Representatividad del DMI La Cristalina-La Mesa en el SIDAP

population of young adult eyes. J Opt Soc Am A Opt Image Sci Vis. 1995 Oct;12(10):2348-57. PMID: 7500216 [PubMed - indexed for MEDLINE] Subjective transverse chromatic aberration (sTCA) manifest at the fovea was

determined for a population of 85 young adults (19-38 years old) by means of a two- dimensional, two-color, vernier alignment technique. The statistical distribution of sTCA was well fitted by a bivariate Gaussian function with mean values that were not

significantly different from zero in either the horizontal or the vertical direction. We conclude from this result that a hypothetical, average eye representing the population mean of human eyes with medium-sized pupils is free of foveal sTCA. However, the absolute magnitude of sTCA for any given individual was often significantly greater than zero and ranged from 0.05 to 2.67 arcmin for the red and the blue lights of a computer monitor (mean wavelengths, 605 and 497 nm, respectively). The statistical distribution of the absolute magnitude of sTCA was well described by a Rayleigh probability

distribution with a mean of 0.8 arcmin. A simple device useful for population screening in a clinical setting was also tested and gave concordant results. Assuming that sTCA at the fovea is due to decentering of the pupil with respect to the visual axis, we infer from these results that the pupil is, on average, well centered in human eyes. The average magnitude of pupil decentration in individual eyes is less than 0.5 mm, which

corresponds to psi = 3 deg for the angle between the achromatic and the visual axes of the eye.

93. Winn B, Bradley A, Strang NC, McGraw PV, Thibos LN. Reversals of the colour-depth illusion explained by ocular chromatic aberration. Vision Res. 1995 Oct;35(19):2675-84. PMID: 7483309 [PubMed - indexed for MEDLINE] Although many colour-depth phenomena are predictable from the interocular difference in monocular chromatic diplopia caused by the eye's transverse chromatic aberration (TCA), several reports in the literature suggest that other factors may also be involved. To test the adequacy of the optical model under a variety of conditions, we have

determined experimentally the effects of background colour on perceived monocular chromatic diplopia and perceived depth (chromostereopsis). A Macintosh colour monitor was used to present red, blue, and green test stimuli which were viewed monocularly or binocularly (haploscopically) through 1.78 mm artificial pupils. These apertures were

41 displaced nasally and temporally from the visual axis under controlled conditions to induce a variable degree of TCA. Monocular chromatic diplopia and binocular

chromostereopsis were measured for red and blue targets, and also for red and green targets, presented on either a black background or on a background which was

composed of the sum of the targets' spectral composition (e.g. red and blue presented on magenta; red and green presented on yellow). In all cases, chromatic diplopia and chromostereopsis were found experimentally to reverse in sign with this change in background. Furthermore, we found that a given coloured target could be located in different depth planes within the same display when located on different background colours. These seemingly paradoxical results could nevertheless be explained by a simple model of optical TCA without the need to postulate additional factors or mechanisms.

94. Atchison DA, Bradley A, Thibos LN, Smith G. Useful variations of the Badal Optometer. Optom Vis Sci. 1995 Apr;72(4):279-84. PMID: 7609955 [PubMed - indexed for MEDLINE]

The simple Badal Optometer consists of a movable target and a fixed positive power lens placed at its focal distance away from the eye. The perceived angular size of the target is independent of target position and the power scale is linear. Limitations of the simple Badal Optometer include restriction of negative (myopic) ocular vergence range, the need for targets to be small, and the problem of "proximal" accommodation. We describe two modifications to the Badal system in which these limitations may be overcome by the use of a movable auxiliary optical system. In one modification, the movable auxiliary system consists of a target and positive lens which together may provide a virtual "target" for the Badal lens and thus increase the negative range. In the second modification, the Badal lens is positioned as it would normally be, but the target is an image of a distant stimulus created by the auxiliary lens. The target position (and hence the ocular vergence) is changed by moving the auxiliary lens. The distant target eliminates the proximal accommodative stimulus and allows spatial detail near the resolution limit to be displayed.

95. Thibos LN, Elliott DB, Bradley A. Vision and aging: introduction. Optom Vis Sci. 1994 Dec;71(12):725-6. No abstract available. PMID: 7898878 [PubMed - indexed for MEDLINE]

96. Levick WR, Thibos LN. Neurophysiology of central retinal degeneration in cat. Vis Neurosci. 1993 May-Jun;10(3):499-509. PMID: 8494801 [PubMed - indexed for MEDLINE]

Receptive fields of ganglion cells have been studied in cats possessing a chronic, arrested lesion of central retinal degeneration. Lesions were characterized by an ophthalmoscopically sharp border separating apparently normal retina from the region of the lesion. Under direct ophthalmoscopic guidance, a succession of recordings was obtained from ganglion cells having cell bodies at various positions relative to the lesion. Cells located more than 1 deg outside the ophthalmoscopic border had normal visual sensitivity as assessed by area-threshold experiments. Inside the lesion cells within 1 deg of the border had reduced sensitivity which often precluded functional classification

42 by the usual visual tests. Ganglion cells located more than 1 deg inside the border of large lesions were blind and some had abnormal patterns of maintained discharge of action potentials. Nevertheless, the antidromic latencies of these blind cells fell into the familiar conduction groups (T1/T2/T3). Receptive-field maps of cells near the border of the lesion often appeared truncated, with the missing portion of the field covered by the lesion. These observations were consistent with the abnormal form of area-threshold curves. Although the responsiveness of cells near the lesion was abnormally low for grating stimuli, cutoff spatial frequency and orientation bias of these cells were within normal limits.

97. Thibos LN, Bradley A. New methods for discriminating neural and optical