Correlation between confocal tomography of the optic nerve (HRT) and the perimetric frequency doubling technology

To correlate the five phases of optic nerve (ON) damage staging, as assessed by means of confocal tomography (HRT) with the five stages of visual field, assessed by conventional perimetry (standard automatic perimetry, SAP) and classified in five stages according to the "GLAUCOMA STAGING SYSTEM". The second step was to correlate the same optic nerve staging system with the results of the visual field tested with non-conventional perimetry using the frequency doubling technology (FDT) employing the Humphrey-Zeiss and Welch-Allyn perimeter. The five stages of FDT visual field data evolution were classified according to the new "FDT STAGING SYSTEM". 58 visual fields of 58 consecutive selected patients with either ocular hypertension or glaucoma with an age-range between 15 and 65 years. Visual field examination was performed with conventional (Octopus G2 threshold test) and non-conventional perimetry (FDT N30 threshold test), and the ON was assessed with confocal tomography (Heidelberg Retina Tomograph). In 40 % of the visual fields tested normal with conventional perimetry, non-conventional perimetry (FDT) detected glaucomatous visual field defects corresponding topographically with the optic nerve damage revealed by HRT. New non-conventional perimetric techniques such as FDT enable the very early detection of visual field defects topographically correlated to optic nerve damage.