§ 404.1583 - How we determine disability for blind persons who are age 55 or older.
We will find that you are eligible for disability insurance benefits even though you are still engaging in substantial gainful activity, if -
(a) You are blind;
(b) You are age 55 or older; and
(c) You are unable to use the skills or abilities like the ones you used in any substantial gainful activity which you did regularly and for a substantial period of time. (However, you will not be paid any cash benefits for any month in which you are doing substantial gainful activity.)