Final answer:
Patients on Tamoxifen should report changes in vision because of the increased risk of irreversible eye problems including cataracts.
Step-by-step explanation:
A breast cancer patient treated with Tamoxifen should report changes in vision, as its negative side effects can include an increased risk of cataracts or other eye problems, which could be irreversible. Tamoxifen has a well-documented risk profile, with potential side effects including increased risk of stroke or heart attack, blood clots, endometrial cancer, and other types of cancer such as colon and ovarian cancer, as well as gall bladder disease and possibly dementia or depression. As such, patients should be vigilant for symptoms such as unusual bleeding or discharge, lumps, changes in warts or moles, and persistent coughing or hoarseness as well as any changes in their vision.