The lens free Opthalmoscope is designed by Dr Roger H. Armour and is a simple device made from thick card stock and a reflective surface. I applied the design to a 3D printable device. The device can be printed for little cost on basic 3D printers and taken into the field for general use at minimal cost.
Dr Armour's basic design started with a hollow cylinder that could fit a simple pen light and a reflective top section at an angle of 45°. Inserting a pen light into the cylinder allowed reflected light to enter a patients cornea and reflect back through a hole to the examiners eye to visualize the back of the patients eye.
Development of the 3D Design:
1 - Size of the devices holes were unproven for a 1/2":13 mm diameter disposable pen light.
After multiple tests it was found that 2 mm to 2.5 mm was of optimum size for the sighting hole. An 8 mm was the optimum size for the exiting light stream on a cylinder of 13 mm diameter and 6 mm the distance between the holes.
2 - There was a need to develop a shelf within the device to shade the viewing hole from the originating stream of light. A baffle was also needed to attenuate the originating light from the penlight to the reflecting surface. The reflecting surface needed to be modifiable so that improvised reflecting materials could be used. The device needed to be capable of disasembly for cleaning and reflective material replacement.
An insert was made offset by a few millimetres at 45° to offer a shelf to shade the viewing hole and to reflect light. The base of the insert was made with a 3 mm hole to act as a baffle for the originating light. The insert was made to be fixed within the hollow cylinder with water soluble glue so that after soaking the insert could be removed and the reflective materials renewed or cleaned.
3 - Bright modern day penlights are to bright for simple examination and very uncomfortable for the patient.
The device is designed to fit a 1/2"-13 mm diameter disposable pen light using an incandescent bulb. In using a bright LED bulb tissue paper can be inserted into the cylinder to dim the LEDs brightness.
