Light therapy repairs color contrast sensitivity in older patients
Researchers exploring mitochondrial function in patients with age-related visual decline found that light therapy significantly improved color contrast sensitivity for the blue visual axis among those 40 years old and older.
“Human aging is a major societal problem, and the retina ages faster than other organs, partly due to its high metabolic rate,” Harpreet Shinhmar, MSc, from the Institute of Ophthalmology, University College London, and colleagues wrote. “Here, 30% of central rods die, and cones have reduced function by 70 years of age. Mitochondrial density is greatest in photoreceptors, and their decline can be linked to reductions in retinal function and the onset of age-related disease.”
The researchers noted, however, that aged mitochondrial performance can be improved optically because mitochondria absorb longer wavelengths.
“Light-induced improvements in mitochondrial function are associated with an increase in mitochondrial membrane potential and [adenosine triphosphate] production,” they wrote. “Further, long wavelength light can improve retinal and general central nervous system function that has declined due to age or mitochondrial insult.”
Shinhmar and colleagues enrolled 24 healthy patients with an age range of 28 to 72 years who received brief, daily exposures to 670 nm light therapy for 2 weeks. The researchers assessed rod thresholds and color contract sensitivity among different sets of patients based on age.
The overall study population had improved color contrast sensitivity in the tritan axis from baseline (14%; P < .001), but the researchers found best results among those 40 years old and older compared with younger patients (47% vs. 20%; P < .0001).
When divided into younger and older groups, Shinhmar and colleagues found that there were positive improvement shifts in those 38 years old and older (22%; P .001) with no significant change among younger patients.
Protan thresholds also improved by 10% in older patients, although this did not meet significance.
“While there is general acceptance that longer wavelengths improve aged or damaged central nervous system function, its route of action remains partly obscured,” the researchers wrote. “Our understanding of the temporal variations in the efficacy of long wavelength light usage is limited and needs considerable exploration before its use can be applied to maximal effect.”