Henry Messier is listed as an optometrist in Taunton for the last time in the 1937 City Directory. (See all attachments.) The listing in the 1938 Taunton Directory, in the residential section reads:
Messier, Edna G. Widow Henry. h[ome]194 B'way.
Messier, Henry - (C. Robert Ascha) optometrist, eyes
examined, glasses fitted and prescriptions filled.320 Bay
Messier, Henry Sr. (Edna G) died July 13, 1937.
Messier, Henry, student. Residence 194 B'way)
A listing in the 1939 Taunton Directory, in the Business Index section, notes:
Messier, Henry, C. Robt. Ascha successor, 320 Bay.
In the 1939 Residential section of the Directory, there is a listing for Messier, Edna, widow Henry, living at 317 Bay.
Listed at the same address is Henry E. Messier, dentist. So evidently Henry Messier Sr's son Henry chose dentistry as his profession!
I believe the C. Robert Ascha is the same person as Robert C. Ascha listed Charles R. Ascha living in Northampton, MA on the 1930 census. He is listed there as an optometrist.
I hope this helps.