INS and glaucoma: In this phase I trial in patients with glaucoma, daily topical insulin at 100 u/ml and 500 u/ml (approximately 4 u/drop and 20 u/drop, based on a 40 μl drop volume) proved to be safe and well tolerated, and a statistically significant increase in RNFL thickness, along with case examples of structure–function–correlated improvement in some patients, together support the plausibility of biological activity at the level of the retina or optic nerve.