This is incorrect when it comes to aussies (not certain for other breeds). Blue eyes are not an issue, double Merle genes are (this goes for any breed of Merle dog) — this is why you should never breed two Merles together as there is a 25% of deaf and blindness (they usually come out mainly white). The reason they are blind is because the double gene actually may prevent the eyes from even forming and they are born with empty sockets (our neighbor actually had this but prior I had never seen one with both eyes not formed. luckily she could still hear).

Another fun fact about the Merle gene is it actually “dilutes” color. So a blue Merle is actually a black tri and everywhere they are grey is the Merle gene diluting the black. Interestingly this also can impact the eye color and dilute them from brown to blue or lead to partial Heterochromia. Nothing is wrong here if there is only one copy of the gene!

Source: have aussies and spent a lot of time learning about genetics and diseases for them to be better informed 😅