the hemodialysis group Inclusion Criteria:  Older than 18 Hemodialysis patient The subject understands the purpose of this clinical trial and agrees to sign an informed consent form.  the hemodialysis group Exclusion Criteria:  Previous history of ocular trauma or surgery History of wearing contact lenses Can Not Stop the use of dry eye caused by drugs and other drugs may directly affect the stability of tear film tears Eyelid abnormalities (such as eyelid insufficiency, entropion and ECTROPION, tumor, severe trichiasis) There have been peritoneal dialysis, kidney transplant surgery patients.  the normal group Inclusion Criteria:  Older than 18 Healthy people do not have other systemic diseases, such as diabetes and hypertension The subject understands the purpose of this clinical trial and agrees to sign an informed consent form.  the normal group Exclusion Criteria:  Previous history of ocular trauma or surgery History of wearing contact lenses Can Not Stop the use of dry eye caused by drugs and other drugs may directly affect the stability of tear film tears.