Retinal vascular permeability determined by dual-tracer fluorescence angiography

Area of Science:

• Ophthalmology
• Vascular Biology
• Biomedical Engineering

Background:

• Diabetic retinopathy is a leading cause of blindness in working-age adults.
• Early breakdown of the blood-retinal barrier is a key event in diabetic retinopathy progression.
• Current methods for assessing the retinal vascular barrier in vivo are limited in sensitivity and quantitation.

Purpose of the Study:

• To develop and validate a quantitative method for assessing the retinal vascular barrier in vivo.
• To evaluate the sensitivity of the developed method to changes induced by hyperosmolar stimuli.

Main Methods:

• Combined fluorescence microangiography with simultaneous use of two fluorescent tracers.
• Adapted indicator dilution techniques to quantitatively assess retinal vasculature in Long Evans rats.
• Measured permeability-surface area over flow (PS/F) and estimated sodium fluorescein permeability.

Main Results:

• Established a baseline PS/F of 0.086+/-0.031 in Long Evans rat retinal vasculature.
• Estimated sodium fluorescein permeability to be approximately 1.2 x 10(-5) cm/s.
• Demonstrated that a 1.6 M mannitol infusion significantly increased PS/F, indicating increased blood-retinal barrier permeability.

Conclusions:

• Dual-tracer fluorescence angiography is a sensitive, quantitative method for assessing the retinal vascular barrier in vivo.
• The method can detect increases in blood-retinal barrier permeability induced by hyperosmolar mannitol.
• This minimally invasive technique holds promise for quantitatively tracking retinal vascular permeability changes in disease states.