Whether or not a submucosal cyst in the right maxillary sinus is harmful depends on the condition of the lesion. Small cysts that do not have surrounding compression do not pose a particular risk. A larger cyst with chronic inflammation, resulting in compression of the surrounding bone and blockage of the sinus opening, can cause a series of symptoms, including headaches, abnormal vision and infection and other symptoms. 1. Headache: Large cysts with chronic inflammation can cause persistent dull headache. 2. Abnormal vision: The compression of the surrounding bone caused by the cyst leads to abnormalities of the extraocular muscles and optic nerves, resulting in decreased vision and impaired eye movement. 3. Infection: Obstruction of the opening of the tract will easily cause infection of the cyst in the sinus cavity, which will cause obvious pus formation and bone destruction. The right maxillary sinus cyst is large in size and accompanied by obvious clinical symptoms, which requires timely medical observation and standardized treatment under the guidance of clinicians.