Mich. Comp. Laws § 500.3406u

Sec. 3406u. (1) An insurer that delivers, issues for delivery, or renews in this state a health insurance policy that provides coverage for prescription eyedrops shall not deny coverage for a refill of the prescription if all of the following apply: (a) For a 30-day supply, the amount of time has passed within which the insured should have used 75% of the dosage units of the drug according to the prescriber's instructions, or 23 days have passed after either of the following: (i) The original date the prescription was distributed to the insured. (ii) The date the most recent refill was distributed to the insured. (b) The prescriber indicates on the original prescription that additional quantities are needed. (c) The prescription eye drops prescribed by the prescriber are covered under the health insurance policy. (2) As used in this section, "prescriber" means that term as defined in section 17708 of the public health code, 1978 PA 368, MCL 333.17708.