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.     

Blue-on-yellow and achromatic perimetry in diabetic children without retinopathy

OBJECTIVE: We compared blue-on-yellow perimetry with achromatic perimetry to determine whether the first was more sensitive in detecting visual field defects. RESEARCH DESIGN AND METHODS: We studied 50 children and adolescents (22 male, 28 female) with IDDM, ranging in age from 10.1 to 16.3 years (mean 13.3+/-2.1 years), with a disease duration of 5.2-10.0 years (mean 7.1+/-1.9 years). Patients were divided into subgroups according to the presence of persistent microalbuminuria. No one had signs of diabetic retinopathy when studied with fluorescein angiography. RESULTS: By achromatic perimetry, the analysis of subareas of the central 30 degrees of the visual field (0-9 degrees; 10-18 degrees; out of 18 degrees) showed no differences between diabetic subgroups in the central 18 degrees of the visual field, while a significant difference between the same subgroups was found outside the 18 degrees of the 24-2 program of the Humphrey perimeter (P = 0.027). By blue-on-yellow perimetry, in all three of the perimetric subareas evaluated, the sensitivity was lower in microalbuminuric patients than in normoalbuminuric ones. The differential sensitivity between the perimetric tests performed with blue-on-yellow and with achromatic stimuli showed statistically significant data, with a higher level of significance in the central 18 degrees (P < 0.0001) than outside the 18 degrees (P = 0.033). CONCLUSIONS: Our study suggests that blue-on-yellow perimetry is more useful and more sensitive than achromatic perimetry in the detection of preclinical visual field defects in diabetic children with microalbuminuria but without clinically detectable retinopathy.     

Red, green, and red-green hybrid pigments in the human retina: correlations between deduced protein sequences and psychophysically measured spectral sensitivities

To analyze the human red, green, and red-green hybrid cone pigments in vivo, we studied 41 male dichromats, each of whose X chromosome carries only a single visual pigment gene (single-gene dichromats). This simplified arrangement avoids the difficulties of complex opsin gene arrays and overlapping cone spectral sensitivities present in trichromats and of multiple genes encoding identical or nearly identical cone pigments in many dichromats. It thus allows for a straightforward correlation between each observer's spectral sensitivity measured at the cornea and the amino acid sequence of his visual pigment. For each of the 41 single-gene dichromats we determined the amino acid sequences of the X-linked cone pigment as deduced from its gene sequence. To correlate these sequences with spectral sensitivities in vivo, we determined the Rayleigh matches to different red/green ratios for 29 single-gene dichromats and measured psychophysically the spectral sensitivity of the remaining green (middle wavelength) or red (long wavelength) cones in 37 single-gene dichromats. Cone spectral sensitivity maxima obtained from subjects with identical visual pigment amino acid sequences show up to a approximately 3 nm variation from subject to subject, presumably because of a combination of inexact (or no) corrections for variation in preretinal absorption, variation in photopigment optical density, optical effects within the photoreceptor, and measurement error. This variation implies that spectral sensitivities must be averaged over multiple subjects with the same genotype to obtain representative values for a given pigment. The principal results of this study are that (1) approximately 54% of the single-gene protanopes (and approximately 19% of all protanopes) possess any one of several 5'red-3'green hybrid genes that encode anomalous pigments and that would be predicted to produce protanomaly if present in anomalous trichromats; (2) the alanine/serine polymorphism at position 180 in the red pigment gene produces a spectral shift of approximately 2.7 nm; (3) for each exon the set of amino acids normally associated with the red pigment produces spectral shifts to longer wavelengths, and the set of amino acids normally associated with the green pigment produces spectral shifts to shorter wavelengths; and (4) changes in exons 2, 3, 4, and 5 from green to red are associated with average spectral shifts to long wavelengths of approximately 1 nm (range, -0.5 to 2.5 nm), approximately 3.3 nm (range, -0.5 to 7 nm), approximately 2.8 nm (range, -0.5 to 6 nm), and approximately 24.9 nm (range, 22.2-27.6 nm).     

A study of response to achromatic and chromatic stimuli.

Tests the hypothesis that responses to chromatic stimuli are more effective in discriminating groups from each other than are responses to achromatic stimuli. The rationale for the study was based upon Shapiro's view that various types of response to color reflect different levels of psychological and perceptual organization. The MMPI was used to select 3 groups of 15 male college Ss to represent 3 different levels of psychological and perceptual organization. These Ss were asked to respond to 2 achromatic and 2 chromatic stimuli under 2 different experimental conditions. It was found that the chromatic stimuli were not more effective than the achromatic stimuli in differentiating the groups used in this study. However, the data evinced a progressive increase of capacity to delay and increase of capacity to respond differentially to different stimuli across groups. It is concluded that further research that utilizes Shapiro's rationale is indicated. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of conventional and high-pass resolution perimetry in a prospective study of patients with glaucoma and healthy controls

The effects of mm-waves 60.22-62.22 GHz and 75 GHz on A-type K+ currents and the effects of 61.22 GHz on Ca2+ currents of Lymnaea neurons were investigated using a whole-cell voltage-clamp technique. The open end of a rectangular waveguide covered with a thin Teflon film served as a radiator. Specific absorption rates at the waveguide outlet, inserted into physiological solution, were in the range of 0-2400 W/kg. Millimeter wave irradiation increased the peak amplitudes, activation rates, and inactivation rates of both ion currents. The changes in A-type K+ current were not dependent on the irradiation frequency. It was shown that the changes in the amplitudes and kinetics of both currents resulted from the temperature rise produced by irradiation. No additional effects of irradiation on A-type K+ current other than thermal were found when tested at the phase transition temperature or in the presence of ethanol. Ethanol reduced the thermal effect of irradiation. Millimeter waves had no effect on the steady-state activation and inactivation curves, suggesting that the membrane surface charge and binding of calcium ions to the membrane in the area of channel locations did not change.     

Perimetric motion thresholds are elevated in glaucoma suspects and glaucoma patients

The purpose of this study was to determine if a clinically feasible perimetric motion test utilizing random-dot kinematograms could identify glaucomatous visual field defects. Using a staircase procedure, an automated perimetric motion test and a larger foveally presented target were given to normal (n = 30), glaucoma suspects (n = 31) and primary open-angle glaucoma patients (n = 19). Motion thresholds at specific locations throughout the whole visual field were significantly elevated in glaucoma patients (P < or = 0.001). Perimetric motion testing identified 84.2% of the primary open-angle glaucoma patients and 25.8% of the glaucoma suspects as abnormal. A larger foveal stimulus was unable to distinguish between the different subject groups (P < or = 0.185). Perimetric motion thresholds were significantly correlated with Humphrey standard visual field thresholds in the glaucoma and glaucoma-suspect patients (P < or = 0.0002).     

Analysis and reduction of losses in ferroalloy production

Losses of material in ferroalloy production are analyzed, and means of reducing such losses are proposed.     

Absence of linear subthreshold summation between red-green and luminance mechanisms over a wide range of spatio-temporal conditions

We have tested the independence of red-green chromatic and luminance mechanisms at detection threshold using a method of subthreshold summation. Stimuli were isoluminant red-green gratings and yellow-black luminance gratings that uniquely activate the red-green color and luminance mechanisms, respectively. Stimuli were Gaussian enveloped 0.25, 1 or 4 cpd sinewave gratings, counter-phase flickered at 0, 5 or 9 Hz. The threshold detection of red-green color contrast was measured in the presence of a subthreshold amount of luminance contrast, and vice versa. The results allow a model of linear summation between the color and luminance mechanisms to be rejected, but are well fitted by a model, assuming that these mechanisms are independent but combine to determine detection by probability summation, with a high summation index (median value = 4). We conclude that there are independent red-green chromatic mechanism and luminance detection mechanisms over this range of spatio-temporal conditions.     

The development of chromatic and achromatic contrast sensitivity in infancy as tested with the sweep VEP

Swept-contrast visual evoked potential (VEP) techniques were used to measure the development of contrast sensitivity functions (CSFs) for achromatic and red/green isoluminant chromatic gratings. Subjects were infants of 8, 14, 20 and 32 weeks of age, and adults. Stimuli were 20 deg, 0.3-4 cyc/deg sinusoidal gratings, counterphased at 6 Hz and modulated through white. Achromatic and chromatic CSFs for all ages could be fit simultaneously with a double exponential equation of a common, lowpass shape. Both achromatic and chromatic CSFs exhibited developmental shifts in both sensitivity and spatial scale. From 8 weeks to adulthood, sensitivity increased by 0.64 log units for achromatic gratings and by 0.91 log units for chromatic gratings, yielding an 0.27 log unit larger sensitivity change for chromatic than for achromatic stimuli. Spatial scale shifts were closely similar across achromatic and chromatic CSFs, and were consistent with the factor of about four predicted on the basis of changes in foveal receptor packing density and eye size. The question of uniform vs differential loss of sensitivity for chromatic vs achromatic stimuli at fixed spatial frequencies is discussed.     

Evaluation of the Brusini glaucoma staging system for follow-up in glaucoma

There is evidence that bronchial responsiveness to allergen is quantitatively correlated with bronchial responsiveness to nonspecific stimuli in subjects with allergic asthma. This association has been questioned in occupational asthma due to low molecular weight substances. It was the aim of this study to assess the quantitative association of bronchial responsiveness to methacholine (MCH) and platinum salts (Pt), in the form of hexachloroplatinic acid, in workers with occupational asthma due to Pt salts. Fifty-seven subjects with exposure to Pt, work-related asthma, and a positive bronchial challenge with Pt underwent skin prick test with Pt and bronchial challenge with MCH. Using the provocation concentration causing a > or = 50% fall in specific airway conductance (PC50sGaw(Pt)) as a dependent variable, anamnestic data (period from first symptoms to removal, period between removal from exposure and diagnosis, and smoking), season of the investigation, skin prick tests with environmental allergens, total immunoglobulin E (IgE), skin reactivity to Pt (Pt concentration causing a 2 mm wheal), and PC50sGaw(MCH) were included as independent variables for regression analysis. Fifty-two subjects (91%) showed a PC50sGaw(MCH) < 8 mg.mL-1 (geometric mean for all subjects 1.6 mg.mL-1). Responsiveness to Pt varied widely between subjects (geometric mean of PC50sGaw(Pt) 9 x 10(-5) mol.L-1, range 2 x 10(-7) to 10(-2) mol.L-1). There was no univariate correlation between bronchial responsiveness to MCH and Pt, but there was a correlation between skin reactivity to Pt and PC50sGaw(Pt) (r = 0.6). This association could not be improved by considering PC50sGaw(MCH), the period from first symptoms to removal, or the period between removal from exposure and diagnosis. The parameters that showed the highest (negative) associations with PC50sGaw(Pt) were skin reactivity to Pt and the period between removal from exposure and diagnosis (r = 0.65). We conclude that there is a moderate association between bronchial responsiveness to platinum salts and skin reactivity to platinum salts. However, there is no association between methacholine responsiveness and bronchial responsiveness to allergen in occupational asthma due to platinum salts.     

Copper losses and thermodynamic considerations in copper smelting

A relationship between copper in slag and copper in matte during copper sulfide smelting has been derived using industrial data from 42 plants employing blast furnaces, reverberatory furnaces, flash furnaces, and Mitsubishi smelting furnaces together with the available thermodynamic equilibrium data for Cu-Fe-S-O, FeO-SiO₂, and Cu-Fe-S systems and laboratory slag-matte equilibrium information. A copper smelting diagram showing oxygen potential; sulfur potential; and copper, magnetite, and sulfur contents in slag during the smelting of different grades of copper mattes is developed for mattes containing less than 70 pct copper. The data presented can be used to determine the entrained copper losses in slag. Further, by combining the calculated value of the entrained matte with the corresponding plant data for the sulfur content of the slag, it is possible to derive the dissolved sulfur content of the slag. These calculated values were in excellent agreement with the experimentally determined sulfide capacity of fayalite slags. It is shown that there is no need to assume the presence of dissolved copper sulfide species in industrial slags. The existing equilibrium data that relate the copper content of slags to oxygen potential adequately describe the copper losses in industrial slags.     

Family history of glaucoma and risk factors in pigmentary glaucoma. A new clinical study

BACKGROUND: Whether a family history of glaucoma (FHG) in patients with pigmentary glaucoma (PG) is a prognostical indicator, is unknown. Therefore the aim of this study was to evaluate the influence of FHG on the severity of the disease in PG and pigment dispersion syndrome (PDS). Furthermore risk factors in PG and PDS were evaluated. METHODS: The findings of 207 patients with PG and PDS, who were able to give information about FHG, were evaluated (149 PG, 43 PDS with ocular hypertension (OH), 15 PDS without OH). RESULTS: Significance of FHG: FHG was found in 39.1%, and in one third of the patients more than one relative had the disease. FHG was found in PG not more frequent than in PDS. Pigmentary glaucomas in advanced stages of the disease did not have a higher incidence of FHG than patients in beginning stages. Out of 207 patients with PG and PDS 71% were male and 29% female (p < 0.001). In patients with FHG the share of men was 64.2% and not significantly different to the group without FHG with 75.4%. The sex distribution in parents and grandparents having a glaucomatous disease was 1:1. Risk factors: The pf1p4nts with and without FHG in PDS with and without OH, PG, and within the different stages of visual field loss, showed no significant differences in risk factors, for example in maximum intraocular pressure, refraction and cup-disc ratio. Myopia: Patients with PG had a significantly higher myopia than patients with PDS (p < 0.01). The higher the myopia, the earlier the disease was diagnosed (p = 0.008). Krukenberg spindle: During miotic therapy the Krukenberg spindle decreased in the upper half of the cornea. Time of diagnosis: PG was diagnosed at a higher age compared to PDS. CONCLUSION: FHG does not influence the severity of the disease in PG. Family history of glaucoma is a risk factor in patients with PG, but no prognostical indicator. Patients with FHG do not have primarily larger cup-disc ratios than patients without FHG. Myopia is a risk factor.