Going Outside on Shabbos with Glasses
26. ‘Pince-nez’. Once, people wore pince-nez, which are similar to modern-day glasses, except they were placed on the nose and did not have pieces that went around the ear. They fell off easily and were not worn constantly; people put them on when they needed to. The poskim wrote that they may not be worn outside without an eiruv out of concern they may fall and be carried four amos in a reshus horabim (חיי אדם, מ"ב סי ש"א סקמ"ד).
27. Modern-day glasses. Nowadays that people wear glasses constantly and they are held in place snugly over the ears and do not fall often, all the poskim allow wearing them in a reshus horabim. This is the accepted minhag (שו"ת שואל ומשיב מהדו"ג ח"א סי' ק"ט, מנח"י ח"ב סי' קי"ב ועוד).
28. One should not wear his glasses on top of his head or on his forehead in a reshus horabim. They should be worn in place over the nose and ears so they do not fall off easily.
29. Some are machmir not to wear glasses outside on Shabbos if they do not always wear them in general. The Chazon Ish was machmir for this reason (ארחות רבינו ח"ג עמ' רל"). If one always wears glasses, just he removes them in the street during the week for shmiraseinayim reasons, he is considered as one who wears them constantly and may go outside wearing them on Shabbos.
30. Reading glasses. One who only wears glasses when reading, learning, looking something up in a sefer etc. may not wear them in a reshus horabim, even if they are on tightly. Those who make reading glasses gemachs in shuls in places without an eiruv are doing a commendable service.
31. Sunglasses. One whose doctor instructed him to wear sunglasses to prevent eye disease may wear them outside on Shabbos. Otherwise, one should not wear them if there is no eiruv.
32. One who has prescription sunglasses that he wears regularly [in the summer..] may go outside with them on Shabbos without concern that he may remove them while outside.
Transition Lenses, reactor light
33. One may go outside with transition-lens/reactor light glasses on Shabbos without any issue of tzovei’a since the glasses darken due to the nature of the chemical on the lenses. Going out into the sun is not considered an act of tzovei’a (שו"ת שבט הלוי ח"ד סי' כ"ג אות ה', שו"ת מחזה אליהו ח"א סי' ס"ה, חוט שני פי"ט סק"ו).
