Application of B-flow imaging and its enhanced mode in perforator mapping.

AIM: To explore the value of B-flow (B-mode blood flow) imaging and its enhanced mode in perforator mapping. MATERIALS AND METHODS: Before surgery, B-flow imaging, enhanced B-flow imaging, colour Doppler flow imaging (CDFI), and contrast-enhanced ultrasound (CEUS) were used to detect the skin-perforating vessels and small vessels in the fat layer of the donor site. Taking the intra-operative results as the reference standard, the diagnostic consistency and efficiency of the four modes were compared. Statistical analysis was performed using the Friedman M-test, Cochran's Q-test, and the Z-test. RESULTS: Thirty flaps were excised, with 34 skin-perforating vessels and 25 non-skin-perforating vessels, as confirmed during surgery. In order of the number of skin-perforating vessels detected, the results showed that enhanced B-flow imaging detected more vessels than B-flow imaging and CDFI (all p<0.05), CEUS detected more vessels than B-flow imaging and CDFI (all p<0.05), B-flow imaging detected more vessels than CDFI (p<0.05). All four modes had remarkable and satisfactory diagnostic consistency and effectiveness, but B-flow imaging was the best (sensitivity 100%, specificity 92%, Youden index 0.92). In order of the number of small vessels in the fat layer detected, the results showed that enhanced B-flow imaging detected more vessels than CEUS, B-flow imaging, and CDFI (all p<0.05). CEUS detected more vessels than B-flow imaging and CDFI (all p<0.05). CONCLUSION: B-flow imaging is an alternative method for perforator mapping. Enhanced B-flow imaging can reveal the microcirculation of flaps.

STYXL1 promotes malignant progression of hepatocellular carcinoma via downregulating CELF2 through the PI3K/Akt pathway.

OBJECTIVE: This study was aimed to investigate the expression characteristics of STYXL1 in hepatocellular carcinoma (HCC), and to further analyze its regulatory role in promoting HCC development by targeting CELF2 to activate the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway. PATIENTS AND METHODS: Expression levels of STYXL1 in 25 pairs of HCC tissue specimens and paracancerous normal ones collected from HCC patients were examined by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). Meanwhile, qRT-PCR was also performed to further verify the expression of STYXL1 in HCC cell lines. In addition, after STYXL1 knockdown model was constructed by lentivirus transfection in HCC cell lines Hep3B and Huh7, the Cell Counting Kit-8 (CCK-8), cell colony formation, 5-Ethynyl-2'-deoxyuridine (EdU), and flow cytometry assays were performed to analyze the influence of STYXL1 on HCC cell functions. Furthermore, an in-depth study of the relationship between STYXL1 and CELF2 was conducted to figure out the underlying mechanism. RESULTS: The results of qRT-PCR revealed that the expression level of STYXL1 in HCC samples was remarkably higher than that in adjacent ones, and the difference was statistically significant. Compared with HCC patients with low expression of STYXL1, patients with high expression of STYXL1 had a higher overall survival rate. Similarly, the proliferation ability of HCC cells in sh-STYXL1 group remarkably decreased compared with controls, while the apoptosis ability was oppositely enhanced. In addition, Western Blotting results indicated that STYXL1 could elevate the expressions of PI3K/Akt pathway-related proteins. Meanwhile, a negative correlation between CELF2 and STYXL1 was identified in HCC tissues. Finally, the result of cell reverse experiments demonstrated that STYXL1 could affect the malignant progression of HCC via modulating CELF2 expression. CONCLUSIONS: STYXL1 expression was remarkably upregulated in HCC tissues, as well as in cell lines. Its level was closely related to the poor prognosis of HCC patients. In addition, STYXL1 might be able to accelerate HCC proliferation rate and inhibit cell apoptosis via downregulating CELF2 through the PI3K/Akt pathway.

Genetic association of HLA-DRB1 multiple polymorphisms with dermatomyositis in Chinese population.

Genetic variation in HLA plays an important role in the pathogenesis of dermatomyositis (DM). The aim of this study was to investigate the association of HLA class II with DM in China. Two hundred and twenty-four DM patients and 300 healthy controls were randomly enrolled at China-Japan Friendship Hospital. High-resolution typing of HLA-DRB1 alleles was performed by sequencing based typing. The HLA-DQA1 and HLA-DQB1 alleles were determined by polymerase chain reaction sequence-specific primers. The frequencies of HLA-DRB1*09:01 (28.6% vs 11.3%, P < .0001, odds ratio, OR = 3.14, 95% confidence interval, CI = 2.47-3.99) and HLA-DRB1*12:01 (29.0% vs 11.0%, P < .0001, OR = 3.30, 95% CI = 2.59-4.20) in DM patients were significantly higher than that in healthy controls. No significant difference was found in HLA-DQA1 or DQB1 alleles between DM patients and healthy controls. Furthermore, DM patients with anti-melanoma differentiation-associated gene 5 antibody (anti-MDA5) had a significantly higher frequency of HLA-DRB1*12:01 compared to that for patients without anti-MDA5 (P < .0001, OR = 4.77, 95% CI: 2.29-9.93). Multivariate binary logistic regression analysis was performed to identify the risk factors for interstitial lung disease. The HLA-DRB1*09:01 allele was a poor prognostic factor (P = .01, OR = 9.21, 95% CI: 1.47-57.50) for DM patients with anti-MDA5 autoantibody. In summary, our findings indicate that HLA-DRB1*09:01 and HLA-DRB1*12:01 alleles may contribute to susceptibility of adult DM in Han Chinese population. In addition, the DRB1*12:01 genotype is significantly associated with the presence of anti-MDA5 antibody in DM patients.

Quercetin ameliorates LPS-induced inflammation in human peripheral blood mononuclear cells by inhibition of the TLR2-NF-κB pathway.

Quercetin, a dietary flavonoid abundant in fruits, vegetables, and herbs, presents various pharmacological effects. This study aimed to investigate the anti-inflammatory effect and the underlying mechanism of quercetin in lipopolysaccharide (LPS)-stimulated human peripheral blood mononuclear cells (PBMCs). Cell viability was measured by the Cell Counting Kit-8 assay. The mRNA expression of Toll-like receptor 2 (TLR2) was assessed by quantitative real-time polymerase chain reaction. Inflammatory cytokine secretions and nuclear factor (NF)-kB levels were analyzed by enzyme-linked immunosorbent assay. Our findings showed that quercetin significantly reduced LPS-induced cytotoxicity in human PBMCs. Quercetin suppressed the secretion of tumor necrosis factor-a, interleukin (IL)-1b, and IL-6 in LPS-stimulated human PBMCs. Moreover, quercetin reduced the LPS-induced increase in the expression of TLR2 mRNA and decreased the NF-kB concentration in LPS-stimulated human PBMCs. The data indicates that quercetin plays an important role in LPS-induced inflammation in human PBMCs via suppression of the TLR2-NF-kB pathway.

Smoking cessation and carotid atherosclerosis: the Guangzhou Biobank Cohort Study--CVD.

INTRODUCTION: Smoking has been shown to be associated with carotid atherosclerosis in cross-sectional and prospective studies in Western populations. However, few studies have examined the reversal of risk resulting from quitting smoking, and the results are conflicting. METHODS: 959 men aged 50-85 years were randomly selected from phase III (2006-2007) of the Guangzhou Biobank Cohort Study into this cross-sectional study. Common carotid artery intima-media thickness (CCA-IMT) was measured by B-mode ultrasonography, and carotid artery plaques were identified. Major cardiovascular risk factors, including fasting triglyceride, low-density and high-density lipoprotein (LDL and HDL) cholesterol and glucose, and systolic and diastolic blood pressure, were assessed. RESULTS: CCA-IMT and the number of carotid plaque increased from never to former to current smokers (both p≤0.001). Among former smokers compared to current smokers, after adjustment for cigarette pack-years and other potential confounders, the adjusted ORs (95% CI) for quitting for 1-9, 10-19 and 20+ years were 0.77 (0.47 to 1.26), 0.45 (0.26 to 0.79) and 0.37 (0.17 to 0.77) for the presence of CCA atherosclerosis, and 0.69 (0.43 to 1.12), 0.47 (0.27 to 0.82) and 0.45 (0.23 to 0.96) for the presence of carotid plaques, respectively. Longer duration of quitting smoking was also significantly associated with decreasing risk of the severity of CCA atherosclerosis and carotid plaques (all p≤0.001). CONCLUSION: Smoking cessation was beneficial in attenuating the risk of carotid atherosclerosis associated with cigarette smoking. The short duration of cessation in earlier studies is a likely explanation for the inconsistent results.

An overview of the Guangzhou biobank cohort study-cardiovascular disease subcohort (GBCS-CVD): a platform for multidisciplinary collaboration.

The Guangzhou Biobank Cohort Study (GBCS, n=30 519, age >or=50 years) was established to examine the effects of genetic and environmental influences on health problems and chronic disease development. Guangzhou is undergoing massive economic development, but from a baseline that had remained unchanged for millennia. The Cardiovascular Disease Subcohort (GBCS-CVD) consists of 2000 participants who have been intensively phenotyped including a range of surrogate markers of vascular disease, including carotid artery intima-media thickness, cerebral artery stenoses, arterial stiffness, ankle-to-brachial blood pressure index and albuminuria, as well as coagulatory and inflammatory markers. Plasma and leukocytes are stored in liquid nitrogen for future studies. Preliminary demographic data show the female volunteers are younger than the male ones, but present with greater levels of adiposity including central obesity (31 vs 16%). Women had more body fat (33 vs 24%) and associated levels of adipokines. Despite this, body mass index and hip circumferences were similar, which contrasts with Caucasian populations. Men had more physician-diagnosed vascular disease (6.1 vs 2.5%), hypertension (42 vs 34%) and hyperglycaemia (36.6 vs 29.6%) than the women, but were less insulin resistant. In men, smoking (40 vs 2%) and drinking alcohol (67 vs 50%) was more common and they also had lower energy expenditures. The genotype distributions of the 15 typed single nucleotide polymorphisms were all in Hardy-Weinberg equilibrium. This article describes the rationale and methodology for the study. Given the comprehensive characterization of demographic and psychosocial determinants and biochemistry, the study provides a unique platform for multidisciplinary collaboration in a highly dynamic setting.

Determination of particulate-bound formaldehyde from burning incense by solid phase microextraction.

This work studied the feasibility of using a solid phase microextraction (SPME) fiber for sampling and analysis of gaseous formaldehyde as well as particulate-bound formaldehyde from burning Chinese incense. The SPME fiber with PDMS/DVB coating were partially coated with o-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine hydrochloride (PFBHA), and used for sampling formaldehyde. The sampling rate for formaldehyde and its dependence on temperature, relative humidity and sampling time were observed. The same PFBHA treated fibers were, in parallel, exposed to incense burning smoke with pre-filtration and without pre- filtration for 0.5-1 min. The NIOSH method 2541 using an XAD-2 tube at a flow rate of 0.1 Lpm was also applied for sampling simultaneously. The results demonstrate that commercially available PDMS/DVB fibers partially coated with PFBHA are capable of sampling the gas phase of formaldehyde as well as particulate-bound formaldehyde. The determined level of formaldehyde was close to the result obtained by the NIOSH method 2541. However, a reduction of the fiber's formaldehyde loading capacity in the aerosol sampling in comparison with gas sampling was noticed. This indicates that the particulate characteristics, and their bound chemicals other than formaldehyde may influence the maximum loading capacity of formaldehyde, and some characteristic particulates in high concentrations may even deteriorate the fiber coating.

Alteration of bone cell function by RANKL and OPG in different in vitro models.

BACKGROUND: Receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG) are well-documented potent regulators of osteoclast development. However, their effects in mature bone cells and in organ cultures have not been well studied. It is uncertain whether their activities in different experimental models are comparable. MATERIALS AND METHODS: RANKL and OPG were evaluated for their activities in mouse calvarial organ cultures, mouse bone marrow cultures, isolated rat mature osteoclast assays and rat primary osteoblast cultures. Results In murine calvarial organ culture, both muRANKL (> or = 10 ng mL(-1)) and rRANKL (> or = 100 ng mL(-1)) significantly stimulated (45)Ca release, while OPG (> or = 50 ng mL(-1)) was an inhibitor of bone resorption. Meanwhile, [(3)H]-thymidine incorporation in this assay was also modulated (indicating proliferation increases in the osteoblast lineage of cells) although these peptides had no direct effect on [(3)H]-thymidine incorporation in isolated osteoblast assays. In mouse bone marrow cultures, muRANKL (> or = 1 ng mL(-1)) and rRANKL (> or = 5 ng mL(-1)) significantly stimulated osteoclastogenesis. The number of nuclei per osteoclast was also significantly increased. OPG strongly inhibited this index, with over 90% suppression at 1 ng mL(-1). Both muRANKL (10 ng mL(-1)) and rRANKL (100 ng mL(-1)) stimulated, while OPG (10 ng mL(-1)) inhibited osteoclast activity in isolated mature osteoclast assays. CONCLUSION: The current study demonstrated that bone resorption modulated by RANKL and OPG, in murine calvarial organ culture, leads to changes in osteoblast proliferation, suggesting a feedback mechanism from osteoclasts to osteoblasts. In addition, it was found that RANKL and OPG have more potent effects on osteoclastogenesis than on the activity of mature osteoclasts.

Preptin, another peptide product of the pancreatic beta-cell, is osteogenic in vitro and in vivo.

Several hormones that regulate nutritional status also impact on bone metabolism. Preptin is a recently isolated 34-amino acid peptide hormone that is cosecreted with insulin and amylin from the pancreatic beta-cells. Preptin corresponds to Asp(69)-Leu(102) of pro-IGF-II. Increased circulating levels of a pro-IGF-II peptide complexed with IGF-binding protein-2 have been implicated in the high bone mass phenotype observed in patients with chronic hepatitis C infection. We have assessed preptin's activities on bone. Preptin dose-dependently stimulated the proliferation (cell number and DNA synthesis) of primary fetal rat osteoblasts and osteoblast-like cell lines at periphysiological concentrations (>10(-11) M). In addition, thymidine incorporation was stimulated in murine neonatal calvarial organ culture, likely reflecting the proliferation of cells from the osteoblast lineage. Preptin did not affect bone resorption in this model. Preptin induced phosphorylation of p42/p44 MAP kinases in osteoblastic cells in a dose-dependent manner (10(-8)-10(-10) M), and its proliferative effects on primary osteoblasts were blocked by MAP kinase kinase inhibitors. Preptin also reduced osteoblast apoptosis induced by serum deprivation, reducing the number of apoptotic cells by >20%. In vivo administration of preptin increased bone area and mineralizing surface in adult mice. These data demonstrate that preptin, which is cosecreted from the pancreatic beta-cell with amylin and insulin, is anabolic to bone and may contribute to the preservation of bone mass observed in hyperinsulinemic states such as obesity.

Preoperative plasma N-terminal pro-brain natriuretic peptide as a marker of cardiac risk in patients undergoing elective non-cardiac surgery.

BACKGROUND: Plasma N-terminal pro-brain natriuretic peptide (NTproBNP) is a sensitive marker for heart failure. This study tested whether the preoperative plasma level of NTproBNP could predict cardiac complications in patients undergoing non-cardiac surgery. METHODS: A total of 190 consecutive patients who underwent elective non-cardiac surgery that required general anaesthesia were studied. In addition to routine preoperative evaluation, a blood sample was taken for estimation of plasma NTproBNP concentration. Postoperative cardiac complications were defined as cardiac death, acute coronary syndrome, heart failure and haemodynamic compromise from cardiac arrhythmias. RESULTS: Fifteen of the 190 patients had a cardiac complication: four had acute coronary syndrome and 13 had congestive heart failure. NTproBNP concentration was significantly higher in patients with a cardiac complication; a level greater than 450 ng/l was predictive of cardiac complications with a sensitivity of 100 per cent and a specificity of 82.9 per cent. Other factors associated with cardiac complications were a higher American Society of Anesthesiologists grade, age and clinical cardiac impairment, but in a multivariate analysis NTproBNP level was the only independent factor. CONCLUSION: Preoperative plasma NTproBNP concentration may be an independent predictor of cardiac complications in patients undergoing non-cardiac surgery.

Color vision after laser in situ keratomileusis.

PURPOSE: To evaluate the effect of laser in situ keratomileusis (LASIK) on color vision. SETTING: Department of Ophthalmology, China Medical College Hospital, Taichung, Taiwan. METHOD: This prospective study comprised consecutive patients having LASIK. Patients were eligible for inclusion if they had a best corrected visual acuity of 20/20 or better and a normal color vision test preoperatively and an uncorrected near visual acuity of 20/40 or better postoperatively. Color vision was tested using the Farnsworth-Munsell 100-hue test (FM 100 test) preoperatively and 1 day, 1 week, and 1 month postoperatively. RESULTS: Twenty-nine eyes of 15 patients having LASIK were enrolled in the study. The mean patient age was 29.2 years +/- 2.9 (SD). The mean preoperative spherical equivalent refractive error was -5.6 +/- 1.8 diopters, and the mean preoperative error score of the FM 100 test was 3.79 +/- 1.55. After surgery, no significant change in the error score was observed at 1 day (4.30 +/- 1.07, P =.1039, paired t test), 1 week (3.72 +/- 1.25, P =.8125, paired t test), or 1 month (3.97 +/- 1.29, P =.6149, paired t test). CONCLUSION: Laser in situ keratomileusis did not affect color vision evaluated by the FM 100 test.

Studies on the synthesis of trans-dihydrodiols of polycyclic aromatic thiaarenes as potential proximate carcinogenic metabolites: first synthesis of trans-10,11-dihydroxy-10,11-dihydroacenaphtho[1, 2-b]benzo[d]thiophene and 6,7-dihydroxy-6,7-dihydronaphtho[1, 2-b]thiophene.

Polyaromatic thiophene compounds are found to occur concomitantly with numerous coal-derived products and shale oils and are suspected mutagens and/or carcinogens. The first synthesis of the two title compounds 9 and 16 has been achieved in five or four steps starting from 8,9-dihydroacenaphtho[1,2-b]benzo[d]thiophene (1) and 7-methoxynaphtho[1,2-b]thiophene (12), respectively. Compound 1 was converted to the cis-diol (11) (via treatment with OsO(4)/pyridine) or to trans-diol (3) [via Prevost reaction (PhCOOAg/I(2)) followed by hydrolysis] in 95-98% yield, respectively. Subsequent dehydration (PTS/benzene) of the diol followed by aromatization of the resulting ketone (5) produced the phenolic compound 6 in 97% yield. Oxidation of the phenol with phenyl iododiacetate followed by hydrolysis of the o-quinone monoketal 7 gave the o-quinone (8) in 86% yield. Stereoselective reduction of 8 with NaBH(4)/EtOH under oxygen afforded trans-10,11-dihydroxy-10,11-dihydroacenaphtho[1,2-b]benzo[d]thi oph ene(9) (orange yellow solid) in 55% yield. Compound 16 was obtained as a colorless solid, through the stereoselective reduction of the o-quinone 15 (with NaBH(4)), which in turn was prepared from 12 following the protocol of functional group transformation of methoxy --> phenol --> o-quinone monoketal --> o-quinone, as used in the previous case. The yields for all the steps are very good. The mutagenicity assay of compound 9 and 16 as well as their parent thiaarenes have been performed. The results showed that 9 may not be the proximate carcinogen of acenaphtho[1,2-b]benzo[d]thiophene, while it is likely that compound 16 is one of the possible proximate carcinogens for naphtho[1,2-b]thiophene.

Synthesis of anti-1,2-dihydroxy-3,4-epoxy-1,2,3, 4-tetrahydro-6-nitrochrysene and its reaction with 2'-deoxyguanosine- 5'-monophosphate, 2'-deoxyadenosine-5'-monophosphate, and calf thymus DNA in vitro.

The remarkable carcinogenic activity of 6-nitrochrysene (6-NC) in several animal models, and its environmental presence, suggest its potential importance with regard to human cancer development. Depending on the bioassay model, 6-NC can be activated by simple nitro reduction, ring oxidation, or by a combination of ring oxidation and nitro reduction. Only the first pathway has been clearly established. Thus, this study purports to unequivocally define the other pathways. Toward this end, we report for the first time the synthesis of anti-1,2-dihydroxy-3,4-epoxy-1,2,3, 4-tetrahydro-6-nitrochrysene (6-NCDE), a likely ultimate carcinogenic metabolite of 6-NC. Also, we describe our initial investigation of its binding with calf thymus DNA, 2'-deoxyguanosine-5'-monophosphate (2'-dGuo), and 2'-deoxyadenosine-5'-monophosphate (2'-dAdo) in vitro. These adduct markers were then employed for comparison with those obtained in the rat after in vivo treatment with 6-NC. On the basis of the results, it appears that the major adduct formed in the liver of rats treated with 6-NC is not derived from 6-NCDE.

Natural history of central islands after laser in situ keratomileusis.

PURPOSE: To assess the incidence and natural history of central islands following laser in situ keratomileusis (LASIK) and evaluate the association of central island characteristics with visual acuity. SETTING: Department of Ophthalmology, China Medical College Hospital, Taichung, Taiwan. METHODS: A consecutive series of 406 eyes of 212 patients who had LASIK was retrospectively evaluated. Uncorrected visual acuity (UCVA) was measured and corneal topography performed preoperatively and 1 week and 1, 3, 6, and 9 months postoperatively. Best spectacle-corrected visual acuity (BSCVA) was evaluated preoperatively and 1, 3, and 6 months postoperatively. RESULTS: The topographic images obtained at 1 week demonstrated central islands in 23 eyes of 20 patients (5.7%). No new cases of central island formation were identified after 1 week. Of the 23 eyes with central islands, the 6 month post-LASIK maps were available in 20 eyes of 18 patients. There was a significant difference in the size and power of the central islands between 1 week and 6 months. However, the power and size decreased slowly. Within 6 months, only 5 of 20 central islands (25.0%) had resolved. Eight eyes were undercorrected, and 1 eye lost 2 lines of BSCVA. Central islands larger than 1.8 mm or 3.0 diopters (D) were significantly correlated with lower UCVA. CONCLUSION: Most central islands that occur with LASIK persist more than 6 months. Large central islands (>/=1.8 mm or >/=3.0 D) are risk factors for lower UCVA. Preventive measures are necessary.

Antioxidant and hepatoprotective effects of Anoectochilus formosanus and Gynostemma pentaphyllum.

Anoectochilus formosanus Hay. and Gynostemma pentaphyllum Makino are popular folk medicines that have been used for treating hepatitis, hypertension and cancer in Taiwan. Our previous studies showed that these crude drugs exert antiinflammatory activity and hepatoprotective activity against CC14-induced liver damage. In this study, the antioxidant effect of these crude drugs and their hepatoprotective activity on acetaminophen-induced liver injury in rat was evaluated. Our results suggest that A. formosanus and G. pentaphyllum do have antioxidant effects. On acetaminophen-intoxicated model, the increased levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) by acetaminophen administration were reduced by treatment with these two herbs. In histological observation, gross necrosis in the centribular area, sinusoidal congestion, infiltration of the lymphocytes and Kupffer cells around the hepatic central vein, and loss of cell boundaries and ballooning degeneration were reduced with herbal treatment. However, the effect of A. formosanus and G. pentaphyllum is biphasic. Methanol extract (100 and 300 mg/kg) and water extract (300 and 500 mg/kg) of A formosanus and water extract (100, 300 and 500 mg/kg) of G. pentaphyllum enhanced the recovery of liver injury while treatment with 500 mg/kg of A. formosanus methanol extract resulted in serious hepatic injury.

Ablation centration after active eye-tracker-assisted photorefractive keratectomy and laser in situ keratomileusis.

PURPOSE: To evaluate the ablation centration after active eye-tracker-assisted photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) and to investigate the effect of surgery, patient, and surgeon on the centration. SETTING: Department of Ophthalmology, China Medical College Hospital, Taichung, Taiwan, Republic of China. METHODS: This retrospective study comprised 177 eyes of 101 patients: 16 eyes had PRK and 161, LASIK. All laser treatments were performed with the aid of an eye tracker. The amount of decentration was analyzed by corneal topography. The factors influencing centration were divided into surgery related (PRK/LASIK), patient related (low/high myopia and effect of learning), and surgeon related (learning curve). RESULTS: The mean decentration was 0.33 mm in PRK eyes and 0.35 mm in LASIK eyes. For the surgery-related factor, there was no significant difference between the PRK and LASIK eyes. For the patient-related factors, centration was better in the second eye (effect of learning) and decentration was more severe in eyes with high myopia (low/high myopia). For the surgeon-related factor, there was no significant difference between eyes that had the first 50 LASIK procedures and those that had the last 50 procedures. CONCLUSIONS: An eye tracker, which makes the laser beam follow the eye's movements, helps to avoid severe decentration. This study showed, however, that an active eye-tracking system alone cannot ensure good centration. Patient cooperation and fixation are important.