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The location of CNV is defined in relation to the lesions distance to the geometric center of the foveal avascular zone (FAZ). Lesion of subfoveal CNV is under FAZ; lesion of juxtafoveal CNV occurs between 1μm and 199μm from the FAZ; extrafoveal CNV is defined as a lesion situated at least 200μm from the FAZ. Studies on eyes with subfoveal classic CNV (which could also have an occult CNV component) found the decrease of ≥3 lines of visual acuity in 60% to 80% of patients during two years’ followup. If CNV is not detected early and treated promptly, the rapid vision loss could have severe consequences for patients. Several studies on subfoveal classic CNV due to AMD indicated a poor prognosis for vision loss in this type of lesion. The data showed that the visual acuity loss in many AMD patients resulted from subfoveal classic CNV which occurs during the first two years after diagnosis. Visual acuity often deteriorates rapidly in eyes with juxtafoveal CNV, with most eyes (≥80%) losing at least 2 lines of visual acuity within two years and almost 90% losing 2 lines in five years. There is also a very high risk (≥90%) that untreated juxtafoveal lesions will progress to subfoveal lesions within five years. The studies on the natural course of extrafoveal classic CNV demonstrated a decrease of ≥3 lines of visual acuity in 56% to 86% of patients through two years of followup. There also appears to be a tendency for CNV to extend towards the center of FAZ (i.e., to become subfoveal in location). Some studies showed that extrafoveal occult CNV demonstrates a slower progression of visual loss than juxtafoveal classic CNV[5]. In the present study, there were 42 eyes of subfoveal CNV in which 30 eyes had visual acuity less than 0.1, 14 eyes of juxtafoveal CNV, 3 eyes of extrafoveal CNV. Clinically, CNV may be associated with subretinal fluid, subretinal hemorrhage, lipid exudation, or RPE detachment and finally with the development of fibrovascular disciform scars and loss of the outer retinal tissues. These events usually lead to progressive and variable amounts of irreversible central vision loss.
In conclusion, suspected AMD patients are performed FFA, which will provide important information for AMD patients including early detected CNV, the quality and location of lesion confirmed, timely and appropriate treatment indicated. This will help to prevent or slow down the declining of visual acuity of AMD patients.
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