Bill Harvey: Have mercy white light
Author: Bill Harvey
Two statements found in the journals this week. ‘There is little evidence at this time to support the use of blue-blocking filters to minimize near work-induced asthenopia.’ ‘Sunlight exposure may not be associated with increased risk of AMD based on current published data.’
The first comes from a study in Optometry and Vision Science by Professor Mark Rosenfield, ex-pat optometrist and renowned expert in digital eyestrain. Near work asthenopia needs to be managed by assessment of refraction, binocular status and viewing habits. It seems the role of blue light is still unproven.
The second is from an excellent meta-analysis in BMC Ophthalmology which summarises any evidence for a link between sunlight exposure and AMD. I often see records where a UV or blue-blocking filter has been recommended to an elderly, phakic patient on the pretext that it will prevent any shorter wavelength-induced maculopathy. This is despite the fact that the crystalline lens, especially once brunescence is established, is a very effective short wavelength barrier. So, though UV-protection is important for anterior structures, the macula is unlikely to be vulnerable unless the eye is aphakic or has an odd IOL.
And to keep the light theme going, I was interested to see the World Health Organisation cite shift work as a modifiable risk factor for cardiovascular and malignant diseases. This is an important recognition of the growing body of evidence showing the significance of our light-controlled body clocks. And a nice study in this month’s JAMA has described how cataract adversely affects our body clocks, concomitant with poor health problems, and that careful IOL selection can help to rectify this.
If we are going to talk to patients about light influence, then I think we would be better explaining circadian rhythms rather than selling unnecessary filters.