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Biomedical subjects

A Heijl

Publications and source records attributed to A Heijl.

At least 73 records · Page 4Linked to original sources
PubMed1989

Visual field interpretation with empiric probability maps.

Automated visual field charts may be difficult to interpret partly because of the magnitude and complex nature of normal threshold variability. We devised two types of empiric probability maps in which this variability is taken into account and the significances of measured threshold values are displayed. These maps are highly sensitive to nonobvious but significant paracentral field loss but will at the same time deemphasize false-positive patterns commonly found more peripherally. They also frequently show field defects before these are obvious in conventional threshold printouts. In addition, they differentiate between generalized loss of sensitivity and localized field defects.

Cataract↗
PubMed1989

Effect of IOP on the visual field in ocuLar hypertension and glaucoma.

The traditional opinion that increased intraocular pressure is the cause of glaucoma is controversial, probably mainly because of the fact that firm evidence for the value of pressure reduction is largely lacking. The present article reviews results from short term studies of visual fields before and after pressure reduction. It also reviews published and unpublished preliminary results from studies addressing the problem of whether the long term visual field prognosis, in glaucoma and in ocular hypertension, is affected by pressure lowering therapy. There is no convincing agreement among results from modern studies using computerized perimetry indicating that acute lowering of the ocular tension results in an improvement of the glaucomatous visual field. Long-term result are equally conflicting, and often negative. We have noted from a preliminary analysis of our own masked, prospective study of patients with 'high risk' ocular hypertension, that the same results may be interpreted in quite different ways. The results of available studies certainly indicate that pressure reduction does not automatically lead to clear and positive effects on the visual field. The studies have often been small, however, and have usually not had the power of detecting small effects of treatment. Also, pressure reduction has usually not been dramatic and many treated patients have maintained 'elevated' pressure levels. Patients with very high pressures have not been included, and the effect of pressure reduction in this situation has therefore not been investigated at all. More controlled, prospective therapeutic studies are necessary and ethical. It seems particularly important to study the long-term effects of non-pharmacologically induced pressure reduction in patients with manifest field loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Glaucoma↗
PubMed1989

Computerized perimetry in glaucoma management.

The present article discusses the role of computerized perimetry in the management of patients with suspect and manifest glaucoma. The value of visual field examination is compared to that of inspection and photography of the optic disc and to some extent to retinal nerve fibre layer photography. Computerized perimetry is related to standard manual visual field examination. Guidelines are offered for the choice of test programs and for the interpretation of results.

Computers↗
PubMed1989

Lack of diffuse loss of differential light sensitivity in early glaucoma.

We studied the differential light sensitivity in 83 patients who were prospectively followed with computerized threshold preimetry and optic disc pathography because of suspect glaucoma. Eyes with media opacities were excluded from the analysis. Fourteen eyes developed progressive optic disc cupping and/or localized visual field loss. In this glaucoma group light sensitivity in the 10 best points in the visual field did not deviate more from estimated age-corrected standard values than in the remaining groups of 115 eyes with increased intraocular pressure and 18 normotensive eyes. The results do not support the concept that diffuse loss of differential light sensitivity should be common in early glaucoma.

Follow-Up Studies↗
PubMed1989

Normal visual fields as assessed by computerized static threshold perimetry in patients with untreated primary hypothyroidism.

In this prospective study, 25 consecutive patients with untreated primary hypothyroidism were tested with a highly sensitive perimetric technique, since a high prevalence of visual field defects has been described in this condition. All patients had clinical hypothyroidism, a serum TSH value greater than 20 mU/l (reference range 0.4-4.0) and decreased/low normal serum total T4 concentration. Visual fields were tested with fully automated threshold-measuring computerized perimetry of the central 30 degrees field. Interpretation of fields included computer-assisted analysis provided by a perimetric statistical programme package. In 23 patients, conventional inspection and computer-assisted analysis showed no visual field defects. Two patients were excluded from the latter analysis: one patient who did not respond adequately at computerized perimetry and in whom manual field tests were entirely normal: one patient who had low sensitivity values in the uppermost parts of both visual fields owing to markedly swollen upper eye lids. In conclusion, although pituitary hyperplasia has been well documented in primary hypothyroidism, the present prospective study clearly indicates that visual field defects are not a common finding in patients with this disease.

Adult↗
PubMed1989

Diagnosis of early glaucoma with flicker comparisons of serial disc photographs.

We evaluated flicker comparison, a technique for detecting differences in serial fundus photographs. Serial optic disc photographs and computerized threshold visual fields were obtained every 3 months for an average of 40 months in 131 eyes of 81 patients with elevated intraocular pressure and normal visual fields. Two serial monophotographs were projected, optically aligned, and superimposed; analysis was done by alternately viewing first one and then the other image. We found flicker analysis of serial disc photographs to provide results which were closely correlated with those of computerized threshold perimetry. Thus, of those 12 eyes which developed field defects, eight showed definite change and two showed highly suspected change in optic disc configuration. Only two eyes showed a definite alteration in optic disc anatomy without the development of field loss, and field defects appeared in only one of 109 eyes in which there was no change or suspected change on flicker comparison. The flicker method was more sensitive than conventional nonflickered comparisons, but changes could usually be seen also with conventional inspection once they had been detected by the flicker method. Our findings suggest that flicker analysis may offer a considerable improvement over current standard methods of analyzing serial photography and may be a useful complement to routine perimetry. However, this method requires special equipment; requires that the photographs be similarly centered; and is time-consuming. Alignment of photographs by means of computerized image analysis techniques could make the method clinically practicable.

Diagnosis, Differential↗
PubMed1988

Evaluation of adaptive spatial enhancement in suprathreshold visual field screening.

Sixty-three normal subjects and 94 abnormal patients, most of whom had glaucoma, were tested in the central visual field using a threshold-related, eccentricity-compensated, spatially adaptive suprathreshold screening program and a full-threshold program on the Humphrey field analyzer. The initial stimulus locations on the screening test were identical to those of the threshold test; additional screening stimuli were presented surrounding each missed initial stimulus. Surprisingly, this spatial enhancement strategy did not improve sensitivity or specificity rates of the screening beyond that achieved by considering the initial stimulus locations alone. Points missed during screening often showed a depressed sensitivity rate (measured threshold greater than 6 dB below the age-corrected normal reference value) in the same area of the threshold field. This was true in fields from abnormal and normal subjects. This finding of persistent shallow defects in the same test session among otherwise normal persons has disturbing implications for the importance of "confirmed" defects in the diagnosis of disease.

Adolescent↗
PubMed1987

Normal variability of static perimetric threshold values across the central visual field.

We assessed the variability of results in normal subjects of computerized static threshold perimetry of the central 30 degrees field. Variability of measured threshold values was highly dependent on eccentricity. This included variability among individuals, test-to-test variability within individuals, and intratest variability. All values were significantly larger in the midperiphery than centrally. We found that the mean sensitivity decrement with age was eccentricity dependent, so that the age-corrected normal visual field became not only depressed but also steeper with age. Distributions of individual pointwise deviations from the age-corrected normal mean thresholds were significantly nongaussian. The dependency of variability on test point location, the nongaussian distributions of deviations from age-corrected means, and the variability of age-induced sensitivity reduction should all be considered in the interpretation of computerized visual fields, and particularly in the design of statistical programs for field analysis. Programs not considering these factors are likely to result in misleading analyses.

Adult↗
PubMed1986

Technique for testing the patency of laser iridotomies.

With laser iridotomy it may often be difficult to achieve total penetration of the iris, particularly in very light or very dark irides. It may be impossible to determine with the slit-lamp whether a small laser iridotomy is functionally penetrating. We describe a straightforward method to test iridotomies for aqueous flow patency. Transcorneally introduced fluorescein is used to delineate any aqueous bulk flow from the posterior to the anterior chamber.

Aqueous Humor↗
PubMed1986

Frequent disc photography and computerized perimetry in eyes with optic disc haemorrhage. A pilot study.

Two patients (one with glaucoma with field loss, one with ocular hypertension) with previously known optic disc haemorrhage were followed with frequent disc photography, computerized perimetry and tonometry for a period of one year. Nine haemorrhages were seen in three of the four eyes studied. Three bleedings showed sudden enlargements, interpreted as re-bleedings, during the absorption phase. Haemorrhages were not associated with any stepwise localized or general worsening of the visual field, nor did the fields deteriorate during the period of the study. No structural changes of the optic nerve head were seen after the bleedings during the observation time of one year. The duration of the haemorrhages varied, but no bleeding lasted less than one week. Before disappearing they were often so small that they could only be detected when series of photographs were examined in chronological order. Haemorrhages large enough to be discernible on isolated slides were present in 20% of the disc photographs. Thus disc haemorrhages are transient and easy to overlook. Many careful observations may be necessary before the first haemorrhage is seen. Each individual bleeding is a minor vascular incident which usually leaves no measurable functional or structural trace.

Computers↗
PubMed1985

Computerised perimetry.

During the last few years computerised perimetry has become a clinical reality. This new technique eliminates the operator's error, ensures reproducibility of test procedures and parameters and makes visual field testing of large numbers of patients possible. Great differences exist between computerised perimeters. Differences in hardware for example, the way in which stimuli or field charts are produced may be striking but even more important are differences in software, especially test algorithms. The results obtained with some instruments and test programmes are of such high quality that the same level of performance may be almost impossible to obtain with manual perimetry, at least in a clinical setting. Nevertheless, improvements can be expected in the future particularly in adaptive tests and in computerised interpretation of the fields.

Computers↗
PubMed1984

The frequency distribution of earliest glaucomatous visual field defects documented by automatic perimetry.

2500-3000 eyes with ocular hypertension, with or without established glaucoma in the fellow eye, were followed with automatic perimetry for several years. Forty-five eyes showed a documented change from repeated normal fields to reproducible glaucomatous visual field loss. The location of the defective points in the first pathological field of each eye was registered. The resulting frequency distribution is shown and discussed.

Computers↗
PubMed1984

The short-term effect of laser trabeculoplasty on the glaucomatous visual field. A prospective study using computerized perimetry.

Several earlier studies have shown improvement of glaucomatous visual fields after pressure reduction achieved by acetazolamide or filtering surgery, while other studies have given conflicting results. In the present study laser trabeculoplasty was used to reduce the IOP in 42 eyes with glaucomatous visual field defects. Although good pressure reduction was achieved, no general regression of field defects was observed. The changes of the visual field were not correlated to the degree of pressure reduction. The results do not support the hypothesis that glaucomatous field defects are reversible when the IOP is reduced.

Adult↗
PubMed1984

One- and two-session laser trabeculoplasty. A randomized, prospective study.

Seventy-seven eyes with primary open angle glaucoma and exfoliation glaucoma were subjected to laser trabeculoplasty and followed in a prospective way. The full 360 degrees circumference was treated, but the patients were randomized in two groups: In group 1 the full treatment was given in one session, and in group 2 it was divided into two sessions one month apart. During the follow-up time of 3 to 18 (mean: 12) months both methods of treatment gave the same reduction of IOP. The only three cases with high post-operative transient pressure spike-occurred in group 1. Although this difference of course not is statistically significant it is in agreement with other studies suggesting that a two-session approach might be safer than treating the full circumference in one session. One month after the laser treatment the eyes of group 1, where the full circumference of the trabecular meshwork had been treated, showed only a slightly larger pressure reduction (not statistically significant) than the eyes of group 2 one month after treating 180 degrees of the meshwork.

Adult↗