The Power of Focal Loss Volume (FLV%) and Global Loss Volume (GLV%) in the Diagnosis and Management of Glaucoma as Measured by Visual Field Progression
The analysis of the Ganglion Cell Complex is a measure of thinning of the inner retinal layers…the neurological representation of the retina. There are a number of ways to assess the Ganglion Cell Complex (GCC) thickness metric available on SD-OCT devices. Overall average thickness may be depressed in a number of conditions including normal tension glaucoma, primary open angle glaucoma, retinal arterial occlusive disease, type 1 diabetic retinopathy, sleep apnea, and the dementias. There may be isolated pockets of thinning in the GCC in other conditions such as normal tension glaucoma and ischemic optic neuropathy. Asymmetry, which is critical to all differential diagnosis, is highlighted by most SDOCT instruments.
More attention is now being directed at other quantifiable aspects of this Ganglion Cell Complex feature including the metrics focal loss volume percentage and global loss volume percentage. The only devices currently approved to calculate Focal Loss Volume Percentage (FLV%) and Global Loss Volume Percentage (GLV%) are those manufactured by Optovue, Inc Fremont CA. The FLV% and GLV% concept is illustrated in the following graphic. FLV% demonstrates “the potholes in the topography of the Ganglion Cell Complex” and GLV% shows an “overall thinning of the topography of the Ganglion Cell Complex.” Both the FLV% and GLV% are now revealing potential in assistance in differential diagnosis and management of ocular disease.