Wavelet based diagnostic distortion measure for the Optic disc

The analysis of diagnostic features such as the optic disc(OD) provides important clues for the diagnosis of various retinopathic diseases. In this paper, a wavelet based distortion measure for the optic disc (WODDM) in retinal image is proposed. The wavelet analysis shows that different subbands carry optic disc information to a different level. The distortion measure is defined as the sum of wavelet weighted root of the normalized mean square error between subbands. The proposed measure is evaluated against other wavelet based distortion measures such as the wavelet mean square error(WMSE), Relative WMSE(Rel WMSE) and root of the normalized WMSE(RNWMSE). The experimental results show that the WODDM emphasizes the distortion in optic disc more strongly compared to the minimum response for the distortion in other diagnostic features. The distortion measure shows a low value when evaluated for the case of distortion in clinically insignificant regions.