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Identification of glaucoma-related visual field abnormality with the screening protocol of frequency doubling
1Dana Center for Preventive Ophthalmology, The Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. hquigley@welchlink.welch.jhu.edu
Purpose:
To evaluate the predictive power of frequency doubling technology to distinguish glaucoma suspects from persons with glaucoma visual field loss.
Methods:
A consecutive series of 76 subjects referred to a glaucoma service underwent perimetry in one eye with frequency doubling technology in a screening mode and Humphrey 24-2 threshold testing in random order, and had optic disk and clinical nerve fiber layer grading.
Results:
All subjects performed perimetry with both instruments satisfactorily, with an average test time of 1.8 +/- 0.7 minutes per eye for the frequency doubling technology (instrument time). Of 33 eyes classified as abnormal by glaucoma hemifield test, 91% (30/33) were abnormal on frequency doubling technology (two or more abnormal locations of 17), whereas 94% (31/33) of glaucoma suspects with normal Humphrey fields had normal results with frequency doubling technology. Frequency doubling technology results were highly correlated with Humphrey mean deviation by linear regression (r2 = .74, P = .047) and with corrected pattern standard deviation probability value. A frequency doubling technology error score for each quadrant of the field was highly correlated with the number of severely abnormal points per quadrant in Humphrey threshold tests (r2 = .63, P = .034). There was close agreement between clinical examination of the optic disk and nerve fiber layer and frequency doubling technology results. Three-level quantification of abnormality in frequency doubling technology results did not add to diagnostic accuracy.
Conclusion:
Frequency doubling technology testing shows promise as a screening method in glaucoma.