Background: In recent years, remarkable advancements in the comprehension of glaucoma pathophysiology have highlighted the necessity of looking beyond the conventional focus on mean intraocular pressure (IOP) levels. IOP fluctuations have been identified as a potential factor that could exert a substantial impact on the progression of glaucoma. Main text: IOP exhibits dynamic variations throughout a 24-h cycle. Glaucoma patients exhibit substantially more pronounced IOP fluctuations compared to healthy individuals, even when the mean IOP remains within the normal range. This implies that IOP fluctuations may play a role in glaucoma progression through mechanisms independent of elevated mean IOP. In this review, an exhaustive examination of studies spanning the past decade was conducted to analyze the relationship between IOP fluctuations and disease progression in primary open-angle glaucoma (POAG), ocular hypertension (OHT), normal tension glaucoma (NTG), and primary angle-closure glaucoma (PACG). While a few studies present conflicting results, the majority of research supports the notion that elevated IOP fluctuations significantly contribute to disease progression in POAG patients. This association has also been confirmed in PACG patients. However, in NTG or OHT patients, other risk factors may outweigh IOP fluctuations in disease progression or glaucoma conversion. Additionally, we summarized common factors affecting IOP fluctuations to provide a basis for the identification of patients prone to significant daily IOP variations. Finally, the efficacy of various IOP-lowering interventions in modulating IOP fluctuations is concisely summarized, offering insights for the formulation of comprehensive treatment strategies that incorporate IOP fluctuation management. Conclusions: IOP fluctuations play a significant role in disease progression in POAG and PACG. Individuals with certain systemic or ocular characteristics are more predisposed to pronounced and recurrent IOP fluctuations. Consequently, a comprehensive assessment of IOP fluctuation that transcends mean IOP values, as well as the integration of IOP fluctuations management into glaucoma treatment strategies are of paramount importance.