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PubMed1983

Analysis of tonic and accommodative vergence disorders of binocular vision.

Tonic and accommodative vergence disorders of binocular vision are analyzed with separate methods. The center of symmetry and the associated phoria of forced duction fixation disparity curves are two criteria used for prismatic correction of tonic vergence disorders. The associated phoria is corrected physiologically when patients who have tonic disorders are able to develop prism adaptation with orthoptic exercises. Graphical methods are used to analyze accommodative disorders resulting from mutual interactions between accommodation and convergence. Graphic analysis illustrates that patients with high AC/A ratios have greater demands upon fusional divergence than other patients with similar ocular deviations who have normal or low AC/A ratios. Prism adaptation, which has no direct influence upon the open-loop accommodative response, replaces corrective fusional vergence innervation and thereby eliminates the main stimulus to convergence accommodation and its exaggeration of accommodative convergence. Because prism adaptation has a response time of 15 to 30 sec, abnormal accommodative convergence interactions exaggerated by convergence accommodation can be transient in patients with normal prism adaptation. Accommodative convergence disorders in patients who lack prism adaptation are classified as sustained. Orthoptic exercises which develop fast fusional vergence are recommended for the transient disorders and additional exercises to develop prism adaptation are recommended for the sustained disorders of accommodative vergence interactions.

Accommodation, Ocular↗
PubMed1984

Horopter shifts due to a magnification change.

Both the equidirection ( nonius ) and the equidistance horopter criteria were used on a group of subjects with and without the application of a 5% overall magnifier before the right eye. For three of six subjects, shifts in the equidirection horopter induced by this afocal lens could not be predicted on the basis of the magnification properties of the lens and the assumption that corresponding points are fixed. Equidistance horopter plots showed reasonably systematic reductions in slope between the predicted and the measured values for all subjects. Irregularities in all data were accounted for by shifts in the vergence angles during the experiment.

Aniseikonia↗
PubMed1984

Clinical trial with commercial aspheric aphakic lenses.

A clinical trial with 11 subjects was conducted to compare the Armorlite Multiple Drop, the Signet Hyperaspheric, the Sola Hi-Drop, and the American Optical Fulvue types of aspheric aphakic lenses. Reasonable off-axis visual acuities were obtained with the Signet, Sola, and Fulvue types, but poor visual acuities were found with the Armorlite type. Similar visual field limits were found with the armorlite, Signet, and Sola types. Considerably larger limits were found with the Fulvue type than with the other types. However, subjects failed to appreciate these larger limits; this was attributed to the extremely poor image quality near the edge of the visual field with this lens type. Some subjects disliked the poor off-axis image quality with the Armorlite lens type, and it had poor acceptance relative to the other types. Concerning subjective perception of weight, cosmetic appearance, and visual field size, and subjective evaluation of performance of everyday activities, there were no significant differences between lens types. It was concluded that reducing lens off-axis power errors, corresponding to the rotating eye, should remain the most important principle of aphakic spectacle lens design.

Aged↗
PubMed1991

Effect of chromatic aberration on isoluminance stereothreshold.

The results of a previous experiment have shown that stereothreshold varies as a function of the luminance difference between a target and its background. When the luminance of the target is the same as that of the background (isoluminance) the stereothreshold was elevated by a factor of 3 as compared with a situation where there was maximum luminance difference between the target and the background. Generally, if the target and the background have the same color, stereothreshold at a particular luminance difference level was lower (stereoacuity better) than if the target and the background have different colors. This indicates a possible effect of chromatic aberration on stereothreshold which could be responsible for the 3-fold increase in threshold at isoluminance. This possibility has been investigated in this experiment. The results show that even though stereothresholds are sensitive to chromatic aberration this factor cannot explain the elevated stereothreshold at isoluminance.

Color Perception↗
PubMed1991

Wavefront aberration of the eye: a review.

The concept of monochromatic wavefront aberration is discussed in relation to ray aberration, and methods for its measurement in the case of the eye are described. Examples are given of the measured aberration in individual eyes: in general the aberration falls within the Rayleigh quarter-wavelength criterion for pupil diameters less than 2 to 3 mm but significantly degrades image quality for larger pupils. The use of wavefront data to explore both the modulation and phase transfer functions of the eye as a function of pupil diameter and focus is described, together with typical results. Potential applications to clinical problems such as the effects of contact lenses, intraocular implants, refractive surgery, and pathology on the optical quality of the eye are outlined.

Eye↗
PubMed1992

Chromatic aberration and optical power of a diffractive bifocal contact lens.

Although diffractive contact lenses have been well documented in theory, no definitive experimental data have been reported which confirm that the near image is in fact created by diffraction rather than by refraction. We have tested the diffraction hypothesis for one type of diffractive contact lens (the Hydron Echelon bifocal) experimentally by measuring its longitudinal chromatic aberration in isolation and when worn on the eye. The basis of this test is that, according to theory, diffractive lenses should have chromatic aberration which is opposite in sign to that measured for the eye. Objective measurements of chromatic aberration were made with a focimeter when the lens was in a wet cell. Subjective measurements were made with a Badal optometer when the lens was worn on the eye. Four control experiments were conducted to provide baseline measurements of the eye's chromatic aberration, against which we compared the results obtained for the diffractive contact lens. The data were also compared with conventional measurements of refractive error obtained by standard subjective techniques and by an automated infrared refractor. Our results showed that the longitudinal chromatic aberration of the diffraction image of the Echelon bifocal lens was about one-half that obtained under the four control conditions: for the naked eye, for the nondiffraction image of the Echelon lens, or for either image of a refractive bifocal contact lens (CIBA Bisoft). These results are consistent with the theoretical prediction that the negative chromatic aberration of a diffractive contact lens should partially cancel the positive chromatic aberration of the human eye.(ABSTRACT TRUNCATED AT 250 WORDS)

Color Perception↗
PubMed2005

Neuro-otologic findings in unilateral isolated narrow internal auditory meatus.

OBJECTIVE: To report neuro-otologic findings concerning the four nerves in the internal auditory meatus (IAM) in patients with isolated congenitally narrow IAM and explore the implications regarding ontogeny of the nerves in the IAM. DESIGN: Retrospective case series study. SETTING: University hospital. SUBJECTS: Five consecutive patients between 1997 and 2002 with unilateral isolated narrow IAM demonstrated by high-resolution computed tomography whose chief complaint was hearing loss (1 male and 4 females, 4 right sides and 1 left; age range 5-37 years, mean 20 years; IAM diameter at the porus: 26-33% of that on the normal side). MAIN OUTCOME MEASURES: Functional studies concerning the VIIth cranial nerve and the three branches of the VIIIth cranial nerve. RESULTS: In all ears, auditory brain stem responses were absent, the speech discrimination score was 0%, and otoacoustic emissions were absent or markedly reduced compared with those on the normal side. Caloric responses were absent in two ears, reduced in two ears, and normal in one ear. Galvanic body sway tests showed no responses in the two ears in which caloric responses were absent. Inferior vestibular nerve function was estimated as normal in all ears on the basis of vestibular evoked myogenic potential recordings. Facial nerve functions were normal in all patients. CONCLUSIONS: In isolated congenital stenosis of IAM, dysfunction of each nerve in the IAM can occur independently. In the ontogeny of the VIIIth cranial nerve, the cochlear and superior vestibular nerves tended to be involved together, whereas the cochlear and inferior vestibular nerves appeared independent of each other.

Adolescent↗
PubMed2003

Exacerbation of psychosis by misinterpretation of physical symptoms.

Impaired processing of perceptual information is often a prominent aspect of psychotic disorders. Physical symptoms such as pain or discomfort may be either incorrectly perceived or misinterpreted by psychotic patients. Presented here is a series of cases in which somatic symptoms occurred in psychotic patients and worsened their psychotic states but only later were recognized as physical problems. Psychotic patients may be unable to comprehend or describe their physical symptoms adequately. Physical disorders of psychotic patients may be overlooked if clinicians are not vigilant and thorough in assessing the patients' complaints, especially if such complaints sound delusional or bizarre.

Adult↗
PubMed2003

Projecting sensations to external objects: evidence from skin conductance response.

Subjects perceived touch sensations as arising from a table (or a rubber hand) when both the table (or the rubber hand) and their own real hand were repeatedly tapped and stroked in synchrony with the real hand hidden from view. If the table or rubber hand was then 'injured', subjects displayed a strong skin conductance response (SCR) even though nothing was done to the real hand. Sensations could even be projected to anatomically impossible locations. The illusion was much less vivid, as indicated by subjective reports and SCR, if the real hand was simultaneously visible during stroking, or if the real hand was hidden but touched asynchronously. The fact that the illusion could be significantly diminished when the real hand was simultaneously visible suggests that the illusion and associated SCRs were due to perceptual assimilation of the table (or rubber hand) into one's body image rather than associative conditioning. These experiments demonstrate the malleability of body image and the brain's remarkable capacity for detecting statistical correlations in the sensory input.

Galvanic Skin Response↗
PubMed1982

Neuropsychological studies of object recognition.

It is well established that disorders of visual perception are associated with lesions in the right hemisphere. Performances on tasks as disparate as the identification of objects from unusual views of objects drawn so as to overlap, of fragmented letters, of familiar faces, and of anomalous features in drawings, have been shown to be impaired in patients with focal right posterior lesions. A series of investigations are reviewed, directed towards analysing the basis of these deficits. Explanations in terms of primary visual impairment can be rejected, as can an account in terms of faulty figure-ground organization. It is argued that a wide variety of such perceptual deficits--all of which are concerned with meaningful visual stimuli--can be encompassed by the notion of faulty perceptual categorization at an early post-sensory stage of object recognition. Moreover, there is evidence suggesting that some of these various perceptual deficits can be mutually dissociated. The concept of perceptual categorization is discussed in the wider context of tentative model of object recognition.

Brain Damage, Chronic↗
PubMedDate not supplied

Patterns of interference in sequence learning and prism adaptation inconsistent with the consolidation hypothesis.

The studies reported here used an interference paradigm to determine whether a long-term consolidation process (i.e., one lasting from several hours to days) occurs in the learning of two implicit motor skills, learning of a movement sequence and learning of a visuo-motor mapping. Subjects learned one skill and were tested on that skill 48 h later. Between the learning session and test session, some subjects trained on a second skill. The amount of time between the learning of the two skills varied for different subjects. In both the learning of a movement sequence and the learning of a visuo-motor mapping, we found that remote memories were susceptible to interference, but the passage of time did not afford protection from interference. These results are inconsistent with the long-term consolidation of these motor skills. A possible difference between these tasks and those that do show long-term consolidation is that the present tasks are not dynamic motor skills.

Adaptation, Physiological↗
PubMedDate not supplied

Meta-analysis of theory-of-mind development: the truth about false belief.

Research on theory of mind increasingly encompasses apparently contradictory findings. In particular, in initial studies, older preschoolers consistently passed false-belief tasks-a so-called "definitive" test of mental-state understanding-whereas younger children systematically erred. More recent studies, however, have found evidence of false-belief understanding in 3-year-olds or have demonstrated conditions that improve children's performance. A meta-analysis was conducted (N = 178 separate studies) to address the empirical inconsistencies and theoretical controversies. When organized into a systematic set of factors that vary across studies, false-belief results cluster systematically with the exception of only a few outliers. A combined model that included age, country of origin, and four task factors (e.g., whether the task objects were transformed in order to deceive the protagonist or not) yielded a multiple R of .74 and an R2 of .55; thus, the model accounts for 55% of the variance in false-belief performance. Moreover, false-belief performance showed a consistent developmental pattern, even across various countries and various task manipulations: preschoolers went from below-chance performance to above-chance performance. The findings are inconsistent with early competence proposals that claim that developmental changes are due to tasks artifacts, and thus disappear in simpler, revised false-belief tasks; and are, instead, consistent with theoretical accounts that propose that understanding of belief, and, relatedly, understanding of mind, exhibit genuine conceptual change in the preschool years.

Child↗