ISCEV and IPS guideline for the full-field stimulus test (FST).

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.

Laparoscopic loop ileostomy with a single-port stab incision technique.

Loop ileostomy is an effective means of temporary fecal diversion. It is technically easy to create and manage. Moreover, ileostomy closure does not require a formal laparotomy. With the advent of laparoscopy, many of these loop ileostomies are being performed with laparoscopic assistance. Studies have proved the beneficial effects of laparoscopically created loop ileostomy for fecal diversion. Techniques for performing laparoscopic loop ileostomy have been described using two or more 10- to 12-mm ports with Hassan's technique at the umbilical site for pneumoperitoneum creation. We describe a modified technique, wherein pneumoperitoneum is created using a 10-mm port at the site of the future ileostomy, and a second 5-mm port is placed under vision at the umbilical site. This procedure requires minimal intervention and a reduced pneumoperitoneum time. Since the umbilical port site is 5 mm, it does not require closure, and it also reduces the chances of port-site hernia, formation, patient discomfort and scarring. Because intervention is minimally invasive, operative time is reduced, and there is less of chance postoperative ileus and adhesion formation.

Backward and forward visual masking in schizophrenia and its relation to global motion and global form perception.

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.

Low spatial frequency contrast sensitivity deficits in migraine are not visual pathway selective.

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.

A two-stage neural spiking model of visual contrast detection in perimetry.

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.

Foveal contrast processing of increment and decrement targets is equivalently reduced in glaucoma.

BACKGROUND: Psychophysical measurement of the function of individual precortical visual pathways (magnocellular, parvocellular and koniocellular) has enabled the development of sensitive tests for glaucoma and has enhanced understanding of its pathophysiology. Such pathways can be further subdivided into their "On" and "Off" components, which have anatomical and physiological asymmetries. This study investigated whether On and Off subdivisions of the magnocellular (M) pathway are differentially affected by glaucoma. METHODS: 20 participants with glaucoma and 20 controls underwent two psychophysical procedures that have been shown to assess the M pathway (steady pedestal task) and its On and Off subdivisions (pedestal-delta-pedestal task) respectively. Luminance discrimination thresholds were measured foveally, using both increment and decrement stimuli. RESULTS: The steady pedestal (undifferentiated M-pathway) task separated the glaucoma and control groups (p = 0.04) with equivalent outcomes for increment and decrement targets. The pedestal-delta-pedestal task (isolated On and Off M-pathway subdivisions) also differentiated between groups (p = 0.025), but the outcome was not dependent on which subdivision was isolated. CONCLUSIONS: This study found that increment and decrement targets can be used with equal effectiveness for detecting contrast processing deficits in early glaucoma. Outcomes further suggested that glaucoma affects On and Off subdivisions of the M-pathway equivalently.

Motion perception in migraineurs: abnormalities are not related to attention.

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.

Do migraineurs have difficulty judging direction of simulated heading?

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.

Streptococcus intermedius liver abscesses and colon cancer: a case report / Abscesos hepáticos por Streptococcus intermedius y cáncer de colon: reporte de un caso

Certain species of bacteria are known to be associated with colorectal cancer. We report a case of adenocarcinoma of the colon with bacteraemia and liver abscesses due to Streptococcus intermedius. The isolation of this organism should prompt investigation for colorectal neoplasm, which may be present but asymptomatic, without metastases, and therefore at a curative stage.

Se sabe que ciertas especies de bacterias están asociadas con el cáncer colorectal. El presente trabajo reporta un caso de adenocarcinoma del colon acompañado de bacteriemia y abscesos hepáticos debidos a Streptococcus del grupo intermedius. El aislamiento de este organismo debe impulsar la investigación del neoplasma colorectal, el cual puede estar hallarse presente pero de forma asintomática, sin metástasis, y por consiguiente en una fase en que la cura es aún posible.

Streptococcus intermedius liver abscesses and colon cancer: a case report.

Certain species of bacteria are known to be associated with colorectal cancer. We report a case of adenocarcinoma of the colon with bacteraemia and liver abscesses due to Streptococcus intermedius. The isolation of this organism should prompt investigation for colorectal neoplasm, which may be present but asymptomatic, without metastases, and therefore at a curative stage.

Motion processing deficits in migraine.

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 degrees 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.

An analysis of the factors associated with visual field deficits measured with flickering stimuli in-between migraine.

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.

Measurement error of visual field tests in glaucoma.

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.

Variability components of standard automated perimetry and frequency-doubling technology perimetry.

PURPOSE: To evaluate and compare intra- and intertest variability components for both standard automated perimetry (SAP) and frequency-doubling technology (FDT) perimetry in a small group of normal individuals and patients with glaucoma. METHODS: The method of constant stimuli (MOCS) was used to examine matched test locations with both SAP and FDT perimetry stimuli in a group of eight normal individuals and seven patients with glaucoma. Subjects were tested weekly at three predetermined visual field loci for 5 consecutive weeks. Frequency-of-seeing (FOS) curves were generated and used to quantify threshold sensitivity (50% seen on FOS, in decibels), intratest variability (FOS interquartile range, in decibels), and intertest variability (interquartile range of weekly repeated threshold determinations, in decibels). RESULTS: In patients with glaucoma, SAP intra- and intertest variabilities were found to increase with sensitivity reductions, as previously reported. FDT perimetry revealed that both intra- and intertest variability components did not appreciably change with reductions in sensitivity. With the measurement scales used in this investigation, both intra- and intertest variability components were significantly greater for SAP than for FDT perimetry (P < 0.001 and P = 0.003, respectively). Intratest variability exceeded intertest variability for both SAP (P = 0.001) and FDT perimetry (P < 0.001). CONCLUSIONS: For both SAP and FDT perimetry, variability occurring within a single test session contributed more to total variability than between-session variability. When the measurement scales available on commercial instrumentation were used, FDT perimetry exhibited significantly less variability than SAP, especially within regions of visual field sensitivity loss. FDT perimetry therefore shows promise as an effective test for detecting progressive glaucomatous visual field loss, although prospective longitudinal validation is still required to determine sensitivity to change.

Visual dysfunction between migraine events.

PURPOSE: To evaluate interictal visual dysfunction in persons with migraine in terms of spatiotemporal selectivity and location within the visual pathways. METHODS: The vision of a group of 15 persons who had experienced migraine with aura was compared with that of 15 normal age-matched control subjects. A range of thresholds was measured to evaluate precortical (background modulation, contrast thresholds for static, and moving stimuli), area V1 (orientation discrimination and motion discrimination thresholds), and higher order (global dot motion thresholds) visual processes. Testing was performed centrally and at 10 degrees in the superior visual field. For each of the tests, the spatial and temporal parameters of the stimuli were selected to bias detection toward either parvocellular or magnocellular visual mechanisms. RESULTS: No defects were found for parvocellular processes. Significant (P: < 0.05) losses were apparent with the temporal background modulation method (16 Hz), orientation discrimination (0.5 cyc/deg), and global dot motion tasks. CONCLUSIONS: Both cortical and precortical visual dysfunction were identified in migraine group 7 days after the headache. This loss was selective for targets with temporal modulation of approximately 16 Hz.

Aliasing for rapidly counterphasing stimuli: a failure to demonstrate an M-cell sampling limit to resolution.

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.

Spatiotemporal filters in the detection of background modulation targets.

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.

Visual field losses in subjects with migraine headaches.

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.