Most intraocular metastases are detected in the choroid, iris, ciliary body, or retina. Conversely, tumors rarely metastasize to the optic disc, and they even less frequently present as the initial sign of cancer. In this study, we presented the case of a patient who first visited the ophthalmology department because of gradual visual impairment without any systemic symptoms, and she was ultimately diagnosed with non-small-cell lung cancer. This case report illustrated that visual impairment may be the first sign of non-small-cell lung cancer; therefore, we should not neglect ocular metastasis even when the patient has no systemic symptoms on her/his first visit to the ophthalmology department.