Abstract
Purpose::
Standard perimetry, such as the Humphrey Field Analyzer (HFA) ,may fail to detect early glaucomatous abnormalities due to sparse test points. We developed a new, automatic, fundus-oriented ,small target perimeter and assessed its ability to detect abnormalities in the corresponding visual fields of patients with preperimetric glaucoma and a retinal nerve fiber layer defect (RNFLD).
Methods::
Thirty eight eyes of 38 patients with preperimetric glaucoma, 38 eyes of 38 patients with primary open-angle glaucoma (POAG) and 30 eyes of 30 normal subjects were examined. All preperimetric glaucoma and POAG eyes had a definite RNFLD. HFA results (30-2 SITA standard program, white on white perimetry) of POAG eyes met Anderson’s criteria. The new perimeter was composed of two liquid crystal monitors, one for a campimeter and the other for an examiner’s operation. Test points were arbitrarily selected by the examiner on the fundus images displayed on the monitor and test targets, equivalent to the selected area, were displayed on the campimeter. The entire area of the RNFLD or equivalent retinal area for normal subjects was included in the test area. The size of white test targets was 2.3 minutes in diameter and the distance between two adjacent targets was 60 minutes. Stimulus intensity was 434 asb on a background luminance of 10 asb. Exposure duration was 100ms. Two- to three- hundred points were tested once in the upper or lower hemi-field. Sensitivity and specificity of the new perimeter were calculated.
Results::
The new perimeter could detect scotoma due to major retinal vessels. False negative ratio was 2% in normal subjects. Thirty three (86.8%) eyes with preperimetric glaucoma and 38 (100%) eyes with POAG showed scotoma in association with the RNFLD. The best cut-off point for discrimination between preperimetric glaucoma and normal eyes was derived when abnormalities were defined as two contiguous test points being scotomatous. Sensitivity and specificity under these conditions were 73.7% and 76.7%, respectively.
Conclusions::
Fundus-oriented, small target perimetry is a new method to detect visual field abnormalities in preperimetric glaucoma.
Keywords: perimetry • nerve fiber layer • visual fields