Optometrists who work in solo practice or with a partner tend to work longer hours because they must tend to administrative duties in addition to their medical ones. According to the American Optometric Association surveys, optometrists worked about 49 hours per week, on average, in 2004, and were available to see patients about 38 hours per week.
Source: Bureau of Labor Statistics, U.S. Department of Labor, Occupational Outlook Handbook, 2008-09 Edition