In some double dapples, there are varying degrees of vision and hearing loss, including reduced or absent eyes. Not all double dapples have problems with their eyes and/or ears, which may include degrees of hearing loss, full deafness, malformed ears, congenital eye defects, reduced or absent eyes, partial or full blindness, or varying degrees of both vision and hearing problems; but heightened problems can occur owing to the genetic process in which two dapple genes cross, particularly in certain breeding lines. Dapple genes, which are dominant genes, are considered "dilution" genes, meaning whatever color the dog would have originally carried is lightened, or diluted, randomly; two dominant "dilution" genes can cancel each other out, or "cross", removing all color and producing a white recessive gene, essentially a white mutation. When occurring genetically within the eyes or ears, this white mutation can be detrimental to development, causing hearing or vision problems.
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