There are many types of fundus diseases and their causes are complex. They can be caused by metabolic factors or inflammatory factors. Fundus examination and imaging examination tools are the main methods for diagnosing fundus diseases. However, in terms of determining the cause and early diagnosis, if the intraocular fluid detection technology can be reasonably combined, the advantages will be greater. Intraocular fluid is the general term for fluid in the eyeball, including aqueous humor, vitreous humor, etc. The molecular components that can be tested include DNA, RNA, antigens, antibodies, and cytokines. With the advancement of molecular testing technology and equipment, intraocular fluid testing as an evidence-based method has gradually been incorporated into the consensus and guidelines of more fundus disease experts, and is mainly used for infectious fundus diseases and camouflage syndromes. Reasonable use of intraocular fluid testing can help improve the personalized diagnosis and treatment of fundus diseases and reduce unnecessary drug overuse. However, it is worth noting that intraocular fluid detection is only one of many tools and cannot replace other examinations and clinical experience. Excessive intraocular fluid testing not only increases the risk of clinical infections because of invasiveness, but also increases the burden on patients.