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Does frequency doubling technology perimetry reliably detect neurological visual field defects?
K C S Fong1, D B Byles, P H Constable
1Department of Ophthalmology, Royal Berkshire Hospital, Reading, UK. fongcsk@yahoo.co.uk
Aim:
To determine the ability of frequency doubling technology (FDT) perimetry to detect visual field defects of neurological origin.
Methods:
A total of 15 eyes of nine patients who all had complete hemianopias or quadrantanopias underwent the FDT 20-5 screening mode test and Humphrey 24-2 SITA Fast visual field test (HFA). The FDT results were scored according to the number of abnormal test locations (out of a maximum of 4) in each affected quadrant. FDT locations showing a defect of P< 2% were considered abnormal.
Results:
Of the 15 eyes, six showed complete superior quadrantanopic and nine complete hemianopic field defects on HFA. Of 96 FDT test locations in these quadrants or hemifields only 38 were abnormal on FDT testing (40%). For the quadrantanopic field defects, five out of 24 locations were abnormal (21%). For the hemianopic field defects, 33 out of 72 locations were abnormal (49%). In three eyes (two with quadrantanopias and one with complete hemianopia), FDT perimetry failed to demonstrate any corresponding abnormality.
Conclusions:
The FDT screening test can fail to demonstrate complete hemianopic and quadrantanopic field defects. Users should be aware of this deficiency when using FDT to screen for field defects.
