Some of the earliest eye changes in diabetes mellitus can be detected by measurement of altered fluorescein dye leakage from retinal vessels, say St Louis researchers who have used the technique with more than 500 patients.
The technique is called vitreous fluorophotometry (JAMA [MEDICAL NEWS] 240:2403-2406, 1978). Washington University School of Medicine researchers who are using it suggest that it detects changes "before there is irreversible structural damage" to the eye.
The fluorescein is injected intravenously into the patient's arm. It changes from orange to fluorescent green as it absorbs light at certain wavelengths and picks up energy. A contact lens, connected by an optical fiber to a photodetector, is placed on the eye. The slit lamp-like photodetector, originally designed for determining low light levels, measures the light reflected as fluorescein leaks from retinal vessels into the vitreous.
Why the blood-retinal barrier often breaks down in diabetic patients is not