Foveal

About: Foveal is a research topic. Over the lifetime, 2652 publications have been published within this topic receiving 94120 citations.

Determination of foveal location using scanning laser polarimetry.

Abstract: The fovea is the retinal location responsible for our most acute vision. There are several methods used to localize the fovea, but the fovea is not always easily identifiable. Landmarks used to determine the foveal location are variable in normal subjects and localization becomes even more difficult in instances of retinal disease. In normal subjects, the photoreceptor axons that make up the Henle fiber layer are cylindrical and the radial orientation of these fibers is centered on the fovea. The Henle fiber layer exhibits form birefringence, which predictably changes polarized light in scanning laser polarimetry imaging. In this study 3 graders were able to repeatably identify the fovea in 35 normal subjects using near infrared image types with differing polarization content. There was little intra-grader, inter-grader, and inter-image variability in the graded foveal position for 5 of the 6 image types examined, with accuracy sufficient for clinical purposes. This study demonstrates that scanning laser polarimetry imaging can localize the fovea by using structural properties inherent in the central macula.

Eye Movements in Reading: Eye Guidance and Integration

Abstract: Eye guidance in reading and control of fixation durations are discussed and relevant data reviewed. It is concluded that the location of fixations in reading is determined in a nonrandom manner and that fixation durations are affected by cognitive activities occurring during the fixation. Recent experiments on the integration of information across successive saccades are described. These experiments suggest that I) eye movements per se are not necessary for integration since similar patterns of results were obtained when subjects made eye movements and when the saccade was simulated; 2) attentional allocation is tied to the direction of an eye movement; and 2) purely visual information obtained from parafoveal vision is not overlapped with visual information in foveal vision after the saccade. On the basis of the data and experiments reviewed, a tentative processmonitoring view of eye movements in reading is proposed. Saccadic eye movements during reading generally extend about 8 character spaces (or 2 deg of visual angle), while the mean duration of the fixational pauses separating each saccade is 200–250 msec. However, there is a great deal of variability in both these eye movement characteristics so that the range of saccades is often 1 to 20 character spaces and the mean fixation duration is from 100 to over 500 msec (Rayner & McConkie, 1976). Recently, there have been a large number of studies utilizing eye movement data as dependent variables in attempts to understand the reading process (see Rayner, 1978a, for a review.)

Target size and luminance in apparent brightness of the peripheral visual field.

Abstract: Four target sizes between 15 and 120 min. of arc with six luminance levels covering the range between 398.1 and 1.26 cd/m2 in steps of .5 log units were presented to 0, 20, 40, 60, and 80 degrees nasal retinal loci. In both peripheral and foveal viewing, magnitude estimates to apparent brightness judged by 12 Ss changed as a function of target size and luminance. The exponent of the power function was not dependent on retinal loci but on target size. However, when target size increased, the apparent brightness was slightly greater with peripheral viewing than with foveal viewing.