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: METHODS : We noted abnormal ocular motility in 10 consecutive patients with retinoblastoma who had received subtenon carboplatin .
### Output Text:
METHODS : We noted abnormal ocular motility in 10 consecutive patients with retinoblastoma who had received subtenon <span class="chemical">carboplatin</span> . 