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Biomedical subjects

C W Tyler

Publications and source records attributed to C W Tyler.

At least 91 records · Page 5Linked to original sources
PubMed1984

Photopic flicker sensitivity losses in simplex and multiplex retinitis pigmentosa.

Psychophysical tests for flicker sensitivity were conducted on a group of retinitis pigmentosa patients classed as either simplex or multiplex on the basis of the familial incidence of this disease. The results were compared with those obtained from normal observers. A similar pattern of losses, predominantly at high temporal frequencies, was shown by all patients. The pattern cannot be reproduced in normal observers by reducing the luminances of the test stimuli; nor can it be explained by a simple reduction in the signal-to-noise ratio of the visual system.

Adult↗
PubMed1984

The relation between visual sensitivity and intraocular pressure in normal eyes.

Intraocular pressure and flicker modulation sensitivity at 25 and 40 Hz were measured in 22 normal observers, with an age range from 20-71 years. Significant correlations up to 0.67 were found between intraocular pressure and flicker sensitivity at several points in the visual field. There was no correlation between flicker sensitivity and age of the observers. Thus intraocular pressure may affect neuronal function in the normal eye.

Adult↗
PubMed1983

Cesarean section. Risk and benefits for mother and fetus.

We studied the effects of cesarean section on neonatal mortality for breech infants and low--birth weight vertex infants using data from the Georgia neonatal surveillance network on 392,241 singleton deliveries between 1974 and 1978. The risk of neonatal death for breech infants weighing 4,000 g or less delivered vaginally was significantly higher than the risk for those delivered by cesarean section. The lower the birth weight, the higher the risk for a vaginal breech delivery. For breech infants weighing 1,000 to 2,500 g, the risk was almost 21/2 times greater for a vaginal delivery v a cesarean delivery. The best outcome for high-risk vertex infants weighing 1,000 to 1,500 g was for those delivered by cesarean section in a tertiary perinatal center. An increase in the cesarean section rate may be associated with increased neonatal survival; however, the benefits must be weighed against the costs of an increased maternal mortality and morbidity.

Birth Weight↗
PubMed1983

A comparison of primary and secondary homicides in the United States.

In 1979, over 20,000 people in the United States were victims of homicide, but public health agencies have not yet defined their role in its prevention. Role definition might begin with differentiating various forms of homicide, so the authors used data on all homicides reported by law enforcement agencies for 1976-1979 to determine whether homicides that did not occur during the perpetration of another crime (primary homicides) differ from those that occurred during the perpetration of another crime (secondary homicides). Primary and secondary homicide rates were highest in the South and West, respectively. The relative risk for Standard Metropolitan Statistical Areas (SMSAs) compared with non-SMSAs was 2.4 for secondary homicide but only 1.3 for primary homicide. It was found that 17% of primary homicides and 3% of secondary homicides had a female offender. Primary homicides were more frequently intersexual and intraracial than were secondary homicides. Victim and offender ages were similar to one another in primary homicides and dissimilar in secondary ones. Over 75% of primary homicides involved family members or acquaintances, compared to only 24% of secondary homicides. The authors conclude that primary and secondary homicides are epidemiologically dissimilar, and they suggest that public health concern should focus on primary homicide. Prevention and intervention measures should concentrate on discussed target populations. Techniques might include stress reduction and conflict avoidance.

Adolescent↗
PubMed1983

Epidemiologic characteristics of primary homicides in the United States.

Homicide is one of the five leading causes of death for all persons 1-44 years of age. Over half of the homicides occurring in 1979 did not involve the perpetration of another crime. The authors have defined these as primary homicides and suggest that these deaths require the formulation of public health and social services prevention strategies. An epidemiologic assessment of primary homicides in the United States for 1976 through 1979 showed the following. Sixty per cent of primary homicides were male victim/male offender events; 40% involved a female as a victim and/or as an offender. Three per cent of primary homicides were female victim/female offender events; 97% involved a male as a victim and/or as an offender. Primary homicides involving female victims or offenders were more frequently intrafamilial than those involving males, but rates of intrafamilial homicides by males were greater than those involving females. The preponderance of all primary homicides occurred between acquaintances, but the relationship between victim and offender varied with age, sex, and race. The weapons used varied with the victim's and offender's age, sex, and race, and with the relationship between victim and offender. Based on the described patterns, prevention measures should be divided into three broad areas: intrafamilial violence, extrafamilial violence, and male patterns of aggression. Key target populations for the first area include females, rural households, and the very young or very old. A key target population for the second area is teenage males.

Adolescent↗
PubMed1983

Underrecording of infant homicide in the United States.

Homicide rates for infants dropped suddenly between 1967 and 1969. The abrupt nature of this decline suggested the change was artifactual. Investigation suggests that two classification revisions instituted at this time were causes of this decline: changes in related codes set forth in the Eighth Revision of the International Classification of Diseases, Adapted, and revision of the standard certificate of death in 1968. Infant homicides may have been disproportionately underrecorded after 1968. (Am J Public Health 1983; 73:195-197.)

Adolescent↗
PubMed1983

Spatial characteristics of static and dynamic stereoacuity in strabismus.

The spatial and temporal organization of stereoscopic depth perception were compared in normal and strabismic observers. The minimum and maximum disparities for stimulating static and dynamic stereopsis in strabismus were examined as a function of spatial separation of disparate stimuli. Disparities and their spacing were produced by spatial modulation of two vertical lines viewed haploscopically. Most strabismics had normal upper disparity limits but elevated static and dynamic stereothresholds. Moderate stereothreshold elevations (100 arc sec) were constant for spatial separations greater than 15 arc min. Two new types of spatial crowding effects upon stereopsis were observed. The first type resulted from the constant elevation of the disparity threshold. The second type consisted of a reduced maximum disparity limit for stereopsis. In both cases, the constriction of the range of perceivable depth produced a reduction in the spatial and temporal frequency limits for depth perception. Clinical tests of stereoacuity that crowd stimuli closer than 0.25 degree underestimated the strabismic patients' potential stereoacuities by a factor of 2 to 4. Similarly, tests of dynamic stereopsis that use temporal frequencies greater than 1 Hz will underestimate optimal dynamic stereoacuity.

Depth Perception↗
PubMed1983

Homicide as a cause of pediatric mortality in the United States.

Homicide is a major cause of pediatric mortality. National law enforcement data were analyzed to characterize and differentiate neonaticide, infanticide, filicide, and overall child homicide. Results include the following: Neonaticides often involved parents or unidentified perpetrators and occurred proportionately more in rural areas than did other types of child homicide. Infanticide appeared to be one end of the spectrum of child homicide and not a distinct entity. Filicide rates were higher for sons than daughters and the crime was committed by more fathers than mothers. Overall child homicide predominately involved young male offenders who were acquaintances of the victim. At remarkably early ages, homicide characteristics began to resemble those of adult homicide. Further research in this area should attempt to gain detailed information concerning the child, his family, and their social network. Pediatricians should be actively involved in determining risk factors for child homicide and in screening children for risk when these factors are determined.

Adolescent↗
PubMed1982

Perversions.

Explore the source record for details and available documents.

Discrimination Learning↗
PubMed1982

Child abuse in Georgia: a method to evaluate risk factors and reporting bias.

From July 1975 through December 1979, the Georgia Department of Protective Services Central Registry recorded population-based data on confirmed, non-confirmable, and ruled-out child abuse reports. We propose that reporting biases are reflected in the differential characteristics of confirmed and ruled-out reports of child abuse. Characteristics, households, or groups equally or more prevalent in the latter category cannot necessarily be considered associated with increased risk of child abuse, even if they are represented in the confirmed abuse population more than in the general public. Important examples of factors or categories for which an association was suggested in other studies but which are not supported by this analysis are: urban residence, teenage motherhood, infancy, and mothers and other female perpetrators. These are conditions or categories associated with greater surveillance; therefore, risk assessment is not possible using the data in this registry. Certain households do appear to be at increased risk for child abuse. These include large families, families without a biological mother or biological father, and families ever needing Aid to Families with Dependent Children (AFDC). This increased risk, however, is slight. Improved surveillance requires identification of reporting biases. A comparison of confirmed and ruled-out reports is an inexpensive and system-specific step toward achieving this aim.

Age Factors↗