The study, published in the latest issue of the journal PLoS ONE, shows that the magnitude and orientation coincide with the blurring of the retinal image projected by its own optical system.

The optical system of the eye, comprising the cornea and the lens, projecting the images from the outside world on the retina. The imperfections of these lenses and misalignment between them produce a retinal image degradation. For example, when looking at a point on the retina is formed actually a degraded image, a spot usually smudged with asymmetries. The degree of visual blurring varies for each person and the concept of what is too blurry, too sharp, or a neutral image depends on the visual experience of each.

"The study shows that are considered less smudged those images degraded by imperfections similar to those present in the eyes, even if the amount of blurring is similar," says Susana Marcos, CSIC researcher at the Institute of Optics.

"We hate to see through other eyes"

To determine the pattern of blurring that each person considered optimal, the research team, which also included scientists from Schepens Eye Research Institute at Harvard University, has used a psychophysical method based on an image classification system.
Scientists asked a group of people to evaluate the quality of hundreds of images with the same magnitude of optical blurring (an automatic detection of the considered image quality like), but with varying orientations of blurring, which corresponded to the measurements over 100 different eyes. To ensure that the images projected on the retina were the same in all cases, eliminated the imperfections eye of each person with an adaptive optics system.

"So only able to evaluate the neural perception. Although all images were optically equivalent participants chose those that were blotted with imperfections similar to those of their eyes, and the others discarded. The reality is that we do not like to see through different eyes, "says the researcher at the Institute of Optics Lucie Sawides, first author of the study.

The results show, for the first time the internal visual code blurring of each person, but also have clinical implications, since different ocular pathologies or corrections can change the orientation of blurring using lenses or surgery.

Sawides Lucie, Carlos Dorronsoro, Andrew M. Haun, Eli Peli and Susana Marcos. Using Pattern Classification to Measure Adaptation to the Orientation of High Order Aberrations. PLoS ONE. http://dx.plos.org/10.1371/journal.pone.0070856