This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Euphrasia officinarum C. B. & Linn. Eyebright: a small herb, with little, oval, serrated leaves, set in pairs, without pedicles: in their bosoms, towards the tops of the stalks, come forth labiated, monopetalous, whitish flowers, streaked internally with purple and yellow; followed each by a slattish capsule, full of small whitish seeds. It is annual, grows wild in uncultivated grounds, and flowers from July to September.
This plant has long been celebrated as an ophthalmic, both taken internally, and applied externally. Hildanus says, he has known aged people, who had their sight impaired, recover it again by the use of this herb; but later practitioners have not been so happy as to meet with the like success. It may indeed, in some cases, be of service as a mild corroborant; for it discovers an astringent quality to the taste, and, in a more sensible manner, by striking a black colour with solution of chalybeate vitriol. The astringent matter is extracted both by water and spirit; and when concentrated by infpiffating the tinctures, is still found to be very weak.