Purpose: To determine the differences in the retinal sensitivities obtained by microperimetry with a single cross or a circular fixation target in normal individuals.
Methods: Thirty-two eyes of 16 healthy volunteers (mean age 28.9±1.4 years, range 24-44 years) were studied. The retinal sensitivity of the central 0 degrees and of the mean central 2 degrees consisting of 8 points were determined independently using the two different fixation targets with Microperimeter 3. The Goldmann III stimulus with a luminance of 1.0 cd/m2 was presented for 200 ms on a white background.
Results: The retinal sensitivity of the central 0 degrees was significantly better with the circular target than that with the cross target (P=0.003, right eyes; P=0.001, left eyes). The mean retinal sensitivity in the central 2 degrees was not significantly different between the cross and circular fixation targets. (P=0.07, right eyes; P=0.08, left eyes).
Conclusion: These results indicate that the circular fixation target is a better target to use to evaluate the central retinal sensitivity. The difference in the retinal sensitivity is most likely due to the cross fixation target overlapping the test stimulus target.
Keywords: fixation targets; microperimetry; retinal sensitivity; stimuli.