Early cataract diagnostics explored using tryptophan fluorescence
Livingston, Scotland--Edinburgh Instruments (EI), together with NHS Princess Alexandra Eye Pavilion and Heriot-Watt University (both in Edinburgh, Scotland), are exploring the possibility of early cataract diagnostics based on tryptophan fluorescence (TF).1 According to the World Health Organization, cataracts are the leading cause of blindness worldwide, affecting some 17 million people and resulting in 1.3 million cataract operations annually in the United States alone.
Current cateract-detection techniques inadequate
Currently, methods of cataract detection are based on subjective observations of lens opacity by Rayleigh light scattering. However they cannot provide the protein-level detail offered by TF due to the limitations of these scattering techniques, as the sizes of the structural defects must be comparable with the wavelengths of light used (400 to 600 nm). Hence, observations of Rayleigh light scattering do not reveal structural changes at the molecular level.
TF has been widely used for monitoring protein changes in biophysical research to detect protein folding, conformation, and aggregation by virtue of shifts in the emission spectrum in different polar microenvironments.
TF shows cataracts early
By creating artificial cataracts in the lenses from pigs' eyes by means of UV radiation, experiments show that TF offers a sensitive method for monitoring very early changes in the lens structure that cannot be detected by the standard slit-lamp method. Spectral measurements were taken using an EI spectrometer in a temperature-controlled 1 cm quartz cuvette in phosphate buffer solution at 22°C; this temperature retained uniform tissue viability over 16 hours.
Exploiting this discovery should allow the development of a clinically useful tool sensitive enough to detect, diagnose, and monitor lens changes before significant damage, light-scattering, aggregation, and visual impairment occur. This method could help to establish the point at which the irreversible crystalline protein change has occurred, triggering the need for surgical intervention. It could also act as a more-precise screening method for possible pharmacological treatment.
In addition, clinical applications of this method would help in diagnostics of early stages of metabolic disorders such as diabetes, the preventive treatment of which could delay the development of chronic diseases.
REFERENCE:
1. Dmitry M. Gakamsky et al., J. R. Soc. Interface, published online before print April 20, 2011, doi:10.1098/rsif.2010.0608.
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John Wallace | Senior Technical Editor (1998-2022)
John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.