One study of Ultiva given for ICU sedation found that the chances of being extubated within 3 days with remifentanil based analgesia and sedation was 1.9 times greater than conventional treatment. However one particular serious but non-life threatening side effect was blindness. What characteristic of Ultiva could explain the blindness?

Study link http://ctr.gsk.co.uk/Summary/Remifen..._ULT101653.pdf