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At least 613 records · Page 34Linked to original sources

PubMed2006

[Refractive aspects of modern cataract surgery].

OBJECTIVE: Modern cataract surgery is a refractive procedure whereby one basically can achieve the targeted postoperative refraction. METHODS: To achieve this goal, according to the patient's wishes, biometry, mathematical calculation of IOL power and astigmatism management are important factors. On the other hand, multifarious developments in intraocular lens technology also contribute to this target. RESULTS: The individual choice of incision (on axis surgery: incision in the steeper meridian, length, shape and location concerning cornea or sclera) reduces the preoperatively existing astigmatism. Biometry with personalised data and formulas of the third generation are important factors to achieve the targeted refraction. In addition to this, the development of manifold lens designs in the last years to improve intraocular lens quality has enabled progress within various domains, for example, the use of optimised intraocular lenses to compensate corneal aberration, the implantation of toric lenses for corrections of higher pre-existing corneal astigmatism or the use of phacic intraocular lenses to correct higher ametropia. CONCLUSION: Patient satisfaction postoperatively depends on the precise refractive result as desired. With our current operative and technical possibilities we are able to achieve this with high probability and safety.

Astigmatism↗

PubMed2003

Intrauterine growth restriction is accompanied by decreased renal volume in the human fetus.

OBJECTIVE: Intrauterine growth-restricted fetuses are at risk for the development of adult hypertension and related cardiovascular diseases. Congenital oligonephropathy has been postulated as the primary mechanism. The objective of our study was to determine whether ultrasonically obtained in utero measurements of renal volume or renal artery Doppler blood flow differ between fetuses that are intrauterine growth restricted and fetuses that are not. STUDY DESIGN: The study population consisted of women who were referred for a prenatal ultrasound evaluation at a large community medical center. The women were divided into two groups: women with fetal biometry that was consistent with intrauterine growth restriction and women with biometry within normal range. Information was collected on maternal demographics and other factors known to affect fetal growth. We performed detailed fetal renal anthropomorphic and Doppler blood flow measurements in addition to standard fetal biometric measurements on all patients, specifically comparing renal volume and renal artery flow data between the two groups. RESULTS: No differences were observed in maternal age, race, parity, or fetal gestational age. Renal volume in the intrauterine growth-restricted fetuses was 31% (95% CI, 20%-40%), which was less than that in the group of fetuses that were not intrauterine growth restricted after an adjustment was made for gestational age. The ratio of renal volume to estimated fetal weight was 15% (95% CI, 1%-26%), which was less than the same ratio in the fetuses that were not intrauterine growth restricted. There were no differences seen in the renal artery Doppler measurements. CONCLUSION: Intrauterine growth restriction appears to be associated with a decrease in fetal renal volume. Because renal volume is a likely proxy for nephron number, this study supports the hypothesis that intrauterine growth restriction may be linked to congenital oligonephropathy and potentially to hypertension in later life.

Adult↗

PubMed2003

Doppler predictors of adverse neonatal outcome in the growth restricted fetus at 34 weeks' gestation or beyond.

OBJECTIVE: The study was undertaken to assess whether prenatal Doppler variables can identify cases of fetal growth restriction (FGR) approaching term who are at risk for adverse neonatal outcome. STUDY DESIGN: From a cohort of FGR cases delivered at >or=34 weeks, fetal biometry and pulsatility indices (PI) of fetal arteries obtained less than 2 weeks before delivery were related to adverse neonatal outcome, defined as admission to the neonatal intensive care unit (NICU) for indications other than low birth weight alone. RESULTS: Stepwise regression analysis showed that after controlling for gestational age at delivery and fetal biometry, only the last umbilical artery (UA) PI percentile was significantly predictive of adverse neonatal outcome (odds ratio=1.02, 95% CI 1.01-1.03, P=.02). Receiver operating characteristic curve analysis identified a UA PI at the 65th percentile as optimal predictor of adverse neonatal outcome (sensitivity=60%, false-positive rate=30%). CONCLUSION: In FGR cases delivered at >/=34 weeks' gestation, Doppler PI at the UA independently predicts the likelihood of admission to the NICU for reasons other than low birth weight alone.

Biometry↗

PubMed2003

Agreement between Scheimpflug photography and A-scan ultrasonography in anterior segment ocular measurements in children.

PURPOSE: The Scheimpflug principle, as a method of performing biometry on the anterior segment, has not been widely used in the clinical setting compared with ultrasonography. The purpose of this study was to examine the agreement in anterior chamber length and lens thickness measurements between A-scan ultrasonography and Scheimpflug photography. METHODS: A total of 252 children aged between 6 and 12 years participated in this study. All subjects had instillation of cycloplegic eye drops before measurement. Scheimpflug photography and A-scan ultrasonography were performed in this sequence on the same day. The anterior segment length on the Scheimpflug images was taken as the axial corneal thickness added to the anterior chamber depth. A-scan ultrasonography was performed by placing the probe on the corneas after topical anesthesia. Differences were obtained by subtracting the A-scan ultrasonography measurements from the Scheimpflug measurements. Data were analyzed using difference vs. mean plots. RESULTS: For anterior chamber length, the mean difference between the two methods was -0.03 +/- 0.16 mm, with 95% limits of agreement of -0.35 to +0.30 mm. However, Scheimpflug readings were greater than that of ultrasonography for smaller measurements, and the opposite was true for larger measurements. For lens thickness, the mean difference was -0.2 +/- 0.10 mm, with 95% limits of agreement of -0.40 to +0.00 mm. For the measurement of lens thickness, adding a correction factor of 0.2 mm to Scheimpflug's readings should replace that of A-scan readings reasonably well. CONCLUSIONS: The readings obtained from these two methods of biometry must be used with the knowledge of the instruments. We discuss the possible reasons for the difference in readings obtained using these two instruments.

Anterior Eye Segment↗

PubMed2000

The problematic unity of biometrics.

The word "biometry" may be less than 200 years old, but it can be argued that work we would now consider biometric dates back even to the pre-Christian era. The unity of biometry is attested through examples spanning two millennia, and a lesson from Francis Galton is recalled from a century ago.

Biometry↗

PubMed2004

Ultrasonic fetal size measurements in Brisbane, Australia.

The purpose of this paper was to construct population-specific charts of fetal biometry for 11-41 weeks gestation in relation to known gestational age from a large population of normal Australian pregnancies when examination is performed to a standard protocol by experienced operators. All consenting eligible women attending a large Brisbane clinic between January 1993 and April 2003 were recruited. Menstrual history was taken prior to examination. Measurements were performed to a standard protocol. Prospective assessment was made about the association between gestational age from the last menstrual period and biometry. Exclusion principles were applied. Statistical analyses were performed using polynomial regression models and thorough diagnostic checks were undertaken. Included within the study were separate scans for 20 555 pregnancies from 17 660 women. Equations, means and 95th reference intervals were derived and reported for the following sonographic measurements: biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL). Population-specific regression equations for BPD, HC, AC and FL have been proposed for Australian pregnancies. Once validated by others, we believe they will warrant consideration for adoption by the Australasian Society for Ultrasound in Medicine.

Australia↗

PubMed2006

Paediatric secondary intraocular lens estimation from the aphakic refraction alone: comparison with a standard biometric technique.

AIM: To compare the following two methods of paediatric secondary posterior chamber intraocular lens (PCIOL) determination with the Holladay formula: (1) estimation from the aphakic refraction alone (using assumed keratometry (K) of 44 diopters); and (2) calculation based on preoperative measured biometry. METHODS: (1) Retrospective medical record review in a referral eye hospital of children with aphakia aged < or =12 years who underwent secondary PCIOL implantation with an Alcon MA60BM lens; (2) PCIOL determination for a plano refraction by the above two methods (estimation and calculation); and (3) prediction of pseudophakic refraction for the PCIOL actually implanted by the above two methods compared with the actual pseudophakic refraction. RESULTS: 50 eyes of 30 children with aphakia were studied. The estimated (mean, 95% confidence interval (CI)) secondary PCIOL values (25.81, +/-1.65 D) and the calculated secondary PCIOL values (26.35, +/-1.50 D) were not significantly different (mean absolute value of the difference 1.86 D, 95% CI +/-0.41 D) by the two-tailed paired t test at alpha = 0.05 (p = 0.11). For each eye, the pseudophakic refractions predicted by the two methods for the PCIOL that was actually implanted differed, both from each other and from the actual pseudophakic refraction (repeated-measures analysis of variance, p<0.001; Tukey test, p<0.01). CONCLUSIONS: The method of PCIOL estimation from the aphakic refraction alone provides values similar to those obtained by a standard technique and can be useful if biometry is unavailable. Targeting a pseudophakic refraction in paediatric aphakia is prone to error.

Aphakia↗

PubMed1989

Accuracy of routine intraocular lens power calculation in a district general hospital.

To assess the accuracy of routine preoperative biometry we reviewed all cases of extracapsular cataract extraction with posterior chamber implant performed at Queen Alexandra Hospital in 1985. Of 471 eyes included in the survey 67.9% were within 1.0 D of the expected refraction and 90.7% within 2.0 D. Factors influencing accuracy are discussed. The necessity of routine preoperative biometry is emphasised.

Biometry↗

PubMedDate not supplied

A regression model for correcting intraocular lens power after refractive surgery independent of preoperative data.

PURPOSE: To find a method of calculating intraocular lens (IOL) power that may be independent of preoperative data in eyes that have previously undergone myopic laser in situ keratomileusis (LASIK). METHODS: In 148 eyes of 75 patients, before and 6 months after LASIK, IOL power was calculated with SRK/T formula utilizing the spherical equivalent as the desired target refraction. Assuming that LASIK does not alter the crystalline lens refractive properties, IOL calculation error (CER) was estimated with this formula: CER = [pre-LASIK IOL power]/[post-LASIK IOL power]. Then the authors used postoperative biometry and Orbscan II corneal topography data in multiple regression models to find the best variables to predict the CER. Predicted amount of error which is calculated independent of preoperative data could be used to correct the post-LASIK calculated IOL: [corrected post-LASIK IOL power] = CER x [post-LASIK IOL power]. RESULTS: A regression model with these predictors was found: axial length in millimeters (L), radius of the anterior corneal surface best fitted sphere in millimeters divided by radius of the posterior corneal surface best fitted sphere in millimeters (AntBFS/PostBFS), corneal central 5 millimeters mean power in diopters divided by corneal central 3 millimeters mean power in diopters (mean 5 mm/mean 3 mm), the post-LASIK IOL power, and the post-LASIK simulated K reading. The model R square was 0.88. CONCLUSIONS: There is correlation between post-LASIK biometry values and IOL power correction factor. This study presents a new model for further investigation.

Adult↗

PubMed1995

Difficulties in the prenatal diagnosis of microcephaly.

Our objective was to determine whether the diagnosis of microcephaly present at birth is apparent using standard biometry in the second trimester. Fetuses with prenatally suspected microcephaly (biparietal diameter > or = 3 standard deviations below mean) who had a first sonogram prior to 22 weeks' gestation and a confirmation of microcephaly after birth were included in the study. We excluded all fetuses who had neural tube defects or other major associated abnormality that would lead to a suspicion of microcephaly. We therefore included fetuses who either had normal-appearing brains sonographically or intracranial calcifications as the only sonographic abnormality seen prior to 22 weeks' gestation. Seven fetuses met these criteria. One fetus was diagnosed as having microcephaly prior to 22 weeks' gestation. The other six fetuses had a normal head size prior to 22 weeks' gestation and were diagnosed as having microcephaly at 27 weeks' gestation and later. Only one of the seven fetuses had a karyotypic abnormality. We conclude that the prenatal diagnosis of microcephaly is not excluded by normal biometry on second trimester sonography.

Adult↗

PubMed1975

[The place of ultrasound diagnosis in obstetrics].

A review is presented of the diagnostic applications of the ultrasonic scan technique in obsterics. In the 1st trimester of pregnancy the demonstration of the gestational sac and of an embryo is most important. During the further course of pregnancy the growth of the gestational sac and motions of the fetus can be observed. A disturbance in the development of the pregnancy can be deduced from these parameters. The various types of abortion can be differentiated by means of the scan. In the 2nd trimester the biometry of the fetus is most important. The motion behaviour of the fetus seems to be a good indicator of its well-being. The location of the placenta and the evidence of twins are easily demonstrable. In the 3rd trimester the biometry of the fetus is a good parameter of its maturity. The diagnosis of the fetal position is important for the management of delivery. Apart from these applications of ultrasound in obstetrics, the procedure is of great value in the diagnosis of tumours and the measurement of the true pelvis in pregnancy.

Abortion, Threatened↗

PubMed2005

[Significance of ultrasound assessment of placental tissue in diagnostics of post-term pregnancy].

The purpose of this work was to determine the value of ultrasound investigation of the placental tissue in fetal assessment during post-term pregnancy. 80 pregnant women from 39 weeks gestation till delivery were examined in this long term study. The investigation was performed every 5-7 days until the labor. They were divided into three groups. The first group included 40 pregnant women with post term pregnancy, the second, 30 women with prolonged pregnancy. The control group consisted of 10 practically healthy pregnant women. Ultrasound parameters of fetal biometry such as the BPD, APTD, TTD and dynamics of placental thickness changes were analyzed. Our results suggest that the post term pregnancy can be differentiated from prolonged pregnancy by ultrasound assessment of placental tissue (monitoring of changes in placental thickness) and results of fetal biometry (BPD, APTD, TTD).

Adult↗

PubMed1987

[Calculating the diameter of the anterior chamber before implanting an artificial lens].

Anterior chamber lenses sized correctly and positioned properly yield excellent results. Problems reported with anterior chamber implants are related to improper length/or lens placement to the scleral spur. In clinical routine examinations the "white to white data plus one mm" determine the overall length of an anterior chamber lens. However, variability of limbal anatomy causes great variations in estimations of corneal diameter. Approximation of corneal profile can be achieved by using ellipsoid or paraboloid functions. These data together with ultrasound measurements and keratometer readings serve as prerequisites for computations. For biometry an Ocuscan DBR 400-ST unit is used; the corneal refraction (r0) is measured with an automatic keratometer (Humphrey). The peripheral measurements are performed 13.5 degrees nasally and temporally (r1, r2). Using Euler's formula the horizontal radius is calculated (R0, R1, R2). Taking the constant epsilon 2 (epsilon 2 = r2-r0(2)/r2sin2 phi) the diameter can be calculated with the formula h = square root of (2ap-p2)(1-epsilon 2). Model A: two asymmetric halves are computed, the addition gives the corneal diameter (H = h1 + h2). Model B and C: only one symmetric half is computed, the double distance gives the corneal diameter (H = 2 h). The distance p is taken from biometry data; the distance from the anterior corneal surface to the posterior lens surface (ACD + LE) should be multiplied with the factor 0.32: p = (ACD + LE) 0.32. 250 eyes were examined comparing the optical data with the calculated results of our corneal model; the mean value for p was 2.4811 millimeter. Based on a control system the computer eliminated 35 eyes (14%). In the rest group of 215 eyes (100%) the difference to the optical measurements was not greater than +/- 0.25 mm in 181 calculations (84.2%). We noticed a tendency to predict too short internal diameters with external methods. Using optical measurements 1.25 millimeters should be added assuring correct position of the haptics. Using our computer-program for calculations of corneal diameter new anatomic conditions in eyes with abnormal dimensions may be detected.

Anterior Chamber↗

PubMed1983

Fetal biometric data obtained in a sole population with emphasis to sex differences.

Several biometrical parameters have been studied on an homogeneous population sample of 7548 fetuses. The measurement of numerous body and organ sizes on a sole population of fetuses is the only method of considering fetal biometry as a whole and allowing study of the clinical value of some ratios, indices and products of dimensions (not discussed here). The possibility of referring to separate norms for male and female fetuses increases the discriminant power of biometry in detecting fetal growth.

Biometry↗

PubMed2006

The relation between fetal nasal bone length and biparietal diameter in the Korean population.

OBJECTIVE: To evaluate the relation between fetal nasal bone length (NBL) and biparietal diameter (BPD) at 15-19.9 (20) weeks of gestation by ultrasonography in the Korean population. METHODS: The study population included 1268 Korean women (aged between 19 and 45 years) with a singleton pregnancy who registered at the Maternal Fetal Medicine Unit of Samsung Cheil Hospital between September 2003 and February 2005. Ultrasound measurements of NBL were performed using a strict sagittal plan of the fetal head. Other fetal biometry profiles were conducted before amniocentesis for fetal karyotyping. RESULTS: NBL and fetal biometry profiles were measured successfully in 77.9% (988/1268) of the fetuses. NBL was found to increase linearly as a function of BPD (P < 0.001) with a median NBL of 4.4 mm (range 1.9-7.9). NBL increases through 15-19.9 (20) weeks of gestation were given by the equation NBL (mm) = 0.0836 x BPD (mm) + 1.368 (R2 = 0.1, P < 0.001). CONCLUSIONS: Fetal NBL and BPD are linearly related in the second trimester. Fetal NBL in the Korean population is likely to be shorter than that reported for Caucasians and African-Americans.

Adult↗

PubMed2004

Focal sonographic periventricular pattern associated with mild ventriculomegaly in foetal cytomegalic infection revealing cytomegalic encephalitis in the third trimester of pregnancy.

OBJECTIVES: To report focal sonographic periventricular pattern related to residual germinal matrix lesions in foetal cytomegalic infection in association with mild ventriculomegaly seen during the third trimester of pregnancy correlating with neuropathological findings of encephalitis. METHODS: We reviewed prenatal cerebral sonographic examination performed in three patients, during the third trimester of pregnancy, looking for either late 'isolated' ventriculomegaly (n = 2) or sonographic follow-up of cerebral structures following a known primary CMV infection in the early stage of pregnancy (n = 1). In cases of isolated ventriculomegaly, serological examination identified prenatal CMV infection. Magnetic resonance imaging (MRI) was performed in all cases. Imaging findings were compared with those following neuropathological examination. RESULTS: In all cases, ultrasound examination revealed an abnormal focal symmetrical bilateral periventricular pattern on the mid-lateral border of the lateral ventricles, including a mainly hyperechogenic lesion containing a few microcysts (case 1), a mixture of echogenic tissue and cysts (case 2) and mainly cystic areas (case 3). No alteration of cephalic biometry was noted. Neuropathological examination correlated these abnormal areas with lesions of the residual germinal matrix including inflammation and necrosis, but revealed also an extensive inflammatory process of the whole foetal brain. CONCLUSIONS: This focal sonographic periventricular pattern associated with mild ventriculomegaly without any abnormalities of the cerebral and cerebellar organogenesis nor cephalic biometry alteration in the third trimester of pregnancy should be considered as a marker of encephalitis following CMV infection of the foetal brain.

Adult↗

PubMed2005

Third-trimester ultrasound dating algorithms derived from pregnancies conceived with artificial reproductive techniques.

OBJECTIVE: To derive an accurate formula for ultrasound estimation of gestational age in late pregnancy. METHODS: A database of 123 singleton pregnancies conceived by artificial reproductive techniques with third-trimester ultrasound measurements was studied. Biometry variables included the fetal head circumference (HC) and femur length (FL). The dataset was equally divided into a derivation sample and a target sample. To derive the equations of best fit, regression analysis was used, with true menstrual age as the dependent variable and fetal biometry measurements as independent variables. The formulae were tested on the target set and the menstrual age estimates were compared with the actual menstrual age. Clinical performance was estimated in terms of systematic and random errors, absolute errors and their 95% CI values. RESULTS: The menstrual ages at time of scanning ranged from 26 to 41 weeks, with a mean of 33 weeks. The best performing derived formula was a combination of HC and FL. This had a random error of 7.5 days and prediction errors within a 95% confidence limit of -13 to +17 days. With FL only, the random error was 8.2 days, whereas using the HC only yielded a random error of 9.4 days. CONCLUSIONS: Ultrasound estimation of gestational age in late pregnancy is better than indicated by older publications. It is more accurately estimated by combining the HC with the FL than by using the FL measurements alone.

Algorithms↗

PubMed2006

Do early pregnancy ultrasound measurements correlate with fetal nuchal translucency at 11-14 weeks?

OBJECTIVE: To assess whether extremes in nuchal translucency (NT) thickness measurements at 11-14 weeks of gestation are preceded by departures from normal in early ultrasound biometry or embryonic heart rate in euploid fetuses. METHODS: This was a retrospective analysis of data from women with singleton pregnancies examined in early pregnancy between June 2002 and January 2003, who subsequently had a nuchal translucency (NT) scan. The early pregnancy scan was performed transvaginally, and the crown-rump length (CRL), mean gestational sac diameter (GS), mean yolk sac diameter (YS) and embryonic heart rate (HR) were measured where possible. At the second scan CRL and NT were measured. RESULTS: A total of 534 singleton pregnancies were included in the analysis. The mean maternal age was 30 (range, 14-45) years, and 59.4% of the patients were nulliparous. The mean CRL was 11.5 (range, 1.4-30.0) mm at the first scan and 62.8 (range, 42.0-88.0) mm at the second scan. GS, YS and HR measurements were obtained in 87.6%, 72.5% and 72.5% of cases, respectively. No statistically significant correlation was observed between NT and Z-scores of early pregnancy: GS (r = 0.013, P = 0.77), YS (r = 0.039, P = 0.44) or HR (r = 0.016, P = 0.76). GS, YS and HR were not significantly different in fetuses with NT measurements below the 10th percentile or above the 90th percentile (P = 0.24, 0.84 and 0.60, respectively). CONCLUSION: Ultrasound biometry and heart rate measured in early pregnancy are not related to nuchal translucency measurements at 11-14 weeks of gestation in chromosomally normal fetuses.

Adolescent↗