Melatonin and Intraocular Pressure - Preview
Like most people, my intraocular pressure (IOP) is lowest at night. This is also when natural levels of melatonin are near their high in the circadian cycle. My IOP is highest in the morning when melatonin is low. There seems to be a correlation between my IOP and melatonin. Recognizing that relationship lead me to have a discussion with my physician.
My physician agreed to carefully monitor my IOP while I try melatonin. I'll tell you how the results of the first day turned out. But first, let me tell you what I know about melatonin.
My physician gave me some background on melatonin. It is known that levels of melatonin in the blood are highest prior to bedtime. He said melatonin is a neurohormone produced in the brain by the pineal gland. The amino acid tryptophan is a precursor for melatonin. The synthesis of melatonin is stimulated by darkness; its release is suppressed by light. For this reason, melatonin is believed to be involved in the circadian rhythms. It is also involved in the regulation of diverse bodily functions.
One of melatonin's diverse functions is to oppose the action of natural corticosteroids (glucocorticoids) and corticosteroid drugs. As you may be aware, corticosteroids are known to increase IOP.
Of additional interest is the fact that melatonin is a well-studied free radical scavenger. There are well over one hundred laboratory and animal studies of the antioxidant (free radical quenching) properties of melatonin. (I won't list those references in this article because I am focusing on the IOP effects). Melatonin is often used as a supplement to prevent or treat many conditions that are associated with oxidative damage. However, there are many other antioxidants I think I would consider before I resorted to using a neurohormone purely as an antioxidant. I understand melatonin can potentially do more for the eye than just lower IOP and serve as an antioxidant, but because it also affects so many other bodily functions, I would not use it primarily as an antioxidant.
In my case, I do have some trouble falling asleep, so melatonin's well-studied effects on improving sleep quality and reducing sleep latency (the time it takes to fall asleep) are of interest to me.
My physician also cautioned me that theoreticallly, melatonin could increase intraocular pressure and the risk of glaucoma, age-related maculopathy and myopia (1), or retinal damage (2) due to effects on photoreceptor renewal in the eye. This is thought to be possible with high doses of melatonin. However, I do not believe these effects have ever actually been seen.
What has been seen is that melatonin may actually decrease intraocular pressure (3, 4). Furthermore, it has been proposed that melatonin may be protective against the optic nerve damage characteristic of glaucoma (5). That's why my physician agreed that we could investigate it as a possible therapy for my glaucoma. Keep in mind that the research in this area is preliminary. There are no studies on melatonin and glaucoma as far as I know. The only study was done on healthy people.
In that one study, supplementing with 0.5 mg of melatonin lowered intraocular pressure of healthy people (3).
I have pigmentary glaucoma. So what happended when I took my first dose of melatonin? I took 2.5 mg sublingually. Within an hour, my IOP had fallen by 26%. By bedtime, 5 hours later, my IOP had fallen 46%. Of course part of that decline is normal. My IOP is always lower around bedtime. So the information that seems most relevant to me is the 26% decrease within an hour of taking the melatonin.
What do these first day results mean? Probably not much. I would want to know a lot more about the effects and side effects over a long period of time before I got too enthusiastic about long term use of melatonin. And for anyone other than me, my simple test means nothing at all. A lot more testing would be needed before anyone could make general recommendations. Quite frankly, I'm not sure I even want to be the guinea pig for continuing my own little experiment. I'm planning to call my physician and tell him that I'm going to discontinue the melatonin until I learn more. I learned enough to understand firsthand that melatonin is probably involved the daily cycle that causes my IOP to be lowest in the evenings. That's worthwhile knowledge and I think I'll stop there for now.
The big problem with melatonin is that no one really knows what problems it could lead to if taken in the morning. And that is when I would need to take it if it were really going to do much to help my IOP.
However, today's results will probably cause me to investigate some other options. For example, because I often have trouble falling asleep, I would be interested in an herbal product that naturally stimulates melatonin.
Chasteberry (Vitex agnus-castus) is an example of a product that may increase natural secretion of melatonin. This is based on preliminary research (mentioned here and here), but I plan to investigate it further. If I find a good traditional herbal formula that contains chasteberry, I will consider trying it while closely monitoring my IOP with my physician.
Another thing to note is that some preliminary studies have found that meditation and yoga prior to bedtime may increase melatonin levels that evening.
But for anyone with glaucoma, the morning intraocular pressure levels probably need more attention than the evening IOP. So it seems that using melatonin, whether directly as a supplement or indirectly via herbs, yoga or meditation, is not a complete solution.
That said, more research on melatonin and glaucoma would be welcome.
DISCLAIMER: Anyone with glaucoma should be monitored by a healthcare professional while taking melatonin.
Check drug interactions with melatonin here. For example, "when supplemental melatonin is taken at the same time as corticosteroids, the effects of the corticosteroid may be decreased."
1. Guardiola-Lemaitre, B. Toxicology of melatonin. J Biol Rhythms 1997;12(6):697-706.
2. Lamberg, L. Melatonin potentially useful but safety, efficacy remain uncertain. JAMA 10-2-1996;276(13):1011-1014.
3. Samples, J. R., Krause, G., and Lewy, A. J. Effect of melatonin on intraocular pressure. Curr Eye Res 1988;7(7):649-653.
4. Viggiano, S. R., Koskela, T. K., Klee, G. G., Samples, J. R., Arnce, R., and Brubaker, R. F. The effect of melatonin on aqueous humor flow in humans during the day. Ophthalmology 1994;101(2):326-331.
5. Moreno MC, Sande P, Marcos HA, de Zavalia N, Keller Sarmiento MI, Rosenstein RE. Effect of glaucoma on the retinal glutamate/glutamine cycle activity. FASEB J. 2005 Jul;19(9):1161-2. Epub 2005 May 2.