Function and Applications
This model is a mechanical copy of an eyeball.
Benefits

The back part of which is formed as a projection surface and is removable
various eyeball lengths can be attained by inserting spacer rings
correction of sight defects is achieved with lenses placed in front of the model
it allows a vivid demonstration ofs hort-sightedness and long-sightedness compared to the normal vision of the human eye and of how such defects can be corrected
the image on the "retina" (projection surface) is not turned rightside up, as it is by brain activity and is so seen upside down. 

Equipment and technical data

Eyeball
2 spacer rings
2 lens
diameter: 110mm