American journal of optometry and physiological optics最新文献

Twenty-three patients suffering from the progressive cone dystrophies (PCD) were evaluated retrospectively, after they had undergone treatment for low vision. All patients were able to read 1 M or smaller print with magnification, despite poor central acuity. Eighteen (78%) patients achieved their primary rehabilitation goal, and 86% of the low vision devices prescribed were used at follow-up. Photosensitivity was reported by a large number of patients. Seven patients indicated that alleviating this problem was their primary rehabilitation goal. Eight (35%) found sun filters to be helpful. Our successful experience with patients with these disorders suggests that examination for, and trial of, low vision devices is warranted.

We investigated the effects of the ophthalmic preservatives thimerosal and sorbic acid on the proliferation and survival of rabbit corneal epithelial cells in tissue culture. Normally, explants of corneal epithelium grow vigorously during the first 7 days in culture. With 0.004% thimerosal present in the culture medium, the normal proliferation of corneal cells is suppressed completely. When 0.1% sorbic acid is present, proliferation is delayed and the lifespan of the corneal cells is reduced. After a 1-h exposure to concentrations of thimerosal of 0.0005% or greater, virtually all corneal cells present in established cultures are killed. These results suggest that use of ophthalmic preparations containing these chemicals may affect the metabolic and proliferative capacity of the corneal epithelium adversely.

Sphero-cylinders and refractive errors can be represented by matrices. Matrix algebra provides methods whereby sphero-cylinders can be added, subtracted, multiplied, inverted, and raised to powers and can have roots extracted. These operations are defined for sphero-cylinders and examples are given. In terms of these operations a number of means of refractive errors are defined: the arithmetic, harmonic, and quadratic means. Furthermore it is possible to define a variance and standard deviation for refractive errors. These quantities should provide a basis for a formal approach to the statistical analysis of populations of refractive errors.

The distance heterophoria was measured using both the von Graefe and Maddox rod clinic procedures under standard reduced illumination conditions and in total darkness. Tonic vergence was measured in total darkness. The phoria measures were more divergent than tonic vergence, with the von Graefe being the more divergent of the two measures. The difference between the phoria and tonic vergence position is believed to be due to accommodative divergence derived from the decrease of accommodation, relative to the tonic level, required to focus the distance phoria target. Equations were derived to predict tonic vergence from the phoria value.

This paper reviews psychophysical evidence that the visual performance and, by inference, the underlying neural losses of strabismic and anisometropic amblyopes are fundamentally different. The data of amblyopes are considered in the light of recent models for normal spatial vision. It is argued that the spatial deficits which are found in anisometropic amblyopes can be understood largely in terms of reduced resolution and contrast sensitivity, as would be expected on the basis of early experience with a defocused image in one eye. In contrast, the spatial deficits found in strabismic amblyopes are more profound than can be predicted on the basis of either resolution, or contrast sensitivity, and may have their basis in a coarse cortical spatial sampling grain.

Health care is undergoing significant changes and one effect in the optometric profession has been the establishment of comanagement centers. These centers provide specialty optometric and ophthalmologic services to community optometrists on a referral basis. The centers are having an impact on traditional optometric/ophthalmologic referral patterns. This study surveyed all optometrists practicing near a comanagement center in order to determine the extent of participation, the factors affecting participation, and to design a predictive model for participation. The model identified three practice variables and five provider variables as being important in predicting participation in center activities.

Imaging of human brain structure and activity with particular reference to visual function is reviewed along with methods of obtaining the data including computed tomographic (CT) scan, magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), and positron emission tomography (PET). The literature is reviewed and the potential for a new understanding of brain visual function is discussed. PET is reviewed from basic physical principles to the most recent visual brain findings with oxygen-15. It is shown that there is a potential for submillimeter localization of visual functions with sequentially different visual stimuli designed for the temporal separation of the responses. Single photon emission computed tomography (SPECT), a less expensive substitute for PET, is also discussed. MRS is covered from basic physical principles to the current state of the art of in vivo biochemical analysis. Future possible clinical applications are discussed. Improved understanding of the functional neural organization of vision and brain will open a window to maps and circuits of human brain function.

To evaluate the observer's ability to self-monitor and correct accommodation voluntarily, a slit aperture, incorporating the Scheiner principle, was used as an accommodative stimulus. The Scheiner image consisted of two horizontal lines, which were perceived as superimposed into a single line when the observer's accommodation was conjugate with the optical distance of the target. The observer's task was to maintain superimposition of the monocularly viewed lines. During the task, accommodation was assessed with a Badal optometer that incorporated gratings of several spatial frequencies. By varying the optical distance of these gratings it was possible to determine the location of minimum blur, and thus the accommodation response. Results from two observers indicated that a Scheiner image can be used effectively for voluntary adjustments in accommodation for several optical distances.