Is a woman required to remove her contact lenses from her eyes before she immerses in a Mikveh? If this is required, and a woman forgot to remove her lenses before immersing, must she repeat the immersion?
Hacham Ovadia Yosef addresses this question in his work Taharat Habayit (vol. 3, p. 26), where he cites a responsum from the work Shebet Halevi (Rabbi Shemuel Wosner, contemporary). The Shebet Halevi distinguishes in this regard between contact lenses that are normally removed each night, and lenses which are made to remain in the eyes for an extended period. When it comes to lenses that are removed daily, although they do not, strictly speaking, constitute a Hasisa (interruption) between the woman’s body and the water, she should nevertheless remove them before immersing. Rav Moshe Feinstein (Russia-New York, 1895-1986), in his work Iggerot Moshe (Yore De’a 104), rules that if a woman immersed without removing the contact lenses, she need not repeat the immersion. The Shebet Halevi, however, writes that it is preferable for the woman to repeat the immersion, unless she had already been with her husband, in which case she does not repeat the immersion.
Regarding lenses that remain in the eyes for an extended period, such as lenses that are removed only once a month or so, a woman is not required to remove them before immersing in the Mikveh. Even "Le’chatehila" (on the optimal level of Halachic observance), she may immerse with the contact lenses in her eyes.
Summary: A woman who wears contact lenses that she removes from her eyes each night must remove them before immersing in the Mikveh. If she mistakenly immersed without removing the lenses, she should repeat the immersion, unless she had already been with her husband, in which case she need not immerse again. If a woman wears lenses that remain in the eye for an extended period, such as for a month, they do not have to be removed before immersion.