Breast cancer is the leading malignancy among women worldwide, with endocrine therapy (e.g., selective estrogen receptor modulators, aromatase inhibitors) serving as a cornerstone of treatment; although these therapies are effective against hormone-sensitive breast cancer, they alter patients’ systemic hormone profiles, which may disrupt the balance of the ocular surface microbiota that maintains ocular homeostasis. This review systematically examines the mechanisms of mainstream breast cancer endocrine therapies, the dynamics of the ocular surface microbiota, the association between hormonal imbalance and ocular surface homeostasis, as well as the relationship between ocular surface flora alterations, and therapy-related ocular complications, integrating evidence from oncology, endocrinology, and ophthalmology to propose research frameworks and prevention strategies for therapy-related ocular complications.