Mydriasis (pupil dilation) in response to conjunctivally applied naloxone hydrochloride has been demonstrated using an innovative electronic binocular pupillometer in 40 opiate dependent patients, on maintenance methadone treatment. 2. No pupillary response to naloxone was seen when an identical procedure was carried out in a control population of 12 healthy volunteers. 3. After a baseline measurement of pupil size, two drops of naloxone hydrochloride were instilled into the conjunctival sac of one eye. Serial binocular pupillometry was then carried out at 5, 10, 15, 20, 25, 30, 35, 40 and 45 min post-instillation. 4. Discriminant analysis between the control and patient groups showed that the false negative rate (error of misclassification to the wrong population) was lowest (20%) at 40 min post-eyedrop instillation, with no false positives in the control group. 5. The study has therefore shown an improvement in the previously reported false negative rate (25%) [1,2], of the conjunctival naloxone test of opiate dependence, with the use of our innovative electronic binocular pupillometer.
