Reference for Bekhorot 6:33

דלמא אתי בהו לידי תקלה

And as for your question that the [same ruling] should apply to the case of an animal with two large and two small eyes, [the answer is that] there [in the latter instance] if [the change is] because of the animal's extra obesity, the two eyes need to be large, and if because of its unusual leanness, then both [eyes] have to be lean [small].<span class="x" onmousemove="('comment',' So that two large or small eyes constitute no change. Now since we can after all deduce from the Mishnah that a change renders the animal blemished, one can still raise the question, what is there novel in R. Johanan's ruling? (R. Gershom) .');">²⁰</span>

Jastrow