A method of monitoring a subject for medical conditions includes causing light to impinge on at least one eye of the subject, directing reflected light from such light beam to photosensors, converting the received reflected light to corresponding electrical signals which are delivered to a processor. Processing the signals by effecting a comparison between stored information regarding the medical condition and the data provided by the monitoring to determine if an undesired medical condition exists and, if so, communicating such result. The cycle is repeated at predetermined intervals which may be short or prolonged. The method may be employed for a wide variety of medical conditions and preferably is employed with frequent cyclic monitoring for conditions such as miosis, carbon monoxide poisoning, and blood flow related conditions. A related apparatus is provided.