Aspects of frequency doubling perimetry in the detection of early glaucoma

Abstract

Background : Frequency Doubling Perimetry ( FDP ) is a recently developed form of perimetry, which may be more sensitive for detecting visual field loss from glaucoma than conventional Achromatic Automated Perimetry ( AAP ). This thesis was undertaken to study aspects of FDP for the detection of early glaucoma. Method : FDP was compared with other forms of perimetry at one point in time using one dataset ( n = 83 ) and longitudinally over a four - year period with another dataset ( n = 62 ). Several aspects were studied : ( 1 ) the ability of FDP to detect visual field loss earlier than AAP, ( 2 ) its ability to detect early functional abnormality in the presence of mild glaucomatous structural abnormality ( 3 ) visual field topography compared with other perimetry and ( 4 ) its ability to predict future field loss when only the nasal quadrants were considered. Results : When subjects at risk of glaucoma with initial visual field loss on FDP were followed over a three - year period, a significant proportion developed field loss with AAP, whilst those without initial FDP loss did not. FDP detected cases of early glaucomatous optic disc damage, which had not been detected using AAP ; however, there was still a proportion of those with abnormal optic discs which remained normal on FDP. FDP field topography was hill - shaped with the most sensitive point centrally ; however, it was considerably flatter and more sensitive than AAP. Finally, if FDP field loss was only considered significant when it occurred within the nasal step location of the visual field, then this may improve the accuracy of glaucoma diagnosis. Conclusion : This thesis has demonstrated that FDP is not only more sensitive than AAP in the detection of glaucomatous optic disc damage, but it is able to predict future field loss on AAP. FDP may therefore be useful in the early detection and management of glaucoma.