Is it permissible to get a permanent eyebrow tattoo for eyebrows that have gaps, knowing that the goal is to fill the gaps and not for beautification?

The gist of the Fatwa: It is permissible to apply a suitable dye to the hair to compensate for thinness or fill in gaps, provided it can be removed for purification (wudu/ghusl) or does not form a barrier preventing water from reaching the skin. It is not permissible if it prevents water from reaching the skin. Hair transplantation is permissible if there is a disfiguring blemish that attracts attention. However, if it is solely for increasing beauty, it is not permissible.