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At least 127 records · Page 7Linked to original sources
PubMed2006

Can ultrasound fetal biometry predict fetal hyperinsulinaemia at delivery in pregnancy complicated by maternal diabetes?

OBJECTIVE: The aim of this study was to determine whether there is an association between ultrasound fetal biometry and amniotic fluid insulin levels at delivery in women with pre-existing diabetes or impaired glucose tolerance in pregnancy. STUDY DESIGN: This retrospective cohort study identified 93 women who had amniotic fluid insulin levels measured at time of delivery. Standardised estimated fetal weight and fetal growth velocity were calculated from serial third trimester fetal ultrasound measurements. RESULTS: Women with pre-existing diabetes had significantly greater mean growth velocity [1.39 (95% CI: 0.43-2.23) versus 0.39 (95% CI: -01.7-0.95); p=0.04], significantly greater mean estimated fetal weight (EFW) Z score prior to delivery [2.36 (95% CI: 1.82-2.9) versus 1.38 (95% CI: 1.02-1.74); p=0.002] and greater mean birthweight centile [82 (95% CI: 0.74-0.89) versus 67 (95% CI: 58-76); p=0.02] than those with GDM/IGT. Amniotic fluid insulin levels demonstrated a similar significant difference between the pre-existing and GDM/IGT groups [20.5 (95% CI: 12.9-28.1) versus 8.5 (95% CI: 5.4-11.7); p=0.001]. An association between fetal growth and size and amniotic fluid insulin was observed in women with pre-existing diabetes. Positive likelihood ratios were 1.67 and 2.08, respectively, for the prediction of liquor insulin greater than the 95th centile in women with pre-existing diabetes. CONCLUSION: Ultrasound measures of fetal size and growth used in this study are not sufficiently accurate to predict those infants likely to be at risk from the adverse effects of fetal hyperinsulinaemia.

Amniotic Fluid↗
PubMed2006

[Quality control of prenatal ultrasound. A role for biometry].

Because of an increasing demand for limited health care resources as well as an increasing impact of legal aspects in ultrasound practice, it has become necessary to ensure that screening procedures are cost-effective and clinically effective and to develop systems that could help sonographists in certifying their practice. Based on the literature, various approaches for quality control are reviewed. Special emphasis is put on the use of fetal biometry and statistical tools to develop quality control systems based on both qualitative and quantitative approach. Besides their potentials for audit and quality control, such tools could also be useful during the process of training.

Biometry↗
PubMed2005

Signal quality of biometry in silicone oil-filled eyes using partial coherence laser interferometry.

PURPOSE: To assess the practical feasibility and signal quality of axial length measurements by partial coherence laser interferometry in silicone oil-filled eyes with previous complicated vitreoretinal surgery. SETTINGS: Department of Ophthalmology, University Cologne, Cologne, Germany. METHODS: Using a Zeiss IOLMaster, axial length measurements and signal-to-noise ratios of optical biometry in silicone oil-filled eyes (n=45) and contralateral eyes without tamponade (n=41) were analyzed. RESULTS: Axial length measurements with signal-to-noise ratio > or =2 were feasible in 41 of 45 silicone oil-filled eyes (91%) and 37 of 41 eyes without tamponade (90%). Cataract, central retinal detachment, vitreous hemorrhage, and emulsified oil droplets attached to the intraocular lens were reasons for failure of partial coherence laser interferometry. The signal-to-noise ratio of the first 2 measurements was significantly smaller (P=.04) in silicone-filled eyes (4.4 +/- 2.0) than in eyes without tamponade (5.5 +/- 3.0). Axial lengths of the oil-filled eye and the contralateral eye showed a significant intraindividual correlation (P<.0001, Spearman r=0.84). CONCLUSIONS: Partial coherence laser interferometry shows good clinical practicability in silicone oil-filled eyes with previous complicated vitreoretinal surgery. Further studies are needed to assess the reliability of these measurements with regard to postoperative refraction after combined oil removal and cataract surgery.

Biometry↗
PubMed2005

Optical biometry of the anterior eye segment: interexaminer and intraexaminer reliability of ACMaster.

PURPOSE: To evaluate the interexaminer and intraexaminer reliability of corneal thickness, anterior chamber depth (ACD), and crystalline lens thickness measurements using a commercially available anterior segment optical biometry instrument (ACMaster, Carl Zeiss Meditec) based on partial coherence interferometry (PCI). SETTING: Medical University of Vienna, Vienna, Austria. METHODS: Interexaminer reliability and intraexaminer reliability were evaluated in 10 eyes of 10 young volunteers and 11 eyes of 11 cataract patients. The measurements of the interexaminer reliability were taken by 3 examiners. Corneal thickness, ACD, and lens thickness of the intraexaminer reliability were measured twice in all eyes by 1 examiner. To evaluate the effect of cycloplegia on the variability, the measurements were performed on 5 volunteers under cyclopentolate 1%. Measurements were performed using the prototype of the ACMaster based on PCI. RESULTS: The interexaminer/intraexaminer reliabilities were 99.9% for corneal thickness and ACD. The reliability of lens thickness could not be estimated because of a large number of missing values in the cataract patient group. The median interexaminer variability (SD) was 1.9 microm for corneal thickness, 7.5 microm for ACD, and 10.6 microm for lens thickness. The median intraexaminer variability (SD) was 1.6 microm for corneal thickness, 10.8 microm for ACD, and 8.7 microm for lens thickness. With cycloplegia, both the interexaminer variability and intraexaminer variability were smaller than without cycloplegia. CONCLUSIONS: Partial coherence interferometry measurements of anterior chamber distances (corneal thickness, ACD, lens thickness) using the prototype of ACMaster were highly reliable, allowing examiner-independent measurements. However, lens thickness measurements in cataract eyes were often difficult.

Adult↗
PubMed2004

In vivo biometry in the mouse eye with low coherence interferometry.

PURPOSE: A major drawback of the mouse model of myopia is that the ocular dimensions cannot be measured in vivo, and that histological techniques post-mortem suffer from limited resolution. We have tested the potential of a newly developed technique, optical low coherence interferometry (OLCI), adapted for short measurement distances by Meditec, Carl Zeiss, Jena, Germany (the "ACMaster"). Using this technique, ocular biometry was performed in mice with normal vision and after deprivation of form vision. METHODS: Axial eye length, corneal thickness and anterior chamber depth were measured in 23 mice, aged 25-53 days, and standard deviations from repeated measurements in the same eyes, as well as intra-individual and inter-individual variability were determined in different age groups. The data were compared to those from a preceding study in which biometrical data were obtained from frozen sections [Vision Res. 44 (2004) 1857]. Refractions were measured by automated infrared photorefraction. Mice had either normal visual exposure or were monocularly deprived of form vision for 14 days. RESULTS: Using OLCI, axial length could be determined with an average standard deviation of 8.0 +/- 2.9 microm, corneal thickness with 3.5 +/- 2.1 microm, and anterior chamber depth with 10.6 +/- 12.3 microm. Neither axial length, nor corneal thickness, nor anterior chamber depth were significantly different in left and right eyes of individual mice that had normal visual experience (mean absolute difference between axial lengths: 17 +/- 18 microm, between corneal thickness 5.1 +/- 4.8 microm, and between anterior chamber depths 16.7 +/- 14.8 microm). Compared to the variability that was previously found in frozen sections, the variability of axial length measurements with OLCI was 2.7 times less. After two weeks of form deprivation, OLCI revealed a significant axial elongation in the occluded eyes, compared to the contralateral fellow eyes (+38 +/- 36 microm or 1.16%, p = 0.045, n = 7, paired t-test). In this sample, no accompanying myopic shift was observed in the occluded eyes but this observation is not unexpected given the inherently variable responses of mouse eye growth to visual deprivation. CONCLUSION: OLCI had sufficient resolution in living mice to detect axial length changes in vivo that were equivalent to a dioptric change of 2 D. Using this technique, it was confirmed that mouse eyes respond to form deprivation by axial elongation, similar to the eyes of other animal models. The lack of a myopic shift in this sample, despite the axial elongation, demonstrates that biometric data are particularly important when the mouse eye is used as a model to study myopia.

Animals↗
PubMed2000

Growth pattern of twins of different chorionicity evaluated by sonographic biometry.

OBJECTIVE: To determine differences between growth patterns of monochorionic and dichorionic twins, and of concordant and discordant twins of both chorionicities. METHODS: We studied 70 cases of concordant twins (24 monochorionic, 46 dichorionic) and 45 cases of discordant twins (25 monochorionic, 20 dichorionic). In each case, growth was measured longitudinally by ultrasound biometry and the growth pattern was depicted. RESULTS: There were no differences in incremental growth between concordant monochorionic and dichorionic twins. The growth curve of concordant twins of both chorionicities was almost the same as that of a singleton until 34 weeks' gestation. However, in the discordant twins, the growth of the larger twin matched the growth curve of a singleton or concordant twin, but the growth of the smaller twin gradually decreased to the range of growth restriction. The growth curves for monochorionic discordant twins appeared to be representative of two groups, one of which had onset of discordancy before 24 weeks. CONCLUSION: It is clinically important to determine chorionicity early in twin pregnancies, to calculate the percentage of discordancy between the fetuses, and to examine longitudinal fetal growth curves in each chorionicity.

Biometry↗
PubMed2005

[Ocular biometry using Orbscan].

Orbscan is a recent optical device that combines the Placido disk of the videokeratoscope and a scanning slit. The scanning slit measures the elevation of both the corneal surface (anterior and posterior) and the anterior iris-lens surface. Biometric measures of the anterior segment such as corneal thickness, anterior chamber depth, corneal diameter, and iridocorneal angle are obtained using spatial coordinates of various ocular surfaces. Orbscan is not only a corneal topograph but a versatile device capable of measuring the biometry of the anterior segment of the eye.

Biometry↗
PubMed1998

Fetal biometry and outcome in monochorionic vs. dichorionic twin pregnancies; a retrospective cross-sectional matched-control study.

Fetal biometry, amniotic fluid volume distribution and perinatal outcome were determined in a retrospective, cross-sectional matched-control study design, including 20 monochorionic (MC) twin pregnancies and 20 dichorionic (DC) twin pregnancies (historic controls). Intertwin differences for fetal abdominal circumference were larger in the MC subset than in the DC subset. Fetofetal transfusion syndrome, based upon a combination of oligohydramnios in one sac and polyhydramnios in the other sac, existed in 40% (8 of 20) of the MC twin pregnancies, but in none of the DC twin pregnancies. Mean gestational age at delivery was significantly shorter in the MC subset (30.9 weeks) than in the DC subset (34.3 weeks). The perinatal death rate was significantly higher in MC twin pregnancies (50%) than in DC twin pregnancies (15%). No differences were established for intertwin weight estimates by ultrasound and birth weight between both subsets. The poor perinatal outcome in monochorionicity is mainly a result of the degree of premature delivery.

Amniotic Fluid↗
PubMed2000

Fetal biometry in different ethnic groups.

OBJECTIVE: The aim of this study was to determine whether differences in ultrasound-measured fetal biometry exist between pregnant woman of autochthonous Belgian origin and migrant women from Morocco and Turkey. METHOD: A prospective cross-sectional study was performed in which fetal biparietal diameter, head circumference, abdominal circumference and femur length were measured in pregnant women presenting between 18 and 40 weeks of gestation. Fetal weight was calculated using the formulae by Shepard and Hadlock. Only uncomplicated singleton pregnancies with a certain date of the last menstrual period, confirmed by early ultrasound, were included. The father of the child had to be of the same ethnic origin as the mother. Polynomial regression of the different measurements was performed for women of autochthonous Belgian origin and for migrant women from Morocco and from Turkey. RESULTS: Singleton fetuses numbering 524 were examined, including 369 Belgian, 78 Moroccan and 77 Turkish. Polynomial regression was performed for the three groups for the biparietal diameter, head circumference, abdominal circumference, femur length and estimated fetal weight. No significant difference between the three different ethnic groups could be demonstrated for the biparietal diameter (P = 0.39). There was a significant difference for the head circumference (P = 0.017), the abdominal circumference (P = 0.0015), the femur length (P = 0.0014) and the estimated fetal weight for both formulae (Shepard P = 0.047; Hadlock P = 0.0006). CONCLUSION: In this set of cross-sectional data no significant difference for ultrasound-measured fetal biparietal diameter between autochthonous Belgian women and migrant women from Morocco and from Turkey could be demonstrated. Differences do exist for the head circumference, the abdominal circumference, the femur length and the estimated fetal weight. The use of adapted charts of fetal size for pregnant women of Turkish or Moroccan origin should be considered.

Belgium↗
PubMed2002

Biometry of cataractous eyes using partial coherence interferometry: clinical feasibility study of a commercial prototype I.

PURPOSE: To evaluate the clinical feasibility of the prototype version of a commercial partial coherence interferometry instrument (axial length measurement, ALM, Carl Zeiss Jena) for noninvasive, high-precision biometry in cataractous eyes. SETTING: Department of Ophthalmology, Vienna General Hospital, and Institute of Medical Physics, University of Vienna, Austria. METHODS: The preoperative axial length in 49 eyes of 37 cataract patients was measured with the commercial (ALM) and laboratory (PCI) prototypes of the partial coherence interferometry instrument, as well as with immersion ultrasound (IUS). RESULTS: Axial length measurements with the ALM and PCI did not differ significantly (P = .23). Both prototypes assessed longer axial lengths than the IUS technique (P < .0001; median 203 microm; range -476 to +635 microm). The precision of the axial length measurement was 18 microm, 28 microm, and 54 microm with the PCI, ALM, and IUS, respectively. CONCLUSIONS: Partial coherence tomography is a high-precision, high-resolution, noncontact biometric technique.The commercial PCI prototype is practical in clinical use, with improved comfort for patients, no need for anesthesia, and a reduced risk of infection. However, the difference between the PCI and IUS in axial length measurement must be considered when using the constants supplied by intraocular lens (IOL) manufacturers for IOL power calculations.

Adult↗
PubMed1991

Clinical variability in keratometry, ultrasound biometry measurements, and emmetropic intraocular lens power calculation.

We calculated inter-examiner and intra-examiner variability in keratometry and ultrasound biometry when performed by two different examiners. The potential effect on intraocular lens power calculation was also considered. Intra-examiner variability was statistically and clinically significant for axial measurements, particularly in eyes with axial length greater than 24 mm. Thus, variability in biometric examination affected the emmetropic intraocular lens power, especially in myopic eyes.

Adult↗
PubMed1992

Biometry and auto-fluorescence of the anterior ocular segment in diabetics with and without autonomic neuropathy: a case control study.

The biometry and auto-fluorescence of the anterior ocular segment were examined in a case control study of two populations of diabetics. Cases, with diabetic autonomic neuropathy, and controls without neuropathy (forty in each group) were selected from a community based diabetic population and matched individually for age, sex, and type of diabetes. Scheimpflug and auto-fluorescence anterior segment photography were performed and analysed by digital image analysis in a masked fashion. There were differences between the groups in axial lens thickness, front radius of curvature of the lens, anterior chamber depth and lenticular auto-fluorescence. These findings are discussed in the context of the known association between autonomic neuropathy and narrow angle glaucoma, and possible common mechanisms of tissue damage in diabetes.

Aged↗
PubMed1999

Biometry of the silicone oil-filled eye.

PURPOSE: The advent of silicone oil tamponade has resulted in improved success rates in complicated retinal detachment surgery. Its use, however, can induce cataract formation in phakic eyes. In selected patients, removal of silicone oil can be combined with phacoemulsification of the cataract and intraocular lens (IOL) implantation, thus avoiding a further operation. This, however, poses a problem when trying to decide the power of IOL to be used, since the echographically measured axial length (AL) of an eye is greater in the presence of silicone oil. We performed ultrasound examination in the presence of silicone oil of viscosity 1300 centistokes, in order to determine whether the measured AL varied from the true AL by a constant factor. METHODS: The ALs of 7 phakic eyes were measured by A-mode echography, with and without silicone oil of viscosity 1300 centistokes in the posterior segment. The retina was attached in all cases. The control group consisted of 6 phakic eyes with attached retinae undergoing vitrectomy without the use of silicone oil. The ALs in the control group were measured before and after vitrectomy. RESULTS: The mean ratio of true AL to measured AL in the presence of silicone oil was 0.71 (standard deviation 0.01; range 0.70-0.73; median 0.71) in the 7 eyes in this study. In the control group, vitrectomy appeared to have no significant effect on AL. CONCLUSIONS: We have established a constant which corrects for the apparent increase in AL induced by silicone oil of viscosity 1300 centistokes. This conversion factor, when used in existing biometry formulae (SRK/T), allows estimation of the power of IOL required in eyes undergoing combined cataract extraction, removal of silicone oil and lens implantation.

Biometry↗
PubMed2002

Biometry of the silicone oil-filled eye: II.

PURPOSE: In phakic silicone oil-filled eyes, removal of the silicone oil can be combined with phacoemulsification and intraocular lens (IOL) implantation. True axial length (AL) of the silicone oil-filled (viscosity 1300 centistokes) eye can be estimated from the measured AL (MAL) obtained on A and/or B scan echography, by multiplying MAL by a conversion factor of 0.71. IOL power can then be calculated using current biometry formulae (SRK/T). This study aims to evaluate the conversion factor in clinical practice. METHODS: Eleven patients undergoing combined removal of silicone oil and phacoemulsification with IOL implant were studied. Patients were divided into two groups. In Group 1 (seven patients), the IOL was placed in the capsular bag and in Group 2 (four patients) the IOL was placed in the ciliary sulcus. Calculated AL (CAL) was obtained by multiplying the MAL of the silicone oil-filled eye (as measured on A or B scan ultrasonagraphy) by the conversion factor of 0.71. IOL power was then estimated using the CAL in the SRK/T formula. The spherical equivalent of the postoperative refractive error was compared to predicted refractive error. RESULTS: The mean difference in actual and predicted refractive error was 0.74 dioptres (D) (standard deviation 0.75 D) for Group 1 and 1.31 D (standard deviation 1.4 D) for Group 2. CONCLUSIONS: The conversion factor of 0.71 corrects for the apparent increase in AL induced by silicone oil of viscosity 1300 centistokes. This allows accurate prediction of the required IOL power in eyes undergoing combined cataract extraction, removal of silicone oil and lens implant. Sulcus placement of the IOL gives a less predictable result than placement in the capsular bag.

Biometry↗
PubMed2005

Estimating the clinical usefulness of optic disc biometry for detecting glaucomatous change over time.

PURPOSE: First, to determine the absolute measurement precision of scanning laser ophthalmoscopy (SLO) parameters, by expressing them as 95% limits of agreement (LA(95%)). Second, to propose a method for mathematically estimating the clinical ability of a parameter to monitor disease progression, expressed as the Discriminating Capacity Index (DCI). METHODS: We measured the optic disc of 14 healthy volunteers and 14 glaucoma patients. LA(95%)-values were calculated from the average standard deviation of three measurements on the same day for repeatability, and three measurements on separate days within a 6-week period for reproducibility. We then calculated the DCI by dividing the measurement range by its LA(95%) in healthy subjects and glaucoma patients separately. Thus, the DCI takes into account both the dynamic range of disease progression and the extent of measurement variance, providing an index of the possible clinical usefulness of a parameter. As the DCI is dimensionless it allows comparison across various parameters and across technologies. RESULTS: In the glaucoma group, the SLO parameters with the highest DCIs were 'volume below' (DCI, 9.38) and 'mean contour depth' (DCI, 8.02). In the healthy group, 'Neuroretinal rim area' had the highest index (DCI, 2.15). CONCLUSION: SLO optic disc biometry is uniformly reproducible and may prove a clinically useful method for glaucoma follow-up, due to the high DCI found for several parameters. The capacity to detect conversion from health to glaucoma is less pronounced, possibly due to a larger biological variability found in healthy volunteers.

Biometry↗
PubMed2002

Fetal transabdominal biometry at 11-14 weeks of gestation.

OBJECTIVE: To establish comprehensive transabdominal ultrasonographic reference ranges for viable normal singleton human fetuses at 11-14 weeks' gestation. METHODS: Single transabdominal ultrasound measurements were taken once per pregnancy at a gestational age of between 11+0 and 14+0 weeks (crown-rump length, 45-84 mm), in viable singleton fetuses with nuchal translucency < or = 3 mm and without detectable structural anomalies, using four standard planes: (i) biparietal diameter (BPD) and fronto-occipital diameter (FOD) resulting in head circumference (HC), anterior horn (Va), posterior horn (Vp), and hemisphere (HEM); (ii) transcerebellar diameter (TCD) and cisterna magna (CM); (iii) abdominal anteroposterior (AAP) and abdominal transverse diameter (ATD) resulting in abdominal circumference (AC); and (iv) femur length (FL). The respective ratios Va/HEM, Vp/HEM, HC/AC, BPD/FL, BPD/FOD, FL/CRL, FL/BPD and FL/AC and the estimated weight were derived. Reference ranges were constructed and the mean and 5th and 95th centiles were plotted against gestation. RESULTS: There was a general increase in biometric parameters with gestation. The ratios for the ventricles vs. hemisphere and BPD/FL ratio decreased while the BPD/FOD and HC/AC ratios remained constant. Analysis of the reference range for BPD/FL was performed in both 167 and 664 fetuses and the results showed almost the identical type of equation, indicating a high degree of accuracy for the growth charts. CONCLUSIONS: We have established comprehensive reference ranges for first-trimester fetal biometry by transabdominal sonography. These charts may have a role in the diagnosis of early onset symmetrical or asymmetrical growth restriction and in the interpretation of measurements in chromosomally abnormal fetuses, and they may help in the detection of skeletal dysplasias or acrania/anencephaly.

Abdomen↗
PubMed2001

Fetal biometry: clinical, pathological, and technical considerations.

Sonographic measurements of fetal ultrasound parameters are the basis for accurate determination of gestational age and detection of fetal growth abnormalities. Selection of the most useful single biometric parameter depends on the timing and purpose of measurement and is influenced by specific limitations. CRL (crown-rump length) is the best parameter for early dating of pregnancy. Biparietal diameter (BPD) maintains the closest correlation with gestational age in the second trimester. In cases of variation in the shape of the skull, head circumference is an effective alternative. Abdominal circumference is the most useful dimension to evaluate fetal growth, and femur length is the best parameter in the evaluation of skeletal dysplasia. Use of multiple predictors improves the accuracy of estimates. An individual approach to each pregnancy is recommended for fetal growth assessment. The various epidemiological factors involved in fetal growth should be considered and specific charts for different communities should be used when possible. The methods of fetal weight estimation with their limitations and potential errors are presented. Clinical application of fetal biometry in abnormal growth is discussed in cases of small- and large-for-gestational-age fetuses, chromosomal aberrations, and skeletal dysplasias.

Biometry↗
PubMed1997

Comparison of corneal versus through-the-lid A-scan ultrasound biometry.

BACKGROUND: Accurate ultrasonography data on axial ocular dimensions in infants and toddlers are essential for understanding ocular development. Conventional methods using corneal contact with topical anesthesia but without sedation are not feasible for most of these patients. We evaluate an alternative method which places the probe on the closed eyelid. METHODS: We compared A-scan ultrasound biometry measurements taken with the probe directly on the cornea with those with the probe on the closed eyelid on the right eye of 35 young adult subjects. RESULTS: There was no significant difference between methods for mean anterior chamber depth (corneal = 3.83 mm, lid = 3.87 mm, p = 0.13, paired t-test). The mean lens thickness (corneal = 3.63 mm, lid = 3.75 mm, p = 0.0001, paired t-test) and mean vitreous chamber depth (corneal = 17.50 mm, lid = 17.68 mm, p = 0.0440, paired t-test) were significantly different. CONCLUSION: Ultrasonography through the closed eyelid appears to be a viable method with acceptable validity compared with corneal ultrasound. Poorer agreement for lens thickness and vitreous chamber depth may be undesirable, but these data should be useful for planning future studies of infants and toddlers.

Adult↗