Abstract
Purpose: :
To determine the effect of optical defocus for both SAP and CFF perimetry in normal individuals experienced both in Standard Automated Perimetry (SAP) and in Critical Flicker Fusion Perimetry (CFFP).
Methods: :
Sixteen normal individuals attended for perimetry on 2 occasions, each separated by one week. At each visit, each individual was examined in one designated eye with SAP and with CFFP using the Octopus 311 with Program G1 and the TOP strategy at each of 4 levels of defocus: plano, +1.00DS, +2.00DS, +4.00DS. The sequence of defocus was randomized within the given visit and varied between individuals over each of the two visits. The effect of defocus was analysed in terms of the group mean Mean Defect (MD).
Results: :
For SAP, the group mean MD (SD) in the absence of defocus was -0.61dB (SD 1.15) and was 0.26dB (SD 1.11), 1.18dB (SD 1.05) and 3.3dB (SD 1.16) for the +1.00DS, +2.00DS and +4.00DS levels of defocus, respectively. The corresponding values for the group mean MD for CFFP were 0.88Hz (SD 4.27), 0.55Hz (SD 4.24), 0.83Hz (SD 4.14) and -1.21Hz (SD 3.29), respectively. The slope of the group mean Mean Sensitivity for SAP was 0.98dB per dioptre of defocus (i.e. deterioration) and for CFFP -0.52Hz per dioptre of defocus.
Conclusions: :
The difference in the outcomes to defocus merely underlines the different physiological basis for the two types of perimetry. CFFP is clinically unaffected by optical defocus whereas SAP should be undertaken with the optimum refractive correction for the viewing distance of the given perimeter.
Keywords: perimetry • visual fields