This prospective study quantified changes in corneal neovascularization in patients with active keratitis after treatment using color imaging, fluorescein angiography (FA), and indocyanine green angiography (ICGA). The authors conclude that the excellent vessel delineation with ICGA, even in the presence of stromal scars, makes it an ideal agent for measurement of vessel parameters. FA is useful at detecting vessel leakage, and the time to leakage provides a possible measure of vessel staging.
The study included 12 patients. A comparison of corneal neovascularization parameters was undertaken before and after resolution of keratitis. A slit-lamp digital camera acquired images of neovascularization using color imaging, FA, and ICGA. The best-quality images were selected using a grading system, and the neovascular regions of interest were analyzed using automated in-house software. The parameters of analysis were vessel area, diameter, tortuosity, and FA dye leakage.
There was a significant reduction in the area of neovascularization after treatment on color imaging (0.78 mm2; P < 0.05), FA (2.33 mm2; P < 0.01), and ICGA (2.07 mm2; P < 0.01). There also was a significant reduction in mean vessel diameter across the region of interest for each patient, more marked on FA (42.74 to 32.52 µm; P < 0.01) and ICGA (44.77 to 33.29 µm; P < 0.01) than on color imaging (29.10 to 25.17 µm; P < 0.01). A significant change in vessel tortuosity was not observed. There was a significant increase in FA dye leakage time (12.41 seconds; P < 0.05) after treatment.
The authors say the study demonstrated that changes in the area of neovascularization, vessel diameter, distribution of vessel diameters, and, in some cases, vessel tortuosity were particularly evident on FA and ICGA and provided reliable measures of change. These changes were much less evident on color images, with consistently smaller areas of vascularization and an apparent absence of vessels in two patients. The combined use of FA and ICGA clearly provides an improvement over color imaging in the assessment of corneal neovascularization.
They conclude that FA and ICGA together with computer-assisted automated image analysis provide a very reliable method for the detection and characterization of corneal neovascularization and should be considered in studies in which assessment of corneal neovascularization is needed.
They note that there are well-documented adverse reactions (e.g., anaphylactic shock) associated with the administration of ICGA and FA. Although these agents may have a developing role to play in anterior segment clinics, vigilance is necessary for those who may be at risk of anaphylaxis (allergy to iodides) or in whom administration of these agents may be contraindicated (e.g., liver or renal dysfunction).