New York Codes, Rules and Regulations
Title 21 - Miscellaneous
Chapter LVIII - New York State Teachers' Retirement System
Part 5020 - Disability Retirement Determinations
Section 5020.1 - Standard for determining disability retirement for members who last joined the system prior to July 27, 1976, and who meet the eligibility requirements of section 511 of the Education Law

It must be determined that the member is totally and permanently disabled and was so disabled at the time the member ceased performance of duties. To be deemed totally disabled, it must be concluded that the member is unable to perform all the substantial and material acts necessary to the prosecution of teaching duties in a customary and usual manner. 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 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.