N.Y. Comp. Codes R. & Regs. tit. 21 § 5020.3
In order for a member to be entitled to disability retirement under section 605 of the Retirement and Social Security Law, it must be determined that the member is totally and permanently disabled, and that the member was so disabled at the time he ceased performance of duties. To be deemed totally disabled, it must be concluded that the member is physically or mentally incapacitated for the performance of gainful employment. Gainful employment, as used in this section, shall be physical and/or mental activity which a member is regularly able to engage in as a means of earning a living. To be deemed permanently disabled, the condition must be such to justify a deduction that any recovery by the member is far removed in the future and that the end of the disability cannot be foreseen for at least one year. In addition, total disability is not permanent if, during the period for which recovery is sought or at any time thereafter, the member may alleviate or control the condition by availing himself or herself of a standard treatment which is not inherently dangerous. The member shall have the burden of establishing all of the foregoing to the satisfaction of the Retirement Board.
N.Y. Comp. Codes R. & Regs. Tit. 21 § 5020.3