Detection of central fixation using short-time autoregressive spectral estimation during retinal birefringence scanning

•Retinal birefringence scanning was used to detect central fixation.•Very short lasting episodes of central fixation, are difficult to detect in children.•Good resolution in both time- and frequency domains is needed for detection.•Autoregressive spectral estimation was compared to FFT in short-lasting intervals.•Autoregressive spectral estimation performed better than the FFT for 5 ms intervals.

The manuscript reports on the implementation of autoregressive spectral estimation aimed at improving the accuracy of detecting short-lasting events in signals acquired by a retinal birefringence scanning device that was reported earlier. A signal consisting of two frequency components is generated, where each frequency is a multiple of the scanning frequency. One frequency is produced during central fixation, while another one prevails during off-central fixation. These components may be of a very short duration, presenting a challenge for the FFT to identify them with sufficient time- and frequency resolution. Autoregressive spectral estimation using the Burg algorithm provided a satisfactory solution, capable of reliably differentiating between the two frequency components (96 and 192 Hz) on signal segments of duration as short as 5 ms. The device and the signal analysis methods were developed originally with the purpose of checking for eye alignment and strabismus – a major risk factor for amblyopia. The method enables the technology to work with less-cooperative patients, such as young children. Other medical and non-medical applications are possible.