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: OBJECTIVE : To report our clinical experience with abnormal ocular motility in patients treated with subtenon carboplatin chemotherapy .
### Output Text:
OBJECTIVE : To report our clinical experience with abnormal ocular motility in patients treated with subtenon <span class="chemical">carboplatin</span> chemotherapy . 