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: Topical IOP - lowering medication was administered in 74 . 8 % of implanted eyes , and IOP - lowering surgeries , most of which were trabeculectomies ( 76 . 2 % ) , were performed on 36 . 6 % of implanted eyes .
### Output Text:
Topical IOP - lowering medication was administered in 74 . 8 % of implanted eyes , and IOP - lowering surgeries , most of which were trabeculectomies ( 76 . 2 % ) , were performed on 36 . 6 % of implanted eyes . 