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Biomedical subjects

F S Mikelberg

Publications and source records attributed to F S Mikelberg.

At least 19 recordsLinked to original sources
PubMed1998

The ability of scanning laser ophthalmoscopy to identify various glaucomatous optic disk appearances.

PURPOSE: To compare four distinct glaucomatous disk appearances using scanning laser ophthalmoscopy and determine the ability of a previously described discriminant analysis to detect glaucomatous damage for each group. METHODS: Two thousand three hundred eighty-eight stereoscopic optic disk photographs of 2,388 subjects with glaucoma or suspicion of glaucoma were reviewed to select four pure glaucomatous optic disk types. Twenty-three topographic, volumetric, and morphometric scanning laser ophthalmoscopic variables from one optic disk of each selected subject were compared. Differences between the groups were evaluated using an analysis of variance and the Pearson chi-square test. RESULTS: Forty-four focal ischemic disks, 38 myopic glaucomatous disks, 30 senile sclerotic disks, and 28 disks characterized by generalized cup enlargement were studied. Significant intergroup differences were found for the majority of the evaluated optic disk variables. The accuracy with which the discriminant analysis model was able to detect disks with glaucomatous visual field damage was 93.2% for focal ischemic disks, 81.6% for myopic disks, 66.7% for senile sclerotic disks, and 78.6% for disks with generalized cup enlargement. CONCLUSIONS: By comparing mean values for certain optic disk variables, scanning laser ophthalmoscopic optic disk assessment can distinguish groups of disks with specific appearances. However, the ability of presently available software to detect glaucomatous damage varied considerably with disk appearance. Expert clinical optic disk evaluation remains an important part of the assessment of patients suspected of having glaucoma, although refinement of computerized scanning laser ophthalmoscopic disk assessment may eventually make this easier.

Analysis of Variance↗
PubMed1998

Retinal nerve fiber layer height in high-tension glaucoma and healthy eyes.

PURPOSE: To determine the correlations between the retinal nerve fiber layer height measured by Heidelberg Retina Tomograph, version 1.11, and visual field indices in healthy individuals and patients with glaucoma. METHODS: One eye was randomly chosen from 48 patients with glaucoma and 60 healthy individuals. All participants were classified using Humprey visual field, program 30-2 (Humphrey Instruments, Inc., San Leandro, CA, U.S.A.); mean deviation, pattern standard deviation, short-term fluctuation, and corrected pattern standard deviation were measured. Superior and inferior mean deviation were calculated. For each participants the mean Heidelberg Retina Tomograph was generated from three 10 degrees Heidelberg Retina Tomograph pictures. The Student t test was used to compare healthy and glaucomatous retinal nerve fiber layer (RNFL) mean degree values every 5 degrees. A global measurement, superior sector (25 degrees-125 degrees), nasal sector (130 degrees-230 degrees), inferior sector (235 degrees-335 degrees), temporal sector (340 degrees-20 degrees), and polar sector (superior + inferior) were calculated. The global, superior, nasal, inferior, temporal, and polar RNFL height (RNFLH) were compared between healthy individuals and patients with glaucoma. The correlation between global, superior, inferior, and polar retinal nerve fiber layer height and visual field was calculated. RESULTS: A significant difference was found for RNFLH mean from 45 degrees to 330 degrees and for the distribution of the means (as reflected by the standard deviation) from 85 degrees to 100 degrees, 260 degrees to 295 degrees, and 335 degrees to 5 degrees. From these data we created three new sectors: new superior sector (from 85 degrees to 100 degrees), new inferior sector (from 260 degrees to 295 degrees), and new polar sector (combining the new superior and the new inferior sector). Comparing the healthy individuals to the patients with glaucoma, the mean RNFLH values for each sector were found to differ significantly (p < 0.001), with the exception of the temporal sector. Significant correlations (p < 0.001) between the global RNFLH and mean deviation (r = -0.36), pattern standard deviation (r = 0.49), and corrected pattern standard deviation (r = 0.48) were found in healthy participants and those with glaucoma. The strongest correlations (p < 0.001) were found between the pattern standard deviation and the corrected pattern standard deviation with the new polar sector (r = 0.60 and r = 0.59, respectively). CONCLUSIONS: We found that the strongest correlations with the visual field were with the new polar and new inferior sector.

Aged↗
PubMed1997

The effect of optic disc size on diagnostic precision with the Heidelberg retina tomograph.

PURPOSE: The authors evaluated the ability of a confocal scanning laser ophthalmoscope to detect glaucomatous visual field loss by using their previously described discriminant formula on a prospectively obtained cohort. The relationship of optic disc size to diagnostic classification was also evaluated. METHODS: One eye was chosen randomly from each of 153 subjects. Sixty control eyes had intraocular pressure less than 21 mmHg and normal visual fields; 93 glaucomatous eyes had intraocular pressure greater than 21 mmHg and abnormal visual fields. The optic disc status purposely was not used for classification purposes. All subjects were examined with the Heidelberg Retina Tomograph (HRT; Heidelberg Engineering GMBH, Heidelberg, Germany) and Humphrey Perimeter, program 30-2 (Humphrey Instruments, Inc., San Leandro, CA). Visual fields were considered abnormal by the authors' previously published criteria. The HRT classification used age, adjusted cup shape measure, rim volume, and height variation contour to classify the optic disc as normal or glaucomatous. Then the authors assessed the sensitivity, specificity, and diagnostic precision for the entire group, and for three subsets classified by disc area: disc area less than 2 mm2, between 2 and 3 mm2, and more than 3 mm2. RESULTS: The entire group had a sensitivity, specificity, and diagnostic precision of 74%, 88%, and 80%, respectively. The specificity was 83% when disc area was less than 2 mm2 and improved to 89% when disc area was more than 2 mm2. The sensitivity tended to improve from 65% to 79%, and to 83% if the disc area increased, but the difference was not statistically significant. CONCLUSIONS: In a prospective cohort of patients, the HRT discriminant analysis formula was capable of detecting glaucomatous visual field loss with good precision. Unusually small optic discs continue to present diagnostic difficulties.

Adult↗
PubMed1997

Correlation between the visual field indices and Heidelberg retina tomograph parameters.

PURPOSE: We wished to determine whether a relationship exists between Heidelberg retina tomograph (HRT) parameters and the visual field indices. METHODS: One eye was randomly chosen from 59 normal patients [normal visual field and normal optic nerve head (ONH) and intraocular pressure (IOP) < 21 mm Hg], 64 ocular hypertensive patients (normal visual field and normal OHN and IOP > 22 mm Hg), 124 high-tension glaucoma patients (abnormal visual field and/or abnormal optic nerve and IOP > 22 mm Hg) and 47 low-tension glaucoma patients (abnormal visual field and or optic disc and IOP < 21 mm Hg). All the patients were examined with Humphrey Perimeter, program 30-2, and HRT. Findings were assessed by analysis of variance, Pearson's correlation coefficient, and multiple linear regression. RESULTS: Among all subjects, we noted a statistically significant correlation (Pearson's r, p < 0.001) between cup area, cup/disc area ratio, rim area, rim volume, cup shape measure, and retinal nerve fiber layer cross-section area with mean deviation and corrected pattern SD. Multiple linear regression analysis demonstrated that rim area was the most important predictor of mean deviation and corrected pattern SD. CONCLUSIONS: The presence of significant correlations between some HRT parameters, such as rim area and cup shape measure and visual field indices, suggests that these HRT parameters could be good indicators of the degree of glaucomatous ONH damage.

Glaucoma, Open-Angle↗
PubMed1997

ROC analysis of Heidelberg Retina Tomograph optic disc shape measures in glaucoma.

OBJECTIVE: To determine the capacity of the Heidelberg Retina Tomograph (HRT) optic disc shape measures to detect glaucomatous damage. DESIGN: Prospective study. SETTING: Department of ophthalmology at a university-affiliated hospital in Vancouver. PATIENTS: Ninety-seven consecutive patients from the glaucoma centre and 129 healthy subjects selected from volunteers and employees of the department. One eye of each subject was chosen randomly. OUTCOME MEASURES: Visual fields, as assessed with the Humphrey perimeter, program 30-2, and 12 HRT shape characteristics: disc area, cup area cup/disc area ratio, rim area, cup volume, rim volume, mean cup depth, maximum cup depth, cup shape measure, height variation contour, mean retinal nerve fibre layer thickness and retinal nerve fiber layer cross-section area. ROC (receiver operating characteristic) curves were used to analyse the capacity of each HRT characteristic to detect glaucoma. RESULTS: Statistically significant difference were found between the control and glaucoma groups in age, cup area, cup/disc ratio, rim area, cup volume, rim volume, mean cup depth, cup shape measure, mean retinal nerve fibre layer thickness and retinal nerve fibre layer cross-section area (p < or = 0.003, t-test). The largest (i.e., best) ROC curve area was found for cup shape measure (area = 0.812), rim area (0.809), cup/disc area ratio (0.804) and rim volume (0.768). The mean reference height was 0.31 mm (standard deviation [SD] 0.14 mm) for the control group and 0.29 mm (SD 0.12 mm) for the glaucoma group, a nonsignificant difference. CONCLUSIONS: Cup shape measure was the most predictive HRT shape characteristic.

Adult↗
PubMed1997

A comparison of healthy, ocular hypertensive, and glaucomatous optic disc topographic parameters.

PURPOSE: To compare the optic discs of 62 healthy individuals 68 patients who have ocular hypertension (OH), and 182 patients with primary open-angle glaucoma (132 high-tension glaucoma (HTG) and 50 normal-tension glaucoma (NTG)), and determine whether disc size exerted an influence on the group differentiation. PATIENTS AND METHODS: Standard criteria were used to define glaucoma and normality. Ocular hypertension was defined as having raised intraocular pressure, a normal visual field, and a healthy optic disc/retinal nerve fiber layer (RNFL). The optic disc of one eye from each individual was analyzed using a confocal scanning laser ophthalmoscope (Heidelberg Retina Tomograph software version 1.11, Heidelberg Engineering, Heidelberg, Germany). Thirteen topographical, volumetric, and shape parameters were compared between the three diagnostic groups. In addition, the individuals were divided into subgroups on the basis of disc size to determine any effect of disc size on the differentiating ability of the confocal scanning laser ophthalmoscope. Differences between the groups were evaluated using an analysis of variance. RESULTS: Glaucomatous optic discs were found to differ from both healthy and OH discs, although no differences in disc area between the groups were identified. On the basis of disc size, differentiating the glaucomatous discs was best for midsized discs of 2 mm2 to 3 mm2. However, no difference was found between healthy and OH discs, even when allowing for disc size. CONCLUSIONS: Ocular hypertensive optic discs (with a clinically normal appearance) could not be distinguished from healthy discs using a confocal scanning laser ophthalmoscopic technique. Glaucomatous optic discs were found to differ from both healthy and OH discs, with a limited effect of disc size.

Analysis of Variance↗
PubMed1997

Sector-based analysis of optic nerve head shape parameters and visual field indices in healthy and glaucomatous eyes.

PURPOSE: To evaluate the correlations between the sector optic nerve head parameters measured by Heidelberg Retina Tomograph (HRT, Heidelberg Engineering, Heidelberg, Germany), version 1.11S, and the visual field. METHODS: One eye was randomly chosen from 55 individuals with glaucoma and 50 healthy individuals. Each participant had at last one Humphrey visual field, program 30-2 (Humphrey Instruments, San Leandro, CA, U.S.A.), and three 10 degrees HRT pictures. From the mean of the three HRT pictures, global measurements, superior (45 degrees-135 degrees), nasal (135 degrees-225 degrees), inferior (225 degrees-315 degrees), and temporal (315 degrees-45 degrees) sector measurements were calculated for the following parameters: disc area, effective area, area below reference, mean height of contour, volume below surface, volume above surface, volume below reference, volume above reference, and third moment. From the visual field results, mean deviation (MD), superior MD, and inferior MD were calculated. For each HRT parameter we calculated the "r" Pearson correlation with the corresponding visual field measures. RESULTS: Within the combined healthy and glaucomatous groups we found highly significant (p < 0.001) correlations between the following HRT parameters and the visual field MD: inferior and mean high of contour (r = -0.53), inferior and third moment (r = -0.52), global and third moment (r = -0.49), inferior and volume above reference (r = 0.47), superior and third moment (r = -0.46), and superior and area below reference (r = -0.44). Correlations between global mean deviation and nasal or temporal sector parameters were generally smaller and less significant. CONCLUSIONS: Inferior and superior HRT sector parameters were correlated with the respective visual field indices. In many cases these correlations were as strong or stronger than with the global equivalent shape measures.

Diagnostic Techniques, Ophthalmological↗
PubMed1996

Comparison of psychophysical and electrophysiological testing in early glaucoma.

PURPOSE: To compare the sensitivity and specificity of a wide range of psychophysical and electrophysiological tests in the detection of early glaucomatous damage. METHODS: Forty-three normals and 43 patients with early glaucoma, some still without field defects, were tested with differential light threshold perimetry, short-wavelength automated perimetry, high-pass resolution perimetry, motion detection, flicker contrast sensitivity, flickering and isoluminantly matched letter tests, and pattern and flash electroretinography, including photopic, scotopic, oscillatory potentials, and 30 Hz flicker. Receiver operating characteristic analysis was applied to continuous variables derived from each of the tests. RESULTS: Most parameters reflected glaucomatous loss to some degree, even though only single variables were analyzed separately in the receiver operating characteristic analysis. The pattern electroretinogram and some of the letter acuity tests had the best sensitivity and specificity, followed by short-wavelength automated perimetry and high-pass resolution-perimetry. Motion detection, flicker contrast, and flash electroretinogram parameters scored poorly. Six patients with normal results on the Humphrey field test had abnormal results on many of the other tests. CONCLUSIONS: Applying different psychophysical and electrophysiological tests may add to our ability to detect early glaucomatous damage.

Contrast Sensitivity↗
PubMed1995

Optic nerve axon count and axon diameter in patients with ocular hypertension and normal visual fields.

BACKGROUND: At postmortem examination, the authors obtained eight eyes of five individuals with elevated intraocular pressure and normal visual fields to study the axon count and mean axon diameter. METHODS: Automated image analysis was used to calculate the total axon count and mean axon diameter per nerve and per nerve segment for each eye. The authors applied the method of identification analysis to compare each study eye with a corresponding normal eye of patients of the same age. RESULTS: There was no statistically significant difference compared with control subjects for total axon count or segmental axon count for any of the eyes. Two eyes showed a statistically significant difference for mean axon diameter for the whole nerve but not for individual segments of the nerve. CONCLUSIONS: Some eyes subjected to varying duration and magnitude of intraocular pressure elevation with normal visual fields may maintain normal axon counts and mean axon diameters.

Aged↗
PubMed1995

Ambulatory blood pressure monitoring in glaucoma. The nocturnal dip.

PURPOSE: Hypoperfusion of the optic nerve head may be among the significant factors relating to glaucoma damage. The physiologic nocturnal blood pressure "dip" may be exaggerated in some patients and may compromise local vascular supply. METHODS: Twenty-four-hour ambulatory blood pressure recording was performed on 38 patients with normal-tension glaucoma and on 46 with primary open-angle glaucoma. Eleven control subjects of similar age also were tested. The means of the systolic and diastolic blood pressures, mean arterial pressure, and pulse pressure for 24 hours, taken during the daytime (6 AM-10 PM) and night (10 PM-6 AM) periods were determined. The percentage nocturnal dip for each patient was calculated. A masked assessment of Humphrey visual fields for progression or stability was done on those 52 patients who had numerous fields plotted for more than 2 years. RESULTS: The results of the control subjects confirmed that the authors' technique produces values similar to cardiologic studies from large healthy populations. The mean results from all the authors' patients with glaucoma were within the ranges reported for control subjects in the literature. The blood pressure parameters of the normal-tension glaucoma and primary open-angle glaucoma groups did not differ significantly. All nocturnal pressure parameters (except pulse pressure) were lower in the 37 patients with progressive field defects compared with the 15 patients whose pressure parameters were stable, whereas the systolic, diastolic, and mean arterial pressure dips were significantly larger (systolic dip, P = 0.001). CONCLUSION: The nocturnal reduction in blood pressure may be an additional risk factor in patients with glaucoma.

Aged↗
PubMed1995

The short-time effect of latanoprost on the intraocular pressure in normal pressure glaucoma.

Latanoprost, a prostaglandin analogue, was given topically to 20 patients with normal pressure glaucoma in a double masked randomized study. Either latanoprost 0.006% or placebo (vehicle) was administered twice a day for 14 days. Latanoprost caused a statistically significant (p < 0.001) reduction in intraocular pressure from a diurnal baseline level of 16.8 to 14.3 mmHg, as measured on day 14. Latanoprost was well tolerated.

Administration, Topical↗
PubMed1994

Pattern electroretinograms from hemifields in normal subjects and patients with glaucoma.

PURPOSE: Because glaucomatous visual field loss predominantly occurs in one hemifield, a baseline ratio of pattern electroretinogram (PERG) hemifield amplitudes (upper field:lower field) was determined in normal subjects and then examined in patients with glaucoma. METHODS: In 26 normal subjects and eight patients with glaucoma with typical arcuate field loss involving the test area (central 20 degrees), hemifield PERGs were recorded using checkerboard screens of check size 0.5 degrees and frequency 3.75 reversals per second (transient) and 15 reversals per second (steady state). RESULTS: The ratios obtained for normal central upper:lower amplitudes were 0.95 +/- 0.13 (transient) and 0.93 +/- 0.10 (steady state Fourier second harmonic). Wide nasal-field (52 degrees x 42 degrees) PERG ratios recorded on two subjects confirmed that the ratio held across large retinal areas. The ratio did not change with age or check size. The ratio showed less variability between patients than PERG amplitudes. In the patients with glaucoma, the hemifield PERG amplitude correlated with summed visual field thresholds for that area. Patients with glaucoma could be discriminated from normals by an abnormal ratio (> 2 SD) in seven of the eight patients. In two additional patients with more peripheral scotomas, the ratio remained normal. CONCLUSIONS: In normals, the upper:lower hemifield PERG ratio is slightly < 1.0 and remains stable with age. In glaucoma, visual field defects are associated with PERG reductions in the corresponding hemifield. An abnormal PERG hemifield ratio can be found in many patients, although more peripheral and symmetrical losses may still be missed.

Adult↗
PubMed1993

Axonal loss in band atrophy of the optic nerve in craniopharyngioma: a quantitative analysis.

Automated image analysis was used to examine the optic nerves of a patient with previous craniopharyngioma and bitemporal hemianopsia. On histologic study the right optic nerve showed extensive damage, and the left optic nerve showed a band of damage horizontally across the nerve. Automated image analysis of the left nerve showed that the superior and inferior poles of the nerve had lost approximately 50% of their total nerve fibres, indicating that these areas contain a mixture of crossed and uncrossed fibres; the temporal portion showed a variable amount of loss. To our knowledge this is the first report illustrating quantitatively the pattern of axonal loss in this type of lesion.

Adult↗