Analysis of diabetic vitreopathy with dynamic light scattering spectroscopy - problems and solutions related to photon correlation

. Purpose: To explore the molecular alterations of the vitreous by dynamic light scattering (DLS) spectroscopy (quasi-elastic light scattering spectroscopy, photon-correlation spectroscopy) in normals and in patients afflicted with various degrees of non-proliferative and with proliferative diabetic retinopathy. Methods: Dynamic light scattering spectroscopy was employed to analyze the vitreous of normals and of patients with diabetes non-invasively to estimate both the sizes and diffusion coefficients of mobile macromolecules and/or microparticles. Results: Abnormal molecular behaviour of vitreous molecules was observed in patients with diabetes afflicted with various degrees of diabetic vitreo-retinopathy. In the non-proliferative (background) retinopathy, both the diameters of the microparticles increase and the diffusion constants decrease significantly and progressively as the diabetic disease progresses. In the proliferative phase, a significant trend in the direction of smaller particles and greater diffusion constants is evident. These behaviours could also be interpreted as an increase in the viscosity of the intermolecular substance in the first case and as a decrease in the second. Conclusions: The vitreous in normals and even more so in diabetics with diabetic vitreo-retinopathy is optically a highly non-isotropic, multidispersive structure, making an optical analysis difficult. Advanced, but available models and technology, however, permits a major step forward in the optical analysis of the normal and the diseased vitreous.