BLOG: Will cataract surgery improve your patient’s sleep?
Click Here to Manage Email Alerts
Our exposure to light powerfully regulates the daily cycle of alertness, relaxation and sleep.
We might, therefore, expect that the tremendous increase in light influx after cataract surgery, and perhaps even the type of IOL implanted, will affect this cycle. But does it?
The role of rods and cone cells in entraining the sleep-wake cycle was well-known, but in 2002, work by researchers at Brown University revealed the presence of previously unknown light-sensitive cells in the retina: intrinsically photosensitive retinal ganglion cells (ipRGCs). These cells do not contribute to vision at all, but instead wire through the hypothalamus to the pineal gland, regulating the release of melatonin. The ipRGCs are maximally photosensitive in the blue range, 460 nm to 480 nm — the very wavelengths most strongly blocked by nuclear cataracts (Tosini G).
Melatonin, the “hormone of darkness,” triggers relaxation and sleep. The diurnal cycle of exposure to blue light has a crucial role in the synchronization of this circadian clock. In addition to regulating sleep, melatonin stabilizes mood, enables learning, governs body temperature, decreases inflammation, lowers the risk of diabetes, enhances the scavenging of free radicals and even suppresses the growth of many tumors.
The reduction of blue light by cataracts correlates with insomnia and degradation of sleep quality (Kessel L, et al). Multiple studies have now shown that cataract surgery has a small beneficial effect on the regulation of the circadian rhythm and on sleep health (Erichsen JH, et al). Cataract surgery shortens the time to sleep, called sleep latency, and significantly improves sleep quality (Alexander I, et al).
If removing a cataract improves sleep, would replacing it with a blue-blocking IOL reduce this benefit? Blue-blocking IOLs were thought to be protective against retinal disease, but they do so by filtering out a portion of ultraviolet and blue wavelengths shorter than 500 nm, the very spectrum to which the ipRGCs are sensitive. Fortunately, research does not show a measurable effect, finding identical sleep scores between clear and blue-blocking IOLs. One study did suggest a detrimental effect on mood with blue-blocking IOLs, however, and theorized that this was due to alteration of circadian rhythms (Zambrowski O, et al).
Although blue-blocking IOLs have become less popular, one advanced multifocal IOL has recently come to market with a distinctive violet filter intended to reduce glare and haloes (Tecnis Synergy, Johnson & Johnson); fortunately, the wavelengths blocked (200 nm to 440 nm) are not crucial to the circadian cycle.
Currently, evidence shows that cataract surgery with any type of IOL will bestow a modest improvement in sleep, especially by shortening sleep latency. Although blue-blocking IOLs may subtly affect circadian rhythm and even mood, the effect is too small to reliably measure.
References:
- Alexander I, et al. Invest Ophthalmol Vis Sci. 2014;doi:10.1167/iovs.14-14054.
- Erichsen JH, et al. J Cataract Refract Surg. 2015;doi:10.1016/j.jcrs.2015.09.009.
- Kessel L, et al. Sleep. 2011;doi:10.5665/SLEEP.1242.
- Tosini G, et al. Mol Vis. 2016;201(22):61-72.
- Tosini G. Optom Vis Sci. 2022;doi:10.1097/OPX.0000000000001866.
- Zambrowski O, et al. Aging Ment Health. 2018;doi:10.1080/13607863.2017.1348482.
For more information:
Oliver Kuhn-Wilken, OD, is a staff optometrist at Pacific Cataract and Laser Institute’s Tualatin Clinic in Oregon.
Collapse