Higher-order optical errors of the human eye are often responsible for reduced visual acuity in spite of an optimal spherical or cylindrical refraction. These optical aberrations are of natural origin or can result from operations on the eye involving optical structures. The presented wavefront analyzer is based on Tscherning's aberroscope. A collimated laser beam illuminates a mask with regula...

Visual imagery is the invention or recreation of a perceptual experience in the absence of retinal input.The degree to which the same neural representations are involved in both visual imagery and visual perception is unclear. Previous studies have shown that visual imagery interferes with perception (Perky effect). We report here psychophysical data showing a direct facilitatory effect of visu...

We present a new form of contrast masking in which the target is a patch of low spatial frequency grating (0.46 c/deg) and the mask is a dark thin ring that surrounds the centre of the target patch. In matching and detection experiments we found little or no effect for binocular presentation of mask and test stimuli. But when mask and test were presented briefly (33 or 200 ms) to different eyes...

It has been known that if an image containing many random items suddenly disappears, visual persistence and iconic memory vanish within approximately 0.2 seconds, such that observers are unable to report the identities of the items not graced by attention. We show that effects of the salience of image items can remain for up to more than a second longer, influencing both eye movements and expli...

Continuous flash suppression (CFS) is a powerful interocular suppression technique, which is often described as an effective means to reliably suppress stimuli from visual awareness. Suppression through CFS has been assumed to depend upon a reduction in (retinotopically specific) neural adaptation caused by the continual updating of the contents of the visual input to one eye. In this study, we...

Optic neuritis (ON) has detrimental effects on the transmission of neuronal signals generated at the earliest stages of visual information processing. The amount, as well as the speed of transmitted visual signals is impaired. Measurements of visual evoked potentials (VEP) are often implemented in clinical routine. However, the specificity of VEPs is limited because multiple cortical areas are ...

A modification of iris recognition algorithm using Hermite transform to find iris key points has been developed. The iris image mask for the areas free of eyelids, eyelashes and glares is constructed. The key points are found inside the masked iris region. The use of eye rotation compensation based on Polar Hermite Transform before iris parameterization makes the method more effective. The prop...

The retina has one of the highest oxygen consumptions of any tissue in the body [1] and this is mainly due to the photoreceptors and the rods in particular [2]. The rod consumption of oxygen is at its greatest when the retina is dark-adapted [3] and the rods generate dark current. At such time the choroid, the main vascular supply to the photoreceptors, is at its most sluggish and so greater de...