Ureteric stent versus percutaneous nephrostomy for acute ureteral obstruction - clinical outcome and quality of life: a bi-center prospective study

BACKGROUND

To compare quality of life (QoL) indices between ureteral stent (DJS) and nephrostomy tube (PCN) inserted in the setting of acute ureteral obstruction.

METHODS

Prospective bi-centered study. Over the span of 2 years, 45 DJS and 30 PCN patients were recruited. Quality of life was assessed by 2 questionnaires, EuroQol EQ-5D and 'Tube symptoms' questionnaire, at 2 time points (at discharge after drainage and before definitive treatment).

RESULTS

Patients' demographics and pre-drainage data were similar. There were no clinically significant differences in patient's recovery between the groups, including post procedural pain, defeverence, returning to baseline renal function, and septic shock complications. More DJS patients presented to the emergency room with complaints related to their procedure compared to PCN patients. At first, DJS patients complained more of urinary discomfort while PCN patients had worse symptoms relating to mobility and personal hygiene, with both groups achieving similar overall QoL score. At second time point, PCN patients' symptoms ameliorated while symptoms in the DJS group remained similar, translating to higher overall QoL score in the PCN group.

CONCLUSIONS

The two techniques had a distinct and significantly different impact on quality of life. Over time, PCN patients' symptoms relieve and their QoL improve, while DJS patients' symptoms persist. Specific tube related symptoms, and their dynamics over time, should be a major determinant in choosing the appropriate drainage method, especially when definitive treatment is not imminent.

Vitreo-retinal traction and anastrozole use

Abstract #1147

Background: Menopause is known to increase the risk of vitreo-retinal tractional events such as macular holes and posterior vitreous detachments (PVDs). This suggests that aromatase inhibitors (AIs), which virtually abolish estrogen synthesis in post-menopausal women, may lead to an increased degree of vitreo-retinal traction. To evaluate the hypothesis that AIs lead to heightened vitreo-retinal traction, this study tested the prediction that the foveal shapes of anastrozole users are distorted systematically.
 Material and Methods: Retinal thickness along the horizontal meridian through the fovea was measured using optical coherence tomography (OCT) for each of 3 groups of amenorrheic women ages 47-69 years: (1) anastrozole users and (2) tamoxifen users using their respective medications as adjuvant therapy for early-stage breast cancer, and (3) age-matched control subjects not using any hormonally acting medication. All subjects had 20/20 or better best-corrected visual acuity, no diabetes, and no high myopia, which itself is a risk factor for PVDs. Foveal shape indices were derived from the OCT data by normalizing each subject's retinal thickness data to her individually determined locus of minimal foveal thickness. OCT images were used to identify subjects with PVDs, which necessitated exclusion from most analyses. The information in the Results section is for subjects without PVDs.
 Results: For anastrozole users (n=13), the distance to the temporal side of the fovea was significantly less than the distance to the nasal side at a sufficient height above the foveal base. This effect did not exist for control subjects (n=24), and the between-group difference was significant (unadjusted p = .006). The data from tamoxifen users (n=19) appeared to be intermediate to the data of the other 2 groups, but the differences were not significant. At the base of the fovea, the distance to the temporal side minus the distance to the nasal side correlated significantly with the degree of myopia for the control subjects (r = -.54, p = .008) but not for the anastrozole users (r = -.23). However, the anastrozole users were observed to be significantly less myopic than the control subjects, which may have led to the negative result.
 Discussion: The foveas of women who use anastrozole are subjected to a greater amount of vitreo-retinal traction than are the foveas of women not using any hormonal medication. The data from control subjects reveal the action of an additional force that pulls on the fovea from its scleral side in the opposite direction, i.e., away from the optic nerve head, which not only anchors the vitreous but which also interferes asymmetrically with intraocular stretching related to myopia. The net result of the 2 forces may be retinal shear. The low prevalence of myopia among the anastrozole users suggests that our cross-sectional study may have excluded anastrozole users with vision change. Longitudinal studies with baseline data need to be conducted.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1147.

Comparison of three different solid-phase microextraction fibres for analysis of essential oils in yacon (Smallanthus sonchifolius) leaves

A headspace solid-phase microextraction (HS-SPME) procedure based on three commercialised fibers (100 microm polydimethylsiloxane, 65 microm polydimethylsiloxane-divinylbenzene and 50/30 microm divinylbenzene-Carboxen-polydimethylsiloxane) is presented for the determination of a selected essential oils in dried leaves of yacon (Smallanthus sonchifolius). The extraction performances of these compounds were compared using fibers with one, two and three coatings. The optimal experimental procedures for the adsorption and desorption of target compounds were determined. Significant parameters affecting sorption process such as sample weight, sorption and desorption time and temperature were optimised and discussed. Finally, the optimised procedures were applied successfully for the determination of these compounds in various yacon species. The relative concentration factors of three characteristic components of yacon were measured for relative evaluation of the fiber efficiency. Main essential oils were isolated from dried yacon leaves by appropriate solid-phase microextraction fiber and semi-quantitative analysis of the target volatiles was conducted by gas chromatography-flame ionisation detection (GC-FID) using a capillary column. Three compounds--beta-pinene, caryophylene and y-cadinene were found as the predominant essential oils. Its relative content was important for specification of yacon varieties. Solid-phase microextraction in combination with gas chromatography enabled a rapid and simple determination of relative content of essential oils in yacon.

Determination of acrylonitrile in materials in contact with foodstuffs

Monitoring of the content of free acrylonitrile in plastics used for the preparation of viands is necessary due to its negative effect on human health. A content of 20 ppb is the maximal value of free acrylonitrile in such samples. In this case, head-space gas chromatography is most favourable analytical method when combined with the standard addition method together with a mass-spectrometry detector because of a very low concentration of the analyte. In samples taken for analysis, the content of free acrylonitrile was found to be within 5.1 and 10.3 ppb (microg/kg).

Short wavelength automated perimetry and tamoxifen use

BACKGROUND/AIMS

Oestrogen receptors (ORs) have been reported to be present in the retina, and the selective oestrogen receptor modulator tamoxifen has been reported to affect colour vision. This study aimed, therefore, to determine whether standard doses of tamoxifen affect visual sensitivities mediated via short wavelength sensitive (SWS) cones.

METHODS

Two types of visual fields were measured for middle aged women who were being treated with 20 mg of tamoxifen daily as adjuvant therapy for early stage breast cancer. Visual fields were measured using short wavelength automated perimetry (SWAP) and frequency doubling perimetry (FDP). For SWAP, 24-2 visual fields were analysed. No subjects had tamoxifen retinopathy or other eye disease. For each type of visual field, mean deviations (MDs) were assessed as a function of the duration of tamoxifen use, using a cross sectional design. In addition, the difference between the two types of MDs was computed after standardisation of each type of MD separately, and this difference itself was evaluated as a function of the duration of tamoxifen use. Duration dependent changes for SWAP were further evaluated as a function of eccentricity within the visual field, and the visual field data were compared with foveal data obtained psychophysically.

RESULTS

SWAP sensitivities depended on the duration of tamoxifen use. Subjects who used tamoxifen for about 2 years or less were significantly more likely than subjects who had longer use to have high MDs. The difference between the standardised SWAP and FDP MDs likewise was significantly related to the duration of use, whereas duration of use effects for FDP itself were reduced or absent. Although the duration of use effect observed for SWAP was strongest in the peripheral portion of the visual field, there was evidence of changes in SWS cone mediated vision even at the fovea.

CONCLUSION

Standard dosages of tamoxifen can affect SWAP visual fields. The effects of tamoxifen are not equivalent for SWAP and FDP, indicating that tamoxifen affects some types of visual pathways preferentially or selectively. SWS cone pathways, in particular, are affected. SWAP appears able to reveal effects of tamoxifen occurring years before completion of the standard 5 year regimen of use.

Flashed stimuli and the suppression of flicker response from long-wavelength-sensitive cones: integrating two separate approaches

The selective suppression of flicker response from LWS cones has been investigated with two approaches. One approach has emphasized the use of light-adaptation conditions, and the other has emphasized the use of dark-adaptation conditions. In both cases, stimuli are arranged to restrict or exceed the ability of adaptation processes to maintain an afferent flicker response, and long-wavelength stimuli are used to overload spectrally opponent processes. By integrating these two approaches, this study shows that diverse manifestations of flicker response suppression can be closely related mechanistically. For instance, the steep flicker TVI slopes that resulted from superimposing temporally modulated (100% contrast) test stimuli on flashed backgrounds corresponded to the disappearance of flicker that resulted from increasing the time-averaged illuminance of temporally modulated stimuli (contrast x < 100%) that were flashed alone in an otherwise dark field. For the stimulus parameters of this study, flicker response suppression was more evident for small (19' diameter) than for large (1 degree diameter) stimuli. However, flicker response suppression was elicited reliably for both sizes by adding a spatially coincident short-wavelength stimulus to the interstimulus interval between presentations of the long-wavelength stimuli. By showing that temporal contrast can be treated as an independent variable for an important set of test/background stimulus combinations, the results of this study make it possible to investigate the means by which changes of contrast gain help to maintain flicker response as assessed in a conventional flicker TVI paradigm. The reduced degree of suppression for relatively large stimuli probably is related to the increased action of spatially extensive contrast gain-control processes. These contrast gain-control processes might not act independently of spectrally opponent processes.

Flicker sensitivity and cardiovascular function in healthy middle-aged people

OBJECTIVE

To establish normative relations between measures of visual function and cardiovascular variables that are important for age-related disease, including various forms of glaucoma.

METHODS

Foveal flicker sensitivities, resting blood pressures and heart rates, and intraocular pressures were measured in 18 individuals aged 40 to 68 years. All subjects had 20/20 or better visual acuity in the test eye and no evidence of eye disease or glaucoma suspicion on clinical evaluation and medical history. No subjects were using medication to lower blood pressure. Flicker sensitivity was measured by increasing the illuminance of a fully modulated 20-Hz test stimulus until flicker was perceived. Two test-background stimulus combinations were used: a 570-nm ("yellow") test on a predominantly long-wavelength ("magenta") background and a 580-nm ("yellow") test on a 580-nm ("yellow") background. The illuminance of the yellow background was dimmer than that typically used for short-wavelength automated perimetry, whereas the illuminance of the magenta background was greater.

RESULTS

The 2 flicker sensitivity measures were distinguished by the strong dependence of the magenta background measure on the ratio of mean arterial blood pressure to heart rate. Log flicker sensitivity on this background generally could be modeled as a linear combination of age, intraocular pressure, and ratio of mean arterial blood pressure to heart rate. The optimal model accounted for 84% of the variance (R = 0.92) from all but 2 outlying individuals. After age and intraocular pressure effects were partialed out, an increasing ratio of mean arterial blood pressure to heart rate was strongly associated with decreasing flicker sensitivity.

CONCLUSIONS

Reduced cardiovascular function impacts the ability of the normal visual system to adapt and regulate flicker sensitivity. Elevated intraocular pressure and increased age reduce flicker sensitivity relatively uniformly across a range of stimulus conditions. Because the ratio of mean arterial blood pressure to heart rate equals total peripheral vascular resistance multiplied by cardiac stroke volume, and because total peripheral resistance is determined largely at the arterioles, it is likely that even modest changes in arteriolar function are associated with measurable alterations of visual function. Arch Ophthalmol. 2000;118:1049-1055

Equivalence between temporal frequency and modulation depth for flicker response suppression: analysis of a three-process model of visual adaptation

We analyze adaptation processes responsible for eliciting and alleviating flicker response suppression, which is a class of phenomena characterized by the selective reduction of visual response to the ac component of a flickering light. Stimulus conditions were chosen that would allow characteristic features of flicker response suppression to be defined and manipulated systematically. Data are presented to show that reducing the sinusoidal modulation depth of an 11-Hz stimulus can correspond precisely to raising the temporal frequency of a fully modulated stimulus. In each case there is a nonmonotonic relation between flicker response and dc test illuminance. The nonmonotonic relation cannot be explained by adaptation models that postulate multiplicative and subtractive adaptation processes followed by a single static saturating nonlinearity, even when temporal frequency filters are incorporated into such models. A satisfactory explanation requires an additional contrast gain-control process. This process enhances flicker response at progressively lower temporal response contrasts as the illuminance of a surrounding field increases.

Sexual behavior associated with low Verbal IQ in youth who have severe mental illness

A retrospective chart review was used to examine sexual behavior (hypersexual, exposing, and victimizing) and cognitive impairment in 200 youth who had serious mental illness. Lower IQ was associated with increased sexual acting-out. For more serious victimizing sexual behaviors, only Verbal IQ differences reached statistical significance. Overall, sexual behavior was strongly associated with a history of sexual abuse. Sexual abuse history was significantly associated only with lower Performance IQ. Therefore, the association between low Verbal IQ and sexual victimizing behavior is distinct from the effects of sexual abuse. Results underscore the importance of verbal cognitive abilities, regardless of overall cognitive level, in the etiology and treatment of sexual behaviors, especially among individuals without a history of sexual abuse.

Relationship between sexual abuse, gender, and sexually inappropriate behaviors in seriously mentally ill youths

OBJECTIVE

To examine gender differences in sexual abuse histories and in the development of inappropriate sexual behaviors in a sample of seriously mentally Ill youths.

METHOD

A retrospective chart review was completed for all patients from 1987 through 1992 at a tertiary care public sector psychiatric hospital for youths (N = 499). Subjects were categorized by gender, sexual abuse status, and whether they had sexually reactive or victimizing behaviors.

RESULTS

Girls were more likely to have been sexually abused, and their abuse histories were more severe. Sexual behavior problems in girls were almost exclusively associated with sexual abuse, whereas 29% of boys with victimizing behaviors had no sexual abuse history. Among sexually abused youths, boys were more likely to display victimizing behaviors, whereas both genders displayed similar rates of sexually reactive behaviors. Of the 19 girls who displayed victimizing behaviors, 95% were chronically sexually abused and one third had also received a major injury due to physical abuse.

CONCLUSIONS

Boys appear to have a lower threshold of abuse exposure required to develop sexually inappropriate behaviors and are significantly more likely to display victimizing behaviors. Conversely, victimizing behaviors in girls may require a catastrophic maltreatment history. These gender differences should be incorporated into treatment interventions directed at sexual abuse victims.

Pattern of age-related maculopathy in the macular area. The Beaver Dam Eye Study

PURPOSE

To describe the distribution of lesions associated with age-related maculopathy by location in the macula in a population of adult Americans.

METHODS

Four thousand nine hundred twenty-six persons ranging in age from 43 to 84 years and living in Beaver Dam, Wisconsin, at the time of a census (1987-1988) were examined from 1988 to 1990. Lesions typical of age-related maculopathy were determined by masked grading of stereoscopic color fundus photographs using the Wisconsin Age-Related Maculopathy Grading System. The extent and prevalence of different types of lesions were determined for each of nine macular subfield regions: central, inner superior, inner nasal, inner inferior, inner temporal, outer superior, outer nasal, outer inferior, and outer temporal.

RESULTS

Lesions associated with early age-related maculopathy were distributed in specific patterns. Soft indistinct drusen were more prevalent in the temporal and superior quadrants than in the nasal and inferior quadrants, whereas pigmentary abnormalities associated with age-related maculopathy were more prevalent in the superior or nasal quadrants than in the inferior or temporal quadrants. After weighting for subfield area, all types of lesions were most prevalent in the central macular region.

CONCLUSION

Various lesions associated with early age-related maculopathy were located in specific patterns in the macula. It is not known whether these patterns resulted from environmental, anatomic, or physiologic factors.

Age of onset of sexual abuse: relationship to sexually inappropriate behaviors

OBJECTIVE

To examine how the age of onset of sexual abuse predicted inappropriate sexual behaviors in a sample of seriously mentally ill youths.

METHOD

A retrospective chart review was completed for all youths treated from 1987 through 1992 at a tertiary care public sector psychiatric hospital (n = 499). Subjects were grouped according to the age at which they were first sexually abused: no sexual abuse (n = 225), 0 through 3 years (n = 78), 4 through 6 years (n = 105), 7 through 12 years (n = 71), and 13 through 17 years (n = 19).

RESULTS

The rates of sexually inappropriate behaviors in subjects with sexual abuse histories were quite substantial, ranging from 79.5% of the 0- through 3-year group to 42.1% of the 13- through 17-year group. Subjects first abused during early childhood, especially during the ages 0 through 3 years, had significantly elevated rates of hypersexual, exposing, and victimizing sexual behaviors. They also were significantly younger at the time of admission, came from more disrupted family settings, and had significantly higher rates of physical abuse, neglect, chronic sexual abuse, sexual abuse by either parent/stepparent and a higher total number of victimizers. When logistic regression analyses were done to examine the predictive power of potential risk factors, early age of onset of sexual abuse was the most significant predictor of all three types of inappropriate sexual behaviors.

CONCLUSIONS

Onset of sexual abuse prior to 7 years of age was significantly associated with hypersexual, exposing, and victimizing sexual behaviors. Early sexual abuse is also associated with a number of other poor prognostic factors, and further research is needed to define how these variables interact.

Foveal adaptation abnormalities in early glaucoma

Foveal sensitivities were measured after onset of adapting background fields for each of the following four groups of subjects aged 40-70 years: (1) low-tension glaucoma subjects with minimal field loss in the test eye, (2) primary open-angle glaucoma subjects with minimal field loss in the test eye, (3) normal control subjects, and (4) subjects originally enrolled as control subjects but subsequently found, on the basis of masked clinical evaluation, to be suspect for glaucoma despite ostensibly normal intraocular pressures. We found that the desensitization of a short-wavelength-sensitive-cone-mediated response after onset of a 580-nm background field was diminished from that of normal observers for low-tension glaucoma subjects but not for primary open-angle glaucoma subjects. The desensitization was also diminished for a glaucoma-suspect subjects aged 60-70 years. In contrast, the flicker sensitivity instabilities that persisted after onset of a long-wavelength background field for the majority of subjects with primary open-angle glaucoma [J. Glaucoma Suppl. 3, S19 (1994)] occurred only infrequently among the other subject groups. These results imply that glaucoma often involves the fovea, probably by affecting retinal subtractive adaptation processes, although with different consequences for different types of glaucoma. The results also suggest that undiagnosed low-tension glaucoma may not be rare in the general aging population.

Suppression of flicker response with increasing test illuminance: roles of temporal waveform, modulation depth, and frequency

This study examined the detectability of flicker for small foveal long-wavelength test stimuli centered within surrounding long-wavelength annular adaptation stimuli. Flicker threshold-versus-illuminance (tvi) curves were analyzed for four different test-stimulus waveforms--sine-wave, square-wave, and rapid-on sawtooth and rapid-off sawtooth flicker--at temporal frequencies ranging from 12 to 21 Hz and at temporal modulation depths ranging from approximately 50% to 100%. For all stimulus combinations that were examined involving temporal frequencies above 12 Hz, the resultant flicker tvi curves shared the following characteristic features: First, at operationally dim surround illuminances, there was always a single elevated threshold for detection of flicker. Second, some surround illuminance always could be found for which flicker threshold decreased abruptly, typically by approximately 1.5 log units within 0.1 log unit of surround illuminance increase. Third, when test illuminance was incremented above this lower flicker threshold, flicker always vanished; when test illuminance was incremented still further, flicker reappeared. Finally, at sufficiently bright surround illuminances flicker did not disappear with increasing test illuminance. Although these effects held for all waveforms, the abrupt decrease of flicker threshold occurred at brighter surround illuminances for sawtooth than for sine-wave flicker, and at brighter surround illuminances for sine-wave than for square-wave flicker, at least for fully modulated waveforms (of a given temporal frequency). Moreover, when modulation depth was adjusted so that any two different waveforms had the same first-harmonic contrast, the resultant flicker tvi curves became identical when plotted as first-harmonic amplitude versus surround illuminance. This identity held for any given temporal frequency, even though the flicker tvi curves for 12-Hz fully modulated sine-wave or square-wave flicker did not manifest flicker response suppression, whereas the flicker tvi curves for sawtooth flicker did. These and other results imply that the first-harmonic contrast of the test stimulus fully determines the shape of the entire flicker tvi curve and that the dc component of the test stimulus helps to cause flicker response suppression. The results also demonstrate that first-harmonic equivalence is only a necessary, not a sufficient, condition for linearity.

Nonmonotonic effects of test illuminance on flicker detection: a study of foveal light adaptation with annular surrounds

This study examined the detectability of flicker for small long-wavelength foveal test stimuli centered within larger long-wavelength surround stimuli. Flicker visibility was evaluated as a function of surround and test illuminance and as a function of test wavelength, of the time elapsed following test or surround onset, and of surround dimensions. Consistent with prior flicker threshold-versus-illuminance results [Vision Res. 26, 917 (1986)], flicker threshold decreased abruptly once the surround illuminance became sufficiently great. However, as test illuminance was increased above flicker threshold, flicker again vanished. Flicker reappeared at still higher test illuminances, as middle-wavelength-sensitive (M-) cone-mediated flicker threshold was exceeded. Meanwhile, the time required for the surround to render flicker visible increased at a rapidly accelerating rate with decreasing surround illuminance; it increased at a more sporadic rate with increasing test illuminance. At bright enough surround illuminances, flicker did not vanish with increasing test illuminance. These and other results are compatible with a framework derived from previous dark-adaptation data [Vision Res. 32, 1975 (1992)]. In that framework the test stimulus itself induces losses of flicker sensitivity by sufficiently perturbing retinal response during states or stages of adaptation that fail to cause spectrally antagonistic processes to redress that perturbation adequately. The relevant adaptation processes, which can require minutes, involve an adaptation pool that includes (and is affected by) the test stimulus.

Foveal flicker sensitivity abnormalities in early glaucoma: associations with high blood pressure

This study tested the hypothesis that (a) evidence of foveal visual dysfunction could be elicited in glaucoma subjects by measuring flicker sensitivity as a function of time after onset of an adapting field for a suitably chosen set of test and adaptation parameters and that (b) such dysfunction would be related to high blood pressure. Three groups of subjects were tested: (a) subjects with primary open-angle glaucoma but only minimal field loss, (b) normal control subjects, and (c) control subjects found to be suspect for glaucoma. The protocol included measurement of pulse rate and blood pressure, administration of Humphrey 30-2 visual fields and optic nerve head photography, and administration of a battery of psychophysical tests in Maxwellian view. This battery included a test of flicker sensitivity measured at middle wavelengths as a dynamic function of time after onset of a long-wavelength adapting field. The dynamic light-adaptation functions of subjects with glaucoma were much more likely to be unstable than were the corresponding functions of normal subjects. In addition, the dynamic light-adaptation functions of subjects with high blood pressure for their pulse rate were significantly less stable than the correspond ing functions of subjects without high blood pressure for their pulse rate. Moreover, the ratio of mean arterial pressure to pulse rate was significantly less for normal subjects than for either glaucoma subjects or for glaucoma-suspect subjects. We infer that among people with primary open-angle glau coma but with only minimal field loss, there often is foveal dysfunction associated with cardiovascular disease. Evidence of such dysfunction appears to require the use of stimulus conditions that tax the ability of the visual system to respond appropriately.

Visual function and the subsequent development of exudative age-related macular degeneration

The eyes of 47 subjects with exudative age-related macular degeneration in the fellow eye were tested with a battery of visual function tests at baseline and followed for at least 18 mo. Fundus photographs also were obtained at baseline. These photographs were used to verify the absence of exudative lesions in the 47 eyes tested. Functional and funduscopic baseline data each were compared against outcome data obtained typically at 18 mo. The baseline data were analyzed for their ability to distinguish eyes that had developed detectable exudative age-related macular degeneration from eyes that had not. Eyes with relatively slow foveal dark adaptation rates despite low foveal quantum absorption capabilities (as inferred from the effects of test area on the Rayleigh color match) were especially likely to develop subretinal neovascularization. The resulting sensitivity/specificity and odds ratios were comparable to those of the most effective funduscopic risk indicators. Low S (blue) cone-mediated sensitivity also was associated with an exudative outcome.

Losses of flicker sensitivity during dark adaptation: effects of test size and wavelength

The losses of flicker sensitivity that occur during dark adaptation following extinction of a bleach depend greatly on the test stimuli that are used to measure those losses. Generally, the larger the test size is for a given test wavelength, the later is the loss of flicker sensitivity; for sufficiently large tests, losses become progressively more gradual. Similarly, the shorter the test wavelength is (between about 660 and 580 nm) for a given test size, the later is the loss of flicker sensitivity; for sufficiently short test wavelengths, losses become progressively more gradual. Although the pattern of flicker sensitivity loss as a function of test size is the same both foveally and parafoveally, foveal losses occur later and/or more gradually for a given test stimulus. The results suggest that losses of flicker sensitivity occur when spectrally antagonistic response(s) to the test are no longer adequate to maintain the flicker-response to that test. The results suggest also that the adequacy of such spectral antagonism depends on the local adaptation state of the retina, which becomes increasingly more light-adapted with increasingly large test size.

Profound reductions of flicker sensitivity in the elderly: can glaucoma involve the retina distal to ganglion cells?

Flicker sensitivities were measured for more than 100 people age 60 and older with stimulus-conditions originally designed to obtain estimates of preretinal absorption by the lens and macular pigment. Flicker sensitivities were measured on two chromatic backgrounds: a 1000-td, 480-nm background and a 5800-td, Wratten 33 background (approximately metameric with 633 nm). Testing sessions were administered at 18-month intervals across a 3-yr period. No subject tested had a history of glaucoma or ocular hypertension at the time of entry into the study. For ten subjects, however, flicker sensitivity was sometimes reduced by more than 2.0 log units from the mean norm for at least one of the two backgrounds. For most other subjects, flicker sensitivities were within 0.5 log units of the mean norms. On retrospective analysis, the profound reductions of flicker sensitivity (PRFS) were associated significantly with (a) advanced age (perhaps especially when combined with relatively high intraocular pressure), and (b) the use of cardiovascular medications. The PRFS probably were associated with (c) female sex, and (d) large intraocular pressure fluctuations. In addition, the majority of subjects with PRFS were found to have evidence of glaucomatous cupping or field loss. These results suggest that PRFS result from glaucoma or share etiologies with low-tension glaucoma. The use of cardiovascular medications suggested that PRFS could depend on retinal dysfunction rather than on optic nerve compromise alone. Predicted results from two additional subject populations support this possibility. For young healthy subjects, flicker threshold vs illuminance curves attained very steep slopes for sufficiently short wavelength tests on sufficiently extreme long wavelength backgrounds (655 nm, 50,000 td); the steep slopes coincided with the breakdown of effective M-cone isolation. Reductions of flicker sensitivity on the 5800-td Wratten 33 background depended correspondingly on test wavelength for subjects with well-documented low-tension glaucoma.

Relations between fundus appearance and function. Eyes whose fellow eye has exudative age-related macular degeneration

Foveal visual function was compared with fundus appearance for 41 eyes that had good acuity but whose fellow eye had exudative age-related macular degeneration (AMD). The visual functions tested were among those reported to be compromised by AMD. They included: (1) dark adaptation, (2) absolute sensitivity, (3) S cone-mediated sensitivity, and (4) color matching. The fundus features used to evaluate the risk of developing exudative AMD included: (1) drusen confluence, (2) drusen size, and (3) focal hyperpigmentation. For the group of eyes defined by the presence of one or more high-risk fundus characteristics, all visual functions were compromised significantly. In particular, all 21 eyes with abnormally slow rates of dark adaptation had high-risk fundi, and all 16 eyes with abnormal color matching (ie, a small effect of test area on the color match or rejection of all potential color matches) had high-risk fundi. Conversely, 30 of the 32 eyes with high-risk fundi had abnormally slow rates of dark adaptation or abnormal color matching. In addition, reduced acuity in the fellow exudative eye was associated significantly with a high-risk fundus in the nonexudative eye.

Losses of foveal flicker sensitivity during dark adaptation following extended bleaches

Flicker sensitivity to a small foveal test stimulus can decrease appreciably during the period of dark adaptation that follows extinction of a bleach. For 20 min diameter, long wavelength tests that followed 70% L cone bleaches of various wavelengths, 18 Hz flicker sensitivity decreased precipitously (i.e. within about 45 sec) by about 1.5-2.0 log units beginning at about 100-200 sec following extinction of the bleach. For short wavelength tests that followed long wavelength bleaches, the corresponding precipitous losses of flicker sensitivity were relatively small and early; flicker sensitivity decreased by about 0.6-1.0 log units beginning no later than 60 sec following extinction of the bleach. Whenever flicker sensitivity decreased precipitously, the losses of flicker sensitivity were followed by plateaus of M cone dominated flicker sensitivity. For combinations of test and bleaching wavelengths that did not cause flicker sensitivity to decrease precipitously, flicker sensitivity instead decreased gradually over a prolonged period of time, and incorporated a substantial L cone contribution. The precipitous suppression of flicker sensitivity found for certain combinations of bleaching and test wavelengths appears to depend on the action of a broadly tuned, red-green spectrally opponent process.

Sensitivities in older eyes with good acuity: cross-sectional norms

We measured several indices of foveal visual function for a large group of people aged 60 and older. The data reported in this paper are from individuals who had good acuity in each eye and met a number of other criteria for good ocular health. For each index, we described the rate of cross-sectional change with age using linear regression statistics. We found age-related change for eyes having 20/20 or better acuity to exist for several different indices. Sensitivity mediated by the blue-sensitive cones decreased with age, as expected. However, the rate of decrease was faster for females than for males. At least part of the difference was associated with different rates of lenticular change. Absolute sensitivity at long wavelengths also decreased with age, but at the same rate for each sex. Rayleigh color matches changed with age in a manner consistent with underlying age-related decreases of effective foveal cone photopigment density. However, not all indices showed age-dependent changes. For instance, the time constant describing the rate of photopic dark adaptation did not appear to change with age.

Sensitivities in older eyes with good acuity: eyes whose fellow eye has exudative AMD

We compared several indices of foveal visual function between two groups of people aged 60 and older. One group was comprised of individuals who had good acuity in one eye, but had a history of exudative aging macular degeneration (AMD) in the other eye. We measured visual function in these individuals' good eyes only. The second group was a normative group; it was comprised of individuals who had good acuity in each eye. None of the eyes which we tested from either group had funduscopic evidence of macular pathology other than macular drusen and/or hypopigmentation. We found that eyes whose fellow eye had suffered from exudative AMD themselves suffered compromised foveal function, even when they retained 20/20 or better acuity. Losses of sensitivity mediated by blue-sensitive cones tended to be greater for 1 degree than for 3 degrees diameter test stimuli. Absolute sensitivity losses at long test wavelengths were probably due to several factors, including decreased effective cone photopigment density. Slow rates of recovery during dark adaptation were associated with the presence of many macular drusen and/or macular hypopigmentation. Eyes whose fellow eye had suffered from exudative AMD had more macular drusen and hypopigmentation than eyes whose fellow eye had not suffered from exudative AMD.

Total occlusion does not disrupt photoreceptor alignment

Previous measurements of the photopic Stiles-Crawford function (SCF) in human observers prior to, during, and after (1) total occlusion, and (2) displacement of the eye's pupil, indicate by inference the presence of a phototropic mechanism which actively maintains photoreceptor alignment. In an attempt to replicate and expand the conclusions of these experiments, full SCFs were measured on three normal eyes and one abnormal eye prior to and after at least 6 days total occlusion. Counter to previous reports, total occlusion induced few if any alterations in the SCF rho value in both the normal and abnormal eyes.

A LOW-COST CONTACT LENS FOR GREEN-ONLY ARGON-LASER PHOTOCOAGULATION

Filtration of argon laser light to eliminate the blue wavelengths and create a green-only light may be clinically useful in treating macular lesions. To that end, an inexpensive, easy method of modifying a posterior pole contact lens for use with any ophthalmic argon laser to allow only green, not blue, laser light to be used for macular photocoagulation is described.

Flicker photometric study of chromatic adaption: selective suppression of cone inputs by colored backgrounds

Flicker photometric equivalence is both additive and transitive when the test and standard are alternated upon a relatively more intense colored background. When the balance of red versus green cone excitation from the background is unequal, the contribution of one cone type to flicker photometric spectral sensitivity may be depressed in relation to that of the other by at least 1 order of magnitude more than Weber's law predicts. The resultant spectral sensitivity is determined predominantly by only one class of cone. The cone spectral sensitivities of normals are then seen to be the same as those of dichromats, although there is some individual variation. A model is developed to explain this surprising phenomenon.

Blue-sensitive cones do not contribute to luminance

By using violet backgrounds we selectively altered blue-cone sensitivity but found no change in flicker photometric sensitivity. This indicates that blue cones do not contribute to luminance as defined by flicker photometry.

Static pressure-flow relation in the total systemic vascular bed of the dog and its modification by the baroreceptor reflex

To evaluate arterial baroreceptor reflex control of total systemic vascular resistance, we studied the relation between mean arterial blood pressure (P) and mean aortic flow (Q) before and after the reflex was abrogated. In 12 dogs with a perfusion pump interposed at the vena-caval-right atrial junction, Q was kept at 60, 80, 100, 120, and 140 ml/min kg-1 for up to 20 minutes. There was little time-dependent change in P at any of these flows. When the reflex was intact, the mean P-Q curve was only slightly convex to the pressure axis; its linearized slope was 0.55 mm Hg-min-kg/ml and its pressure axis intercept was 44 mm Hg. After section of the sinovagal nerves, administration of hexamethonium (30 mg/kg, iv) and norepinephrine (3-5 mug/kg min-1, iv), or both, the slope became 0.96 mm Hg-min-kg/ml and the pressure axis intercept was about 3 mm Hg. Similar findings were obtained in 3 closed-chest dogs in which P was servocontrolled and Q was measured. Therefore, we think that the conventional practice of calculating total peripheral resistance as P/Q and evaluating reflex control of it in terms of the changes in that value involves only a small error in the moderately sub -and supranormal flow range.