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Danthurebandara VM, Sharpe GP, Hutchison DM, Denniss J, Nicolela MT, McKendrick AM, Turpin A, Chauhan BC. Enhanced Structure-Function Relationship in Glaucoma With an Anatomically and Geometrically Accurate Neuroretinal Rim Measurement. Invest Ophthalmol Vis Sci 2014; 56:98-105. [DOI: 10.1167/iovs.14-15375] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Abstract
This study was designed to determine whether cortical motion processing abnormalities are present in individuals with migraine. Performance was measured using a visual motion coherence task (motion coherence perimetry, MCP) thought to depend on the operation of cortical area V5. Motion coherence thresholds were measured using stimuli composed of moving dots at 17 locations in the central ± 20° of visual field. Pre-cortical visual function was also measured using frequency doubling perimetry (FDP) at the same 17 locations. Several migraine subjects demonstrated significant pre-cortical visual functional abnormalities, however, most subjects had normal visual fields measured with FDP. Abnormal MCP performance was measured in 15 of 19 migraine-with-aura subjects, and 11 of 17 migraine-without-aura subjects. A decreased ability to detect coherent motion may possibly be explained by an increase in baseline neuronal noise, such as would be consistent with the concept of cortical hyperexcitability in migraine.
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Vaughn CB, Weinstein R, Bond B, Rice R, Vaughn RW, McKendrick A, Ayad G, Rockwell MA, Rocchio R. Ferritin content in human cancerous and noncancerous colonic tissue. Cancer Invest 1987; 5:7-10. [PMID: 3580949 DOI: 10.3109/07357908709020300] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Tumor tissue samples from 25 patients with adenocarcinoma of the colon, twelve related samples of normal colons as well as five serum specimens from the same patients were analyzed for ferritin. The average ferritin content of the tumor tissue was 788 ng/mcp with a range of 47-1,745 ng/mcp. The average ferritin content of normal colon mucosa was 115 ng/mcp with a range of 32-230 ng/mcp. Two specimens of metastatic colon cancer taken from the retroperitoneal space and liver, respectively, contained 3,867 and 2,827 ng/mcp of ferritin. The ferritin content of the tumor tissue was higher than that of the normal colon in 8 of 9 patients who had specimens obtained from both sites. The amount of ferritin found in tumor tissue was independent of sex, age, and the site of the original tumor. This study shows that the ferritin content of colon neoplasms is elevated and indicates that the tumor tissue may be the direct source of elevated serum levels of ferritin previously observed in cancer patients.
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Turpin A, Artes PH, McKendrick AM. The Open Perimetry Interface: An enabling tool for clinical visual psychophysics. J Vis 2012; 12:12.11.22. [DOI: 10.1167/12.11.22] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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McKendrick AM, Badcock DR. An Analysis of the Factors Associated with Visual Field Deficits Measured with Flickering Stimuli in-between Migraine. Cephalalgia 2016; 24:389-97. [PMID: 15096228 DOI: 10.1111/j.1468-2982.2004.00682.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have previously demonstrated that perimetric performance measured with flickering stimuli is not normal in some individuals who experience migraine with aura in the period between their attacks. In this study, flicker perimetric performance is measured in a broad group of migraineurs to determine whether the existence of such visual field deficits is dependent on the presence of visual aura, is correlated with the duration of migraine history, or frequency of attacks. Twenty-eight migraine with aura, 25 migraine without aura, and 24 non-headache control subjects participated. The performance of the migraine groups was not significantly different from each other. The migraine groups showed significantly lower general sensitivity across the visual field and higher incidence of localized visual field deficits relative to controls. Both length of migraine history and frequency of migraine occurrence over the past 12 months were significantly correlated with lower general sensitivity to flickering visual stimuli.
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McKendrick AM, Badcock DR, Badcock JC, Gurgone M. Motion Perception in Migraineurs: Abnormalities are Not Related to Attention. Cephalalgia 2016; 26:1131-6. [PMID: 16919064 DOI: 10.1111/j.1468-2982.2006.01182.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Migraine groups have impaired ability to identify global motion direction in noisy random dot stimuli, an observation that has been used as evidence for cortical hyperexcitability. Several studies have also suggested abnormalities in cognitive processing, particularly in the domains of attention, visuo-spatial processing and memory. This study aimed to determine whether poor performance by migraineurs in motion coherence tasks could be explained by non-visual cognitive factors such as attention. Twenty-nine migraineurs and 27 non-headache controls participated. Global motion coherence thresholds were measured along with measures of neuropsychological function, using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). The migraine group had significantly higher motion coherence thresholds than controls. No significant difference in attention or any other RBANS index score was found between groups. Index scores did not correlate with motion perception thresholds. This study does not support inattention or other cognitive abnormality as an explanation for motion perception anomalies in migraine.
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Abstract
This study was designed to investigate the relationship between the astigmatic axes of right and left eye pairs, with particular attention given to determining the degree to which either direct or mirror symmetry (enantiomorphism) of the astigmatic axes exists. A sample of 192 "nonvisually" selected adults participated, with refractive error and corneal curvature data being measured using autokerato-refractive equipment. Total, corneal, and residual astigmatism were investigated, with residual astigmatism being taken as the vector difference between total and corneal astigmatism. There was no evidence for a predominance of either mirror or direct symmetry of the astigmatic axes within this sample. The patterns of astigmatic axis distribution of right and left eyes were remarkably similar but, within this context, there was no definite evidence for a definable association between the axis of the left and right pairs of individuals. These findings remained unchanged when the effect of the modulus of astigmatism was incorporated, either through weighting the frequency distributions or through analyzing a subgroup of the overall population (those individuals with greater than 0.50 D of astigmatism). We believe these findings contradict commonly held clinical impressions regarding the symmetry of astigmatic axes, and should be considered when performing statistical analysis of astigmatic data.
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McKendrick AM, Brennan NA. Distribution of astigmatism in the adult population. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 1996; 13:206-214. [PMID: 8558348 DOI: 10.1364/josaa.13.000206] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We have quantified statistically the astigmatic frequency distribution. Vectorial analysis was used, as it enables formal multivariate statistical techniques to be applied to astigmatic data, allowing the simultaneous inclusion of both modulus and axis in the analytical procedure. These methods were applied to population data for each of total, corneal, and residual astigmatism from a sample of 198 adults. Right and left eyes were analyzed separately. All the distributions were found to depart significantly from a normal distribution. All the distributions were significantly leptokurtic (p < 0.005), and the distributions of total right eye, corneal right eye, and residual left eye astigmatism were also found to be significantly skewed (p < 0.05). Significant mild correlations were found between total and corneal astigmatism (p < 0.05). These findings add to the database of knowledge of astigmatic refractive error and may be of interest to those investigating refractive-error development.
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Comparative Study |
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Spry PGD, Johnson CA, McKendrick AM, Turpin A. Measurement error of visual field tests in glaucoma. Br J Ophthalmol 2003; 87:107-12. [PMID: 12488273 PMCID: PMC1771451 DOI: 10.1136/bjo.87.1.107] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AIM Psychophysical strategies designed for clinical visual field testing produce rapid estimates of threshold with relatively few stimulus presentations and so represent a trade-off between test quality and efficiency. The aim of this study was to determine the measurement error of a staircase algorithm similar to full threshold with standard automated perimetry (SAP) and frequency doubling perimetry (FDP) in glaucoma patients. METHODS Seven patients with early open angle glaucoma (OAG) were prospectively recruited. All were experienced in laboratory based psychophysics. Three matched test locations were examined with SAP (externally driven Humphrey field analyser) and FDP (CRT) in a single arbitrarily selected eye of each subject. Each location was tested twice with a 4-2-2 dB staircase strategy, similar to full threshold, and then with the method of constant stimuli (MOCS). Accuracy (threshold estimation error) was quantified by determination of differences between "true" threshold measurements made by MOCS and single staircase threshold estimates. Precision (repeatability) was quantified by the differences between repeated staircase threshold estimates. RESULTS Precision was relatively high for both tests, although higher for FDP than SAP at depressed sensitivity levels. The staircase strategy significantly underestimated threshold sensitivity for both test types, with the mean difference (95% CI) between staircase and MOCS thresholds being 4.48 dB (2.35 to 7.32) and 1.35 dB (0.56 to 1.73) for SAP and FDP respectively. Agreement levels (weighted kappa) between MOCS and staircase thresholds were found to be 0.48 for SAP and 0.85 for FDP. Although this "bias" appeared constant for FDP across all sensitivity levels, this was not the case for SAP where accuracy decreased at lower sensitivity levels. CONCLUSION Estimations of threshold sensitivity made using staircase strategies common to clinical visual field test instrumentation are associated with varying degrees of measurement error according to visual field test type and sensitivity. In particular, SAP significantly overestimates the "true" level of sensitivity, particularly in damaged areas of the visual field, suggesting that clinical data of this type should be interpreted with caution.
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research-article |
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Brittain PJ, Surguladze S, McKendrick AM, Ffytche DH. Backward and forward visual masking in schizophrenia and its relation to global motion and global form perception. Schizophr Res 2010; 124:134-41. [PMID: 20685082 DOI: 10.1016/j.schres.2010.07.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2010] [Revised: 04/28/2010] [Accepted: 07/09/2010] [Indexed: 10/19/2022]
Abstract
Whilst visual backward masking deficits in schizophrenia have been reliably reported and may reveal magnocellular dysfunction, forward masking, which may rely more heavily on the parvocellular system, has been under investigated. In a group of 64 schizophrenia patients and 65 matched controls we undertook a visual masking paradigm containing both conditions, together with tests of 'global motion' and 'global form' perception, two 'down-stream' visual tasks reflecting later processing linked to magnocellular and parvocellular function respectively. In the patient group, a significant but small deficit on the masking task, equivalent across forward and backward conditions was seen. Correlations between the masking and motion/form tasks supported the predominant theoretical framework describing the neural processes involved in masking. Performance on the motion and form tasks was differentiated by a trend-level motion processing deficit but near-normal form processing. The results suggest an 'early visual' processing deficit in both magno- and parvocellular systems but one which is only transferred to 'down-stream' processing areas with predominantly magnocellular input.
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Turpin A, Lawson DJ, McKendrick AM. PsyPad: A platform for visual psychophysics on the iPad. J Vis 2014; 14:16. [DOI: 10.1167/14.3.16] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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McKendrick AM, Sampson GP. Low spatial frequency contrast sensitivity deficits in migraine are not visual pathway selective. Cephalalgia 2009; 29:539-49. [PMID: 19250285 DOI: 10.1111/j.1468-2982.2008.01817.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Some people who experience migraine demonstrate reduced visual contrast sensitivity that is measurable between migraines. Contrast sensitivity loss to low spatial frequency gratings has been previously attributed to possible impairment of magnocellular pathway function. This study measured contrast sensitivity using low spatial frequency targets (0.25-4 c/deg) where the adaptation aspects of the stimuli were designed to preferentially assess either magnocellular or parvocellular pathway function (steady and pulsed pedestal technique). Twelve people with migraine with measured visual field abnormalities and 17 controls participated. Subjects were tested foveally and at 10 degrees eccentricity. Foveally, there was no significant difference in group mean contrast sensitivity. At 10 degrees , the migraine group demonstrated reduced contrast sensitivity for both the stimuli designed to assess magnocellular and parvocellular function (P < 0.05). The functional deficits measured in this study infer that abnormalities of the low spatial frequency sensitive channels of both pathways contribute to contrast sensitivity deficits in people with migraine.
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Research Support, Non-U.S. Gov't |
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Mittal V, David W, Young S, McKendrick A, Gentile T, Casalou R. Improved continuity of care in a community teaching hospital model. ARCHIVES OF SURGERY (CHICAGO, ILL. : 1960) 1999; 134:555-8. [PMID: 10323430 DOI: 10.1001/archsurg.134.5.555] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
HYPOTHESIS We created an ambulatory resident clinic in a community teaching hospital to improve the continuity of care in a surgery residency program. DESIGN A retrospective chart review analysis. SETTING A community hospital, general surgery residency training program, and its ambulatory practice. INTERVENTIONS Providence Hospital, Southfield, Mich, has established a new model, the Surgical Associates of Michigan, which is an association comprising private practice physicians serving as full-time faculty in the Department of Surgery. In addition to clarification of teaching requirements and reimbursement for educational activities, the most dramatic feature is the relocation of private practice offices and the staff surgical office to one central location within the hospital. The proximity of the staff and private surgical offices facilitates closer interaction of attending physicians, residents, and patients. MAIN OUTCOME MEASURES Compliance rates of continuity of patient care provided by the same resident, as presented by the Surgery Residency Review Committee, including confirmation of diagnosis, provision of preoperative care, discussion with attending physician, selection and provision of intervention, direction of postoperative care, and postdischarge follow-up. RESULTS Since the inception of this arrangement at our institution, surgical residents have seen 229 staff patients and 465 private patients in the offices under supervision. Compliance rate of continuity of care was defined as patient follow-up with the same senior surgical resident who performed an operation or evaluated the patient on initial presentation to the emergency department or offices. We achieved a compliance rate of 92.8% (169/182) in the staff surgical clinics. A compliance rate of 63.5% (205/323) for private general surgical patients and 70.4% (100/142) for vascular surgical patients was obtained. With the establishment of the teaching faculty group and the relocation of offices, we were able to achieve a dramatic improvement in continuity of care. CONCLUSIONS In addition to fulfilling the Surgery Residency Review Committee requirements, we believe our model facilitates broader education of surgical residents and improves risk management. We recommend further similar studies, greater involvement of primary care specialties in recruiting staff surgical referrals, and implementation of a specialized computer program to continue to improve continuity of care in surgery residency programs.
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Gardiner SK, Swanson WH, Demirel S, McKendrick AM, Turpin A, Johnson CA. A two-stage neural spiking model of visual contrast detection in perimetry. Vision Res 2008; 48:1859-69. [PMID: 18602414 DOI: 10.1016/j.visres.2008.06.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2007] [Revised: 03/07/2008] [Accepted: 06/10/2008] [Indexed: 10/21/2022]
Abstract
Perimetry is a commonly used clinical test for visual function, limited by high variability. The sources of this variability need to be better understood. In this paper, we investigate whether noise intrinsic to neural firing could explain the variability in normal subjects. We present the most physiologically accurate model to date for stimulus detection in perimetry combining knowledge of the physiology of components of the visual system with signal detection theory, and show that it requires that detection be mediated by multiple cortical cells in order to give predictions consistent with psychometric functions measured in human observers.
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Research Support, Non-U.S. Gov't |
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McKendrick AM, Battista J. Perceptual learning of contour integration is not compromised in the elderly. J Vis 2013; 13:5. [DOI: 10.1167/13.1.5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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McKendrick AM, Badcock DR, Heywood J, Vingrys AJ. Effects of migraine on visual function. AUSTRALIAN AND NEW ZEALAND JOURNAL OF OPHTHALMOLOGY 1998; 26 Suppl 1:S111-3. [PMID: 9685041 DOI: 10.1111/j.1442-9071.1998.tb01356.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Data is reported from an ongoing trial considering whether visual loss associated with migraine is consistent with a selective deficit in M- or P-cell functioning. METHODS The psychophysical tests used include spatio-temporal contrast thresholds and luminance increment thresholds for a spot drifting across a spatially or temporally modulated background. A migraineur and 15 non-headache controls participated in the present study. Measurements were made foveally and at 10 degrees in the superior field. Static and flicker perimetry were conducted. RESULT/CONCLUSION Regionalized losses occurred for stimuli with moderate temporal frequencies (16 Hz), which is consistent with M-cell dysfunction.
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Sampson GP, Badcock DR, Walland MJ, McKendrick AM. Foveal contrast processing of increment and decrement targets is equivalently reduced in glaucoma. Br J Ophthalmol 2008; 92:1287-92. [DOI: 10.1136/bjo.2007.130880] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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McKendrick AM, Badcock DR, Vingrys AJ. Spatiotemporal filters in the detection of background modulation targets. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2000; 17:836-845. [PMID: 10795631 DOI: 10.1364/josaa.17.000836] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The background modulation method has been proposed as a useful test of early visual mechanisms [Biol. Cybern. 37, 77 (1980); Biol. Cybern. 47, 173 (1983)]. The task involves measuring detection thresholds for a luminous spot (increment) drifting over a spatially or temporally modulated background. The study explores the nature of the detecting mechanism in terms of spatial and temporal filters for both spatial and temporal background modulations. In both cases we find that thresholds can be explained by spatial contrast cues generated by the moving spot and that their spatiotemporal characteristics suggest detection by magnocellular processes.
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McKendrick AM, Johnson CA. Aliasing for rapidly counterphasing stimuli: a failure to demonstrate an M-cell sampling limit to resolution. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2000; 17:1703-1712. [PMID: 11028518 DOI: 10.1364/josaa.17.001703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We investigated whether resolution is sampling limited for stimuli optimized for detection by magnocellular mechanisms. We measured peripheral (15 degrees and 30 degrees) spatial detection and resolution thresholds using 50% and 90% contrast flicker-defined gratings (25 Hz) and 90% contrast counterphasing sinusoidal gratings (25 Hz). Direction-discrimination performance for 90% contrast counterphasing sinusoidal gratings (25 Hz) was measured foveally. Our results indicate that resolution of rapidly counterphasing stimuli is sampling limited in peripheral vision but is consistent with limiting of performance by parvocellular mechanisms. Also, undersampling may not be necessary to account for motion reversals observed with gratings that both drift and flicker.
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McKendrick AM, Turpin A, Webb S, Badcock DR. Do migraineurs have difficulty judging direction of simulated heading? Cephalalgia 2006; 26:949-59. [PMID: 16886931 DOI: 10.1111/j.1468-2982.2006.01154.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Some migraineurs have increased thresholds for the detection of global dot motion. We investigated whether migraineurs show consequential abnormalities in the determination of direction of self-motion (heading) from simulated optic flow. The ability to determine heading from optic flow is likely to be necessary for optimal determination of self-motion through the environment. Twenty-five migraineurs and 25 controls participated. Global dot motion coherence thresholds were assessed, in addition to performance on two simulated heading tasks: one with a symmetrical flow field, and the second with differing velocity of optic flow on the left and right sides of the participant. While some migraineurs demonstrated abnormal global motion coherence thresholds, there was no difference in performance on the heading tasks at either simulated walking (5 km/h) or driving (50 km/h) speeds. Increased global motion coherence thresholds in migraineurs do not result in abnormal judgements of heading from 100% coherent optic flow.
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Controlled Clinical Trial |
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Jolly JK, Grigg JR, McKendrick AM, Fujinami K, Cideciyan AV, Thompson DA, Matsumoto C, Asaoka R, Johnson C, Dul MW, Artes PH, Robson AG. ISCEV and IPS guideline for the full-field stimulus test (FST). Doc Ophthalmol 2024; 148:3-14. [PMID: 38238632 PMCID: PMC10879267 DOI: 10.1007/s10633-023-09962-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Accepted: 12/15/2023] [Indexed: 02/21/2024]
Abstract
The full-field stimulus test (FST) is a psychophysical technique designed for the measurement of visual function in low vision. The method involves the use of a ganzfeld stimulator, as used in routine full-field electroretinography, to deliver full-field flashes of light. This guideline was developed jointly by the International Society for Clinical Electrophysiology of Vision (ISCEV) and Imaging and Perimetry Society (IPS) in order to provide technical information, promote consistency of testing and reporting, and encourage convergence of methods for FST. It is intended to aid practitioners and guide the formulation of FST protocols, with a view to future standardisation.
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research-article |
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McKendrick AM, Vingrys AJ, Badcock DR, Heywood JT. Visual field losses in subjects with migraine headaches. Invest Ophthalmol Vis Sci 2000; 41:1239-47. [PMID: 10752965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023] Open
Abstract
PURPOSE To characterize the visual fields of subjects with migraine headaches using static and temporal modulation perimetry. METHODS Sixteen subjects with migraines (15 with aura, 1 without) and 15 nonheadache controls were tested. Perimetry was conducted 7 days after the offset of a headache with both static and temporally modulated targets using the Medmont M-600 automated perimeter (Medmont Pty Ltd., Camberwell, Victoria, Australia). Flicker thresholds were measured using the autoflicker test, which varies flicker rate with eccentricity. A subset of four subjects with migraines (3 with aura, 1 without) had the temporal tuning characteristics of their loss evaluated using fixed temporal frequencies (4, 6, 9, 12, and 16 Hz). RESULTS Field losses were identified with temporal modulation perimetry in 11 of 16 migraine subjects. The majority of these losses occurred in the presence of normal static thresholds (8/11). The deficits displayed temporal tuning, being greatest for higher temporal frequencies (> or =9 Hz). None of the subjects revealed deficits typical of cortical lesions. The migraine-without-aura subject displayed a selective loss to temporally modulated stimuli, which was consistent with the aura group. This defect altered over time, decreasing for 30 to 40 days but remaining, to a smaller extent, for up to 75 days after the headache event. CONCLUSIONS Visual dysfunction that is selective for temporally modulated targets occurs in migraine subjects. The migrainous pattern of dysfunction shares some features with that identified in early stages of glaucoma and raises the possibility for a common precortical vascular involvement in these two conditions.
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McKendrick AM, Brennan NA. Clinical evaluation of refractive techniques. JOURNAL OF THE AMERICAN OPTOMETRIC ASSOCIATION 1995; 66:758-65. [PMID: 8557954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND The accuracy of two commercially available auto kerato-refractometers (Shin-Nippon Automatic Ref-Keratometer model RC380 and Topcon Auto Kerato-Refractometer model KR-3100) and one autokeratometer (Alcon Systems Auto-Keratometer) was compared to that of subjective refraction and conventional keratometry. METHODS Refractive error and corneal curvature were measured on 20 subjects. Measurements were converted from the standard clinical format of sphere, cylinder and axis to a vector format to assess the contribution of spherical and cylindrical errors simultaneously. RESULTS For measurements of refractive error taken in immediate succession, the Shin-Nippon instrument was found to be more repeatable than the Topcon instrument. This trend reversed when subjects were realigned between measurements. The 95 percent confidence limit for precision for subjective refraction was considerably greater: 93 percent of subjective refractions resulted in visual acuities better than or equal to 6/6, compared with 85 percent for the Topcon instrument and 45 percent for the Shin-Nippon instrument. Each of the methods for measuring corneal curvature showed minimal bias and comparable precision. CONCLUSIONS Although subjective methods of determining refractive error generally achieved the same or better visual acuity as the automated methods, they displayed considerably poorer precision. Each of the methods of measurement of corneal curvature produced similar results.
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Comparative Study |
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Chan YM, Pianta MJ, McKendrick AM. Reduced audiovisual recalibration in the elderly. J Vis 2014. [DOI: 10.1167/14.10.430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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