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: Systemic adverse effects occurred in 8 patients ( 10 . 5 % ) and ocular adverse effects , in 5 ( 6 . 5 % ) .
### Output Text:
Systemic adverse effects occurred in 8 patients ( 10 . 5 % ) and ocular adverse effects , in 5 ( 6 . 5 % ) . 