“The balm of hurt minds, great nature's second course, chief nourisher in life's feast.”
Even back in Shakespeare’s time they understood the benefits of sleep, as the above quote from Macbeth shows. But as more and more studies are revealing, it has to be the right sort of sleep. Interestingly, when it comes to certain conditions, too much sleep can be more harmful than too little sleep.
That’s unfortunately the case when it comes to glaucoma and sleep. The Glaucoma Research Foundation [1] describes Glaucoma as a
“multi-factorial, complex eye disease with specific characteristics such as optic nerve damage and visual field loss.”
That optic nerve damage can be caused by increased levels of pressure inside the eye. Other potential causes include hypoxia from vascular issues and even post inflammatory apoptosis (programmed cell death).
Whilst it is worth noting that there is no specific pressure level which will definitely lead to glaucoma, a rise in an individual’s intraocular pressure (or IOP levels) can be a contributing factor. The AAO (American Academy of Ophthalmology) adds to its definition of glaucoma that the intra ocular pressure (IOP) is too high for the continued health of that eye.
That’s why regular eye checks which can detect a change in eye pressure are so important. The earlier that the potential for glaucoma developing can be identified, the sooner preventative treatments can start.
What’s this got to do with sleep? Well, when we lie down at night, a reduction in the eye’s ability to drain aqueous fluid can lead to IOP levels rising by between ten and twenty percent. Add in the effects of a reduction in blood pressure on the optic nerve when we are asleep and the result could lead to an increased chance of developing glaucoma. A US study [2] concluded that there is a relationship between glaucoma and sleep. Those who slept for ten hours or more each night were three times more likely to have glaucoma-related optic nerve damage than those who slept for seven hours.
Does that mean we should sleep sitting up? Well, the answer to that will depend on the individual, with some sleeping positions potentially leading to other conditions. Interestingly, a Korean study [3] revealed that whilst raising the head of the bed resulted in a smaller rise in IOP levels than when lying flat, the same result wasn’t seen when using multiple pillows to raise an individual’s head.
Adding to the link between sleep and glaucoma, another study revealed that sleep apnoea, in which breathing stops fully or partially on a regular basis during the night, can also be a major risk factor for developing glaucoma [4].
So, it’s not just how much we sleep, but also how we sleep and the quality of our sleep that can make a difference not only to our overall health but also to our ability to see the world clearly each day.
There is yet a great deal of research to be done around this interesting link between glaucomatous optic neuropathy and sleep. Do not go changing your sleep patterns just yet, but it is fascinating to better understand the myriad influences on this most challenging of eye conditions. Glaucoma, the ‘Silent thief of sight’ affects 2% of the population, but 50% is undiagnosed. Better methods of early detection and treatment are essential and ongoing.
[1] https://glaucoma.org/high-eye-pressure-and-glaucoma
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4274296/
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5084493/