From my notes, in breeds where corneal dystrophy is considered a primary condition, the incidence is generally much higher than in Labradors.

In Labs, glycogen storage or lysosomal diseases are known to produce accumulation of certain proteins outside the cells, interfering with cell metabolism. These can be detected in many tissues of the body. When they occur in the eye, CD can be one of the results. Chances are that, if they occur elsewhere, they will not be detected unless they compromise the function of the relevant organ.

Most corneal dystrophies are probably benign but, before ruling out any element of heredity on the basis of the absence of relatives exhibiting the problem, it could be interesting to look for alternative manifestations of an underlying primary disorder. Just throwing that out there - probably not really an option!