American journal of optometry and physiological optics最新文献

The vision decrement associated with deposit accumulation on hydroxyethyl methacrylate (HEMA) contact lenses was assessed in 51 patients presenting consecutively to a large clinic. Both high contrast visual acuity (HCA) and low contrast visual acuity (LCA) (logMAR) decreased with increased deposition (Rudko classification). Apart from being consistently lower than HCA, LCA offered no additional useful information. Both HCA and LCA worsened with lens age, whilst lens deposition increased with lens age (p less than 0.001). No associations between any of the above measures and patient symptoms were revealed. In general, unacceptable vision decrement and deposit formation occurred after 12 months or 4,000 h of daily lens wear. Clinicians can use the data presented in this paper to reconcile vision loss with deposit formation in patients wearing HEMA lenses.

The directional sensitivity (DS) of the red (pi 5), green (pi 4), and blue (pi 1) color mechanisms was measured for both the horizontal and vertical pupil meridians, thus localizing the peak of each pi-mechanism DS function within the two-dimensional pupillary aperture. In the horizontal meridian, there were greater differences among observers in DS function peak locations than there were for any one observer. Along the vertical meridian, peak location differences within observers were similar to those found in the horizontal meridian, whereas among-observer differences were much smaller. Significant differences between horizontal and vertical DS function halfwidths were also found for at least one pi-mechanism of each observer. It is concluded that meridional variations exist in either the morphology or orientational distribution of foveal photoreceptors, and that more than one alignment mechanism is responsible for photoreceptor orientation in the human fovea.

Pre- and post-task measures of dark-focus (DF) were used to assess accommodative adaptation induced by a 45-s near-vision task at 33 cm. Adaptation was measured under monocular and binocular conditions for a group of 10 young emmetropic subjects (mean age 21.6 years). The accommodative response was measured objectively using an infrared optometer (Canon Autoref R-1). Post-task DF was sampled immediately after the task at 1-s intervals over a 90-s period. No significant difference in accommodative adaptation was observed between the monocular and binocular near-vision tasks. The implications of this finding are discussed with regard to the oculomotor constituents of the closed-loop accommodative response.

Phakometry is a technique for measurement of the crystalline lens radii of curvature, usually involving photography of the Purkinje images. We have devised a system of comparison phakometry using commercially available camera equipment. This paper contains a description of the apparatus, technique, and necessary calculations. Reliability of the method is discussed.

Gas permeable (GP) lenses can flex on some eyes producing unpredictable clinical results. A method of measuring the flexibility of hard GP materials has been developed and shown to be repeatable. Materials in the form of flats rather than lenses were used. Differences between materials were found and in general a linear relation was shown to exist between maximum flexing and quoted oxygen permeability (r = 0.78, p less than 0.05). It is recommended that flexibility be measured and reported in the data presented with all new GP polymers. The term "hard" rather than "rigid" in describing GP lenses is suggested.

This paper describes three sisters, triplets, age 7 years, 2 months, two of whom derive from a single ovum, the third from a second ovum. As such, they provide an opportunity to examine the relative impact of heredity on certain of their physical, developed, and acquired abilities and characteristics. In addition to a comparison of such physical traits as height, weight, refractive status, axial length, and so on, certain (developed) sensory-motor and (acquired) cognitive and language measures are reported, such as binocular status, visual and auditory analysis skills, intelligence quotient, and (expressive and receptive) language abilities. Because all three children have lived in (more or less) the same pre- and post-natal environment, we assume that whatever concordance the monozygotic (MZ) pair displays that is not shared by their dizygotic (DZ) sister is attributable to heredity. (It does not necessarily follow, however, that any discordance between the two MZ sisters or any concordance between one of them and their DZ sister is attributable to environment.

We report a meta-analysis of studies of the relation of vision anomalies to reading skill. Meta-analysis is a quantitative technique for combining the results of multiple studies that reduces the subjectivity of literature reviews. The results of the analysis of 34 studies of vision anomalies and reading skill that met the criteria for inclusion in the meta-analysis showed that hyperopia, exophoria at near, vertical phoria, anisometropia, and aniseikonia are associated with below average reading performance. Myopia and esophoria and esophoria at far are associated with average and above average reading performance. Reduced visual acuity, astigmatism, esophoria at near, fusional convergence and divergence, strabismus, nearpoint of convergence, and stereopsis were not found to be associated with reading performance.

The binocular depth of focus of monovision wearers was compared to the sum of the two monocularly determined depths of focus. Observers fell into three groups based upon ocular sighting dominance. Complete binocular summation of the monocular depths of focus was observed in subjects without a preferred fixating eye. Subjects who preferred to fixate with one eye had difficulty suppressing blur of that eye while the binocular target was within the depth of focus of the nonpreferred eye. A third group showed partial summation of the two monocular depths of focus. Similar patterns of accommodative response, measured objectively with the SRI optometer, were observed in subjects wearing monovision corrections. Accommodative response to sinusoidal variations in blur was controlled primarily by the dominant sighting eye. These results demonstrate the effectiveness of interocular suppression of anisometropic blur in monovision correction and the influence of ocular dominance upon this suppression process.