Macular automatic fundus perimetry threshold versus standard perimetry threshold

To evaluate if retinal sensitivity threshold obtained with an automatic fundus perimeter may be compared with a standard perimeter retinal threshold.

Automatic full-threshold fundus perimetry (microperimetry) of the macular area (10 degrees grid, 37 stimulated points) was quantified with a new automatic fundus perimeter (MP1 microperimeter) in nine normal subjects (18 eyes). Retinal threshold was also quantified using an identical grid projected with a standard Octopus 101 perimeter.

Mean threshold registered by MP1 microperimeter was 19.7+/-0.8 dB (range 16-20 dB; 4.38+/-0.96 asb, range 4-10 asb) versus 33.1+/-1.7 dB (range 27-38 dB; 0.53+/-0.22 asb, range 0.16-2 asb) obtained with Octopus perimeter. Mean SD of intraindividual variation was 0.74 dB in MP1 and 1.51 dB in Octopus. No statistically significant differences were documented between right and left eye with both instruments (p=0.64). No reliable mathematical relationship between retinal thresholds could be obtained with the two perimeters.

Fundus perimetry is a precise, functional fundus-related technique which allows threshold determination at selected retinal points even if fixation is unstable and visual acuity is low. This is beyond the possibility of any static standard perimetry. Normal threshold values obtained with MP1 automatic microperimeter cannot be currently compared with those obtained with standard Octopus perimeter.