Abstract
Abstract: :
Purpose: Double–pass measurements permit to directly obtain actual retinal images including higher order aberrations and intraocular scattering and provide quite useful information on the optical quality of the eye. We have derived a qualitative and quantitative classification system based on patterns seen on color–coded retinal images. Methods:We evaluated the retinal images of 461 eyes in 243 normal non operated subjects obtained using a double–pass instrument (OQAS, Visiometrics S.L). Measurements were performed for 2, 4, 5 and 6 mm pupil diameter. The mean subject age was 23.7± 6.8 (range 18 to 52 years). Mean spherical refraction was –1.33±2.23 diopters (range 5.6 to –10 diopters). Best Spectacle Visual Acuity (BSVA) was 20/20 in all of them. Qualitative classification of double–pass images into groups was performed by two masked ophthalmologist and two masked optometrist. Images were classified attending their shape, size and level of scattered light. Different quantitative parameters were analyzed in order to obtaining a quantitative classification of the double–pass images in agreement with the same groups as the qualitative classification. Results:Double–pass images can be classified in round, elliptic, asymmetric and irregular according their shape; in small, medium and big according to their size and with scattering or without scattering according to the presence of scattered light. The classification differences were not statistically significant for different groups considered for spherical refraction. For high values of pupil diameter, retinal images are in general bigger and therefore the classification according to size changes. The level of scattered light increases with age and therefore the classification according to scattered light also changes. In all the cases we obtained a good agreement between qualitative and quantitative classifications. Conclusions:A method to classify retinal images obtained with double–pass measurements has been developed. Classification of normal retinal images is an important step in the process of characterizing the optical quality of vision both in normal and postoperative eyes
Keywords: optical properties • image processing