title: Quality evaluation of digital fundus images through combined measures.
abstract: The evaluation of image quality is an important step before an automatic analysis of retinal images. Several conditions can impair the acquisition of a good image, and minimum image quality requirements should be present to ensure that an automatic or semiautomatic system provides an accurate diagnosis. A method to classify fundus images as low or good quality is presented. The method starts with the detection of regions of uneven illumination and evaluates if the segmented noise masks affect a clinically relevant area (around the macula). Afterwards, focus is evaluated through a fuzzy classifier. An input vector is created extracting three focus features. The system was validated in a large dataset (1454 fundus images), obtained from an online database and an eye clinic and compared with the ratings of three observers. The system performance was close to optimal with an area under the receiver operating characteristic curve of 0.9943.
authors.affiliation: University of Minho , Centro Algoritmi, Azurém, Guimarães 4800-025, Portugal ; ENERMETER , Parque Industrial de Celeirós 2ª Fase, Lugar de Gaião, Lotes 5/6, Braga 4705-025, Portugal.
authors.forename: Diana
authors.initials: D
authors.lastname: Veiga
authors.affiliation: ENERMETER , Parque Industrial de Celeirós 2ª Fase, Lugar de Gaião, Lotes 5/6, Braga 4705-025, Portugal.
authors.forename: Carla
authors.initials: C
authors.lastname: Pereira
authors.affiliation: University of Minho , Centro Algoritmi, Azurém, Guimarães 4800-025, Portugal ; ENERMETER , Parque Industrial de Celeirós 2ª Fase, Lugar de Gaião, Lotes 5/6, Braga 4705-025, Portugal.
authors.forename: Manuel
authors.initials: M
authors.lastname: Ferreira
authors.affiliation: Oftalmocenter , Rua Francisco Ribeiro de Castro, n° 205, Azurém, Guimarães 4800-045, Portugal.
authors.forename: Luís
authors.initials: L
authors.lastname: Gonçalves
authors.affiliation: University of Minho , Centro Algoritmi, Azurém, Guimarães 4800-025, Portugal.
authors.forename: João
authors.initials: J
authors.lastname: Monteiro
keywords: digital fundus photography; focus measures; fuzzy classifier; image processing; image quality