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A Remole

Publications and source records attributed to A Remole.

18 recordsLinked to original sources
PubMed1992

New developments in the application of the multimeridional apparent frontoparallel plane.

This study is a sequel to a previous publication that introduced the multimeridional apparent frontoparallel plane (MAFPP) as a method of measuring aniseikonia. As the term implies, apparent frontoparallel plane (AFPP) responses are obtained not only in the horizontal meridian, but also in oblique meridians. Since the introductory publication, the method has been applied extensively for measuring aniseikonia and has been found to be reliable, accurate, and easily adapted to clinical purposes. This study presents a more detailed and comprehensive account of the underlying theory than did the introductory report. It clarifies some problems inherent in the method originally presented and describes a simplified and improved procedure for measuring aniseikonia. It describes the application of the theory to a number of specific clinical situations. Finally, it is suggested that the method has a much broader application than the clinical measurement of aniseikonia.

Aniseikonia↗
PubMed1992

Multimeridional apparent frontoparallel plane: relation between stimulus orientation angle and compensating tilt angle.

The classical apparent frontoparallel plane (AFPP) setting is typically obtained by having the subject move a series of parallel rods farther or closer until they line up in a plane perceived to be parallel to the face plane. If there is a size difference between the two ocular images, the AFPP setting defined by the rods will exhibit a tilt from the objective frontoparallel plane, about an axis parallel to the rods. The multimeridional apparent frontoparallel plane (MAFPP) is an extension of this procedure to rod orientations other than the vertical meridian. In previous studies, it was found that oblique tilt angle settings corresponding to rod orientations of 45 degrees and 135 degrees are equal to square root 2 times the tilt angle for the vertical rod orientation for the same interocular magnification difference along the meridian perpendicular to the rods. In this study, we measured the tilt angles produced by a series of oblique rod orientations between 15 degrees and 165 degrees, inclusive. Throughout the 150 degrees range tested, the tilt angles were found to be consistently proportional to the cosecant of the rod orientation angle, the factor square root 2 previously used being a specific example of this relation. Within this range, neither empirical cues nor the induced effect cause the cosecant relation to break down. It is suggested that the MAFPP procedure can be applied more extensively than previously anticipated.

Aniseikonia↗
PubMed1990

Effect of induced dynamic aniseikonia on fixation performance during oblique gaze.

This is a sequel to other papers dealing with the effect of induced aniseikonia and optical anisophoria on fixation eccentricity during bifixation. To stimulate the effect of induced anisophoria, controlled amounts of differential prism were induced in the vertical meridian. At the same time, stimuli were presented at various angles from the subject's straight ahead orientation. As demonstrated in other studies, it was found that a vertical prismatic difference will cause the eyes to fixate slightly eccentrically in the horizontal meridian. The eccentricity was measured with the border enhancement method, described and tested in other studies. In addition, it was found that the fixation deviation is increased further by oblique gaze, the greatest obliquity having the greatest effect. It was also found that whereas short-term adaptation reduces the prism effect somewhat, it has less influence on the effect of oblique gaze. In general, the study demonstrates the potential oculomotor problems inherent in optical anisophoria.

Adaptation, Ocular↗
PubMed1990

Effect of induced static aniseikonia on fixation performance during oblique gaze.

In a previous study, it was found that oblique gaze and the prismatic effect inherent in dynamic aniseikonia combine to affect the ability to fixate centrally. In the current study, retinal image differences were introduced, whereas prismatic effects were eliminated. This simulates static aniseikonia as opposed to dynamic aniseikonia. At the same time, oblique gaze was simulated by presenting the stimuli in directions other than straight ahead. The directions of presentation contained both horizontal and vertical components. Fixation eccentricity was monitored by using the border enhancement method, as described in previous experiments. It was found that fixation eccentricity increased as the eyes were directed toward stimuli oriented in directions other than straight ahead. When vertical and horizontal components of oblique gaze were combined, the fixation eccentricity was found to be greater than with either component alone. When differential magnification between left and right retinal images was introduced, the fixation eccentricity increased further, the increment being approximately constant for all directions of gaze.

Aniseikonia↗
PubMed1989

Aniseikonia and fixation performance: effect of retinal stimulus location.

It has been shown previously that induced aniseikonia amplifies any latent fixation eccentricity associated with binocular fusion stress. This study determines if the retinal location of the stimulus plays a part in this effect. The stimulus consisted of a vertical border formed by the juxtaposition of two fields of unequal luminances and a line segment parallel to the border whose distance from the border can be varied. At the same time, the border allowed the application of a previously tested method of measuring fixation eccentricity, based on the border-enhancement response. It was found that the fixation eccentricity produced by aniseikonia is maximal for the smallest distance of the variable target from the border but unaffected by the larger distances tested. It was concluded that the retinal location of the stimulus has an important influence on the response to aniseikonia.

Aniseikonia↗
PubMed1989

Anisophoria and aniseikonia. Part I. The relation between optical anisophoria and aniseikonia.

Part I of this publication demonstrates and explains the close relation between aniseikonia and anisophoria induced by spectacles. It discusses the clinical implications of this relation by discussing certain aspects of aniseikonia theory, prismatic effects during oblique gaze through spectacles as for reading, and a simple formula that presents a comprehensive description of all prismatic effects and prismatic differences produced by a pair of spectacles. It also describes an easy method of specifying iseikonic lenses, as well as some conventional methods of measuring aniseikonia and anisophoria. Part II will deal with the correction and management of anisophoria when induced together with aniseikonia. Parts I and II, together, will convey a new approach toward the management of anisophoric spectacle corrections.

Adaptation, Ocular↗
PubMed1989

Anisophoria and aniseikonia. Part II. The management of optical anisophoria.

Part I of this publication dealt with the simultaneous occurrence of aniseikonia and optical anisophoria when anisometropic spectacles are worn. Part II deals with the correction and management of spectacle-induced anisophoria. It presents simple formulas for calculating the constants of an iseikonic correction that circumvent much of the trial and error inherent in the older methods. It shows how such iseikonic lenses rather than prisms can be used to correct a large portion of optical anisophoria and how such corrections can improve binocular visual performance. It also discusses dynamic phorometry and some new methods for measuring induced anisophoria. The essential message of Parts I and II is that the two effects, aniseikonia and optical anisophoria, should be considered together and not as separate entities.

Aniseikonia↗
PubMed1988

Effect of induced aniseikonia on fixation performance.

The purpose of the study was to determine to what extent induced aniseikonia affects fixation performance. Aniseikonia was induced in the vertical meridian only, whereas fixation alignment was monitored in the horizontal meridian. A previously developed technique based on the dependency of border enhancement bandwidth on fixation eccentricity was used to monitor deviations from central fixation during fusion. Stress on the fusion mechanism was supplied by controlled increments of forced horizontal vergence. It was found that deviation from central fixation in the horizontal meridian generally increases with increasing amounts of vertical aniseikonia. The effect is particularly pronounced for small amounts of aniseikonia.

Aniseikonia↗
PubMed1988

Variation of convergence limits with change in direction of gaze.

Until recently, convergence limits have been measured only in the primary position of gaze. A new instrument permits such measurements in all directions of gaze and at various angular distances from the primary straight-ahead position. Aberration and distortion-free stimuli based on Heine's principle were incorporated in the apparatus. For each of the nine subjects participating, convergence limits were obtained in the primary straight-ahead position, secondary, and tertiary positions and in varying degrees of obliquity of these directions of gaze. The convergence limits were measured in 10 degrees steps away from the straight-ahead position of gaze in 18 different meridians. It was found that convergence limits vary markedly with the direction of gaze, the maximal vergence range usually being found between 10 to 20 degrees below the primary horizontal plane in the lower right-half field, possibly because subjects spend most of their time looking in this direction.

Convergence, Ocular↗
PubMed1987

Effect of vertical prism imbalance on fixation performance.

It is well known that induced vertical imbalance will bring about deviation from central fixation in the vertical meridian. This study seeks to determine if vertical imbalance will affect the fixation performance in the horizontal meridian as well. For this purpose, a technique previously developed for monitoring fixation eccentricity was used. The technique, which is based on the effect of fixation eccentricity on border enhancement, is unaffected by adaptive changes in perceived visual direction. The results show a rapid increase in horizontal fixation misalignment with the first increments of vertical prism difference, followed by a slower increase for additional prism differences. When horizontal forced vergence was applied in addition, fixation misalignment increased throughout the range of vertical vergences. Similarly, vertical fusion misalignment was increased by horizontal fusion stress. It was concluded that forced vergence presented in one meridian will amplify any fusion misalignment that might exist in other meridians. This calls for a reevaluation of existing methods of assessing binocular fixation performance.

Calibration↗
PubMed1979

Contrast thresholds vs border enhancement: sensitivity to retinal defocus.

The two visual responses, contrast threshold and border enhancement, are both affected by retinal image quality. Thus, with increasing defocus of the retinal image contrast thresholds with sinusoidal line gratings increase, and the enhanced region near a border becomes wider. These two visual responses were compared to determine their suitability as gauges of retinal image quality. Border enhancement was found to be more sensitive to deterioration of the retinal image in the form of defocus than contrast thresholds throughout the greater portion of the grating frequency spectrum. However, the contrast threshold increases in sensitivity toward cutoff frequency, and beyond a certain high frequency it surpasses border enhancement in that respect. At the same time, for these optimum frequencies, the contrast range is exhausted within a relatively small defocus range. Therefore, a limitation is imposed on the usefulness of the contrast threshold as an index of retinal image quality.

Humans↗
PubMed1978

A subjective method of monitoring corneal scattering.

Border-enhancement spread is a new criterion for assessing the quality of the retinal image. In one study, it was found that the width of the enhanced region increases with the steepness of a contact lens fit, and this increase was attributed to scattering accompanying corneal edema arising from tight-fitting lenses. The present study tested this hypothesis. Corneal thickness and border-enhancement spread were measured concurrently at regular intervals during and after contact lens wear. It was found that border-enhancement spread generally follows changes in corneal thickness. Since scattering increases with corneal swelling, the findings generally support the hypothesis. However, it was also found that variables not originating in the cornea sometimes modify the retinal-image quality and thus mask the scattering effects. Future applications of the methods are discussed.

Contact Lenses↗
PubMed1977

Border enhancement as an index of contact lens performance.

In simultaneous border contrast enhancement, a border formed by an abrupt luminance discontinuity is perceptually enhanced on the bright side by a band of greater brightness and on the dark side by a band of greater darkness. The width of these perceived bands is very sensitive to small changes in the retinal image quality. This study explored the effect of contact lenses of varying steepness on the border enhancement spread. It was found that, over time, the effect of a contact lens on this spread generates a characteristic function. Furthermore, certain features of this function reflect the degree of steepness of the contact lens. It is suggested that the most important factors determining this function are tear flow and scatter-producing corneal edema.

Contact Lenses↗
PubMed1977

Effect of scattered light on extent of border enhancement.

A contrast border, formed where 2 uniform fields of differing luminance meet, was viewed through filters containing a scattering agent. The filters resembled the cornea and crystalline lens in that the amount of light scattered increased exponentially toward the direction of the indicent light. The perceptually enhanced regions on both sides of the border were measured for various concentrations of the scattering agent. Measurements were obtained for several luminances of the brighter field, the darker field remaining constant. It was found that the width of the enhanced region, both on the bright and on the dark side of the border, increased approximately linearly with the logarithm of the amount of light scattered. The increase was of approximately the same order for all of the luminances tested.

Humans↗