleukin ratios (specifically IL-10:IL-6 $>$ 1), along with polymerase chain reaction (PCR) amplification for clonality, have enhanced diagnostic accuracy. Multimodal imaging approaches and molecular analyses can serve as valuable indicators of visual prognosis, recurrence rates, and the likelihood of progression to central nervous system involvement. Given that misdiagnosis or delayed diagnosis can result in serious treatment delays and potentially life-threatening outcomes for patients with IOL, this review seeks to provide a comprehensive understanding of the clinical manifestations of IOL and the diagnostic methods employed.