American journal of optometry and physiological optics最新文献

Change in fixation disparity was measured as lens sphere power was changed at distance and near on a young adult population. The results were graphed to yield a lens-induced fixation disparity curve. The lens curves found were grouped into four basic types (A through D). Two types (A and B) had increasing eso fixation disparity with increasing minus lens power. Type C had little change in fixation disparity with any change in lens power, whereas type D had an initial increase and then no further change with increasing minus power. In addition, approximately 74% of the 38-subject sample had different curve types at distance and near. Possible clinical uses of the lens-induced fixation disparity curve include the prescribing of near additions for pre-presbyopes based on measures of the binocular vergence response to various lens sphere combinations.

Two experiments examined the effect of reinforcement on infants' performance in a preferential looking acuity task. In experiment 1, performance of 3- and 5-month-old infants was assessed under three conditions. In one condition, reinforcement was contingent upon performance. In another, no reinforcement was provided. In the last condition, reinforcement was provided, but it was not contingent upon performance. Similar performance was observed in all three conditions. In experiment 2, 7-month-olds were tested in the first and second conditions. No differences in performance were observed between these two groups. Thus, the reinforcement used in preferential looking measurements does not appear to improve performance significantly for 3- to 7-month-old infants. Several interpretations of these results are presented. The most plausible is that performance under nonreinforced conditions is already nearly optimal, so the addition of reinforcement has little impact. General implications for estimates of infant visual sensitivity in the laboratory and clinic are discussed.

Among the inherent optical aberrations found in conventional crown glass or resin prisms is the property known as nonuniform relative magnification. Prisms, by definition, displace an image by a given amount. However, the final size of the image is nonuniform, being relatively larger toward the apex than toward the base of the prism. At present, reduction of the amount of nonuniform magnification is achieved by fabricating the prismatic correction on relatively steeper base curves (i.e., +9.00 D). This research deals with an attempt to reduce nonuniform magnification using Fresnel prisms. In this way, image displacement is created only by small prism apices, each of equal power and each producing identical image displacement resulting in a smaller degree of nonuniformity of image size. In this experiment, equal amounts of prism were fabricated on flat and steep base curves, using either conventional or Fresnel prism. The precise magnitude of the nonuniform relative magnification for each set of lenses was measured by a number of observers using the Apparent Fronto-Parallel Plane (AFPP) horopter apparatus. After statistical analysis using both an analysis of variance (ANOVA) and a matched pair t-test, there proved to be no significant reduction in the amount of nonuniform relative magnification when Fresnel prisms were used in place of conventional ground prisms. Furthermore, maximal reduction of this aberration appears to be effected only by fabricating such corrections on steep base curves. Relative magnification is more a function of the orientation of the base-apex meridian and the angle of incident light from an extended object than of effects of prism type or thickness.

A clinical trial was conducted to compare the extended wear performance of rigid gas-permeable (RGP) contact lenses with that of soft lenses. Subjects were fitted with a RGP lens (Boston IV) in one eye and a soft lens (Bausch & Lomb "O" series) in the other eye, and wore them on an extended wear basis for up to 3 months. No subjects developed any acute adverse reactions in the RGP lens-wearing eye. After the initial adaptation period, subject acceptance of RGP extended wear in terms of vision and comfort was superior. The RGP lenses also induced less chronic hypoxic stress than hydrogel lenses of comparable Dk/L, as evidenced by the presence of epithelial microcysts. Several complications of RGP extended wear were observed including lens binding, blepharoptosis, transient pupil size increases, and corneal staining. As hypoxia-induced corneal changes, such as microcysts and striae, were observed in the RGP lens-wearing eyes, we consider that these particular RGP lenses do not have adequate oxygen transmissibility for successful long-term extended wear. However, if RGP lens materials of higher oxygen transmissibility and better designs can be attained, the potential of RGP extended wear would appear promising.

Goldmann perimetry was done on 11 pseudophakic subjects and results were compared to those of age-matched phakic subjects and a third group of aphakic individuals who were wearing rigid gas permeable contact lenses. Testing showed that the I-3 and I-4 fields of the subjects who had had cataract surgery were generally constricted when compared to the normal phakic population. Possible explanations for this include media clarity not being as important a factor in determining field size as was previously thought, peripheral retinal changes, and implant material affecting contrast sensitivity.

Different types of progressive addition lenses were compared with each other. It was our aim to measure all parameters in such a way that they were consistent with the normal wearing situation. The distribution of the spherical power and astigmatism was measured with a special focimeter. The induced distortion, which is important for patient acceptance, was determined by a photographic method. There are significant differences between the various types of progressive addition lenses. However, objective information is not sufficient to resolve the subjective question of patient acceptance.