In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Examinations , including blood pressure , pulse rate , conjunctiva and cornea , intraocular pressure ( IOP ) , pupil diameter , basal tear secretion and margin reflex distance of both upper and lower eyelids , were performed prior to entry and at 1 , 3 , 5 and 7 hours after instillation .
### Output Text:
Examinations , including blood pressure , pulse rate , conjunctiva and cornea , intraocular pressure ( IOP ) , pupil diameter , basal tear secretion and margin reflex distance of both upper and lower eyelids , were performed prior to entry and at 1 , 3 , 5 and 7 hours after instillation . 