Does Astrology say which Planet affects Eyesight the most?

This is going to be a detailed answer and a thorough analysis through example of great freedom fighter Subhash Chandra Bose.

Scientifically, In the process of seeing an object, the following steps occur:

1. Light from a source like the Sun, falls on the object.
2. The object reflects light in all possible directions.
3. The reflected light from the object reaches our eyes.
4. Our brain receives the information from the eyes making us see the object.

As per Medical Vedic Astrology,

1. Sun represents eyesight.
2. Mercury represents neurons which passes message to brain.
3. Saturn represents organized structure of whole.

As per my studies, follwing are the conjunctions which can afflict eyesight of a person:

1. If Mercury is sitting with or aspected by Saturn and Rahu/Ketu, then eye sight may suffer.
2. When Saturn and Mercury aspect or conjuct Sun aspected by Rahu/Ketu also afllict eyesight.
3. Saturn, Mercury and Sun conjuction also afflict eyesight sometimes.

For example: Birth chart of Great freedom fighter Subhash Chandra Bose

As you can see in his birthchart, his Sun is conjuct with Rahu and Mercury aspected by Saturn also.

So from his childhood, he had problems related to eyesight and to wear glasses.

Note: Depending upon the strength of the planet(Sun, Saturn ,Mercury, Rahu and Ketu) according to its degree , results for eyesight afflict may vary from mild to severe.