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"Wouldn’t those changes have to be made in the sperm and egg not lung or eyeball?"

Or the cells that govern their development, sure. The point being, if there are infectious viruses that cause genetic changes to the infected host, then that presents a mutagenic vector for a large segment of a given population during a single lifetime, thereby increasing the likelihood of it being passed on (for better or worse).

This counters the argument that some genetic change that might occur in a SINGLE individual is unlikely to be propagated widely enough to produce significant changes in a population.

It also introduces the possibility that speciation could occur if the change/damage was severe enough. Imagine this:

Some virus infects a population of animals, of which some small percentage is immune. So, no real issue there. For those not immune, some die. For those that don't die, imagine that the genetic damage to the survivor's Gametes are such that they are rendered STERILE, unless they mate with another individual similarly infected. Boom, you now have two groups that are no longer offspring compatible, and speciation has occurred.