A story is told about Rebbetzin Leah Auerbach a”h, wife of Rav Ezriel Auerbach shlit”a, whose doctor (ophthalmologist, perhaps) prescribed photogrey glasses for her[1]. These are glasses with photochromatic lenses, which darken when exposed to direct sunlight, and become transparent when removed from the sunlight. The doctor, attuned to religious sensitivities, explained to her that some authorities feel that one should refrain from wearing them on Shabbos, while others maintain that they are acceptable for Shabbos use. He instructed her to ask her rabbi for a final halachic decision.

But to understand the halachic issues involved, a bit of background is needed. Photochromatic lenses contain millions of molecules of silver chloride or silver halide embedded in them. These molecules are transparent to visible light in the absence of ultraviolet rays, which is normal for artificial lighting. But, when exposed to ultraviolet (UV) rays, as in direct sunlight, the molecules undergo a chemical process that causes them to change shape and absorb portions of the visible light, causing the lenses to darken[2].

The potential issue with wearing such lenses on Shabbos is that of “Tzoveya”, Dyeing, one of the 39 Sabbath-prohibited categories of “creative labor” (melachos)[3]. It must be noted that our potential issue with photogrey glasses cannot be considered part of the actual Biblical prohibition, as that is exclusive to a type of dyeing that leaves a lasting effect (miskayeim)[4]. Rather, it’s a potential Rabbinical prohibition of temporary coloration, arguably similar to makeup application, which falls under this prohibition[5].

Many contemporary authorities debate this issue[6], with the vast majority offering different rationales why photochromatic lenses are dissimilar to the makeup case and should be permissible to be worn on Shabbos. These include:

1. The dyeing that is forbidden on Shabbos is limited to coloration which results from applying one substance to another, i.e. purple dye upon wool. Coloration caused by exposure to the sun’s rays would therefore be excluded from the prohibition[7].
2. There is no tangible action being done by the person himself, rather by the sun and shade. The fact that one is actively walking in and out of the sun is irrelevant, as he is not doing any extra activity to accomplish the lenses' darkening[8].
3. There is no actual dyeing happening; as soon as the lenses are taken out of direct sunlight they revert back to clear, similar to covering and uncovering an object[9].
4. There is no concrete change happening to the glasses, only their appearance changes; the chemicals are always inside and their nature is to transform back and forth depending on exposure to sunlight. Furthermore, they are simply shading the eye from the sun[10].
5. The coloring effect is a temporary occurrence whose existence is continuously dependent upon exposure to the sun[11].
6. The coloring and subsequent reversion to clearness is part of the lenses’ regular designed function[12].

Several decisors mention more that one reason to permit wearing photogrey glasses on Shabbos, while others simply write that there is no issue at all with them[13]. Although some are uneasy about certain aspects of the various halachic rationales[14], nevertheless, the consensus of virtually all contemporary authorities, including Rav Moshe Feinstein, Rav Shlomo Zalman Auerbach, the Debreciner Rav, his brother - Rav Betzalel Stern, the Tzitz Eliezer, Rav Shmuel HaLevi Wosner, Rav Ovadia Yosef, Rav Menashe Klein, the Rivevos Efraim, and Rav Nissim Karelitz, is to rule permissively, and allow photogrey glasses to be worn on Shabbos. This is also how many works written on the Laws of Shabbos conclude[15].

However, there is a minority opinion: that of Rav Yosef Shalom Elyashiv[16]. He maintains that since the glasses do not revert back to clear immediately after going indoors, it might be considered having a slight lasting effect, and possibly might be therefore included in the Rabbinical prohibition of Tzoveya. Due to this potential issue, he advises not to wear photochromatic lenses on Shabbos.

With this halachic background in mind, we return to Rebbetzin Auerbach. As requested of her, she asked the opinions of the greatest rabbis she knew of: her father, Rav Yosef Shalom Elyashiv shlit”a, and her father-in-law, Rav Shlomo Zalman Auerbach, zt”l, none other than the preeminent Gedolei HaDor!

At her next visit, she told the doctor that she was in bit of a quandary as her father told her she should not wear them on Shabbos, while her father-in-law told her she may. “Lady”, the obviously oblivious ophthalmologist replied, “I told you to ask a rabbi, not your parents!!”

Disclaimer: This is not a comprehensive guide, rather a brief summary to raise awareness of the issues. In any real case one should ask a competent Halachic authority.

L'iluy Nishmas the Rosh HaYeshiva - Rav Chonoh Menachem Mendel ben R' Yechezkel Shraga, Rav Yaakov Yeshaya ben R' Boruch Yehuda.

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