Ocular surface changes are a common and early feature of thyroid eye disease. A number of mechanisms affect the ocular surface in TED. Aqueous tear production and quality may be reduced by lacrimal gland involvement, meibomian glands become dysfunctional, and conjunctival inflammation affect tear composition. Proptosis, lid malposition and chemosis can impair blinking, cause corneal exposure and reduce the distribution of tears across the cornea in TED. Whilst some of these changes are features of active disease, not all resolve as TED becomes less active and there is evidence that ocular surface disease actually gets worse with time even for inactive TED patients. This chapter outlines the assessment and treatment of ocular surface disease (OSD) in TED. A step-wise approach can be adopted for OSD of increasing severity, but it may also be necessary to surgically address lid and globe position to successfully control ocular surface symptoms.