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: The ocular hypotensive effects were statistically significant for apraclonidine - treated eyes throughout the study and also statistically significant for contralateral eyes from three hours after topical administration of 1 % apraclonidine .
### Output Text:
The ocular hypotensive effects were statistically significant for <span class="chemical">apraclonidine</span> - treated eyes throughout the study and also statistically significant for contralateral eyes from three hours after topical administration of 1 % <span class="chemical">apraclonidine</span> . 