For people who have had an accident or an illness that has resulted in long term or permanent reduction in the use of a part of their body or bodily function, the impairment rating can be used to measure the loss.
[1] Impairment specifically describes the deviation in a stable condition where, even with further treatment, the impact on the individual's activities of daily living is unlikely to change.
[3] despite these differences impairment rating is commonly used by government organizations as a measure of disability, or to determine compensation owed due to an accident or injury.
Using medical evidence and expert consensus in the field improves the fairness and consistency in an impairment rating.
[4] The AMA guidelines attempt to standardize impairment rating by basing them off of objective measurements such as Decibel Sum Hearing Loss (DSHL) or visual acuity tests.