We evaluated the stability of fixation in 38 healthy eyes (N), 30 eyes with macular degeneration (AMD) and 20 eyes with juvenile macular dystrophy (JMD) during our newly developed automated full-threshold static perimetry using the scanning laser ophthalmoscope (SLO). The point of fixation was recorded for each stimulus presentation. After the examination, the mean fixation point (MFP) as well as the standard deviation from the MFP, the examination time, and the reaction time were evaluated. Healthy eyes did not show a mean SD of more than 0.7 degree from the center of gravity of fixation with one exception. There was only poor correlation between age and deviation from the MFP (r = 0.09 for N; r = 0.18 for AMD; and r = 0.18 for JMD), whereas the correlation between visual acuity (VA) and deviation from the MFP was slightly better (r = 0.22 for N; r = 0.34 for AMD; and r = 0.52; P < 0.02 for JMD). Eyes with functional impairment mostly showed instable fixation (deviation, > 3 degrees), which was observed even in two patients with only slightly diminished VA of 20/25. However, stable fixation was observed in isolated cases even when VA was reduced to 20/100. The deviation of fixation was more pronounced horizontally than vertically in normals (0.40 degree:0.31 degree) and in patients suffering from AMD (0.88 degree:0.68 degree), whereas eyes with macular dystrophy did not show this phenomenon (0.82 degree:0.82 degree). The results demonstrate that there is the possibility of stable fixation even in eyes with a decrease in VA due to morphological changes in the macula.(ABSTRACT TRUNCATED AT 250 WORDS)