Evaluation of the frequency doubling technology perimetry in the detection of an early glaucomatous field loss.Twenty-two patients (40 eyes), who were diagnosed with ocular hypertension were enrolled in the study. The diagnosis was made based on slit lamp examination, 3 measurements of intraocular pressure (IOP) over 21 mmHg. Standard perimetry was performed with Humphrey perimeter and SITA program (30-2 threshold). Then, all patients underwent FDT perimetry with 30-2 threshold program. Patients, who had any changes in FDT visual field had to repeat the test, to confirm the results.Out of 40 eyes with the normal white on white perimetry 5 eyes (5 patients) presented defects in FDT perimetry. They had optic disc c/d asymmetry > 0.1 and the nerve fiber layer defects corresponding to the visual field defects in FDT perimetry.Frequency Doubling Technology perimetry may be useful as a supplemental method of the visual field evaluation, particularly in patients where standard perimetry does not show any functional damage.