American journal of optometry and physiological optics最新文献

This study compares the academic and personal qualifications of women and men entering the University of Houston College of Optometry (UHCO) over a 6-year period, as well as the performance of these women and men throughout 4 years of optometry school. As predicted, women, as a group, presented somewhat higher grade point averages (GPA's) upon application to optometry, whereas men presented higher scores on science, especially physics, and math sections of the Optometry College Admission Test (OCAT). Women also scored significantly higher on an inventory of positive personality traits generally associated with achievement in higher education. Despite these differences, women and men performed at essentially equivalent levels throughout optometry school, both in the classroom and in the clinic. Women were under-represented as dropouts and over-represented as summa cum laude graduates; men received more clinical performance awards. In terms of personality traits, women were more similar to their male peers and female medical students than to college women in general. Strong motivation to achieve, independence, self-confidence, interpersonal skillfulness, and a sensitivity to others--traits generally associated with leadership--typified optometry students, especially women. These findings suggest that the increasing numbers of women graduates will bring to the profession young optometrists who are well qualified, not only to practice optometry, but also to fill positions of leadership in the profession.

Detecting a target in a visually noisy back-ground depends on the ability of the observer to discriminate the target from the surrounding terrain. Visible laser irradiation at less than damage levels may act as a masking source by reducing the observer's ability to resolve differences in the visual scene. The experiment reported here specifically investigates the comparability of shuttered CW and Q-switched visible lasers to alter/degrade color discrimination. Visual evoked potentials (VEP's) were used to examine the short time course effects in monkeys of luminance-matched flashes from a 694 nm ruby Q-switched laser and 100 ms shuttered krypton CW laser (676, 568, and 531 nm lines). The test stimulus was a shifting pattern of alternating luminance-matched 510 and 550 nm green bars. With flashes equated to 4.8 log T-s, similar flash effect curves were seen, demonstrating 1.5-s changes in response magnitude. This level of flash did not extinguish the response to the stimulus. The flash effects curve was "W"-shaped, with an intermediate signal peak occurring at approximately 500 ms after the flash and whose level exceeded the baseline magnitude. The hypothesized mechanism for this result is an induced luminance imbalance caused by a transient shift in the peak color responsiveness of the visual system, which recovers with two different time constants. It is concluded that red and green colored laser flashes shift the color balance transiently in the visual system (yellow flashes to a lesser extent); thus, targets may change both hue and brightness after an observer receives colored flashes.(ABSTRACT TRUNCATED AT 250 WORDS)

Real-time holographic interferometry was used to evaluate the elasticity of the posterior scleral hemisphere of fresh and preserved enucleated bovine eyes. Absolute amplitude values of radial distension were determined for specific locations across the sclera as the tissue was subjected to minute increases in intraocular pressure (IOP). Results indicate that different locations on the globe possess different coefficients of elasticity. Specifically, the supralateral aspect of the posterior globe distended relatively more than the inframedial and medial portions of the globe. Elastic moduli were derived by an areal method in which strain was measured as a change in surface area of the globe, and stress was measured as a change in IOP. Coefficients of elasticity in the range of 3.9 to 9.0 megapascals (MPa) were determined for locations across the posterior scleral hemisphere of the fresh eye used in this study.

One of the main factors determining the comfort of a rigid contact lens is the shape of the edge. The comfort of four different contact lens edge shapes was assessed with four unadapted subjects in a randomized masked trial. Lenses with well rounded anterior edge profiles were found to be significantly more comfortable than lenses with square anterior edges. There was no significant difference in subjective comfort between a rounded and square posterior edge profile. The results suggest that the interaction of the edge with the eyelid is more important in determining comfort than edge effects on the cornea, when lenses are fitted according to a corneal alignment philosophy.

We analyzed the tear pH of a random sample of 100 subjects, divided into 3 groups according to the stability of their precorneal tear film (normal eyes, borderline; and dry eyes). The average pH value obtained was 7.52. The pH for borderline and dry eyes was higher than for normal eyes. The purpose of this study was to determine the influence of air pollution, specifically sulfur dioxide (SO2), on the tear pH. We found that air pollution affected the lacrimal pH, which decreased when the atmospheric SO2 increased. Finally, we studied the effect of soft contact lens wear on tear pH after 7 days of contact lens adaptation by assessing the tear pH decrease. We took into account the influence of the sex and age of subjects on the results obtained.

When stereoacuity was measured, some subjects (but not all) saw the two vertical rods of the test to be tilted. The perceived tilt indicated that the top of a rod was nearer to or farther from the observer than the bottom. Sometimes one rod appeared tilted and sometimes both. It was rare for both to appear tilted in the same direction. There are 9 possible tilt combinations including both rods vertical. All were observed but only 1 of the 3 subjects observed them all. In some instances, the frequency with which a particular tilt combination was seen was influenced by which rod was nearer and by the binocular disparity presented by the rods. During a stereoacuity test, tilt can confuse the identification of the nearer rod. Uncertainty is avoided by regarding the middle of the rods. Lines drawn on paper were also seen to tilt by some subjects.

Matrix methods have been used to examine the paraxial performance of homogeneous systems. This method has been extended to include the presence of gradient lens elements in the optical array. To accomplish this, an inhomogeneous rotation-translation matrix is developed to describe the path of a ray through the lens elements with quadratic radial index gradients. The system matrix elements are then used to predict the paraxial properties of the array. Three examples are examined: the Wood lens, two thin lenses coupled to a radial gradient index rod, and a model of the human eye which contains a radial gradient index crystalline lens.