Biomedical subjects

W M Hart

Publications and source records attributed to W M Hart.

At least 37 records · Page 2Linked to original sources

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↗

PubMed1982

Computer-generated display for three-dimensional static perimetry.

A display method has been developed for imaging the results of static perimetric examinations performed over contiguous areas of the central visual field. Points are examined using a rectangular coordinate pattern. A three-dimensional display surface is interpolated between the recorded points. A two-dimensional representation of the interpolated surface is then drawn, using superposition of foreground elements to produce an illusion of depth. Refinements of surface fit to the data points and truncation and rotation of the images allow immediate appreciation of visual field topography. The use of rectangular coordinate patterns increases the probability of detection of small defects and improves the resolution of structural detail.

Adolescent↗

PubMed1982

The onset and evolution of glaucomatous visual field defects.

Long-term follow-up was recorded on the visual fields of 251 patients with chronic open-angle glaucoma and 826 patients with ocular hypertension. Observation periods exceeded ten years for 73 patients with manifest glaucoma. Initial glaucomatous defects appeared in 98 eyes of 72 patients while under continuous observation. Initial defects were characteristically shallow and were located most commonly in the superior Bjerrum region adjacent to the blind spot. Three-dimensional (contiguous area) static perimetry provided superior resolution in detecting and characterizing the full extent of such shallow defects. The chronologic course of initial defects defects was marked in 22 of the 98 eyes by a phenomenon of a transiently appearing defect. Disappearance and reappearance of transient defects did not occur synchronously with short-term fluctuations in intraocular pressure. Ten-year follow-up of 63 eyes with manifest glaucomatous defects showed a high incidence (73%) of progression to dense involvement of the originally affected altitudinal hemifield. All eyes were treated continuously, but visual field loss occurred in spite of only marginally elevated levels of intraocular pressure.

Female↗

PubMed1981

Computer processing of visual field data. I. Recording, storage, and retrieval.

A minicomputer system has been developed to provide real-time management of visual field data. Records of a large population of patients with glaucoma in a university ophthalmic practice are stored on magnetic disks. Data storage has been semiautomated by means of a microprocessor-controlled recording device for standard perimeters. Existing visual field records may also be digitized by means of a magnetic graphics tablet. Records are retrievable in real time and are graphically displayed at video terminals.

Diagnosis, Computer-Assisted↗

PubMed1981

Computer processing of visual data. II. Automated pattern analysis of glaucomatous visual fields.

Machine algorithms have been developed for automated detection and characterization of glaucomatous defects in visual field records stored in a computer. Using elementary techniques of pattern analysis, the contours defining each visual field are described by a set of primitive graphic and type-descriptive features. A hierarchical structure of logical tests is then used to arrive at intermediate and higher-level conclusions. Decision procedures are tailored for the detection of features commonly found in glaucomatous visual fields. Application of these analysis procedures to a large group of visual field records having a broad range of glaucomatous defects shows a very high sensitivity for detection. Specificity is limited by the extent to which defects are "typical" or obey expected patterns of field loss.

Decision Making↗

PubMed1980

Bilateral optic nerve sheath meningiomas.

A 35-year-old man was initially seen following the incidental discovery of swollen optic disc in both eyes. Over a subsequent 15-year period, the patient experienced an inexorable loss of vision in both eyes, characterized by normal neuroradiologic findings and the presence of opticocillary shunt vessels on both discs. A craniotomy ultimately demonstrated the presence of bilateral optic nerve sheath meningiomas that appeared to have arisen multifocally.

Adult↗

PubMed1980

Disappearing opticociliary shunt vessels and pseudotumor cerebri.

In two patients opticociliary venous shunts occurred in association with pseudotumor cerebri. One patient underwent bilateral optic nerve sheath fenestrations, after which her papilledema resolved, and the opticociliary venous shunts were noted to be markedly decreased in caliber.

Adult↗

PubMed1979

Multivariate analysis of the risk of glaucomatous visual field loss.

In a retrospective study, 92 patients with ocular hypertension, ie, intraocular pressure of 21 mm Hg or higher, and no evidence of glaucomatous visual field defects, were observed for five years. Visual field defects developed in one or both eyes of 33 patients during the five-year follow-up period, while none were detected in the remaining 59. Values for suspected risk factors, determined at the outset of the follow-up period, were subjected to a multivariate analysis with use of linear discriminant analysis and a multiple logistic function. Models of risk providing maximum separation of the two patient groups (visual field loss vs no visual field loss) found that the risk factors having the greatest significance for prediction of visual field loss included vertical estimates of cup/disc ratio, mean IOP during the period of observation, a positive family history of glaucoma, and age. Factors having the lowest predictive values included IOP response to topical dexamethasone, plasma cortisol suppression, and a history of systemic hypertension.

Glaucoma↗