A half-millimetre wide optical fibre could be used to send back images of the inner ear to doctors.
A single fibre-optic cable is used
Its Australian inventor believes that it could improve success rates in operations such as cochlear implants.
Light can be sent down the fibre one way - and a crude image of what it encounters returned in the other direction, reports New Scientist.
Some cochlear implant operations fail because the surgeon cannot find a way past tiny obstructions in the ear.
It is hoped that the probe, developed at the Sydney Cochlear Implant Centre could help surgeons navigate around these obstructions and fit the implant properly.
The cochlea is a shell-like formation in the inner ear about the size of a fingernail, which converts sound pressure waves into nerve impulses which are sent to the brain.
During a cochlear implant operation, electrodes are inserted between one and one-and-a-half turns into its spiral.
The surgeon carries this manoeuvre out by feel, but some patients have bony growths inside the cochlea which block the way.
An estimated 10% of operations fail for this reason.
Looking inside the cochlea is difficult - scans can reveal some information about the problem, but conventional endoscopes - bundles of optical fibres - are far too wide to be inserted into the inner ear.
Normal scopes are wide because they need cables to carry light to the end of the and others to carry that image back down to the controller's screen.
Martijn van Eijkelenborg managed to create a single fibre with microscopic holes running through it which can deliver a light source, and carry an image the other way.
The image is fairly crude, consisting of 224 pixels, but van Eijkelenborg hopes to improve this by adding more holes.
He says that the microendoscope he has created could also be used to probe the interior of smaller blood vessels.
However, Professor Mark Lutman, a cochlear implant specialist from Southampton General Hospital, said that there was no guarantee that seeing the obstruction would make it any easier to get past it.
He said: "These obstructions are often found in people who have lost their hearing through meningitis.
"You can attempt to get past them by drilling, but this will only work if you can get past it in a straight line."