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: Ophthalmologic examinations showed ptosis on the right upper lid and restricted right eye movement without any other neurological signs .
### Output Text:
Ophthalmologic examinations showed ptosis on the right upper lid and restricted right eye movement without any other neurological signs . 