There is an intimate connection between the nerves and muscles of the face and eyes, and allowing the beard to grow strengthens the eyes. It is said that surgeons in the French Army have proven by experiment in Africa that soldiers wearing the beard are much less liable to develop disease of the eye, and it is generally conceded that if one wears a beard, the eye retains its luster and brilliancy much longer.
Reference: Relation of beards and eyes. Daily Constitutionalist. February 1867.
Notes From Our Ophthalmic Heritage. Arch Ophthalmol. 2005;123(6):873. doi:10.1001/archopht.123.6.873