No. Instead, disability is defined according to a condition's impact on your ability to carry out the normal day-to-day activities in your own life.
The law applies a ‘social model’ of disability. This model demands a broad interpretation of the laws supporting disabled workers, emphasising their social purpose, namely removing the barriers to participation at work caused by the environment and by stereotypical attitudes towards disability.
The Code of Practice which accompanies the Equality Act 2010 (PDF, 1.1MB) contains some helpful guidance.