RGD uses the Human Disease Ontology (DO, https://disease-ontology.org/) for disease curation across species. RGD automatically downloads each new release of the ontology on a monthly basis. Some additional terms which are required for RGD's curation purposes but are not currently covered in the official version of DO have been added. As corresponding terms are added to DO, these custom terms are retired and the DO terms substituted in existing annotations and subsequently used for curation.
This disease is characterized by the inability to elevate the adducted eye actively or passively. There is less elevation deficit with the eye in midposition, and minimal or no deficit in abduction. Brown syndrome accounts for approximately 2% of strabismus cases. Ten percent of cases are bilateral, and left- and right-sided unilateral cases are equal in frequency.