Evaluation of Equivalent Keratometry Readings Obtained by Pentacam HR (High Resolution)

Purpose

To assess the repeatability of Equivalent Keratometry Readings (EKRs) obtained by the Pentacam HR (high resolution) in untreated and post-LASIK eyes, and to compare them with the keratometry (K) values obtained by other algorithms.

Methods

In this prospective study, 100 untreated eyes and 71 post-LASIK eyes were included. In the untreated group, each eye received 3 consecutive scans using the Pentacam HR, and EKR values in all central corneal zone, the true net power (K_net) and the simulated K (SimK) were obtained for each scan. In the post-LASIK group, each eye received subjective refraction and 3 consecutive scans with the Pentacam HR preoperatively. During the 3-month post-surgery exam, the same examinations and the use of an IOLMaster were conducted for each eye. The EKRs in all zone, the K_net, the mean K (K_m) by IOLMaster and the K values by clinical history method (K_CHM) were obtained. The repeatability of the EKRs was assessed by the within-subject standard deviation (S_w), 2.77S_w, coefficient of variation (CV_w) and intraclass correlation coefficient (ICC). The bonferroni corrected multiple comparisons were performed to analyze the differences among the EKRs and K values calculated by other algorithms within the 2 groups. The 95% limits of agreement (LoA) were calculated.

Results

The EKR values in all central corneal zone were repeatable in both the untreated group (S_w≦0.19 D, 2.77S_w≦0.52 D, CV_w≦1%, ICC≧0.978) and the post-LASIK group (S_w≦0.22 D, 2.77S_w≦0.62 D, CV_w≦1%, ICC≧0.980). In the untreated group, the EKR in 4mm zone was close to SimK (P = 1.000), and the 95% LoA was (-0.13 to 0.15 D). The difference between K_net and SimK was -1.30±0.13 D (95% LoA -1.55 to -1.55 D, P<0.001). In the post-LASIK group, all the EKRs were significantly higher than K_CHM (all P<0.001). The differences between the EKR in 4mm zone and K_CHM, the EKR in 7mm zone and K_CHM, K_net and K_CHM, K_m and K_CHM, SimK and K_net were 0.64±0.50 D (95% LoA, -0.33 to 1.62 D), 1.77±0.88 D (95% LoA, 0.04 to 3.51 D), -0.98±0.48 D (95% LoA, -1.92 to -0.04 D), 0.64±0.53 D (95% LoA, -0.40 to 1.68 D), and 1.73±0.20 D (95% LoA, 1.33 to 2.13 D), respectively.

Conclusions

The EKRs obtained by the Pentacam HR were repeatable in both untreated eyes and post-LASIK eyes. Compared to the total corneal power obtained by the clinical history method, the EKR values generally overestimated the total corneal power in post-LASIK eyes. So, further calibrations for the EKR values should be conducted, before they were used for the total corneal power assessment in post-LASIK eyes.     

Intraocular lens power calculations using a Scheimpflug camera to measure corneal power

We measured corneal power using an Oculus Pentacam^® to assess its accuracy for calculating intraocular lens (IOL) power after myopic refractive surgery. A series of corneal power measurements were performed on 22 patients (43 eyes) who had undergone myopic refractive surgery. In 37 of the 43 eyes, phacoemulsification and IOL implantation subsequently were performed. Conventional keratometry and three corneal measurements (mean true net power, central true net power, and 4.5 mm equivalent K reading) obtained using a Pentacam were analyzed and compared to values derived from the clinical history method. Prediction errors of three Pentacam corneal power measurements inserted in third generation IOL formulas also were compared. Analysis of the variance showed that only two Pentacam corneal measurements, mean true net power and central true net power, were not significantly different from those of the clinical history method. Mean true net power was correlated more closely with the clinical history method corneal power than other corneal power values. The one-sample t-test showed that of three Pentacam corneal measurements combined with third-generation formulas, only the mean true net power inserted in the SRK/T implant power calculation formula was not significantly different from zero. The percentages of eyes within ± 0.50 D and ± 1.00 D of the refractive prediction error of this method were 67.6% and 86.5%, respectively. Mean true net power inserted in the SRK/T formula can be used to calculate directly IOL power after myopic refractive surgery.     

A Limitation of Hartmann-Shack System in Measuring Wavefront Aberrations for Patients Received Laser Refractive Surgery

PurposeTo explore the relationship between ablation parameters of myopic laser surgery and measurement area of wavefront aberration (WA) with Hartmann-Shack wavefront sensor.Methods58 subjects undergone myopic laser surgeries and 74 uncorrected myopic subjects were enrolled in this experiment. The laser ablation parameters were obtained from surgical records, which included spherical error (Rx), depth, and optical zone (OZ) of ablation. The measured area of WA was tested by the WASCA, and the real pupil size was tested by Pentacam. The corneal eccentricity (E value) and curvature was also measured with the Pentacam. All the measurements were performed under mydriatic condition.ResultsFor uncorrected myopic eyes, the measured area of WA was similar with the real pupil size. But for the corrected eyes, the measured area of WA was smaller than the real pupil size with a mean difference of 0.66 ± 0.54 mm for moderate myopia (t = 6.45, p < 0.0001) and 1.76 ± 0.55 mm for high myopia (t = 18.92, p < 0.0001), but not for mild myopia. The Rx (t = -3.20, p = 0.0017), OZ (t = 64.4, p < 0.0001) and postoperative corneal E value (t = 2.52, p = 0.017) were the independent factors of measured area of WA. Measured area of WA = -0.81*Rx + 1.13*OZ + 0.49*postoperative corneal E value (r² = 0.997).ConclusionsThe WASCA has a limitation in measuring wavefront aberration over the whole pupil area when it’s used for patients received myopic laser surgery. The measured area is smaller than the real pupil size and depends linearly on ablation depth, optical zone and corneal eccentricity.     

A Comprehensive Assessment of the Precision and Agreement of Anterior Corneal Power Measurements Obtained Using 8 Different Devices

Purpose

To comprehensively assess the precision and agreement of anterior corneal power measurements using 8 different devices.

Methods

Thirty-five eyes from 35 healthy subjects were included in the prospective study. In the first session, a single examiner performed on each subject randomly measurements with the RC-5000 (Tomey Corp., Japan), KR-8000 (Topcon, Japan), IOLMaster (Carl Zeiss Meditec, Germany), E300 (Medmont International, Australia), Allegro Topolyzer (Wavelight AG, Germany), Vista (EyeSys, TX), Pentacam (Oculus, Germany) and Sirius (CSO, Italy). Measurements were repeated in the second session (1 to 2 weeks later). Repeatability and reproducibility of corneal power measurements were assessed based on the intrasession and intersession within-subject standard deviation (Sw), repeatability (2.77Sw), coefficient of variation (COV), and intraclass correlation coefficient (ICC). Agreement was evaluated by 95% limits of agreement (LoA).

Results

All devices demonstrated high repeatability and reproducibility of the keratometric values (2.77Sw<0.36D, COV<0.3%, ICC>0.98). Repeated-measures analysis of variance with Bonferroni post test showed statistically significant differences (P<0.01) among mean keratometric values of most instruments; the largest differences were observed between the EyeSys Vista and Medmont E300. Good agreement (i.e., 95%LoA within ±0.5D) was found between most instruments for flat, steep and mean keratometry, except for EyeSys and Medmont. Repeatability and reproducibility of vectors J₀ and J₄₅ was good, as the ICCs were higher than 0.9, except J₄₅ of Medmont and Pentacam. For the 95% LoAs of J₀ and J₄₅, they were all ≤ ±0.31 among any two paired devices.

Conclusions

The 8 devices showed excellent repeatability and reproducibility. The results obtained using the RC-5000, KR-8000, IOLMaster, Allegro Topolyzer, Pentacam and Sirius were comparable, suggesting that they could be used interchangeably in most clinical settings. Caution is warranted with the measurements of the EyeSys Vista and Medmont E300, which should not be used interchangeably with other devices due to lower agreement.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT01587287","term_id":"NCT01587287"}}NCT01587287     

Comparison of Anterior Segment Biometric Measurements between Pentacam HR and IOLMaster in Normal and High Myopic Eyes

Purpose

To compare the anterior chamber depth (ACD), keratometry (K) and astigmatism measurements taken by IOLMaster and Pentacam HR in normal and high myopic (HM) eyes.

Design

A prospective observational case series.

Methods

Sixty-six normal eyes and 59 HM eyes underwent ACD, keratometry and astigmatism measurements with both devices. Axial length (AL) was measured on IOLMaster. The interdevice agreement was evaluated using the Bland-Altman analysis and paired t-test. The correlations between age and AL & ACD were analyzed. Vector analysis was used to compare astigmatism measurements.

Results

The ACD from IOLMaster and Pentacam HR was different for the normal group (P = 0.003) but not for the HM group (P = 0.280). IOLMaster demonstrated higher steep K and mean K values than Pentacam HR for both normal and HM groups (P<0.001 for all). IOLMaster also have higher flat K values for the HM groups (P<0.001) but were statistically equivalent with Pentacam HR for the normal group (P = 0.119) IOLMaster and Pentacam HR were different in astigmatism measurements for the normal group but were statistically equivalent for the HM group. For the normal group, age was negatively correlated with AL, IOLMaster ACD and Pentacam HR ACD (r = -0.395, P = 0.001; r = -0.715, P < 0.001; r = -0.643, P < 0.001). For the HM group, age was positively correlated with AL but negatively correlated with IOLMaster ACD and Pentacam HR ACD (r = 0.377, P = 0.003; r = -0.392, P = 0.002; r = -0.616, P < 0.001).

Conclusions

The IOLMaster and Pentacam HR have significant difference in corneal power measurements for both normal and HM groups. The two instruments also differ in ACD and astigmatism measurement for the normal group. Therefore, a single instrument is recommended for studying longitudinal changes in anterior segment biometric measurements. Age should be considered as an influencing factor for both AL and ACD values in the normal and HM group.     

Keratometric Index Obtained by Fourier-Domain Optical Coherence Tomography

Purpose

To determine the keratometric indices calculated based on parameters obtained by Fourier-domain optical coherence tomography (FD-OCT).

Methods

The ratio of anterior corneal curvature to posterior corneal curvature (Ratio) and keratometric index (N) were calculated within central 3 mm zone with the RTVue FD-OCT (RTVue, Optovue, Inc.) in 186 untreated eyes, 60 post-LASIK/PRK eyes, and 39 keratoconus eyes. The total corneal powers were calculated using different keratometric indices: K_cal based on the mean calculated keratometric index, K_1.3315 calculated by the keratometric index of 1.3315, and K_1.3375 calculated by the keratometric index of 1.3375. In addition, the total corneal powers based on Gaussian optics formula (K_actual) were calculated.

Results

The means for Ratio in untreated controls, post-LASIK/PRK group and keratoconus group were 1.176 ± 0.022 (95% confidence interval (CI), 1.172–1.179), 1.314 ± 0.042 (95%CI, 1.303–1.325) and 1.229 ± 0.118 (95%CI, 1.191–1.267), respectively. And the mean calculated keratometric index in untreated controls, post-LASIK/PRK group and keratoconus group were 1.3299 ± 0.00085 (95%CI, 1.3272–1.3308), 1.3242 ± 0.00171 (95%CI, 1.3238–1.3246) and 1.3277 ± 0.0046 (95%CI, 1.3263–1.3292), respectively. All the parameters were normally distributed. The differences between K_cal and K_actual, K_1.3315 and K_actual, and K_1.3375 and K_actual were 0.00 ± 0.11 D, 0.21 ± 0.11 D and 0.99 ± 0.12 D, respectively, in untreated controls; -0.01 ± 0.20 D, 0.85 ± 0.18 D and 1.56 ± 0.16 D, respectively, in post-LASIK/PRK group; and 0.03 ± 0.67 D, 0.56 ± 0.70 D and 1.40 ± 0.76 D, respectively, in keratoconus group.

Conclusion

The calculated keratometric index is negatively related to the ratio of anterior corneal curvature to posterior corneal curvature in untreated, post-LASIK/PRK, and keratoconus eyes, respectively. Using the calculated keratometric index may improve the prediction accuracies of total corneal powers in untreated controls, but not in post-LASIK/PRK and keratoconus eyes.     

Central and Midperipheral Corneal Thickness Measured with Scheimpflug Imaging and Optical Coherence Tomography

Purpose

To compare corneal thickness measurements using Pentacam (Oculus, Germany), Sirius (CSO, Italy), Galilei (Ziemer, Switzerland), and RTVue-100 OCT (Optovue Inc., USA).

Methods

Sixty-six eyes of 66 healthy volunteers were enrolled. Three consecutive measurements were performed with each device. The mean value of the three measurements was used for subsequent analysis. Central corneal thickness (CCT), thinnest corneal thickness (TCT), and midperipheral corneal thickness (MPCT; measured at superior, inferior, nasal, and temporal locations with a distance of 1 mm (CT_2mm) or 2.5 mm (CT_5mm) from the corneal apex) were analyzed. Differences and agreement between measurements were assessed using the repeated-measures analysis of variance (ANOVA) and Bland-Altman analyses, respectively.

Results

Statistically significant differences (p<0.001) among the four devices were revealed in CCT, TCT and CT_2mmmeasurements. The CCT, TCT, and CT_2mm values were ranked from the thickest to the thinnest as follows: Galilei>Sirius>Pentacam>RTVue OCT. For these measurements, agreement between measurements by Sirius and Pentacam was good, whereas Galilei overestimated and RTVue underestimated corneal thickness compared to Sirius and Pentacam. As regards CT_5mm measurements, Pentacam provided the largest values, whereas RTVue OCT yielded the smallest values. Agreement of the CT_5mm measurements was good between the Pentacam, Sirius, moderate between Galilei and the other two Scheimpflug systems, and poor between the RTVue OCT and the remaining devices.

Conclusions

The Pentacam and Sirius can be used interchangeably for CCT measurements, while the Galilei and RTVue systematically over- and underestimate CCT, respectively. The three Scheimpflug cameras, but not the RTVue, may be used interchangeably for MPCT measurements.     

Analysis of Fundus Shape in Highly Myopic Eyes by Using Curvature Maps Constructed from Optical Coherence Tomography

Purpose

To evaluate fundus shape in highly myopic eyes using color maps created through optical coherence tomography (OCT) image analysis.

Methods

We retrospectively evaluated 182 highly myopic eyes from 113 patients. After obtaining 12 lines of 9-mm radial OCT scans with the fovea at the center, the Bruch’s membrane line was plotted and its curvature was measured at 1-µm intervals in each image, which was reflected as a color topography map. For the quantitative analysis of the eye shape, mean absolute curvature and variance of curvature were calculated.

Results

The color maps allowed staphyloma visualization as a ring of green color at the edge and as that of orange-red color at the bottom. Analyses of mean and variance of curvature revealed that eyes with myopic choroidal neovascularization tended to have relatively flat posterior poles with smooth surfaces, while eyes with chorioretinal atrophy exhibited a steep, curved shape with an undulated surface (P<0.001). Furthermore, eyes with staphylomas and those without clearly differed in terms of mean curvature and the variance of curvature: 98.4% of eyes with staphylomas had mean curvature ≥7.8×10⁻⁵ [1/µm] and variance of curvature ≥0.26×10⁻⁸ [1/µm].

Conclusions

We established a novel method to analyze posterior pole shape by using OCT images to construct curvature maps. Our quantitative analysis revealed that fundus shape is associated with myopic complications. These values were also effective in distinguishing eyes with staphylomas from those without. This tool for the quantitative evaluation of eye shape should facilitate future research of myopic complications.     

The eye of the hooded seal,Cystophora cristata,in air and water

Summary Multiple refractive state measurements were made on a male and female hooded seal (Cystophora cristata) when the eyes were exposed to air and to water. The measures, made by conventional retinoscopy and by photorefraction, show that the seals are moderately hyperopic (2–3 diopters) in water and moderately myopic (2–4 diopters) in air. No significant astigmatism was noted in either medium. The absence of refractive state variation over time suggests that an accommodative mechanism is insignificant or absent, although histological study indicates that the ciliary muscle is well developed.Photokeratoscopy, carried out on two animals with two keratoscopic instruments, show that the cornea is relatively flat (30 mm, or about one-half the diameter of the eye). Furthermore the cornea is only slightly astigmatic (less than 1 diopter). The refractive power of the external corneal surface (in air), calculated from a measurement of corneal refractive index of 1.378, amounts to only 10 or 11 diopters.As in the typical fish eye, hooded seal lenses are spherical or nearly spherical in shape (24–23 mm), and have short focal lengths (30–32 mm). Focal measures for rays at varying distances from the lens center indicate that spherical aberration is well corrected.There is no indication in this seal species, of a previously reported adaptation involving a highly astigmatic cornea which together with a slit pupil can minimize the optical effect of movement from water to air.     

Peripapillary Intrachoroidal Cavitations. The Beijing Eye Study

Purpose

To assess prevalence, size and location of peripapillary intrachoroidal cavitations (PICCs) and their associations in a population-based sample. .

Methods

The population-based Beijing Eye Study 2011 included 3468 individuals with a mean age of 64.6±9.8 years (range:50-93 years). A detailed ophthalmic examination included enhanced depth imaging of the choroid by spectral-domain optical coherence tomography and fundus photography. PICCs were defined as triangular thickening of the choroid with the base at the optic disc border and a distance between Bruch´s membrane and sclera of ≥200μm. Parapapillary large choroidal vessels were excluded.

Results

Out of 94 subjects with high myopia (refractive error <-6.0 diopters or axial length >26.5mm in right eyes), OCT images were available for 89 (94.7%) participants. A PICC was detected in 15 out of these 89 highly myopic subjects (prevalence:16.9±4.0%) and in none of hyperopic, emmetropic or medium myopic subgroups each consisting of 100 randomly selected subjects. Mean PICC width was 4.2±2.3 hours (30°) of disc circumference and mean length was 1363±384μm. PICCs were located most frequently (40%) at the inferior disc border. On fundus photos, a typical yellow-orange lesion was found in 8 (53%) eyes with PICCs. In binary regression analysis, presence of PICCs was significantly associated with optic disc tilting (P=0.04) and presence of posterior staphylomata (P=0.046).

Conclusions

Prevalence of PICCs in the adult Chinese population was 16.9±4.0% in the highly myopic group, with no PICCs detected in non-highly myopic eyes. PICCs were located most frequently at the inferior optic disc border. Only half of the PICCs detected on OCT images showed a yellow-orange lesion on fundus photos. Presence of PICC was significantly associated only with an increased optic disc tilting and presence of posterior staphylomata, while it was not associated with axial length, refractive error or other ocular or systemic parameters.     

Ilex sanqingshanensis sp. nov. (Aquifoliaceae) from Jiangxi Province,China

Ilex sanqingshanensis, a new species of Aquifoliaceae from Jiangxi, China, is described and illustrated with morphological characteristics and ultrastructure of pollen grains. The new species is easily distinguished from the most similar species I. wugongshanensis C. J. Tseng ex S. K. Chen et Y. X. Feng by having smaller leaves that are elliptic, ovate or elliptic‐ovate, with shorter (0.5–1.0 vs 2–3 mm) teeth on the leaf margin, longer pedicels of staminate flowers (2.0–3.5 vs 1.5 mm), smaller pyrenes (3.5–4.0 × 2.0–2.5 vs 4.5–5.0 × 3.0 mm), and woody pyrenes (vs stony pyrenes).     

两株乳酸杆菌益生菌特性的研究

对两株乳酸杆菌作为益生菌的特性进行分析。采用人工胃液、人工肠液,及体外培养人结肠癌细胞株HT-29,模拟 上消化道环境,检测候选菌株L.acidophilus1.1878和L.rhamnosus1.120对上消化道环境的耐受性和粘附性;以琼脂扩散打孔 法,检测候选菌株SCS对4种常见肠道致病菌的抑菌能力。结果表明,两株候选菌株可耐受pH>3.0的人工胃液,及0.2%的 胆盐浓度;光镜观察L.acidophilus1.1878、L.rhamnosus1.120粘附于HT-29细胞边缘,平均4.5～7个/细胞,扫描电镜观察 L.acidophilus1.1878、L.rhamnosus1.120粘附于HT-29细胞表面的刷状缘,且细胞表面结构完整;对4种肠道致病菌的抑菌 圈直径均在12mm以上。证明实验观察的两株乳酸杆菌具有较好的耐酸、耐胆盐及粘附、抑菌特性,符合益生菌的标准。     

Tactile spatial acuity in elderly persons: assessment with grating domes and relationship with manual dexterity

In this study, we sought to better define the limit of spatial resolution at the fingertips of elderly participants (n = 30, age 60-95 years) using an extended set of JVP grating domes, incorporating four new grating dimensions (2.5-, 3.5-, 4.0- and 4.5-mm width). A secondary aim was to examine whether deficits in tactile acuity could be related to hand dysfunction in older adults. Spatial resolution thresholds were determined by the finest grating whose orientation (dominant index finger) could be reported reliably. Manual dexterity was assessed with the Grooved Pegboard Test (GPT). The extended set of domes improved threshold measurements in a majority of participants (21/30). Still, accurate threshold estimates could not be obtained in one third of the participants, mostly in the older age group (8/9, 74-95 years). Grating resolution thresholds at the index finger were strongly correlated (r = 0.66, p<0.01) with dexterity scores derived from the GPT. From these results, we conclude that the 2.5- and 3.5-mm grating domes are suitable additions when assessing spatial acuity at the fingertips of older subjects between 60 and 70 years of age (mean threshold, 2.7+/-0.6 mm). For the older ones, the 4.0- and 4.5-mm domes can improve threshold measurements but interpretation of values can be complicated by the presence of undiagnosed pathologies (e.g., diffuse polyneuropathy) as people advance in age. The strong relationship between grating resolution thresholds and dexterity scores indicates that an impaired spatial acuity at the fingertips may translate into great difficulties in tasks requiring fine manipulations. These findings have important implications for the assessment of hand function in older adults.     

Frequency of heterozygous complete hydatidiform moles,estimated by locus-specific minisatellite and Y chromosome-specific probes

Summary Restriction fragment length polymorphisms identified with three locus-specific minisatellite probes and banding patterns with Y chromosome-specific probes have been examined in 39 cases of complete hydatidiform mole (CHM) and the parents. All 39 cases were shown to be androgenetic. Of the 39 cases, 8 were identified as heterozygous CHM using the minisatellite probes. Estimates for the total number of heterozygous CHM in the series ranged from 23%–29%, higher than previously reported. Of the eight identified heterozygous CHM, six had Y chromosome-specific sequences whereas two were female; this is not significantly different from the 2:1 ratio expected. The low frequency of 46,XX heterozygous CHM in the literature may reflect difficulties in distinguishing them from 46,XX homozygous CHM. Examination of RFLPs with a small panel of locus-specific minisatellite probes provides a powerful method of classifying hydatidiform mole, enabling the rare heterozygous 46,XX CHM to be accurately identified.     

OPTIMIZATION OF SALT CONCENTRATIONS FOR A HIGHER CAROTENOID PRODUCTION IN DUNALIELLA SALINA (CHLOROPHYCEAE)1

Dunaliella salina (Dunal) Teodor, when treated over 25 d with a wide range of NaCl salinities (0.6–4.5 M), showed its maximal growth potentialities at 1.5–3.0 M NaCl and was able to survive even at 4.5 M NaCl. Sodium concentrations increased significantly at the supraoptimal salinities, reaching up to 5 mmol · g^?1 dry weight (dwt) at 4.5 M NaCl. Interestingly, ability of D. salina to take up essential mineral nutrients was not impaired by increased salinity. As for growth, chl concentrations were maximal in the 1.5–3.0 M NaCl range. Interestingly, carotenoid concentrations increased with the increasing salinity. The highest values of total antioxidant activity (5.2–6.9 mg gallic acid equivalents [GAE] · g^?1 dwt), antiradical activity, and reducing power were measured at 1.5–3.0 M NaCl. As a whole, these results showed that at 1.5–3.0 M NaCl, D. salina produce appreciable antioxidant level. But, once it reaches its growth maximum, a salt addition up to 4.5 M could enhance its carotenoid yield.     

Corneal Thickness Profile and Associations in Chinese Children Aged 7 to 15 Years Old

Corneal thickness (CT) maps of the central (2-mm diameter), para-central (2 to 5-mm diameter), peripheral (5 to 6-mm diameter), and minimum (5-mm diameter) cornea were measured in normal Chinese school children aged 7 to 15 years old using Fourier-domain optical coherence tomography. Multiple regression analyses were performed to explore the effect of associated factors [age, gender, refraction, axial length and corneal curvature radius (CCR)] on CT and the relationship between central corneal thickness (CCT) and intraocular pressure (IOP). A total of 1228 eyes from 614 children were analyzed. The average CCT was 532.96 ± 28.33 μm for right eyes and 532.70 ±28.45 μm for left eyes. With a 10 μm increase in CCT, the IOP was elevated by 0.37 mm Hg, as measured by noncontact tonometry. The CT increased gradually from the center to the periphery. The superior and superior nasal regions had the thickest CTs, while the thinnest points were primarily located in the inferior temporal cornea. The CCT was associated with CCR (p = 0.008) but not with gender (p = 0.075), age (p = 0.286), axial length (p = 0.405), or refraction (p = 0.985). In the para-central region and the peripheral cornea, increased CT was associated with younger age, male gender, and a flatter cornea.     

Precision and Agreement of Corneal Power Measurements Obtained Using a New Corneal Topographer OphthaTOP

Purpose

To evaluate repeatability and reproducibility of anterior corneal power measurements obtained with a new corneal topographer OphthaTOP (Hummel AG, Germany) and agreement with measurements by a rotating Scheimpflug camera (Pentacam HR, Oculus, Germany) and an automated keratometer (IOLMaster, Carl Zeiss Meditec, Germany).

Methods

The right eyes of 79 healthy subjects were prospectively measured three times with all three devices. Another examiner performed three additional scans with the OphthaTOP in the same session. Within one week, the first examiner repeated the measurements using the OphthaTOP. The flat simulated keratometry (Kf), steep K (Ks), mean K (Km), J₀, and J₄₅ were noted. Repeatability and reproducibility of measurements were assessed by within-subject standard deviation (Sw), repeatability (2.77 Sw), coefficient of variation (CoV), and intraclass correlation coefficient (ICC). Agreement between devices was assessed using 95% limits of agreement (LoA).

Results

Intraobserver repeatability and interobserver and intersession reproducibility of all measured parameters showed a 2.77 Sw of 0.29 diopter or less, a CoV of less than 0.24%, and an ICC of more than 0.906. Statistically significant differences (P<0.001) were found between the parameters analyzed by the three devices, except J₀ and J₄₅. The mean differences between OphthaTOP and the other two devices were small, and the 95% LoA was narrow for all results.

Conclusions

The OphthaTOP showed excellent intraobserver repeatability and interobserver and intersession reproducibility of corneal power measurements. Good agreements with the other two devices in these parameters were found in healthy eyes.     

Root length and biomass losses during sample preparation with different screen mesh sizes

Data are presented on the differences in root length density (RLD), dry matter (DM), and root diameter values determined on wheat and faba bean using sieves of different mesh size to separate roots from soil during sample preparation. Screens with 0.2, 1, and 2 mm (0.04, 1, and 4 mm²) aperture were used. Roots collected on the 2-mm sieve represented on average 55% of the weight and only 10% of the total length collected using a 0.2-mm sieve. With a 1-mm sieve 75% of weight was retained, but only 34% of the length. In the 0–20 cm soil layer average RLD and DM values ranged between 1.3 and 2.5 cm cm^-3 and 215 and 136 g m^-2 for faba bean and wheat respectively with 2 mm screens and 14.6 and 18.1 cm cm^-3 and 313 and 202 g m^-2 with 0.2 mm sieves. RLD was more affected than weight since losses from coarse screens were largely due to fine root fractions, although the 1-and 2-mm screens retained a small amount of fine roots that were long or attached to main structures. Variability was higher for measurements on coarser screens. The use of screens much coarser than the diameter of fine roots is not recommended for the study of surface-related phenomena in which root length quantification is necessary, while it may be acceptable for gross comparisons of root weight and spatial extent.     

Oleic acid inhibits amyloid formation of the intermediate of alpha-lactalbumin at moderately acidic pH

The effects of oleic acid on amyloid formation of Ca2+-depleted bovine alpha-lactalbumin (apo-BLA) at low pH and the biological impact of the effects were investigated by using thioflavin T, Congo red, far-UV circular dichroism, atomic force microscopy, transmission electron microscopy, and other biophysical methods. The results from the phase diagram method of fluorescence show that two intermediates exist in the conformational transition of apo-BLA induced by low pH. One intermediate populated at pH 3.0 is characterized as a molten globule state and the other accumulates with stable secondary structure and exposed hydrophobic surface at pH 4.0-4.5. Amyloid formation of apo-BLA takes place upon decreasing the pH to 4.5 and is accelerated remarkably as the pH is decreased further. However, amyloid fibrils of apo-BLA are not observed in the pH range of 5.0-7.0 on a time-scale of 30 days. The lag time of fibrillation at pH 4.0 is greatly elongated by the presence of oleic acid, accompanied by a remarkable decline of the maximum thioflavin T intensity. Furthermore, amyloid formation of apo-BLA at pH 4.5 is inhibited completely by oleic acid, and insoluble aggregates are observed. In contrast, the effects of oleic acid on amyloid formation are not remarkable at pH 3.0 or at pH 2.0. Our data demonstrate that oleic acid specifically induces the intermediate of apo-BLA at pH 4.0-4.5 to form insoluble amorphous aggregates, which is responsible for the inhibition of amyloid formation of the protein by oleic acid in this range of pH values.     

Chick embryo liver beta-glucuronidase. Comparison of activity on natural and artificial substrates.

The beta-glucuronidase in homogenates of 12-day chick embryo livers catalyzed the release of glucuronic acid from 4-methylumbelliferyl-beta-D-glucuronide and from the nonreducing terminals of the hexasaccharides of chondroitin-6-SO4 and chondroitin-4-SO4 at rates of 143, 114, and 108 nmol of glucuronic acid/h/mg of protein, respectively, when assayed at pH 3.5 in 0.05 M sodium acetate buffer. During a 60-fold purification of the enzyme, the ratios of the activities on these substrates did not change. When 4-methylumbelliferyl-beta-D-glucuronide was used as substrate the enzyme was active at pH values from 3.0 to 5.5, with maximal activity between pH values 4.0 and 4.5. Concentrations of NaCl from 0.15 to 0.3 M inhibited the activity at low pH values but activated the enzyme between pH 4.0 and 5.5. The enzyme was active on the chondroitin-6-SO4 hexasaccharide from pH 3.0 to 5.5, with a broad optimum between 3.0 and 4.5. NaCl inhibited the activity on the oligosaccharide substrate at all pH values. Eadie-Scatchard plots of rates of 4-methylumbelliferyl-beta-D-glucuronide hydrolysis at substrate concentrations ranging from 2 to 1000 microM showed multiple kinetic forms of the enzyme, a form with a Km of approximately 11 microM, and a second form with a Km of approximately 225 microM. The pH optimum of the low Km form was 3.5 to 4.0; that of the high Km form was pH 4.5. NaCl inhibited the activity of the low Km form, but activated the high Km form of the enzyme. Chondroitin SO4 oligosaccharides competed with 4-methylumbelliferyl-beta-D-glucuronide for the low Km form of the enzyme but had little effect on the hydrolysis of 4-methylumbelliferyl-beta-D-glucuronide by the high Km form of the enzyme. The activities of the beta-glucuronidase on tetra-, hexa-, octa-, and decasaccharides of chondroitin-6-SO4 and chondroitin-4-SO4, measured using a new assay procedure which can detect the formation of 1 nmol of product, were similar, although rates were somewhat lower for the higher oligosaccharides. With the exception of the chondroitin-4-SO4 tetrasaccharide, all of the oligosaccharide substrates saturated the enzyme at concentrations of 20 to 30 microM, indicating Km values of less than 10 to 15 microM for the oligosaccharides. Highly purified beta-glcuronidases from human placenta and from rat preputial gland also showed multiple kinetic forms when assayed using 4-methylumbelliferyl-beta-D-glucuronide as substrate.