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: Eleven patients ( 11 eyes ) underwent surgery for fluocinolone acetonide implant ( 0 . 59 mg ) .
### Output Text:
Eleven patients ( 11 eyes ) underwent surgery for <span class="chemical">fluocinolone acetonide</span> implant ( 0 . 59 mg ) . 