Investigating the sclera fluorescence in order to obtain AGE related diagnostic information

It is known the disadvantages of assessing the content of advanced glycation end products (AGE) in the human body using autofluorescence of the skin. There are dependence on the skin phototypes, influence of hair, surface macrostructure and compression of biological tissues during investigation on AGE readers. On the other hand, the sclera of the eye is also composed of glycated collagen fibers and is available for in vivo fluorescence level estimation. This approach removes restrictions on the skin phototype and reduces the influence of other drawbacks. This study experimentally approves the opportunity of measuring the fluorescence of the human eye sclera in vivo for assessing the content of AGE in biological tissues. A correlation between the fluorescence of the skin of the hand and the sclera was established. The investigation of autofluorescence of the sclera and skin of the inner side of the forearm were carried out using a slit lamp. This lamp was equipped by authors with a semiconductor violet laser with a peak wavelength of 405 nm. This violet laser excites AGE fluorescence. A color camera was utilized as a photodetector. It was covered by a cutting violet light filter made of polyimide film 40 micrometer thick. The diagnostic parameter ("Sclera" or "SL skin") was the ratio of the arithmetic mean of two green pixels, one of which was exposed by violet laser, whereas another one was exposed by white light. The experiments involved 40 practically healthy subjects with ages from 18 till 70. The experimental results demonstrated an expected increase of diagnostic parameters within the age. The calculated values of the Pearson correlation coefficient between the diagnostic parameters "Sclera" / "Skin SL", "Sclera" / "Skin FL", "Skin SL" / "Skin FL" were 0.96; 0.95 and 0.99, respectively, indicating their significant statistical relationship.