In the sentence extracted from biomedical literature, identify all the disease entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="disease"> to denote a disease.

### Input Text: Influence of PAX6 gene dosage on development : overexpression causes severe eye abnormalities .
### Output Text:
Influence of PAX6 gene dosage on development : overexpression causes severe <span class="disease">eye abnormalities</span> . 