The GDx provides highly reproducible, objective measurements of the RNFL, to detect structural changes early. It then compares these measurements to an age-stratified, multi-ethnic normative database, providing you with a unique visual representation. It also uses neural network techniques to calculate a unique Nerve Fiber Index (NFI) to determine the likelihood of glaucoma. A recent study found that the NFI can differentiate between normal eyes and glaucomatous eyes before visual field loss with sensitivity and specificity of 83% and 82%, respectively.