A review on methods used to record and analyze microfluctuations of the accommodation in the human eye

Abstract

In steady state conditions, the accommodation of the human eye presents fluctuations. These fluctuations, called microfluctua-tions, are described in the literature as having an amplitude of less than 1D and a frequency up to a few Hz. Since Collins' report about microfluctuations in 1937 [1], several methods have been used to record and analyze microfluctuations. Results reported in the literature are partially in disagreement; we show how these disagreements could be due to the different methodologies used to record and analyze the accommodation signals. We classify and discuss properties of instruments used to record the microfluctuations and methods used to elaborate the resulting signals. In particular, we catalog the measuring instruments in three families, i.e. wave-front aberrometer, classical IR autorefractometer, and ultrasound; while other three families are defined for the methods of analysis: root mean square (RMS), Fourier transform (FT), short-time Fourier transform (STFT). To conclude we suggest how to validate the instrumentation with comparative experiments and which analysis method to adopt when investigating microfluctuations;in particular we suggest a new statistical approach.