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At least 91 records · Page 5Linked to original sources
PubMed1997

Biometry and primary angle-closure glaucoma among Chinese, white, and black populations.

PURPOSE: Primary angle-closure glaucoma (PACG) is more prevalent among Chinese than whites. The authors tested the hypothesis that Chinese have shallower anterior chambers than do whites, a factor that may be related to PACG prevalence. METHODS: The authors compared anterior chamber depth, axial length, radius of corneal curvature, and refractive error among 531 Chinese, 170 whites, and 188 blacks older than 40 years of age using the same model of instruments and identical technique. RESULTS: Mean anterior chamber depth and axial length did not differ significantly for the three groups. Whites had a significantly higher prevalence of hyperopia > 2 diopters than did Chinese. Radius of corneal curvature was significantly smaller among Chinese than whites or blacks. CONCLUSIONS: These results suggest that Chinese do not differ on a population basis from other ethnic groups in many of the biometric risk factors known to be of importance for PACG. It will be necessary to identify other ocular biometric parameters to explain the excess burden of PACG among Chinese, which may improve the effectiveness of screening for this disease in all populations.

Adult↗
PubMed1997

Ultrasonographic biometry in salivary glands.

Specifications about the size of healthy salivary glands are not available to date. Therefore, we determined the size of the submandibular and the parotid glands by ultrasonography in 50 subjects (25 men, 25 women, mean age 45 y, range 20-68) with no history of disease affecting the salivary glands. The subjects were equally distributed concerning gender and age. Body weight did not differ more than 20% from the ideal weight following Broca's formula (mean body weight 71 kg, range 46-95 kg). In the submandibular glands we found an anterior-posterior length of 35 mm +/- 5.7 mm, a paramandibular dimension to the depth of 14.3 mm +/- 2.9 mm and a dimension in frontal scanning of 33.7 mm +/- 5.4 mm. The parotid glands were measured 46.3 mm +/- 7.7 mm in the axis parallel to the mandibular ramus and 37.4 mm +/- 5.6 mm in the transversel axis. The dimension of the parotid parenchyma was measured with 7.4 mm +/- 1.7 mm lateral to the mandible and 22.8 mm +/- 3.6 mm dorsal to the mandible. No statistically significant difference to the 5%-level was found concerning gender. The dimension of the parotid glands correlated statistically significantly with body weight (p = 0.03). This correlation was not found in the dimension of the submandibular glands. Age did not correlate with the dimension of salivary glands. Results of the submandibular glands were compared with volume measurements of submandibular glands from cadavers.

Adult↗
PubMed1990

Biometry of the posterior lens capsule: a new method to predict pseudophakic anterior chamber depth.

The distance between the anterior corneal vertex and the posterior lens capsule was measured in 60 eyes before and three months after extracapsular cataract extraction with implantation of a posterior chamber lens. The preoperative capsule position ranged from 6.15 mm to 8.60 mm and averaged 7.64 +/- 0.47 mm (+/- SD). All posterior lens capsules had moved anteriorly following surgery. The postoperative capsule position ranged from 4.31 mm to 5.53 mm and averaged 4.93 +/- 0.29 mm. The postoperative capsule position could be predicted by the following optimized multiple linear regression equation: 2.4 + 0.011 x patient age + 0.171 x anterior chamber depth + 0.051 x axial length. The multiple correlation coefficient was 0.48. The postoperative anterior depth could be predicted with a correlation coefficient of 0.61 by subtracting both the averaged value of the clinical "laser space" and the exact central implant thickness from the estimated position of the posterior lens capsule. We suggest that this principle for predicting the postoperative anterior chamber depth may be useful for a number of lenses with different designs.

Adult↗
PubMed1993

Inter-observer variation in clinical optic disc biometry.

This study investigated the inter-observer reproducibility of measurements of the optic nerve head as carried out with a clinical optic disc biometer. This instrument employs a modification of indirect ophthalmoscopy to enable measurement of fundus structures. Measurements were made independently by two observers on 84 eyes of 47 patients. The median inter-observer differences for each measurement were as follows: maximum disc diameter, 0.085 mm; minimum disc diameter, 0.080 mm; maximum cup diameter, 0.098 mm; minimum cup diameter, 0.078 mm; disc area, 0.225 mm2; neuroretinal rim area, 0.215 mm2. Utilising the above measurements, the instrument automatically calculates a 'rim index' to take account of variations in disc size. It then interprets the disc as normal, suspicious or glaucomatous. The optic disc biometer produced seriously conflicting interpretations in 8 discs, 7 of which had been judged by both observers to have indistinct boundaries of the disc or cup.

Biometry↗
PubMed1995

Biometry of the fetal cisterna magna: estimates of the ability to detect trisomy 18.

Measurements of the fetal cisterna magna were obtained from a prospective sample of patients undergoing diagnostic obstetric ultrasound examinations. These normal measurements were then compared to a retrospective sample of ultrasound scans from fetuses with the diagnosis of trisomy 18 by amniocentesis. The fetal cisterna magna increases in size throughout pregnancy. The sample from fetuses with trisomy 18 was different and had a higher rate of small and large cisterna magnas. After the two samples were mixed, it was determined that a cut-off of 2.5 standard deviations for the fetal cisterna magna would give a sensitivity of 26.3%, specificity of 99.1%, positive predictive value of 50.0% and negative predictive value of 97.6% for trisomy 18. The probability that a fetal cisterna magna of abnormal size will predict trisomy 18 in an early second-trimester ultrasound examination with the 2.5 standard deviation cut-off was estimated at 0.019. A fetal cisterna magna that is of abnormal size appears to be of diagnostic value in identifying the fetus with trisomy 18, but its sensitivity is low.

Adult↗
PubMed1987

[Ultrasound biometry in childhood].

Within the last 18 months the authors have measured, in cases of juvenile cataract seen by them, the axial length of the eye and other parameters. As a control group, children from the authors' squint clinic, with various refractive errors, were examined. With the data thus gathered, correlation and regression analyses were performed, postoperative refraction values were calculated, and eye growth in phakic eyes was compared with that in aphakic eyes. Regression formulas were established which enabled the authors to calculate eye length at a given age, to determine the postoperative refraction of their juvenile cataract patients with great accuracy, and, so far, to prove that there is no significant difference between phakic and aphakic eyes as regards growth.

Adolescent↗
PubMed1984

[Biometry of the lens with respect to age and cataract morphology. Evaluation of Scheimpflug photos of the anterior segment].

Thickness of the lens, cortex and nucleus or nucleus with supranuclear layer, respectively, were determined for 58 controls aged 11-69 years (115 lenses), and for 175 patients aged 30-86 years with different types of cataract (247 lenses). Measurements of the densitograms of Scheimpflug photos (taken along the optical axis, magnified 10-fold) were performed, accurate to 0.5 mm (corresponding to 0.05 mm original size). The cataractous lenses were grouped in 5 morphological classes and 3 degrees of opacification (density according to the Scheimpflug photos). As regards normal lenses, the present authors' findings correspond to earlier findings of Niesel et al. (1976). Deviations from the normal pattern are found in typical cortical cataract (water-cleft and spokes cataract, wedge-shaped cataract) where nucleus and nucleus with supranuclear layer are thinner than the normal lenses, while with nuclear cataracts and mixed types the opposite is the case. In eyes with posterior cortical opacities no increase in the thickness of the anterior cortex is found with aging. With the true nuclear cataracts the increase in the thickness of the anterior cortex is negligible. The degree of opacification is closely related to an increase in the thickness of the nucleus and supranuclear layer, which implies a decrease in the thickness of the anterior cortex. Water-clefts and spokes of larger size cause the anterior cortex to become thinner. In eyes with wedge-shaped cataracts the different degrees of opacification did not affect the parameters measured.

Adolescent↗
PubMed1980

[New technique of ultrasonic biometry (author's transl)].

A new measuring system for echo return times is described, which renders it possible to measure simultaneously the three axial lengths of the living eye (length of cornea plus anterior chamber, length of the lens and of the vitreous) with ultrasound in real time and to process the data numerically. The repetition rate for the measurements is optimized up to the limit: each transmitted wave is registered. The computer either generates a measuring protocol with statistical data (mean value, standard deviation) or the variation of the three echo return times is displayed graphically. In clinical practice the unit is used routinely for rapid determination of optimal implant lenses, etc.

Anterior Chamber↗
PubMed1998

Anterior chamber angle biometry: quadrant variation, age change and sex difference.

PURPOSE: To estimate the anterior change angle width (ACAW) in healthy volunteers quantitatively using an anterior eye segment analysis system and to clarify the involvement of aging and sex in ACAW. METHODS: The ACAW of the upper, lower, medial, and lateral quadrants of 42 eyes from 42 healthy volunteers was measured by the NIDEK EAS-1000 anterior eye segment analysis system, a non-invasive in vivo measuring method based on Scheimpflug image analysis. Data from all subjects were employed to investigate aging and quadrant differences; and age-matched male and female subjects were chosen from all subjects to study sex difference and aging. RESULTS: Young subjects showed no significant inter-quadrant differences of ACAW. However, ACAW showed a significant negative correlation with age in all quadrants, but the lateral quadrant showed much more narrowing than the others. The age-matched study revealed that ACAW narrowing was much greater in females than in males, and a polynomial regression analysis showed that this sex difference appeared in subjects older than middle age. CONCLUSIONS: The anterior eye segment analysis system revealed that ACAW decreased with age, especially in the lateral quadrant. The significantly more marked narrowness of ACAW in females older than middle age may be related to the high incidence of angle closure glaucoma in elderly females.

Adult↗
PubMed1994

Chaos in biometry.

Although the study of chaotic and periodic phenomena began as recently as the 1960s, its subsequent development during the past few years has been extremely rapid in terms of both theory and practical application. The purpose of this paper is therefore to present an overview which will enable researchers with little prior knowledge to assess the relevance and potential application of nonlinear systems to problems in medicine and biology. Deterministic dynamic behaviour is examined through discrete logistic-type equations; stochastic behaviour is studied by superimposing an appropriate birth-death structure. Analysis of a variety of insect data sets shows that periodic and chaotic structures do indeed feature in natural populations; the classic Nicholson's blowfly data are viewed from both stochastic limit-cycle and deterministic chaos standpoints. Determination of the attractor dimension can be an invaluable aid to the understanding of biological and medical phenomena, and convincing examples include phase-space comparisons between healthy and sick humans for both EEG and ECG records.

Animals↗
PubMed1991

Microcomputer software applied to corneal stromal biometry.

Here we report a new method for image analysis of the corneal stroma. To obtain the biometric characteristics of a given area, we perform three different treatments of the same image. These automated predictions closely match each parameter (length, surface area, etc.), as measured manually by a "blind investigator." Furthermore, to obtain quantifiable, average values, we have increased the number of successive image measurements, which has led to the development of a series of programs designed to optimize automated data handling. Finally, the acquired, calculated parameters are summarized in the form of intermediate tables for each series of images, and as a final summary table incorporating t-test values and permitting comparison between two stromas (e.g., normal and pathological). Multivariate analysis and an ascending hierarchical classification demonstrate the main trends in differences of pathological vs. normal stroma.

Algorithms↗