A Handicap is a social role that is difficult to fulfill because of disabilities. For example, some jobs may require the ability to read using vision. A person would be handicapped for this type of job. This differentiation is important for several reasons. First, it helps understand the roles of different professionals.
Ophthalmologists are medical eye doctors who are specialists in the health of the eye.
They do eye surgeries and provide drug therapies. They are very much impairments specialists with a knowledge of the body part called the eye. I used to get angry at ophthalmologists until I understood the distinction between impairments, disabilities, and handicaps. Disability specialists, like orientation and mobility instructors, special education teachers, and rehabilitation professionals, these are the people who observe the everyday use of impaired vision systems. Disability specialists can measure functional skills, daily living skills, and social skills because that is their responsibility.