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Biomedical subjects

C R Weir

Publications and source records attributed to C R Weir.

14 recordsLinked to original sources
PubMed2001

Spatial localization after different types of retinal detachment surgery.

PURPOSE: To compare the effect on spatial localization of two different forms of surgery for primary rhegmatogenous retinal detachment. METHODS: Two groups of 30 patients (one group undergoing conventional external scleral-buckling procedures, the other undergoing vitrectomy procedures) were recruited. They pointed at targets appearing on a computer touchscreen without being able to see their hands, while viewing targets with the non-surgically treated eye. The sizes of the horizontal pointing errors were recorded on three separate occasions: before surgery, on the first postoperative day, and approximately 10 days later. RESULTS: On the first postoperative day a significant change in localization of 2.9 +/- 0.9 degrees [SD]) was observed in the scleral-buckling group, compared with 1.3 +/- 0.6 degrees in the vitrectomy group. These changes resolved by the second postoperative assessment. CONCLUSIONS: These results, particularly in patients in the scleral-buckling group in whom greater manipulation of the extraocular muscles inevitably occurs, are consistent with an alteration in the extraretinal eye position information that is used in spatial localization. This is likely to be a consequence of modified efference copy and/or extraocular muscle proprioception.

Adult↗
PubMed2001

Modification of smooth pursuit initiation by a nonvisual, afferent feedback signal.

PURPOSE: To investigate the role of extraocular muscle afferent signals in the initiation and early maintenance of smooth-pursuit eye movements. METHODS: A suction scleral contact lens was used to impede the movements of the right eye while subjects tracked small targets in a step-ramp pursuit paradigm. Movements of the left eye were measured by infrared oculography. Pursuit latency, eye acceleration, and velocity were analyzed trial-by-trial and compared before, while, and after the right eye was impeded. RESULTS: When the right eye was impeded, initial acceleration and eye velocity were reduced. Pursuit latency was unchanged. The velocity effect had a rapid onset and offset; there was no evidence that the effects built up over a number of trials. Detailed analysis suggested that the reduction in velocity occurred approximately 40 msec after pursuit was initiated. CONCLUSIONS: These results are consistent with the hypothesis that extraocular muscle afferent signals provide a feedback signal of the movements of the eyes that may be used to modify the initiation and early maintenance of smooth pursuit on-line. It appears that for pursuit, as with saccades, the priority in these conditions is to maintain conjugacy.

Adult↗
PubMed2001

Developing a taxonomy for research in adverse drug events: potholes and signposts.

Computerized decision support and order entry shows great promise for reducing adverse drug events (ADEs). The evaluation of these solutions depends on a framework of definitions and classifications that is clear and practical. Unfortunately the literature does not always provide a clear path to defining and classifying adverse drug events. While not a systematic review, this paper uses examples from the literature to illustrate problems that investigators will confront as they develop a conceptual framework for their research. It also proposes a targeted taxonomy that can facilitate a clear and consistent approach to the research of ADEs and aid in the comparison to results of past and future studies. The taxonomy addresses the definition of ADE, types, seriousness, error, and causality.

Classification↗
PubMed2000

Spatial localisation: does extraocular muscle proprioception play a role?

Our ability to determine the position of targets in surrounding visual space (spatial localisation) is an important aspect of visual function and requires the integration of both visual (ie retinal) and non-visual (ie extraretinal) information. Afferent signals derived from extraocular muscle proprioceptors are though to contribute to this extraretinal information. However, this has proved to be a contentious issue. This article considers the role of extraocular muscle proprioception in spatial localisation in greater detail by discussing the evidence supporting this viewpoint. This is obtained from two main sources: firstly observations in patients in whom the proprioceptive input has been disrupted either pathologically or surgically, and secondly experimental studies in normal subjects in whom the proprioceptive input has been manipulated. The review concludes by emphasising that whilst proprioception is not the predominant source of extraretinal information that helps us determine visual direction, it is still likely to be a contributory factor.

Animals↗
PubMed2000

Modification of visually guided saccades by a nonvisual afferent feedback signal.

PURPOSE: To investigate the role of extraocular muscle afferent signals in the control of saccadic eye movements. METHODS: A suction scleral contact lens was used to impede the movements of the right eye while subjects executed visually guided saccades to briefly presented targets. Movements of the left eye were measured using infrared oculography. Saccade amplitude, peak velocity, and duration were analyzed trial by trial and compared before, during, and after the right eye was impeded. RESULTS: When the right eye was impeded, the amplitudes of saccades executed by the left eye were reduced. There was no alteration in the main sequence relationships. The amplitude effect had a rapid onset and offset. There was no evidence that the effects built up over a number of trials, nor was there evidence that individual saccades were modified on-line. CONCLUSIONS: These results are consistent with the hypothesis that extraocular muscle afferent signals provide a feedback signal of the movements of the eyes that is used to produce rapid adjustments of oculomotor output when required.

Adult↗
PubMed2000

Spatial localization in esotropia: does extraretinal eye position information change?

PURPOSE: To investigate the accuracy of spatial localization in children with a specific type of convergent strabismus, fully accommodative esotropia. METHODS: Two groups of children, with right and left fully accommodative esotropia, respectively, pointed at targets located centrally and eccentrically on a computer touchscreen without being able to see their hands. The size and the direction of the horizontal pointing responses were recorded under two conditions: when their eyes were aligned (wearing spectacles) and when they were squinting (not wearing spectacles). A group of children without strabismus but with hypermetropia were assessed as controls. RESULTS: For both fully accommodative groups, the pointing responses to the central target shifted in the direction of the nonsquinting eye when deviations were manifest. No difference was found for the eccentric targets. No difference was found for the hypermetropia group with any target. CONCLUSIONS: These results are consistent with an alteration in the extraretinal eye position information (efference copy, extraocular muscle proprioception, or both) that is used in spatial localization.

Accommodation, Ocular↗
PubMed2000

Does user satisfaction relate to adoption behavior?: an exploratory analysis using CPRS implementation.

User satisfaction is commonly assessed in evaluations of information systems as a proxy for user adoption. However few studies actually report directly assessing the relationship between the two constructs. In this study the relationship between four user satisfaction measures and five adoption behaviors were explored in the context of the implementation of the Veteran's Health Administration Computerized Patient Record System 1.0. Findings suggest that the relationship is modest and depends on the measurement system used. Specifically, direct reports of affect and judgements of specific task efficacy related to behavior more often than usability and a general user satisfaction instrument.

Attitude to Computers↗
PubMed1999

An appraisal of the disc-macula distance to disc diameter ratio in the assessment of optic disc size.

The disc-macula distance to disc diameter ratio (DM:DD ratio) has been advocated as a method of supporting the diagnosis of optic nerve hypoplasia. A DM:DD ratio of 3.00 has been claimed to be a satisfactory threshold value for this purpose. This study has critically evaluated the above claim and found a value of 3.00 to be too low. The threshold DM:DD ratio values for the diagnosis of unequivocal ONH for an adult population, 5 and 2 years of age were found to be respectively 4.20, 3.93 and 3.70, the values for the diagnosis of mild ONH being 3.68, 3.44 and 3.23. Lower computed values reduce the predictive power. The method of computation of the DM:DD ratio was modified to abolish potential error due to disc rotation and foveal displacement. In an adult population, there was no correlation between the DM:DD ratio and amblyopia or disc ovalness. There was a trend of increasing DM:DD ratio towards myopia and decreasing DM:DD ratio towards hypermetropia; the DM:DD ratio may therefore be falsely high in high myopia. DM:DD ratio values below threshold should therefore be interpreted with care until formal optic disc biometry can be performed.

Adolescent↗
PubMed1998

Linking information needs with evaluation: the role of task identification.

Action Identification Theory was used to explore user's subjective constructions of information tasks in a primary care setting. The first part of the study involved collecting clinician's descriptions of their information tasks. These items were collated and then rated by another larger group of clinicians. Results clearly identified 6 major information tasks, including communication, patient assessment, work monitoring, seeking science information, compliance with policies and procedures, and data integration. Results discussed in terms of implications for evaluation and assessing information needs in a clinical setting.

Communication↗
PubMed1997

Validity of utilization management criteria for psychiatry.

OBJECTIVE: This study examined the validity of four psychiatric utilization management criteria sets: the 1992 and 1993 InterQual Intensity, Severity, and Discharge (ISD) criteria, the Managed Care Appropriateness Protocol, and an instrument developed by the Department of Veterans Affairs (VA). METHOD: The appropriateness of acute care admission and continued stay for 70 randomly selected VA psychiatric inpatients was retrospectively assessed with each criteria set. The sensitivity and specificity of each instrument were evaluated by comparing its assessments to the consensus of judgments of a panel of expert psychiatrists who reviewed the same cases. Sensitivity was defined as the proportion of admissions or continued-stay days the panel found appropriate for acute care that the criteria judged to be appropriate for acute care; specificity was the proportion the panel found inappropriate for acute care that the criteria judged to be inappropriate for acute care. RESULTS: For admissions, there were only minor differences in the validity of the four criteria sets as assessed by agreement with the panel's judgments. For each of 4 continued-stay days studied, either the sensitivity or specificity of the 1993 InterQual ISD criteria was below 0.30. The specificity of the 1992 InterQual ISD criteria was below 0.60 for 2 days. In contrast, for the Managed Care Appropriateness Protocol, sensitivity was 0.73-0.93 and specificity was 0.78-0.88 over the 4 days. CONCLUSIONS: The findings raise major concerns about the validity of the widely used InterQual ISD psychiatry criteria, suggest that the Managed Care Appropriateness Protocol may be a useful tool for psychiatric utilization management, strongly underline the need to validate all criteria used to assess medical care, and support the appropriateness of the procedures used to perform these assessments.

Adult↗