Nyāya Sūtras 236

And the arrangement of the sense organs is caused by karma and dependent on the purpose of the person.

Just as the conscious [self's] purpose consists in the apprehension of objects and in the apprehension of pleasure and pain is arranged, so the sense organs are structured; and the structuring of the visual ray is for the purpose of reaching objects. Furthermore, the non-manifestation of color and touch is for the purpose of making practical life possible, and the occurrence of obstruction [due to contact] with a specific substance is for the purpose of practical life. The multiform structure of all substances, like the sense organs, is caused by karma and depends on human purpose. But karma, which consists of merit and demerit, is for the conscious [self's] enjoyment.

And because it is invariable, obstruction is an elemental property. And that obstruction of the sense organ with a specific substance, which is due to the perception of an obstruction, is an elemental property; it does not deviate from the elements, for an un-elemental [entity] possessing the property of obstruction is not seen. Non-obstruction, however, is variable, because it is common to both elemental and un-elemental [entities]. As for what might be thought: 'From obstruction [it would follow that] the sense organs are elemental, [and] from non-obstruction that they are un-elemental; and non-obstruction is observed because of apprehension through glass, mica sheets, and crystal'—that is not correct. Why? Because an elemental [substance] is also not obstructed, since the rays of a lamp shine through glass, mica sheets, and crystal, and the cooking fire encounters no obstruction in pots and the like.