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: Fundus fluorescein angiography confirmed macular capillary closure and telangiectasis .
### Output Text:
Fundus <span class="chemical">fluorescein</span> angiography confirmed macular capillary closure and telangiectasis . 