Quantification of diabetic macular edema
R. T. Smith, C. M. Lee, H. C. Charles, M. Farber and J. G. Cunha-Vaz
In a cross-sectional study, 34 diabetic patients with clinically
significant macular edema underwent visual acuity testing, stereo fundus
photography (graded for retinal thickening and hard exudates), fluorescein
angiography (evaluated for macular leakage and the outline of the foveal
avascular zone [FAZ]), and vitreous fluorophotometry (whereby posterior
penetration ratios were calculated). This last ratio provided the highest
single correlation with visual acuity; next highest were patient age and
FAZ grading. Multivariate regression confirmed that these three variables
together best predicted visual acuity. Lesser correlations with acuity were
obtained with angiographic leakage and fundus photography grading.
Cross-correlations among all gradings showed that indicators of breakdown
of the blood-retinal barrier, ie, fluorophotometry, angiographic leakage,
and retinal thickening, were significantly correlated with each other,
whereas FAZ grading was independent of all these factors and correlated
only with acuity. By performing vitreous fluorophotometry and fluorescein
angiography, it is possible to quantitate two major components of diabetic
maculopathy: breakdown of the blood-retinal barrier and macular ischemia,
both of which are highly correlated with visual acuity.
