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Biomedical subjects

S M Drance

Publications and source records attributed to S M Drance.

At least 19 recordsLinked to original sources
PubMed1992

The neuroretinal rim in descending optic atrophy.

We studied seven human eyes in which the changes of the neuroretinal rim areas following complete loss of all axons could be measured planimetrically. The mean diminution of the neuroretinal rim area was 40% (range from 26-72%). The optic nerve pathology causing the loss of axons was in the posterior portion of the nerve and the optic disc was therefore not directly disturbed by the injuries. It appears that less than half of the neuroretinal rim is occupied by nerve fibers.

Axons↗
PubMed1992

The relationship between intraocular pressure and visual field progression in glaucoma.

The purpose of this study was to determine the intraocular pressure characteristics in glaucoma suspects and patients whose visual fields were classified as stable or progressing over a long-term follow-up. We present data from 64 patients who received either medical or laser treatment and who were followed up for a median of 7.4 years. The visual fields of 27 patients were classified as stable and 37 as progressing using predetermined criteria on either the Tübinger or Goldmann perimeter. Patients with initially normal and initially abnormal fields were analysed separately to avoid bias. There were no significant group differences in the mean, highest or interquartile range of intraocular pressure in the follow-up. The largely overlapping distributions over a wide spectrum of the pressure variables in patients with stable and progressing fields show that intraocular pressure alone cannot separate these two groups of patients. Our study does not suggest that pressure reduction in glaucoma has no beneficial effect, but that there may be other factors which determine the fate of the visual field in glaucoma.

Aged↗
PubMed1992

Central function and visual field damage in glaucoma.

82 eyes of 82 patients with different types of glaucoma were examined with various psychophysical tests assessing central and paracentral function, including foveal temporal contrast sensitivity function, FM 100-Hue test, and foveal and parafoveal blue-on-yellow-sensitivity. For all eyes visual field tests were performed with the Humphrey-Field-Analyzer, program 30-2. Global visual field indices were calculated as follows: Mean Sensitivity MS, Mean Deviation MD, and Corrected Pattern Standard Deviation CPSD. Linear regression analysis and multiple regression analysis correcting for a possible influence of age between the central and paracentral criteria and the global indices was performed. For the entire study population highly significant correlations are present between foveal and parafoveal blue-on-yellow-sensitivity and MS, MD and CPSD. Whereas in the Normal Tension Glaucoma subgroup (19/82 eyes) no significant correlations are found, the subgroup of 35/82 eyes with markedly elevated intraocular pressure (> or = 30 mmHg) shows highly statistically significant correlations between the low- and high-frequency end of the foveal temporal contrast sensitivity function and foveal and parafoveal blue-on-yellow-sensitivity and the global field indices. The results of the present study support the idea that there are two different mechanisms of glaucomatous damage, one which is pressure-dependent and one which may be pressure-independent. The pressure-dependent mechanism is responsible for deficits of central or paracentral function which are correlated to overall visual field damage.

Chronic Disease↗
PubMed1992

Diffuse field loss and diffuse retinal nerve-fiber loss in glaucoma.

A total of 61 eyes of 61 patients were examined by light-sense, flicker and resolution perimetry. All fields were classified as being normal or showing diffuse loss, localized defects or diffuse plus localized loss. For the assessment of diffuse field loss, cumulative defect curves were derived. Retinal nerve-fiber layer (RNFL) loss was assessed by a semiquantitative scoring technique. In light-sense and flicker perimetry, the total diffuse and total overall RNFL scores for eyes with diffuse field loss were approximately twice those obtained for eyes without diffuse field loss. These differences were highly statistically significant (P = 0.0055 and 0.0087 for light-sense perimetry, P = 0.0033 and 0.0042 for flicker perimetry). In resolution perimetry, eyes with diffuse field loss also showed higher RNFL scores; the differences, however, were not statistically significant. The results show that diffuse field loss in light-sense and flicker perimetry is accompanied by diffuse nerve-fiber loss.

Adult↗
PubMed1992

The selective effects of elevated intraocular pressure on temporal resolution.

Twenty-seven eyes of 27 patients with normal tension glaucoma (NTG), 68 eyes of 68 patients with primary open-angle glaucoma (POAG), and 11 eyes of 11 patients with special forms of high-tension glaucoma (SHTG) including (pigmentary glaucoma, angle-closure glaucoma, secondary glaucoma, etc.), were examined by automated light-sense and temporal resolution perimetry. Light-sense perimetry was performed with the Humphrey Field Analyzer, using program 30-2. Temporal resolution perimetry was conducted with a system developed by Lachenmayr. Global field indices were calculated for all visual fields and modalities: mean defect (MD) for light-sense perimetry and mean flicker defect (FD) for flicker perimetry. For each of the three glaucoma groups there was a significant linear correlation of FD over MD. The slope of the regression line (regression coefficient a) increased with increasing maximal pressure level of the glaucomatous group: for NTG a = 0.6671, for POAG a = -1.2413, and for SHTG a = -2.235. The differences of the regression coefficients between NTG and POAG and between NTG and SHTG were statistically significant (P = 0.0366 and P = 0.0046, respectively). The results of the present study provide evidence that the relative amount of damage to flicker compared to light-sense perimetry increases with increasing maximal pressure level of a glaucomatous population. Thus, flicker perimetry may be a tool for the identification of eyes with pressure-produced damage.

Adult↗
PubMed1992

Diffuse field loss and central visual function in glaucoma.

Eighty-two eyes of 82 patients with different types of glaucoma were examined with program 30-2 of the Humphrey Field Analyzer. Forty-six of 82 eyes (56.1%) had diffuse field loss and 36/82 (43.9%) eyes had no diffuse field loss according to the cumulative defect curves. Various foveal threshold criteria including temporal transfer and color vision were tested in all eyes. All criteria showed a loss of sensitivity in the presence of diffuse field loss. The loss of sensitivity was statistically significant for the high-frequency end of the foveal temporal contrast-sensitivity function (P = 0.0498), for foveal flicker-fusion frequency (P = 0.0275) and for foveal and parafoveal blue-on-yellow sensitivity (fovea: P = 0.0009; 4 parafoveal points: P = 0.0001; 16 points in the central 10 degrees: P < 0.0001). The loss in sensitivity was not statistically significant for the low and intermediate temporal frequencies of the foveal temporal contrast-sensitivity function and for the FM 100-Hue loss score. All temporal threshold criteria showed a low sensitivity (25-37%) and a low negative predictive value (48-50%) for the presence of diffuse field loss. Their specificity (75-94%) and positive predictive value (65-83%) are high, however. Thus, whenever one of the foveal temporal threshold criteria as used in the present study is abnormal, the probability is very high that there is some diffuse field loss.

Adult↗
PubMed1991

Light-sense, flicker and resolution perimetry in glaucoma: a comparative study.

A total of 106 eyes of 106 patients with different types of glaucoma were examined by automated light-sense, flicker and resolution perimetry (Humphrey Field Analyzer, program 30-2; flicker perimeter as described by Lachenmayr [16, 18]; resolution perimeter as devised by Frisén [4, 6, 8-11]). The fields were classified in a masked fashion as being normal or as having purely diffuse loss, purely localized loss or diffuse as well as localized loss. As compared with light-sense perimetry, resolution perimetry had a markedly lower sensitivity in the detection of glaucomatous damage (77%) but a high specificity (93%); the comparison of resolution perimetry with flicker perimetry showed similar results (sensitivity, 75%; specificity, 85%). When flicker perimetry was compared with light-sense perimetry and vice versa, the sensitivity was high (95% and 94%, respectively), but the specificity was low (57% and 62%, respectively). The prevalence of detection of diffuse loss by both light-sense and resolution perimetry was related to visual acuity, whereas flicker perimetry did not show such a relationship.

Adult↗
PubMed1991

Diffuse and localized glaucomatous field loss in light-sense, flicker and resolution perimetry.

A total of 75 eyes in 75 patients with different types of glaucoma (21 eyes with low-tension glaucoma, 49 with primary open-angle glaucoma and 5 with pigmentary glaucoma) were examined by automated light-sense, flicker and resolution perimetry. All fields were classified in a masked fashion as being "normal" (N) or as having "diffuse loss" (D), "localized loss" (L) or "diffuse plus localized loss" (DL). The frequency distributions for the various field loss categories were plotted against the highest intraocular pressure ever reported in the patients' records. The frequency distribution for the purely localized defects showed a peak at 20 mmHg and were markedly skewed to low pressure values, whereas those for both diffuse plus localized damage and purely diffuse loss peaked at about 30 mmHg. The data suggest that diffuse field loss may be an indicator of pressure-induced damage.

Adult↗
PubMed1991

Correlation of retinal nerve-fiber-layer loss, changes at the optic nerve head and various psychophysical criteria in glaucoma.

In 61 eyes of 61 patients with glaucoma, semiquantitative assessment of retinal nerve-fiber-layer (RNFL) loss and neuroretinal rim measurement of the optic nerve head by means of the Optic Nerve Head Analyzer were correlated to the outcomes of automated light-sense, flicker and resolution perimetry and the Farnsworth-Munsell (FM) 100-Hue test. A significant influence of age on total RNFL and total diffuse RNFL scores was found, but there was no measurable effect of age on neuroretinal rim area. Total RNFL and total diffuse RNFL scores showed a good correlation to the various visual field indices: total RNFL score vs mean flicker frequency as determined by flicker perimetry, r = -0.606, P less than 0.0001; total RNFL score vs mean sensitivity as determined by light-sense perimetry, r = -0.385, P = 0.002; and total RNFL score vs mean ring score as determined by resolution perimetry, r = 0.341, P = 0.007. There was no significant correlation between RNFL scores and the FM 100-Hue score. Correlation between the neuroretinal rim area and the various psychophysical indices was poor and mostly not statistically significant. The high correlation of flicker scores with RNFL loss provides interest for future applications of this perimetric technique.

Adult↗
PubMed1991

Adrenergic and adrenolytic effects on intraocular pressure.

We compared the pressure-lowering effects of timolol, pindolol, epinephrine and the mixture of timolol and epinephrine with that of placebo over a 12-h period. All agents reduced the pressure significantly but with varying time courses. The mixture of timolol and epinephrine reduced the pressure significantly more than did timolol or epinephrine alone, especially at 12 h after the last administration of the drops.

Administration, Topical↗
PubMed1991

Sensitivity and specificity of a diagnostic test determined by repeated observations in the absence of an external standard.

Traditionally, the sensitivity and specificity of a new diagnostic test are derived from its application to two groups of individuals known to have or not to have met the criterion to be detected as judged by means of a "gold standard", some external time-honored test. In this study, a test with unknown accuracy parameters was used to detect an end-point criterion in an ongoing ophthalmological clinical trial. Since no external test method was available to assess the accuracy of this test, equations were derived relating the unknown sensitivity and specificity of the test to data frequencies based on replicate measurements. The solutions to these equations also provided estimates of the incidence rate of the criterion under investigation in the group tested, and of the predictive values of the test. The validity of this method of estimation is discussed, and applications to other situations are suggested.

Glaucoma↗
PubMed1991

Diffuse visual field loss in open-angle glaucoma.

Recent studies have suggested that diffuse field loss and localized visual field loss in glaucomatous patients may have different pathophysiologic mechanisms. Testing that hypothesis requires that some patients present with purely localized field loss and other patients with purely diffuse loss. This article describes four highly selected patients with elevated intraocular pressures, bilateral damage to the optic nerve head, one eye with a classic glaucomatous visual field defect and in the other eye, in the absence of opacities in the media, a diffuse loss of the visual field. Although purely localized loss is very common, the report illustrates purely diffuse loss in the absence of other causes.

Adult↗
PubMed1991

Effect of the number of threshold determinations on short-term fluctuation in automated perimetry.

The authors studied the effect of multiple threshold determinations on local and global (root-mean-square) short-term fluctuation in 30 subjects (10 controls, 10 glaucoma suspects, and 10 glaucoma patients) with a mean age of 56.70 years. Five custom programs were designed on the Octopus perimeter in which the total number of threshold determinations was equal but in which thresholds at 2 principal locations were determined between 2 and 15 times. One randomly selected eye of each subject was first tested with the standard Octopus programs G1 and 31 followed by the custom programs. Local fluctuation initially increased with the number of threshold determinations and then stabilized after five determinations. Global fluctuation was not influenced by the number of determinations and the values obtained by the shorter custom programs were not significantly different from those obtained by the standard programs. Programs that determine thresholds only twice at a given location may underestimate local fluctuation. Furthermore, local fluctuation is de-emphasized by the "watering-down" effect of estimating global fluctuation.

Adult↗
PubMed1991

A comparison of treated and untreated glaucoma suspects.

One hundred forty-three patients with intraocular pressures (IOPs) above 22 mmHg and without visual field defects or any obvious evidence of optic nerve damage were randomly assigned to either a timolol treatment group or no treatment in a 6-year prospective clinical trial. Endpoints were defined as reproducible visual field defects on automatic perimetry, disc hemorrhages, or stereophotographically documented optic nerve head changes. Endpoints developed in 42 patients: 28 visual field defects, 8 changes in disc appearance, and 6 disc hemorrhages. Of the 42 patients, 20 were treated and 22 were not. Survival analysis showed no statistically significant differences in failure time to any endpoints between the two groups. In the untreated group, the time to failure of disc change was related to the mean IOP during the study and also to the changes in the IOP from baseline. A significant correlation was found between initial cup-to-disc ratio and survival time to visual field defects in the untreated group.

Aged↗
PubMed1991

[Diffuse and localized glaucomatous visual field changes in light sense, flicker and visual acuity perimetry. Evidence of pressure damage].

75 eyes of 75 patients with different types of glaucoma (21 eyes with normal-tension glaucoma, 49 eyes with primary open-angle glaucoma and 5 eyes with pigmentary glaucoma) were examined by automated light-sense, flicker and resolution perimetry. All fields were classified as being "normal" (N) or having "diffuse loss" (D), "localized loss" (L) and "diffuse plus localized loss" (DL) in masked fashion. The frequency distributions for the various field loss categories against the highest intraocular pressure ever reported in the patients' records were plotted. The frequency distributions for the purely localized defects show a peak at 20 mmHg and are markedly skewed to low pressure values, while the diffuse plus localized damage and the purely diffuse loss, however, show a peak at about 30 mmHg. The data support the hypothesis that diffuse field loss may be an indicator of pressure-induced damage.

Adult↗
PubMed1990

The use of visual field indices in detecting changes in the visual field in glaucoma.

We present results from 64 glaucoma patients and glaucoma suspects followed up for a median period of 7.4 yr who had a median of seven examinations using Program 31 on the Octopus perimeter. The patients also had manual visual fields recorded on either the Tübinger or Goldmann perimeter during the same period. By examining all manual fields over the follow-up, we classified 37 patients as deteriorating and 27 as nondeteriorating by using predetermined field criteria which we believed to be clinically significant. In a masked fashion, the indices mean defect (MD) and corrected loss variance (CLV), in addition to the three cluster analysis indices SIZ, CLUS, and PCLUS were computed for each patient and regressed on time. When a significant positive index/time slope (P less than 0.05) was defined as indication of deterioration, all indices had remarkably poor sensitivities because their slopes did not reach statistical significance in the great majority of patients. When, regardless of statistical significance, positive slopes were defined as indication of deterioration and negative slopes as nondeterioration, the most sensitive index, PCLUS, still had a sensitivity of less than 65%. The indices were better in detecting the presence or absence of visual field deterioration in fields that were initially normal than in those that were initially abnormal. Since the testing modalities of manual and automated perimetry are different, our study was not designed to compare the sensitivity of one technique over the other. Our study does, however, demonstrate that the indices used currently may not be clinically reliable in the assessment of changes in the visual field.

Analysis of Variance↗
PubMed1990

The size and shape of the optic disc in normal human eyes.

We studied the size, shape, and configuration of connective tissue of the optic disc in normal eye-bank eyes from 60 adults. The mean vertical and horizontal disc diameters were 1.88 and 1.77 mm, respectively. These figures are larger than most estimates of disc diameter using clinical image analysis methods. Within our sample, larger eyes did not have larger discs. The normal variation in disc diameter is sufficient to explain the normal variation in cup-disc ratio. The optic discs of blacks were larger and more oval than those of whites, though the axial lengths of the eyes in the two groups were not significantly different. Women's eyes and discs were smaller than those of men, possibly explaining the smaller cup-disc ratio in women. Larger optic discs and optic nerves have more optic nerve fibers than do smaller discs and nerves. Oblique insertions of the disc were detected in 18% of eyes. These were predominantly centered in the inferior disc and were more commin in white women.

Aged↗