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Biomedical subjects

W M Hart

Publications and source records attributed to W M Hart.

At least 19 recordsLinked to original sources
PubMed1997

A cost analysis of a treatment policy of a deliberate perioperative increase in oxygen delivery in high risk surgical patients.

OBJECTIVE: To investigate the cost implications of a treatment policy of a deliberate perioperative increase of oxygen delivery in high risk surgical patients. DESIGN: A cost-effectiveness analysis comparing 'protocol' high risk surgical patients in whom oxygen delivery was specifically targeted towards 600 ml/min/m2 with 'control' patients. INTERVENTIONS: In a randomised, controlled clinical trial we previously demonstrated a significant reduction in mortality (5.7% vs 22.2%, p = 0.015) and morbidity (0.68 +/- 0.16 complications vs 1.35 +/- 0.20, p = 0.008) in 'protocol' high risk surgical patients in whom oxygen delivery was specifically targeted towards 600 ml/min per m2 compared with 'control' patients. This current study retrospectively analysed the medical care and National Health Service resource use of each patient in the trial. Departmental purchasing records and business managers were consulted to identify the unit cost of these resources, and thereby the cost of treating each patient was calculated. RESULTS: The median cost of treating a protocol patient was lower than for a control patient (6,525 pounds vs 7,784 pounds) and this reduction was due mainly to a decrease in the cost of treating postoperative complications (median 213 pounds vs 668 pounds). The cost of obtaining a survivor was 31% lower in the protocol group. CONCLUSION: Perioperative increase of oxygen delivery in high risk surgical patients not only improves survival, but also provides an actual and relative cost saving. This may have important implications for the management of these patients and the funding of intensive care.

Clinical Protocols↗
PubMed1996

Bilateral optic neuritis originating in a single chiasmal lesion. A case report.

A case of bilateral retrobulbar optic neuritis with profound visual loss is described. Magnetic resonance imaging (MRI) with fat-saturation suppression and gadolinium enhancement done 15 days after the onset of symptoms demonstrated bilateral posterior optic nerve disease in a pattern similar to that seen in previously reported cases. However, subsequent retrospective review of an MRI study done at a different hospital during the first week of disease demonstrated a single focus of gadolinium enhancement within the body of the chiasm. This observation suggests that bilateral demyelination of the posterior optic nerves may begin as a single focus of chiasmal disease that then spreads to involve the proximal portions of the optic nerves.

Aged↗
PubMed1993

Optic nerve sheath decompression for glaucomatous optic neuropathy with normal intraocular pressure.

OBJECTIVE: To report our therapeutic experience with optic nerve sheath decompression in patients with normal-pressure glaucoma. DESIGN: A case series of seven eyes from six patients with glaucoma and normal intraocular pressures who continued to have progressive visual field loss despite conventional therapy. SETTING: A hospital-based, referral glaucoma service. PATIENTS: Three men (67, 67, and 72 years of age) and three women (58, 61, and 70 years of age). INTERVENTIONS: Optic nerve sheath decompression. MAIN OUTCOME MEASURES: Visual field data and visual acuity measurements were obtained at regular intervals during the postoperative periods (range, 3 to 18 months). RESULTS: Two of seven eyes from six patients appear to have enjoyed an initial significant improvement in their visual fields with improved visual acuity in one eye of one patient. The visual fields, however, appear to have deteriorated 18 months after the initial procedure in these two patients. In the remaining four patients, no further improvement or deterioration was observed within a limited follow-up period. CONCLUSIONS: The transient improvement in the visual fields of one eye from each of two patients documents an initial successful use of optic nerve sheath decompression in patients with nerve fiber bundle damage in the absence of optic nerve head swelling. However, the long-term potential of optic nerve sheath decompression in these patients may be of limited value.

Aged↗
PubMed1990

The dyschromatopsia of optic neuritis is determined in part by the foveal/perifoveal distribution of visual field damage.

Most hypotheses of acquired dyschromatopsia invoke the mechanism of selective damage to specific components of the afferent visual system to explain the predominance of red-green and blue-yellow hue-discrimination defects found in neural and retinal disorders, respectively. However, this pattern of hue-discrimination disturbance in ocular disease may vary. There are frequent exceptions which are inadequately explained by existing hypotheses. In an effort to explain the pattern and pathogenesis of acquired dyschromatopsias better, the authors examined patients with nonproliferative diabetic retinopathy (DR) and late-stage retrobulbar neuritis (RBN) using age-corrected Farnsworth-Munsell 100-hue testing and threshold static perimetry. As expected, most DR eyes showed some degree of relative blue-yellow dyschromatopsia (89%) with few showing a greater weighting towards red-green dyschromatopsia (11%). However, an approximately equal number of RBN eyes had a relative blue-yellow (48%) versus red-green dyschromatopsia (52%). For RBN, the authors found a strong association between the spatial distribution of field defect and the type of relative hue-discrimination disturbance. Eyes with greater field depression at the fovea relative to the perifovea showed a relative preponderance of red-green dyschromatopsia (68%) as opposed to blue-yellow dyschromatopsia (32%), whereas eyes with greater relative perifoveal impairment showed a relative preponderance of blue-yellow dyschromatopsia (100%). This relationship between the relative spatial distribution of visual field damage and the relative hue-discrimination deficit in RBN was statistically significant (P = 0.002). Such an association was not found for DR.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Glaucomatous visual field damage. Luminance and color-contrast sensitivities.

Using a modified Humphrey perimeter, we evaluated 16 eyes with primary open-angle glaucoma and visual field loss (defects 0.5-3.0 log units in depth), and 14 normal eyes. Each eye was tested twice in random order with conventional luminance-increment static perimetry and with the perimeter modified to produce a high-luminance yellow adapting background and a blue test stimulus. The background was a broad-spectrum light of 500 nm and above (yellow), while the stimulus was a broad-spectrum light of 500 nm and below (blue). Paired comparisons were made between conventional and blue/yellow sensitivities for every point examined (1184 points in 16 diseased eyes and 1036 points in 14 normal eyes). Defect depths were determined by using the age-corrected norms distributed in the Humphrey Statpac software. In glaucomatous eyes, blue/yellow sensitivity showed greater impairment than did conventional perimetric sensitivity, in which defect depths were less than 1.0 log unit. However, for defects greater than 1.0 log unit in depth, conventional perimetric sensitivity and blue/yellow sensitivity showed equivalent degrees of damage. Receiver operating characteristic (ROC) analysis was used to compare the ability of blue/yellow and of conventional perimetry in distinguishing between glaucomatous and normal eyes. Results indicated that although blue/yellow color-contrast perimetry may be more sensitive for the detection of incipient glaucomatous damage, in the manifest stages of visual field damage blue/yellow color-contrast perimetry is no more sensitive than is conventional (luminance-increment) perimetry for defining the extent of glaucomatous visual field defects.

Adult↗
PubMed1990

Motion perception is abnormal in primary open-angle glaucoma and ocular hypertension.

Several lines of evidence suggest that the large optic nerve fibers, which form the magnocellular retinocortical pathway, are preferentially susceptible to early glaucomatous damage. It is evident from studies of the functional architecture of the visual system that the magnocellular pathway underlies the global perception of motion. Therefore, we have developed a psychophysical technique for assessing motion detection thresholds in patients with ocular hypertension (OHT) and primary open-angle glaucoma (POAG). For this purpose we employed a dynamic random dot display that contained varying degrees of a coherent motion signal embedded within a background of random motion noise. We used this technique to measure motion thresholds in POAG patients (n = 37), OHT patients (n = 14), and age-matched controls (n = 39). Motion thresholds were elevated by 70% for the POAG group and 44% for the OHT group relative to controls. In the same patients, no significant deficit in form discrimination was found as measured by Pelli-Robson charts. Our results demonstrate that significant motion perception deficits are evident in POAG and OHT. These findings support the suggestion that significant and selective damage to the magnocellular pathway occurs in OHT and POAG and indicate that motion threshold testing may reveal preclinical optic nerve disease in early POAG.

Contrast Sensitivity↗
PubMed1989

Topical timolol administration reduces the incidence of glaucomatous damage in ocular hypertensive individuals. A randomized, double-masked, long-term clinical trial.

We conducted a randomized, double-masked, long-term clinical trial to determine whether topical timolol therapy was effective in delaying or preventing the onset of glaucomatous damage in moderate-risk ocular hypertensive subjects. In 62 patients, one eye was chosen randomly to receive timolol therapy twice daily while the fellow eye received placebo. During the course of the study, the mean +/- SD difference in intraocular pressure between the timolol-treated and the placebo-treated eyes was 2.3 +/- 2.6 mm Hg. Reproducible visual field loss developed in 4 timolol-treated eyes and 10 placebo-treated eyes. Progressive optic disc cupping was noted in 4 timolol-treated and 8 placebo-treated eyes. Using a computerized image analysis system, the mean +/- SD increase in optic disc pallor during the course of the study was 0.86% +/- 2.4% in the timolol-treated eyes as opposed to 1.80% +/- 3.6% in the placebo-treated eyes. This study provides evidence that lowering intraocular pressure by medical treatment reduces the incidence of glaucomatous damage in ocular-hypertensive individuals.

Administration, Topical↗
PubMed1988

Modified grid laser photocoagulation for diabetic macular edema. The effect on the central visual field.

Modified grid laser photocoagulation has been shown to stabilize visual acuity in patients with diabetic macular edema, but the effect on extrafoveal visual function is uncertain. Automated static threshold perimetry was performed on 64 eyes of 36 patients before and after modified grid therapy with the argon green or krypton red laser. Twenty-eight eyes underwent two grid treatments for persistent macular edema. For all eyes tested, average threshold sensitivity in the central 5 degrees dropped 3.44 dB (standard deviation [SD], 3.79 dB) after the first treatment and 6.86 dB (SD, 5.02 dB) cumulatively after the second treatment. Qualitatively, the grayscale displays of the central visual field were darker after treatment, but the scotomata from laser photocoagulation could not be distinguished from those due to macular edema. The foveal threshold showed no significant change. In a subgroup of patients tested, color vision was not significantly improved and nearly all patients exhibited a tritan defect before and after treatment. No difference was detected between the argon and krypton groups. This suggests that with modified grid laser photocoagulation visual acuity and foveal threshold are preserved at the expense of generalized loss of threshold sensitivity across the central 10 degrees of the visual field.

Color Perception↗
PubMed1985

Color contrast perimetry. The spatial distribution of color defects in optic nerve and retinal diseases.

Color contrast perimetry was used to evaluate central visual field defects in a group of 28 patients with visual loss resulting from optic nerve or retinal diseases. Kinetic perimetry was performed using colored test objects of constant luminance, equated to a white surround of 10 ft lamberts. Colored test objects were varied in size and in extent of color saturation. Test object color saturation was varied from a white that matched the color and luminance of the adapting background toward either the blue or the red color maxima of a video tangent screen. All central visual field defects that were demonstrable by luminance contrast perimetry were also detected by color contrast testing, and no defects were found for color contrast detection that could not also be demonstrated by conventional luminance increment perimetry. Retinal diseases usually produced scotomas for both color and luminance contrast detection, while optic nerve disorders tended to produce global depressions of both color and luminance contrast sensitivity across the entire visual field in addition to scotomas. There was no systematic difference in visual field defects for either class of disease when comparing color contrast in the blue (tritan) versus the red (protan) axes of color space. The apparent tritan or protan/deutan axes of color confusion found by hue discrimination testing in acquired dyschromatopsias may be determined by the relative spatial distribution of defects in the central visual field rather than by selective impairment of neural mechanisms for color or luminance information processing.

Adult↗
PubMed1984

Static perimetry in chloroquine retinopathy. Perifoveal patterns of visual field depression.

Results of threshold static perimetry in nine cases of toxic retinopathy produced by chloroquine phosphate and hydroxychloroquine sulfate are reported. Pericentral visual field defects in an advanced case correlated well with ophthalmoscopically visible defects in the pigment epithelium. In a less advanced case, perifoveal defects in the visual field of one eye were found to be demonstrable in the absence of any fundus abnormalities by either ophthalmoscopy or fluorescein angiography. In both cases, visual field defects were deepest on the superior or vertical meridian, just above the point of fixation. Since defects were found to be deepest along the superior vertical meridian, threshold static perimetry that includes this location should be the most sensitive method of detecting the early stages of visual field damage in chloroquine retinopathy.

Adult↗
PubMed1984

Color perimetry of glaucomatous visual field defects.

A color video tangent screen has been devised, using microcomputer control of a video display to produce colored perimetric test objects matched in luminance to a white surround at 10-foot lamberts . Perimetric isopters for varying degrees of color saturation were determined by kinetic perimetry. This form of color perimetry was used to examine one eye of each of 40 patients with open-angle glaucoma as well as 20 glaucoma-suspect patients. For the first 23 eyes with manifest glaucomatous visual field defects, a masked comparison was made between the results of color perimetry and conventional perimetry with a Goldmann perimeter. For these 23 eyes, color perimetry did as well as luminance perimetry in 14, was less sensitive in 2, and was more sensitive in 7. All defects that were detectable by conventional perimetry were successfully demonstrated by the color method. Such defects often appeared to be greater in extent when mapped by the color method as compared to conventional luminance perimetry.

Aged↗
PubMed1984

Rhabdomyosarcoma causing rapid bilateral visual loss in children.

Rhabdomyosarcoma commonly involves the orbit resulting in unilateral proptosis, swelling, and restricted ocular motility. We saw two unusual cases of children with nasopharyngeal rhabdomyosarcoma which caused rapid bilateral visual loss due to simultaneous spread of the tumor to the orbital apices. Initial CT scans revealed the tumor, but were misinterpreted as "normal," causing a significant delay in diagnosis. We recommend high resolution CT scans of the nasopharynx, orbits, and suprasellar region in any child with rapid bilateral visual loss to rule out this common childhood tumor.

Blindness↗
PubMed1984

Color contrast perimetry.

A method for color perimetry is proposed in which colored test objects are presented in a white surround, so that the luminance of the object and its surround are identical. The color of the test object then may be varied in its degree of saturation, while maintaining a constant luminance. A color video instrument controlled by a microcomputer is used as a tangent screen. Foveally viewed, colored test objects are adjusted initially in luminance by heterochromatic flicker photometry to match the luminance of a white background at 100 apostilb. The relative foveal scotoma for blue light requires that test objects large enough to include the perifoveal retina be used for flicker photometry of blue test objects. Due to the progressively increasing threshold for luminance contrast detection in extrafoveal retina, differences in luminance between the colored objects and the white surrounding, as the test objects are moved into the extrafoveal visual field, appear to remain subthreshold. Test object detection can thus be expected to be a perimetric measure of color contrast detection, relatively unaffected by luminance contrast detection. This strategy should simplify the use of colored objects for clinical perimetric testing and should provide a specific test of color vision in the extrafoveal visual field.

Adult↗
PubMed1983

Calibration of the Dicon Auto Perimeter 2000 compared with that of the Goldmann perimeter.

We empirically evaluated the calibration of the Dicon Auto Perimeter 2000 by comparing the results of threshold static perimetry with those for the same group of normal subjects examined by conventional manual static perimetry with the Goldmann perimeter. At 10 to 20 degrees of eccentricity in the visual field (including the entire Bjerrum region), there was no significant difference between threshold levels expressed as Goldmann equivalent stimuli by the Dicon instrument and the results obtained by examination with the Goldmann perimeter. The slopes of the linear meridional profiles from the two instruments were significantly different, however. The slope of the profile measured with the Dicon perimeter was flatter than that produced by Goldmann perimetry, so that threshold values inside 10 degrees of eccentricity were higher, whereas threshold values outside of 20 degrees of eccentricity were lower. Though statistically significant, these differences were small (2 dB at most). The difference in slopes can be attributed to a difference in stimulus sizes, because the area of the Dicon stimulus is eight times that of the size I Goldmann test object and twice that of the size II test object.

Adult↗
PubMed1983

Visual field defects in idiopathic intracranial hypertension (pseudotumor cerebri).

Idiopathic intracranial hypertension (pseudotumor cerebri) produces loss of visual field and visual acuity. We conducted a retrospective study of 12 patients (all female, ranging in age from 6 to 44 years) using computerized visual field analysis. In seven of the 12 patients, the visual field loss appeared to be permanent, and follow-up was too short for the final outcome to be determined in two others. The visual field defects were those known to be associated with optic disk lesions. The most common were blind spot enlargement (all 12 cases), isopter constriction (nine cases), and loss on the nasal side of the visual field (seven cases), especially in the inferonasal quadrant. Four patients had diminished visual acuities. The reversibility of the visual field defects was correlated with the presence (nonreversible) or absence (reversible) of ophthalmoscopic signs of chronic papilledema. Because visual loss is reversible if treatment is begun before the onset of the optic disk changes associated with chronic papilledema, patients with idiopathic intracranial hypertension should be monitored carefully with frequent perimetric and visual acuity testing.

Adult↗
PubMed1983

Three-dimensional topography of the central visual field. Sparing of foveal sensitivity in macular disease.

Threshold static perimetry was performed using test object patterns that covered contiguous areas of the central visual field. Computer imaging methods were used to display a three-dimensional surface that was interpolated between the sensitivity values at each of the test object locations. The examinations covered the area out to and including 10 degrees of eccentricity from the point of fixation, corresponding to the same area of the visual field covered by the Amsler grid. The normal visual field surface appears as a high plateau with a smoothly rising level of sensitivity forming a peak at the point of fixation. It was found that in a variety of macular diseases, including those caused by vascular, as well as primary degenerative disorders, central scotomas were characterized by relative sparing of visual sensitivity at the point of fixation. The pattern thus produced was one of a ring-shaped depression within the central 10 degrees of the visual field. This phenomenon was present in 20% of cases with central scotomas resulting from macular disease, but was not found in any eye of 64 patients suffering from central scotomas as a result of optic nerve disease. This pattern of visual field loss may be common, though not frequently recognized. It is proposed that the phenomenon of preservation of foveal sensitivity may be a marker for macular disease, as distinct from central visual field defects arising from optic nerve disease.

Adult↗