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PubMed2005

First-trimester screening for fetal triploidy at 11 to 14 weeks: a role for fetal biometry.

OBJECTIVE: Intrauterine growth restriction in triploidy has been reported as early as in the first trimester. This study was undertaken to evaluate the ability of first-trimester crown rump length (CRL)-based charts to detect triploid fetuses. MATERIAL AND METHODS: Analysis of fetal biometry in cases of triploidy diagnosed in the first trimester over the last three years. Biometry for abdominal circumference (AC), head circumference (HC) and biparietal diameter (BPD) was analyzed in relation to both gestational age (GA)-based charts and to CRL-based charts. RESULTS: Five cases of fetal triploidy were diagnosed at 11 to 14 weeks. Screening based on nuchal translucency (NT) and maternal age showed a risk > 1/300 in only one of the 5 cases of triploid fetus. In all of these five cases, CRL-based biometry was grossly abnormal, although it was abnormal in only two of these five cases in relation to GA-based charts. CONCLUSION: First-trimester CRL-based biometry charts seem to reflect early asymmetrical growth delay in triploidy more accurately than GA-based charts. CRL-based biometry is likely to improve the early detection of triploid pregnancies without leading to dating error.

Abdomen↗
PubMed2005

The impact of choice of reference charts and equations on the assessment of fetal biometry.

OBJECTIVES: The assessment of fetal biometry is usually based on the comparison of measured values with predicted values derived from reference charts or equations in a normal population. This study was undertaken to assess the impact of the choice of reference charts and to develop a Z-score-based tool that could help sonographers to choose the reference charts that best fit their practice. METHODS: Fetal biparietal diameter, head circumference, abdominal circumference and femur diaphysis length measurements were made at 20-24 and 30-34 weeks' gestation by four experienced sonographers. All measurements were transformed into Z-scores calculated according to three prediction equations (Snijders and Nicolaides, 1994; Chitty et al., 1994 and Kurmanavicius et al., 1999). Distributions of Z-scores were compared to the expected standard normal distribution based on mean, SD and Kolmogorov-Smirnov test. Simulations were made to assess sensitivity (Se), specificity (Sp) and Youden's index (Se + Sp - 1) of each reference equation, reflecting their ability to identify fetuses with abnormal biometry in our population. The reference that best fitted our practice was determined based on these results. RESULTS: The Z-scores of all biometric parameters were significantly different (P < 0.001) when using any of the three reference equations, and none of the Z-score distributions could be considered similar to the standard normal distribution. The number of measurements that would be considered as abnormal according to these references ranged from 2.6% to 23.6%. Se and Sp ranged from 39.59% to 67.12% and 90.14% to 99.69%, respectively. CONCLUSION: Assessment of fetal biometry is largely dependent on the choice of reference charts. We suggest that the choice of reference charts for fetal biometry could be controlled using Z-scores in each institution and that this could be the first step towards any quality assessment policy. The method we describe for the choice of the most appropriate fetal biometry reference chart might be used for all size charts.

Biometry↗
PubMed2005

Biometry accuracy using zero- and negative-powered intraocular lenses.

PURPOSE: To audit the accuracy of biometry using the SRK/T formula when negative- or zero-powered intraocular lenses (IOLs) are predicted and to compare the results between A-scan, B-scan, and optical methods of biometry. SETTING: Moorfields Eye Hospital, London, United Kingdom. METHODS: This retrospective analysis comprised 78 eyes of 54 patients having cataract surgery with zero- or negative-powered IOLs. Axial lengths were measured with A-scan, B-scan, applanation, or optical methods. Differences between SRK/T-predicted and actual postoperative refraction were analyzed for 75 eyes having cataract surgery. Ocular comorbidity, visual acuity, and biometry readings were also compared. RESULTS: Forty-one percent of 75 patients analyzed were within +/-1.00 diopter (D) of the predicted refraction, although there was a significant tendency toward a hyperopic overcorrection by 1.14 D (95% confidence interval, 0.89-1.39 D). This overcorrection error was consistent across all 3 biometry methods used to estimate axial length and increased with the use of stronger (more negative) IOLs. CONCLUSION: Surgeons should be aware of the tendency for negative-powered lenses to overcorrect and lead to a hyperopic outcome when using the SRK/T biometry formula in highly myopic eyes. A weaker-powered negative IOL is recommended to aim for a more myopic postoperative outcome by about 1.00 to 2.00 D.

Accommodation, Ocular↗
PubMed2005

Intraoperative optical refractive biometry for intraocular lens power estimation without axial length and keratometry measurements.

PURPOSE: To correlate intraoperative aphakic autorefraction to conventional emmetropic intraocular lens (IOL) calculations and derive an empiric predictive model for IOL estimation based on optical refractive biometry without axial length and keratometry measurements. SETTING: Institutional Review Board of the University of Southern California, Los Angeles County General Hospital, Los Angeles, California, USA. METHODS: A pilot group of 22 eyes of 22 patients scheduled for cataract surgery were enrolled in a prospective trial. All patients had a standard preoperative workup with subsequent cataract extraction and IOL implantation according to conventional biometric measurements and IOL calculations. Intraoperative autorefractive retinoscopy was used to obtain aphakic autorefraction and to measure the aphakic spherical equivalent before lens implantation. A linear regression analysis was used to correlate the aphakic spherical equivalent to the final adjusted emmetropic IOL power to empirically derive a refractive formula for IOL calculation (optical refractive biometry method). A second validation series of 16 eyes was used in a head-to-head comparison between the optical refractive biometry and the conventional IOL formulas. A subset of 6 eyes from the validation series were post-refractive cases having subsequent cataract surgery. RESULTS: Intraoperative retinoscopic autorefraction was successfully obtained in all 22 patients in the pilot group and all 16 patients in the validation group. The spherical equivalent of the aphakic autorefraction correlated linearly with the final adjusted emmetropic IOL power (P<.0001, with adjusted r(2)=.9985). The relationship was sustained over an axial length range of 21.43 to 25.25 mm and an IOL power range of 12.0 to 25.5 diopters (D). In a subsequent validation series of 10 standard and 6 post-laser in situ keratomileusis (LASIK) cataract cases, the optical refractive biometry method proved to be a better predictive model for IOL estimation than conventional formulas; 83% of the LASIK eyes and 100% of the normal eyes were within +/-1.0 D of the final IOL power when aphakic autorefraction was used, compared with 67% of LASIK eyes and 100% of the normal eyes, using the conventional methodology. CONCLUSIONS: A new model for IOL power calculation was derived based on an optical refractive methodology that breaks away from the conventional art introduced by Fyodorov in the 1960s. A purely refractive algorithm is used to predict the power of the IOL at the time of surgery without the need for axial length and keratometry measurements. This method bypasses some limitations of conventional biometry and shows promise in the post-refractive cataract cases.

Biometry↗
PubMed2003

Effect of visual acuity on biometry prediction error after cataract surgery.

PURPOSE: To determine the effect of visual acuity on biometry prediction error. SETTING: Postgraduate teaching hospital. METHODS: The study was an observational case series of the first operated eye of 2149 consecutive patients who had cataract surgery. Biometry prediction error was defined as the difference between the planned refraction determined by biometry and the spherical equivalent of the final refraction. The principal outcome measure was the percentage of eyes within +/-1.00 diopter (D) of the intended refraction. This outcome was calculated for patients with visual loss caused by cataract alone, defined as eyes with a postoperative acuity of 6/6 or better, and eyes with different levels of postoperative visual acuity. RESULTS: Complete data were available for 1978 eyes (92%). Of these, 1438 (73%) were within +/-1.00 D of the intended refraction. When the final corrected visual acuity was 6/6 or better, the percentage of eyes within +/-1.00 D of the predicted refraction was at least 78%. When the preoperative acuity was worse than 6/60, 74% in the counting fingers group and 69% in the hand movements group with a final corrected acuity of 6/6 or better were within +/-1.00 D. This trend bordered on statistical significance (P =.05). There was a rapid reduction in the percentage of eyes within +/-1.00 D of the intended refraction as the postoperative acuity decreased because of ocular comorbidity, with a statistically significant difference between eyes with a postoperative acuity of 6/6 or better and each group with an acuity of 6/9 or worse (P<.01). CONCLUSIONS: In eyes without visually significant ocular comorbidity, cataract must reduce vision to 6/60 or worse before there is an increase in biometry prediction error. In contrast, ocular comorbidity that reduces the postoperative acuity causes an early and marked increase in biometry prediction error.

Biometry↗
PubMed2004

National biometry audit.

PURPOSE: To determine compliance with the Royal College of Ophthalmologists' (RCOphth) biometry guidelines. METHOD: A structured telephone questionnaire of individuals who perform biometry in all eye departments in the United Kingdom (UK). RESULTS: A biometrist was interviewed in 107 of the UK's 178 eye departments. Nurses alone run the biometry service in 58% of departments, orthoptists alone in 13%, junior doctors alone in 6%, optometrists alone in 3%, and a combination of staff in 20%. Of the staff interviewed, 37% had been on external biometry training courses. One intraocular lens (IOL) calculation formula was used for all eyes in 61% of departments with 17% using the obsolete SRK II formula, 36% of departments used two or more formulae and only 4% adhered to the RCOphth guidelines to use Hoffer Q in eyes with axial lengths <22.0 mm, an average of all three formulae in eyes between 22.0 and 24.5 mm, Holladay in eyes between 24.6 and 26.0 mm, and SRK/T in eyes >26.0 mm. Audit of refractive results was claimed by 71% of units but in only 17 (16%) did the biometrist know the percentage of eyes with a prediction error <or=1 D. CONCLUSION: This study demonstrates poor awareness and/or implementation of the RCOphth biometry guidelines and indicates that audits are either not highlighting poor results or are not resulting in a change in practice. The guidelines should be updated to emphasise the importance of customising A constants and to set benchmark standards for prediction error.

Biometry↗
PubMed2003

IOLMaster biometry: refractive results of 100 consecutive cases.

AIMS: To study the refractive outcome of cataract surgery employing IOLMaster biometry data and to compare it with that of applanation ultrasonography in a prospective study of 100 eyes that underwent phacoemulsification with intraocular lens implantation. METHODS: The Holladay formula using IOLMaster data was employed for the prediction of implanted intraocular lenses (IOLs). One month after cataract surgery the refractive outcome was determined. Preoperative applanation ultrasonography data were used retrospectively to calculate the IOL prediction error. The two different biometry methods are compared. RESULTS: 100 patients, 75.42 (SD 7.58) years of age, underwent phacoemulsification with IOL implantation. The optical axial length obtained by the IOLMaster was significantly longer (p<0.001, Student's t test) than the axial length by applanation ultrasound, 23.36 (SD 0.85) mm v 22.89 (0.83) mm. The mean postoperative spherical equivalent was 0.00 (0.40) D and the mean prediction error -0.15 (0.38) D. The mean absolute prediction error was 0.29 (0.27) D. 96% of the eyes were within 1 D from the intended refraction and 93% achieved unaided visual acuity of 6/9 or better. The Holladay formula performed better than the SRK/T, SRK II, and Hoffer Q formulas. Applanation ultrasonography after optimisation of the surgeon factor yielded a greater absolute prediction error than the optimised IOLMaster biometry, 0.41 (0.38) D v 0.25 (0.27) D, with 93% of the eyes within 1 D from the predicted refraction. CONCLUSION: IOLMaster optical biometry improves the refractive results of selected cataract surgery patients and is more accurate than applanation ultrasound biometry.

Adult↗
PubMed1998

Keratometry, ultrasonic biometry, and prediction of intraocular lens power in the feline eye.

OBJECTIVE: To determine ocular dimensions (using A-scan ultrasound biometry) and corneal curvature (using keratometry) in the feline eye and to calculate the appropriate dioptric power for a prototype posterior chamber intraocular lens (IOL) necessary to achieve emmetropia in the eyes of cats undergoing lens extraction. ANIMALS: 25 clinically normal adult mixed-breed cats and 10 eyes from 10 clinically normal adult mixed-breed cat cadavers. PROCEDURE: A-scan ultrasonic biometry was performed on both eyes of each live cat. Cats were tranquilized, and keratometry was performed on each eye. Biometry was performed on the cadaver eyes. Five of the cadaver eyes had the lens extracted and an IOL, designed for use in dogs, was implanted. Biometry was repeated to estimate postoperative IOL position. Using 3 theoretical IOL formulas, data from biometry, keratometry, and postoperative IOL position were used to predict IOL strength required to achieve emmetropia after lens extraction in cats. RESULTS: Mean axial length of eyes in live cats was 20.91 +/- 0.53 mm. Mean preoperative anterior chamber depth (ACD) was 5.07 +/- 0.36 mm, and mean lens thickness was 7.77 +/- 0.23 mm. Predicted postoperative ACD was calculated to be 10.84 mm. Measured postoperative ACD in the 5 cadaver eyes was 8.28 mm. Required IOL strength calculated, using the predicted postoperative ACD, was 73 to 76 diopters. The required IOL strength calculated, using the measured postoperative ACD, was 53 to 55 diopters. CONCLUSIONS AND CLINICAL RELEVANCE: An IOL of substantially higher diopter strength than that needed in dogs is required to achieve emmetropia after lens extraction in average cats; an IOL strength of approximately 53 to 55 diopters will likely be required.

Animals↗
PubMed2001

Reliability of prenatal sonographic lung biometry in the diagnosis of pulmonary hypoplasia.

OBJECTIVE: The purpose of the present study was to assess the value of biometric lung measurements for the diagnosis of severe fetal pulmonary hypoplasia by investigating whether a significant correlation between two-dimensional lung biometry measurements and autopsy findings could be established. METHODS: This was a prospective study carried out between 1995 and 1997. Nomograms for normal fetuses of the anterior-posterior and transverse inner thoracic diameters, which describe the growth and shape of the lung, were used as a basis for diagnosis of pulmonary hypoplasia in fetuses at high risk of developing the condition (the fetuses had bilateral renal agenesis or multicystic kidneys; chronic PROM <25 gestational weeks or hydrothorax). Pregnancy was terminated by abortion or intrauterine death in 29/43 high-risk fetuses and autopsies were performed. Only the 29 fetuses for which there were autopsy findings were included in the study. RESULTS: The best plane for diagnosing pulmonary hypoplasia was the four-chamber view. The diagnostic accuracy for this view as expressed by the sensitivity was 57% for the anterior-posterior diameter and 44% for the transverse diameter; as expressed by the specificity it was 42% for the anterior-posterior diameter and 50% for the transverse diameter. The results for the four-chamber view for the various high-risk conditions were as follows: for fetuses with chronic PROM we obtained sensitivities of 75% and 50% (anterior-posterior and transverse dimensions, respectively) and specificities of 80% and 60% (anterior-posterior and transverse dimensions, respectively). The sensitivities of lung biometry in fetuses with hydrothorax were 1% and 80% for the two diameters, but there was a low specificity. In fetuses with bilateral renal agenesis or multicystic kidneys we obtained sensitivities of 36% and 30% (anterior-posterior and transverse dimensions, respectively) and a specificity of 50% (anterior-posterior dimension). CONCLUSIONS: The present results show that two-dimensional lung biometry is not a suitable method for antenatal detection of pulmonary hypoplasia. However, in individual cases with high risk for pulmonary hypoplasia, lung biometry might prove to be an additional diagnostic parameter.

Autopsy↗
PubMed2001

Pseudophakic correction factors for optical biometry.

INTRODUCTION: The IOLMaster of Carl Zeiss Jena, which has recently become available, is a combined instrument for biometry and intraocular lens (IOL) planning for cataract surgery utilizing partial coherence interferometry for measuring axial length. Whereas measurement data from classical ultrasound biometry, e.g. in pseudophakic eyes, need to be corrected by +0.4 to -0.8 mm--depending on the lens material--smaller corrections are expected to be necessary in optical biometry. Correction factors for various modern IOL materials were estimated theoretically and checked in first clinical measurements. METHODS: Starting from the dispersion relation of PMMA and manufacturers' phase refractive index data at 546 nm, the group refractive indices of different IOL materials were estimated for the IOLMaster wavelength of lambda=780 nm. Then, for an average eye of 23.48 mm, the center thicknesses of emmetropizing lenses of different material were calculated. Finally, comparing the pseudophakic optical axial lengths thus deduced with the respective phakic value, individual material-specific correction factors were obtained. RESULTS: Expressing the true axial length ALtrue by the length ALphak measured in phakic mode and a correction factor delta (ALtrue=Alphak+delta), we obtained values of delta=0.12+/-0.01 mm for all IOL materials considered (PMMA, silicone, collamer, AcrySof, MemoryLens). For aphakic eyes, delta=0.20 mm was deduced. DISCUSSION: The calculations suffered from the fact that hardly any information relating to optical material specifications of IOLs is available from lens manufacturers. Therefore, calculations had to be based on--nevertheless realistic--assumptions. Early clinical results support our theoretical findings. Thus, optical biometry seems to be more reliable and forgiving in pseudophakic eyes than classical ultrasound.

Acrylic Resins↗
PubMed2005

Microbial contamination of immersion biometry ultrasound equipment.

PURPOSE: To investigate the prevalence of microorganisms on ultrasound biometry equipment and cleaning habits. DESIGN: Observational case series. PARTICIPANTS: Thirty-four university-based and private ophthalmology clinics. METHODS: In a prospective multicenter study, clinics representative of every region of the country sampled their fixed immersion biometry equipment (i.e., ultrasound probe, immersion shell, and infusion tubing) for bacteria and fungi. Assessment of the cleaning habits for this equipment was conducted by way of a standard questionnaire that included type of fluid and delivery method, frequency of fluid change, method of cleaning the probe and shell, and frequency of tubing change and/or cleaning. MAIN OUTCOME MEASURES: Frequency (prevalence), descriptive statistics, and type of microorganisms. RESULTS: Eighteen samples (53% [18/34]) grew organisms from either the probe/shell or tubing. Positive cultures were found in 32% (11/34) of the immersion shell/probes and in 31% (10/32) of the infusion tubing samples. The bacteria most commonly cultured from both probe/shell and tubing was coagulase-negative Staphylococcus, whereas Penicillium species was the most commonly cultured fungus (exclusively from the probe/shell). Overall, fungi (Penicillium and Alternaria species) were cultured in 12% of the probe/shell samples. Only 14% of the study sites adequately disinfected the probe/shell according to Centers for Disease Control and Prevention (CDC) guidelines, which recommend a 5-minute soak in antiseptic. CONCLUSIONS: The bacteria and fungi that colonize biometry equipment are not being adequately eliminated by the cleaning/disinfecting techniques employed in most ophthalmology clinics. These results also may apply to contact biometry, pachymetry, and tonometry equipment as well. Clinicians should follow the CDC recommendations for disinfecting instruments that come in contact with the eye, and the infusion tubing should be changed after each patient.

Bacteria↗
PubMed2006

Intraocular pressure changes and ocular biometry during Sirsasana (headstand posture) in yoga practitioners.

PURPOSE: To study the intraocular pressure (IOP) changes in Sirsasana (headstand posture) done by experienced yoga practitioners and correlate the ocular biometric parameters with the IOP changes, and to screen for the prevalence of ocular hypertension in this group of subjects. DESIGN: Prospective case observational series. PARTICIPANTS: Seventy-five subjects (50 Asian Indians and 25 Caucasians) from a yoga training institute volunteered for the study. METHODS: All participants underwent a detailed ophthalmic examination along with ocular biometry and corneal pachymetry. Intraocular pressure was recorded using a Tonopen before, during, and after the Sirsasana. Changes were compared using the paired t test. Age, axial length, anterior chamber depth, lens thickness, corneal curvature, corneal thickness, race, and the length of time for which the practitioner was performing yoga were correlated with the induced IOP difference in a randomly selected eye using Pearson's correlation coefficient with Bonferroni correction for multiple comparisons. MAIN OUTCOME MEASURES: Ocular biometry and induced IOP difference. RESULTS: The mean increase in IOP at baseline and immediately after assuming Sirsasana was 15.1+/-4.1 mmHg (R = 0.07; P = 0.999) and after 5 minutes was 15.8+/-4.6 mmHg (R = -0.25; P = 0.357). The induced increase in IOP during the posture was twice the baseline IOP. There was no correlation between age, ocular biometry, and ultrasound pachymetry when compared with the induced IOP difference. One subject (1.33%) was found to have baseline IOP of more than 21 mmHg. CONCLUSION: There was a uniform 2-fold increase in the IOP during Sirsasana, which was maintained during the posture in all age groups irrespective of the ocular biometry and ultrasound pachymetry. We did not demonstrate a higher prevalence of ocular hypertensives in this cohort of yoga practitioners nor did the risk factors contributing to glaucoma show any correlation with magnitude of IOP raise during the posture.

Adult↗
PubMed2002

Refractive outcome of cataract surgery using partial coherence interferometry and ultrasound biometry: clinical feasibility study of a commercial prototype II.

PURPOSE: To evaluate the refractive outcome of cataract patients 3 months postoperatively using optical biometry obtained with a prototype version (axial length measurement, ALM, Carl Zeiss Jena) of the commercial partial coherence interferometry (PCI) instrument (IOLMaster, Carl Zeiss Jena). SETTING: Department of Ophthalmology, Vienna General Hospital, and Institute of Medical Physics, University of Vienna, Austria. METHODS: Forty-five patients with age-related cataract in both eyes were scheduled for bilateral cataract surgery. Axial length was measured preoperatively with a prototype (ALM) of the commercial PCI instrument as well as with immersion ultrasound (IUS). Immersion US was performed by a single experienced investigator. In each patient, the first eye was randomly assigned to receive an intraocular lens (IOL) using the Holladay IOL power formula based on ALM or IUS biometry. The other biometric technique was used in the contralateral eye. Subjective refractive outcome was assessed 3 months postoperatively. RESULTS: Refractive outcomes with the 2 techniques did not differ significantly (P = .28). The mean numerical error (MNE) (the difference between the refractive outcome 3 months postoperatively and the predicted spherical equivalent) was 0.13 diopter (D) and 0.03 D for the ALM and IUS, respectively. The mean absolute error (MAE) (the absolute value of MNE) was 0.48 D (range 0.00 to 1.58 D) and 0.46 D (range 0.01 to 1.92 D) with the ALM and IUS, respectively. By recalculating the surgeon factor retrospectively to correct the Holladay formula to obtain a postoperative MNE of zero, a theoretical MAE of 0.46 D was obtained with both biometry techniques. CONCLUSIONS: Refractive outcome in cataract patients using PCI biometry was as good as that achieved with optimized IUS. However, the difference in axial length measured by the ALM compared to that measured by IUS must be considered when using the IOL A-constants supplied by the manufacturers.

Aged↗
PubMed1996

A comparison of slit-lamp supported versus hand-held biometry.

Biometry allows determination of the final refractive outcome following cataract extraction with intraocular lens implantation. We compared the accuracy of axial length measurement performed with the slit-lamp supported biometry probe versus a hand-held technique. The two methods of biometry were performed on 32 patients undergoing endocapsular cataract extraction with lens implantation. One of the methods was selected at random in order to predict implant power for a desired refractive outcome using the SRK-T formula. There was no difference in 'within-subject' variance of axial length measurement between the two methods (t = 1.74, p = 0.091), and there was no difference in refractive outcome when the power calculations for the two techniques were compared (t = 0.12, p = 0.906). The hand-held technique provides a useful alternative method of biometry in 'difficult' patients.

Biometry↗
PubMed2000

Fetal biometry at 4300 m compared to sea level in Peru.

OBJECTIVES: The aim of this study was to compare ultrasound fetal size at high altitude and sea level. METHODS: Three hundred and thirty-four women in Cerro de Pasco at 4300 m (14,100 ft) altitude and 278 women in Lima (sea level) were recruited to the study. Ultrasound fetal biometry was carried out between 14 and 42 weeks of gestation. Biparietal diameter, occipitofrontal diameter, abdominal circumference and femur length were measured and head circumference and estimated fetal weight were derived from these data. Two hundred and seventy-seven women (82.9%) in Cerro de Pasco and 216 (77.7%) in Lima had normal singleton pregnancies and certain menstrual dates. These women were selected for statistical analysis. Fractional polynomial regression analysis on gestational age was performed, controlling for maternal height and parity. RESULTS: Fetal biometry measurements were significantly smaller in Cerro de Pasco compared with Lima. When gestation bands were compared this effect was present from 25 to 29 weeks onwards, and was greater in the abdominal circumference than in the head circumference and femur length (ratios Cerro de Pasco: Lima, 0.96, 0.97 and 0.98, respectively). Estimated fetal weight was also significantly lower in Cerro de Pasco (ratio 0.88), as were birthweights (ratio 0.88). If the centiles derived from the Lima population were applied for Cerro de Pasco, 11.2% of all estimated fetal weights would be below the fifth centile, and 1.08% above the ninety-fifth. CONCLUSIONS: These data suggest that at high altitude, all fetal biometry measurements follow a lower trajectory than at sea level. Specific biometry charts should therefore be used for obstetric ultrasound at high altitude.

Altitude↗
PubMed1992

Biometry of the crystalline lens in late onset diabetes: the importance of diabetic type.

Lenticular and anterior chamber biometry were studied in non-cataractous eyes by means of Scheimpflug photography and digital image analysis. The study population consisted of 91 late onset diabetic subjects and 115 non-diabetic controls. Anteroposterior axial lens thickness, cortical thickness, nuclear thickness, anterior clear zone thickness, anterior chamber depth, and anterior and posterior lenticular curvatures were assessed. Age played an important role in determining lens biometry in all subjects, and small but significant differences were found between late onset diabetics and non-diabetics. In the late onset diabetic subgroup, apart from age, diabetic retinopathy was the only significant parameter found which determined lens biometry. These biometric findings in late onset diabetes are in marked contrast to the large overall effect of diabetes and the powerful effect of diabetic duration which we previously reported in early onset diabetes. Further analysis of the data from our previous study has been provided, which clearly demonstrates differences between the impact of early and late onset diabetes on the biometry of the anterior ocular segment.

Adult↗
PubMed2000

Urine hyperglycosylated hCG plus ultrasound biometry for detection of down syndrome in the second trimester in a high-risk population.

OBJECTIVE: To evaluate measurement of levels of urine hyperglycosylated hCG, a form of hCG with abnormally branched oligosaccharide side chains, in conjunction with ultrasound biometry for Down syndrome risk prediction in an at-risk group. METHOD: We prospectively measured urine hyperglycosylated hCG levels, humeral length, and nuchal thickness in women who had second-trimester amniocentesis. Urine hyperglycosylated hCG levels were measured by a two-step enzyme-immunometric assay using monoclonal antibody beta152. Humeral length, nuchal thickness, and hyperglycosylated hCG values were expressed as multiples of the median, and the Down syndrome screening efficiency of the three analytes plus age was determined. A receiver operating characteristic (ROC) curve was generated, and the area under the curve was used to assess the Down syndrome screening performance of the algorithm. RESULTS: There were 23 cases of Down syndrome among 1016 singleton pregnancies. Mean gestational age (+/- standard deviation) was 16.1 +/- 1.2 weeks at the time of amniocentesis. Mean maternal age was 37.1 +/- 3.2 years. Biometry and measurement of hyperglycosylated hCG levels had a 91.3% detection rate at a 3.2% false-positive rate and a 100% detection rate at a 10.7% false-positive rate. The area under the ROC curve was 0.986 (P <.001), and that for measurement of hyperglycosylated hCG levels plus age was 0.941 (P <.001). The area under the curve was significantly larger with combined biochemical and biometry markers compared with measurement of hyperglycosylated hCG levels plus age alone (P <.02), proving that the former was superior to the latter. CONCLUSION: A new Down syndrome biochemical marker combined with ultrasound biometry had a high screening efficiency in a high-risk group. All cases of Down syndrome in this study population would have been detected at an amniocentesis rate of less than 10.7%. Our results appear superior to those found with other second-trimester algorithms. The combination is promising as an alternative to "automatic" genetic amniocentesis in women of advanced maternal age and other high-risk groups.

Adult↗
PubMed1982

[Diagnosis of intrauterine growth retardation--comparison of clinical findings, total oestrogen determination from 24-hour urine and ultrasound biometry (distance measurement, biparietal head diameter and thoraco-abdominal transverse diameter) considering the antepartal and subpartal CTG's].

This article presents the results of clinical examination, total oestrogen determination from 24-h urine and ultrasound biometry -- measurement of the biparietal head diameter and the thoraco-abdominal transverse diameter (under routine conditions) -- for diagnosing intrauterine growth retardation (IUGR). In addition, the antepartal and subpartal CTG's are evaluated in cases of foetal retardation of growth "Single determinations" are confronted with so-called "serial examinations (= observation of the course)". Repeated clinical examinations and multiple determinations of the total oestrogen elimination with the 24-h urine did not result in any clear improvement of the detection rates of deficient development of the foetus (discovery rate with clinical examination = 54%, total oestrogen determination = 60%); there was, in fact, a relatively high rate of false-positive diagnosis (false-positive diagnoses on clinical examination = 31%). On the other hand, simple ultrasound biometry (distance measurements) led to the discovery of about 78% of all foetal growth retardations (perc. less than 10), the false-positive diagnoses rate being only 9%. Pathological antepartal CTG's (less than 8 points according to the Meyer-Menck score) were seen in about 27% of the cases with growth retardation -- with, however, an approximately equal rate of pathological CTG's in newborn of "normal weight". The discovery rate of deficient development of the foetus has been increased by combining ultrasound biometry with the total oestrogen determination from the 24-h urine, to 88% (perc. less than 10). The same applies to the combination of ultrasound biometry with the clinical examination (rate of detection: 87%). Up to 77% of all cases with IUGR have been discovered both by combining the clinical examination with the total oestrogen determination or antepartal CTG, as well as by combining total oestrogen determination with antepartal CTG.

Abdomen↗