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K. Luraas, J. M. Wild; Where Is the Learning Effect for CFF Perimetry in Normal Individuals?. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5897.
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To determine the characteristics of any learning effect for Critical Flicker Fusion (CFF) perimetry in the normal eye.
Fourteen normal individuals naïve to perimetry (mean age 61.3 years SD 9.3) underwent clinical examination including standard automated perimetry (SAP) with the Octopus 311 using Program G1 and the Dynamic strategy. After an interval of two weeks, the individuals underwent CFF perimetry in each eye on five occasions each separated by one week using Program G1 and the TOP strategy and, on a sixth occasion one week later, using the Dynamic strategy. The results were analysed over the five visits in terms of the Mean Defect (MD) and Loss Variance (LV) indices and the examination duration using separate Analysis of Covariance with age as a between-subjects factor and eye and visit as within-subjects factors.
All individuals exhibited a normal field in each eye by SAP. For CFF perimetry, the changes in the MD and in the LV over the five visits did not reach statistical significance (p=0.094 and p=0.947 respectively) in either eye (p=0.886 and p=0.919, respectively). The duration of the examination over the five visits did not change (p=0.428). Considerable variation in performance for CFF perimetry was present over the five visits between individuals and between eyes within an individual. Five individuals exhibited an improvement in both eyes, 4 an improvement in the first eye examined, only, and one an improvement in the second eye examined, only. One individual showed no improvement in performance in either eye although the sensitivity was higher in the second eye examined. The remaining 3 individuals demonstrated a between-visit worsening of sensitivity in the first eye examined with no improvement in the second eye; a finding presumably attributable either to a change in response criterion or from the fatigue effect.
The absence of an unequivocal learning effect for CFF perimetry is at odds with that present for other forms of perimetry and may be due to the difficulty of the CFF task. Such between-individual variation in performance will not facilitate the interpretation of field loss by CFF perimetry.
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