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: CONCLUSIONS : The current study used a protocol of visual acuity and color vision assessment , funduscopy , and Humphrey 10 - 2 visual field testing and shows that visual field defects appeared before any corresponding changes in any other tested clinical parameters ; the defects were reproducible and the test parameters were reliable .
### Output Text:
CONCLUSIONS : The current study used a protocol of visual acuity and color vision assessment , funduscopy , and Humphrey 10 - 2 visual field testing and shows that visual field defects appeared before any corresponding changes in any other tested clinical parameters ; the defects were reproducible and the test parameters were reliable . 