Article: Insights from colour-blind octopus help fight human sight loss
Source: University of Bristol (U.K.), via ScienceDaily
Published: May 4, 2021
Originating as technology to measure how octopuses see polarized light, researchers in the U.K. then adapted the technology to develop a device that measures levels of carotenoids in human eyes. When tested on humans, the researchers found that people are able to see polarization patterns when the light was only 24% polarized. Humans can see polarized light due to birefringence of macular pigments such as the xanthophylls/carotenoids lutein, zeaxanthin, and meso-zeaxanthin in the radially arranged retinal nerve fiber layer of Henle. Birefringence is the refracting of light into two components, perpendicular to one another, and each having a different refractive index. The retardation of polarized light due to birefringence as a result of the thickness of the RNFL can be detected by ophthalmic instruments such as scanning laser polarimeters (GDx). Macular pigments play an antioxidant role in protecting the retina from ultraviolet light, which helps to prevent or delay retinal diseases such as age-related macular degeneration. Carotenoids are derived from food, thus the detection of the amount of macular pigment in the retina can help clinicians provide recommendations about consumption of foods containing carotenoids or wearing sun protection when outdoors. The lead researcher thinks that while there are existing methods to measure a person's amount of macular pigments, those techniques are time-consuming or expensive. His start-up company seeks to develop a device that enables rapid screening as part of regular eye exams.
Personal commentary: Macular pigments show up as the entoptic phenomenon known as Haidenger's brush, wherein polarized light is absorbed in one direction and transmitted in the perpendicular direction. In white light, both the blue and the yellow brushes are seen. The presence of Haidinger's brushes can be detected by instruments such as a Macula Integrity Tester to locate the fovea and assess (eccentric) fixation in clinical applications of vision therapy.
My rating of this study:
⭐⭐⭐Temple SE, How MJ, Powell SB, et al. "Thresholds of polarization vision in octopuses."
Journal of Experimental Biology. 224(7):jeb240812. 15 April 2021.
https://doi.org/10.1242/jeb.240812
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