A fundoscopic examination was a type of medical test conducted on Earth in the 20th century. It was used in cases of head injury to evaluate the extent of the damage and determine an appropriate remedy, if one existed. By the 23rd century, however, it was considered to be "unrevealing" in some cases.
In 1986, Pavel Chekov was injured while back in time from the 23rd century and left in the hands of 20th century doctors after being arrested as a Russian spy. Chekov had fallen from a deck of the USS Enterprise and was suffering from slowing pulse, low respiratory rate, and coma. The doctors of the time conducted a fundoscopic examination and concluded that the way to cure Chekov was "a simple evacuation of the expanding epidural hematoma" which would in turn relieve the pressure on Chekov's brain.
Doctor Leonard McCoy was able to get to Chekov before the surgery could commence and stated that "drilling holes in his head" wasn't the answer and that the correct procedure was to repair Chekov's middle meningeal artery. Doctor McCoy quickly performed the procedure under the amazed gaze of the 20th century doctors and Chekov made a complete recovery. (Star Trek IV: The Voyage Home)