Name the following: 

The photosensitive pigment present in the rods of the retina. (Write scientific term)

Name the following:

The part which equalizes the air pressure in the middle and external ear.

Name the following:

The ear ossicle attached to the tympanum.

Name the following:

The tube which connects the cavity of the middle ear with the throat.

Name the following:

The part of the eye responsible for its shape.

Name the following:

The nerves which transmit the impulse from ear to the brain.

Name the following:

The eye defect caused due to shortening of the eyeball from front to back.

Note the relationship between the first two words and suggest the suitable word/Words for the fourth place.

Cone : Iodopsin :: Rods :_____.