One of the hallmarks of aging is declining vision. In the UK, there are currently around 12 million people over the age of 65 who are affected. In 50 years, that number will rise to around 20 million, and all will experience some visual decline because of retinal aging. Researchers from the Institute of Ophthalmology at University College London (UCL) may have discovered a new eye therapy, practicable at home, which can delay and limit this decline. The results of this study were published in the Journal of Gerontology.
The visual system decreases as we age, and this decline accelerates past 40 years. “Your retinal sensitivity and your color vision are both gradually being undermined,” says Professor Glen Jeffery, lead author of the study. This decline is characterized by the aging of the cells of the retina of the eye and the rhythm of this aging is caused, in part, when the mitochondria of the cell, whose role is to produce energy (called ATP) and to stimulate cell function, also begin to decline. Mitochondrial density is highest in photoreceptor cells in the retina, which have high energy requirements. The retina ages faster than other organs, with a 70% reduction in ATP over the course of life, causing a significant drop in the function of photoreceptors who lack the energy to fulfill their normal role.
The goal of the researchers is to fight effectively and simply against visual decline. “To try to stem or reverse this decline, we have sought to restart aging retinal cells with short bursts of longwave light,” says Glen Jeffrey. The researchers built on their previous findings in mice, bumblebees and flies, all of which found significant improvements in the function of photoreceptors in the retina when their eyes were exposed to deep red light of 670 nanometers (nm ), the unit of measurement for wavelength. “Mitochondria have specific light absorbance characteristics that influence their performance: longer wavelengths from 650 to 1000 nm are absorbed and improve the performance of mitochondria to increase energy production”, noted the searcher. Retinal photoreceptors are made up of cones that mediate color vision and rods, which provide peripheral vision and adapt vision when light is poor.
For the study, 24 people, aged 28 to 72, without eye disease, were recruited. All the participants’ eyes were tested for the sensitivity of their rods and cones at the start of the study. The sensitivity of the rod was measured in eyes adapted to the dark by asking the participants to detect weak light signals. The function of the cone has been tested by identifying colored letters which have very low contrast, and which appear increasingly blurred. All participants were then given a small LED torch to take home to examine its deep red beam of 670 nm for three minutes a day for two weeks. They were then tested again for their rod and cone sensitivity.
The researchers observed significant improvements in participants over 40 years of age, but that did not change in younger individuals. The color contrast sensitivity of cones – the ability to detect colors – has improved by up to 20% in some people aged 40 and over. The improvements were greater in the blue part of the color spectrum, which is more vulnerable to aging. The sensitivity of the rod – the ability to see in low light – also improved significantly in this population, although this was less impressive than in terms of color contrast.