The influence of stimulus size on measured visual field extent in infants.

PURPOSE: To compare measured visual field extent for a 6 degrees stimulus (typical size used in studies of infants) with a 1.5 degrees stimulus (similar to the largest size used in Goldmann perimetry) in young infants. METHODS: A total of 120 infants (60 each at 3.5 months and 7 months of age) and 24 adults were tested monocularly with a kinetic perimetry procedure using a black double-arc perimeter. Each subject was tested with either a 6 degrees or 1.5 degrees white sphere, which was mounted on a black wand and moved smoothly toward the intersection of the perimeter arms at 3.4 degrees /s. Visual field extent along each perimeter arm was defined as the median of 2 to 3 measurements of the position of the leading edge of the stimulus when the subject made an eye movement toward the stimulus. RESULTS: The 6 degrees stimulus produced larger measured visual field extent than the 1.5 degrees stimulus in 3.5-month olds (temporal field only) and in 7-month olds (nasal and temporal field), but not in adults. CONCLUSIONS: Using the testing conditions of the present study, increasing stimulus size beyond the largest used in a Goldmann perimeter (approximately 2 degrees) increases measured visual field extent in young infants, but not in adults. This may relate to differences in peripheral summation areas or to differences in attentional factors between infants and adults.     

Visual acuity results in school-aged children and adults: Lea Symbols chart versus Bailey-Lovie chart.

PURPOSE: To compare visual acuity results obtained using the Lea Symbols chart with visual acuity results obtained with the Bailey-Lovie chart in school-aged children and adults using a within-subjects comparison of monocular acuity results. METHODS: Subjects were 62 individuals between 4.5 and 60 years of age, recruited from patients seen in five optometry clinics. Each subject had acuity of the right eye and the left eye tested with the Lea Symbols chart and the Bailey-Lovie chart, with order of testing varied across subjects. Outcome measures were monocular logarithm of the minimum angle of resolution (logMAR) visual acuity and inter-eye acuity difference in logMAR units for each test. RESULTS: Correlation between acuity results obtained with the two charts was high. There was no difference in absolute inter-eye acuity difference measured with the two acuity charts. However, on average, Lea Symbols acuity scores were one logMAR line better than Bailey-Lovie acuity scores, and this difference increased with worse visual acuity. CONCLUSIONS: The Lea Symbols chart provides a measure of inter-eye difference that is similar to that obtained with the Bailey-Lovie chart. However, the monocular acuity results obtained with the Lea Symbols chart differ from those obtained with the Bailey-Lovie chart, and the difference is dependent on the individual's absolute level of visual acuity.     

Development of grating acuity in infants with regressed stage 3 retinopathy of prematurity

The acuity card procedure was used to measure grating acuity in 17 infants with regressed Stage 3 retinopathy of prematurity (ROP) who had no lasting anatomic changes in the retina or optic nerve. Results were compared with those of 28 healthy preterm infants and 28 infants matched by birth weight and gestational age who did not have Stage 3 ROP. Infants in the ROP group showed delayed grating acuity development until 2 years of age. This difference among groups was significant at the 3-5- and 10-12-month test ages but not at the 0-1-, 8-9-, and 16-18-month test ages. Post hoc analyses indicated that the delay in acuity development shown by the ROP group was due to the poor acuity scores of the infants in that group who had central nervous system abnormalities of periventricular leukomalacia or severe (Grade III or IV) intraventricular hemorrhage. When the data of these infants were removed from the analysis, the ROP group showed acuity development similar to that of both the healthy preterm group and the group of infants with matched birth weights and gestational ages who did not have Stage 3 ROP.     

Immunodiagnosis of Entamoeba histolytica and Ascaris lumbricoides infections in Caucasian and aboriginal Australians

The immunodiagnostic efficiency of an indirect immunofluorescence test (IFAT) and in vitro lymphocyte proliferative responsiveness (cell mediated immunity test, CMIT) used to measure the immunological responses of individuals with known natural Entamoeba histolytica and Ascaris lumbricoides infections, was studied under survey conditions. E. histolytica was common among Aborigines from Cherbourg, Kowanyama and Central Australia, but it was not found in Brisbane Caucasians. The protozoan was selected for the study because it was prevalent and purified antigen was commercially available. Immunodiagnosis for A. lumbricoides was made using an antigen prepared by affinity chromatography. Diagnosis based on frequency distribution of immunological data gave valid assessment of the number of infected individuals in each population studied.     

Smoking and relative body weight: an international perspective from the WHO MONICA Project.

STUDY OBJECTIVE: To investigate the magnitude and consistency of the associations between smoking and body mass index (BMI) in different populations. DESIGN: A cross sectional study. SETTING AND PARTICIPANTS: About 69,000 men and women aged 35-64 years from 42 populations participating in the first WHO MONICA survey in the early and mid 1980s. MAIN RESULTS: Compared to never smokers, regular smokers had significantly (p < 0.05) lower median BMI in 20 (men) and 30 (women) out of 42 populations (range -2.9 to 0.5 kg/m2). There was no population in which smokers had a significantly higher BMI than never smokers. Among men, the association between leanness and smoking was less apparent in populations with relatively low proportions of regular smokers and high proportions of ex-smokers. Ex-smokers had significantly higher BMI than never smokers in 10 of the male populations but in women no consistent pattern was observed. Adjustment for socioeconomic status did not affect these results. CONCLUSIONS: Although in most populations the association between smoking and BMI is similar, the magnitude of this association may be affected by the proportions of smokers and ex-smokers in these populations.     

Validation in the sheep of an ultrasound velocity dilution technique for haemodialysis graft flow

BACKGROUND: A simple, rapid, inexpensive method for measuring the flow in a patient's vascular access would permit routine monitoring during haemodialysis, and hence provide information of access graft deterioration sufficiently early to increase the success of minimally invasive remedial procedures. This paper reports the validation of such a method in animals. METHODS: A PTFE graft was implanted in sheep between the carotid artery and the jugular vein. While the sheep was under general anaesthesia and on an haemodialysis circuit, ultrasound velocity in its blood was perturbed by the injection of a 5-10 ml bolus of isotonic NaCl. The pump tubing flow was measured by a transit-time blood flow meter. This flow was combined with the areas of perturbation generated by the injection before and after mixing in the access flow to estimate graft flow. The calculated graft flow was compared to flow measured directly by a transit-time probe on the same carotid artery. RESULTS: Over a 10-fold range, 120-1260 ml/min, graft flow measured by ultrasound velocity dilution agreed well with graft flow measured directly with a scatter of 76 ml/min about the regression line. CONCLUSION: Ultrasound velocity dilution provides a method for measuring flow in the graft accurate enough for clinical evaluation of patients on dialysis.