Frequency doubling perimetry using a liquid crystal display.
OBJECTIVE
To compare frequency doubling contrast thresholds using a new liquid crystal window display with those obtained with the commercial video-based Frequency Doubling Technology perimeter.


METHODS
One eye of 49 glaucoma patients and one eye of 49 normal controls were tested with the liquid crystal window and Frequency Doubling Technology systems. Both displays employed identical stimulus conditions and test strategies, although the dynamic range of the liquid crystal window-based display was approximately 30% smaller than that of the Frequency Doubling Technology system. Measurements were repeated using the video-based Frequency Doubling Technology perimeter in a subset of 21 eyes. Relationships between and within displays were assessed using a chance-corrected agreement measure (quadratic weighted kappa) and paired measurement differences. Variability was quantified using standard deviation from the mean paired measurement difference.


RESULTS
Over the restricted operating range of the liquid crystal display system, between-display and within-video display variability was 2.3 dB and 3.2 dB, respectively, between-display agreement was 0.66, and within-display agreement (test-retest for Frequency Doubling Technology) was 0.65.


CONCLUSIONS
Levels of agreement and variability between the two frequency doubling displays were of similar magnitude to repeated (test-retest) Frequency Doubling Technology measures, suggesting that contrast threshold measurements made using the two displays may be used interchangeably. However, the operating range of the current liquid crystal window-based display is smaller.
Spry
P G
PG
Discoveries in Sight, Devers Eye Institute, 1225 NE 2nd Ave, Portland, Oregon 92732, USA.
Gibbs
M L
ML
Johnson
C A
CA
Howard
D L
DL
D000368:Aged; D015350:Contrast Sensitivity; D003626:Data Display; D005240:Feasibility Studies; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D014786:Vision Disorders / Q000175:diagnosis*; D058609:Visual Field Tests / Q000295:instrumentation / Q000379:methods*; D014794:Visual Fields