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Background Sirius system,a new Scheimpflug camera combined with Placido topography,improved the capability of imaging the anterior eye segment significantly.However,the study of assessing the repeatability and agreement between Sirius and Pentacam is still lack up to now.Objective This study was to evaluate the repeatability and agreement of the anterior ocular segment measuring parameters by Sirius and Pentacam in myopia received laser in situ keratomileusis (LASIK).Methods Thirty-five myopic eyes of 35 patients received LASIK were included in School of Optometry and Ophthalmology Eye Hospital from 2010 May through 2010 July.Corneal power flat keratometry (Kf),step keratometry (Ks),mean keratometry (Km),thinnest corneal thickness(TCT),the location of TCT,anterior chamber depth (ACD) and anterior chamber volume (ACV) were measured by Sirius and Pentacam in all the eyes,respectively.The repeatability of the measuring results were evaluated using intraclass correlation coefficients (ICC) and Cronbach's coefficient alpha (CoA),and the agreement of measuring parameters between Sirius and Pentacam was analyzed using Bland-Altman plot.Results Both Sirius and Pentacam demonstrated high intraobserver repeatability,with all ICC and CoA more than 0.90.No significant differences were found in Kf values and Ks values between the two methods (t =-1.533,-1.750,P＞0.05).Km value was (39.14 ± 1.95) D by Sirius measurement,which was sígnificantly higher than (39.05 ± 1.91) D by Pentacam measurement (t =3.572,P =0.001).The TCT was (457.6 ± 40.9) μm by Sirius method,showing a significant reduce in comparison with (465.4±37.5) μm of Pentacam method (t =-6.689,P＜0.001).A positive correlation was seen in the TCT between the two methods (r=0.988,P＜0.001).The Bland-Alrman plots showed the 95％ CI-21 μm to 6 pm in the TCT value between the two devices.Pairwise comparison of the location of TCT measurements showed significant differences between the two devices (t =-4.132,-5.696,P＜0.001),with a good correlation (r=0.751,0.775) and the 95％ CI (-0.36-0.17 mm,-0.35-0.12 mm).A very good agreement was seen in ACD between the two devices (-0.02-0.12 mm),but the agreement result was not very well in the ACV between the two devices with the 95％ CI (-27.70-6.20 mm3).Conclusions Sirius and Pentacam measurements for anterior ocular segment parameters have a very good repeatability in post-LASIK eyes.In addition,good agreement results are exhibited in corneal power,TCT and ACD between Sirius and Pentacam with an acceptable maximal different value between them.Sirius and Pentacam can be used interchangeably in clinical examination.However,the two devices can not interchangeably for ACV measurement and TCT location.
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Background Central corneal thickness (CCT) is one of important parameters of the anterior eye segment.It plays a very important part in corneal refractive surgery and diagnosis of glaucoma.Contacted A-scan remains the gold standard for CCT measurement.Ophthalmologists are trying to look for a more convenient and noncontacted instrument to take place of contacted A-scan for CCT measurement.Objective This system analysis was to evaluate the difference between Pentacam and A-scan in CCT measurement.Methods A systematic literature retrieval was conducted from the MEDLINE,EMbase,Google Scholar,CBM disc and CNKI database with the limitation of publishing time from January 2005 to May 2011.The literature text was limited to the comparison of the CCT values measured by Pentacam and A-scan.The statistical analysis was performed using RevMan 5.1.0 software.Sensitive analysis was carried out and the publishing bias was analyzed using inverted funnel plot.Results A total of 26 studies met the requirement were included in this Meta-analysis with the 12 pieces of Chinese article and 14 pieces of English article,with the total eyes 3677.Heterogeneity was found anmong included studies (P =0.0003,I2 =56％) and random effects model was used.The differential value of CCT derived by Pentacam and A-scan was 1.74 μm,and no significant difference was found between Pentacam and A-scan (WMD =1.74,95％ CI:-0.69-4.16,P＞0.05).Fixed effects model was used to exclude the studies with the sample more than 100 eyes as the sensitive analysis.When fixed effect model was used,CCT by Pentacam was 2.73 μm more than A-scan,showing an insignificantly clinical difference.When studies with a sample more than 100 eyes were excluded,the CCT value by Pentacam was 2.64 μm more than A-scan,without clinically significant difference between them.No obvious publishing bias was seen in the included literature.Conclusions The difference between Pentacam and A-scan in CCT measurement is less and could be ignored.
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Background Corneal parameters (such as curvature,thickness,etc) are essential to the diagnosis of corneal related diseases,contact lenses fitting and corneal refractive surgery.Objective The aim of this study was to assess the repeatability and accuracy of corneal parameters obtained by RTVue Fourier-domain optical coherence topography (FD-OCT).Methods In this prospective study,77 eyes of 43 subjects with the refraction from-1.25 D to-10.00 D and astigmatism ＜2 D were enrolled in keratorefractive surgery center,Eye Hospital of Wenzhou Medical College.The anterior and posterior corneal curvature in 3 mm central zone (Ranterior and Rposterior),the ratio of posterior and anterior curvature (Rposterior/Ranterior),corneal central thickness (CCT),total corneal power(Knet),the simulated corneal power (Sim K),the anterior and posterior corneal power (Kanterior,Kposterior)were measured by FD-OCT.Corneal power (Km) was obtained by Topolyzer topography based on Placido ring.Three consecutive scans were acquired in every tested eye.Repeatability of FD-OCT measurement was assessed using the coefficient of variation CV),Cronbach Alpha and intra-class correlation coefficient (ICC).Repeated measure ANOVA was used to analyze the differences among SimK,Knet and Km.Pearson correlation analysis was used to analysis the correlation between SimK and K Knet and Km,SimK and Km.The agreement between Sim K and K Knet and Km,SimK and Km was assessed by Bland-Altman plots analysis.All the subjects understood the purpose of this investigation and written informed consent was obtained prior to the medical examination.Results The Ranterior,Rposterior,Rposterior/Ranterior,Kanterior,Kposterior,Sim K,Knet and CCT were (7.691 ±0.302) mm,(6.532±0.276) mm,0.849±0.014,(48.97±1.92)D,(-6.13±0.26)D,(43.95±1.72) D,(42.95±1.68) D and (545.20± 35.04) μm,respectively.The CV of all parameters was less than 1％.The Cronbach Alpha and ICC were both more than 0.9 except 0.802(ICC)of the Rposterior/Ranterior.SimK was (0.27±0.34) D higher than Km,and Knet was (0.73±0.37) D lower than Km.SimK was (1.01 ±0.11) D higher than K and all the differences showed a statistical significance (P＜0.001).There were close positive correlations between SimK and Km,Knet and Km,SimK and Knet(all r ≥ 0.976,P＜0.001).The Bland-Altman analysis showed a poor agreement between SimK and Km,Knet and Km,SimK and Knet.Conclusions The RTVue FD-OCT measuring corneal curvature and CCT performes good repeatability.The Sim K obtained by RTVue FD-OCT is slightly greater than that obtained by corneal topography,and the Rposterior/Ranterior obtained by RTVue FD-OCT is slightly lower than that from Gullstrand model eye.These results offer a basis for establishing a more accurate standardized model eye.
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Stray light is a physical phenomenon that degrades visual quality when light scattering occurs in the human eye.It is a main cause of the disabling glare.Stray light originates in cornea,iris,sclera,lens and retina,and these ocular tissues contribute to the total amount of stray light in a normal eye.The light scattering intensity increases when the transparency of any optical element mentioned above reduces.Stray light can be measured by several different methods,but the measurements still lacks a standardized procedure and outcome.Further clinical study is necessary to quantify and standardize the measuring method of stray light.This article aims to introduce the concept,source and clinical significance of stray light,and to provide its advanced measurement techniques and methods.
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Background Both functional and morphological changes in amblyopic development are known to occur at various levels in the central visual pathway.However,whether the retina is involved or not during amblyopic progression remains controversial.Objective This study was designed to compare the thicknesses of the fovea and retinal nerve fiber layer (RNFL) of the normal fellow eye of amblyopic eye using optical coherence tomography (OCT) in children with myopic anisometropia.Methods Twenty-two patients with unilateral myopic anisometropic amblyopia were included as the anisometropia amblyopia group.Ten unilateral myopic anisometropic amblyopia subjects received treatment and recovered were used as the amblyopic cure group,and 11 individuals with simple myopic anisometropia without amblyopia were enrolled as the control group.OCT was performed on both eyes of all the subjects with informed consent.Fovea retinal thickness and RNFL thickness from the superior,inferior,nasal and temporal quadrants in the peripapillary region were evaluated.The measurement parameters were bilaterally compared in all the individuals by paired t test.The multiple regression model was used to analyze the correlation of retinal thickness with amblyopia patients.This study was approved by the Ethic Committee of this hospital.Written informed consent was obtain from each subject prior to the eye examination.Results Fovea retinal thickness increased in the amblyopic eyes compared with the fellow eyes,showing a statistically significant difference between them (P =0.001).However,no significant differences were found in the fovea retinal thickness between both eyes in the amblyopic cure group and simple myopic anisometropia without amblyopia group (P =0.778,0.943).Among the anisometropia amblyopia group,amblyopia cure group and simple myopic anisometropia without amblyopia group,the RNFL thicknesses of the temporal quadrant was significantly thicker in the higher myopic lateral eyes than those of the fellow eyes (P＜0.001,P =0.003,P =0.046).However,the differences in the superior,inferior,nasal and the average RNFL thickness were not statistically significant between the two eyes (P＞0.05).A negative correlation was found between the inferior retinal thickness with age (r=-0.559,P=0.016).Conclusions The fovea may be affected in unilateral myopic anisometropic amblyopia.There is no significant difference in the RNFL thickness between simple myopic eye and unilateral myopic anisometropia amblyopic eye.Improvement in amblyopia is coming along with the reduction of the thickness of the fovea.
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Background Central corneal thickness (CCT)is an important parameter to evaluate corneal healthy status and is crucial for surgical planning.However,clinical study found that the center of cornea does not correspond to the thinnest point of cornea.Thus,it is essential to characterize the minimum corneal thickness(MCT) and its location.Objective Present study was to determine the thickness and location of MCT and its relationship to the fellow eye using Pentacam High Resolution technique.Methods The 564 eyes from 282 Chinese myopic patients were reviewed in this study.The CCT,MCT,pupillary central corneal thickness(PCT) and x-y coordinate of thinnest point were bilaterally measured.Written informed consent was obtained prior to the ocular biomedical measurement.Results CCT was (540.07±31.78) μm in the right eyes and (539.24±31.06) μm in the lefi eyes; PCT was (540.25±30.75)μm in the right eyes and (539.48±31.00)μm in the left eyes.MCT was (537.87± 31.91)μm in the right eyes and (536.35±31.24)μm in the left eyes,showing significant differences in all the parameters between the right eyes and left eyes expect for PCT(CCT:P=0.046;PCT:P=0.065 ;MCT:P=0.000).The C CT,PCT and M CT were significantly correlated between the right eyes and left eyes (r =0.97,0.97,0.98,P＜ 0.01).Bland-Altman plot showed a good consistence between the both eyes.The mean distance from the center was (0.50±0.21) mm in the right eyes and (0.56±0.22)mm in the left eyes,showing a significant difference (P =0.000).The difference between CCT and MCT was approximately (2.20±1.74)μm in the right eyes and (2.88±1.75) μm in the left eyes.The location of MCT in both the right eyes and left eyes tended to symmetry along the vertical midline.The distance between the R (x,y) to transformed L (x,y) was (0.29 ± 0.17)mm and the angular distance was (28.28±28.21)degree.Conclusions This study offers a range of MCT and its location in Chinese myopic patients.The difference exists between the CCT and MCT in bilateral eyes.The location of the thinnest point tends to be symmetrical along the vertical midline between the both eyes.The changes of these parameters may be helpful for the diagnosis of some corneal diseases.
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BackgroundIn an ideal eye there would be no light scattering at all,but the eye media is not optically ideal.Intraocular straylight causes a veil of light and reduction in the contrast of the retinal image and thus decrease the quality of vision.ObjectiveThe present study was to investigate the repeatability and reproducibility of C-Quant straylight meter( Oculus,Germany)in measuring retinal straylight of myopia and post-laser in situ keratomileusis(LASIK) corneas.MethodsThis is a prospective research.The consecutive 35 eyes of 21 myopic patients and 34 eyes of 22 patients who received LASIK were included in this trail.Retinal straylight was measured for 7 times at a period of time and analyzed quantificational to evaluate the repeatability of measurement.Thirty-eight eyes of 19 patients were measured again at 3-7 days for 3 times at a period of time to assess the reproducibility of C-Quant straylight meter.The mean standard difference (SD) and coefficient of variation (CV) were used as the credibility evaluation.This clinical study complied with Helsinki Declaration and the informed consent was obtained prior to the medical procedure.ResultsThe straylight Log(s) of 7 times measurement were all less than 0.95.The mean Log(s) were 0.92±0.12 and 0.93±0.17 respectively in myopia group and post-LASIK group,without statistically significant differences among 7 times measurement( F=0.335,P=0.812;F=1.000,P=0.409).The mean SD for the 7 times measurement was 0.07 Log units.SD and CV increased with the number of measurements.The differences of mean SD and CV between 3 times result and 6 times result were significant different (t =-2.080,P =0.045;t =-2.190,P =0.035 ).No difference was found between different time periods( t =-0.531,P=0.598 ).The difference of the results between two measurements from the same patient was 0.013.ConclusionsC-Quant is a noncontact,noninvade,rapid and convenient method for the measurement of straylight in myopia and post-LASIK eyes due to the high repeatability and reproducibility.
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Background Clinical research showed that the corneal endothelial cell density value from different corneal specula microscopies exist diversity.The relevant literature of SP02,Tomey EM-3000 and SP3000P is still seldom up to now. Objective This research was to assess the repeatability of endothelial cell density measurements by SP02,Tomey EM-3000 and SP3000P respectively and the agreement among 3 kinds of endothelial microscopes.MethodsFifty-four healthy volunteers with the age 17-38 years old were included this research.The written informed consent was obtained from each subject before examination.The corneal endothelial cell densities in the right eyes were analyzed with SP02,Tomey EM-3000 and SP3000P respectively for 3 times under the automatic mode,and the analytical procedure of SP3000P measurement were divided into automatic mode SP3000P (A) and manual correction modes SP3000P( M).The repeatability of each specula microscopy was analyzed by calculating the intraclass correlation coefficients (ICC) and coefficient of variation ( CV ),and the 95％ confidence intervals and plotting Bland-Altman graphs were used to analyze the agreement among these methods.ResultsThe mean corneal endothelial cell densities in the population ＜24 years were significantly higher than the ones ≥ 24 years (t =3.692,P＜0.05 ),but no statistical difference was found between different gender ( t =0.335,P =0.739 ).The mean corneal endothelial cell densities were ( 3058 ± 260 ),( 2954 ± 229 ),( 2668 ± 258 ),( 2734 ± 268 ) cell/mm2 ; the ICCs were 0.957,0.940,0.972 and 0.972 and the CV were 0.063,0.061,0.056,0.058 for SP02,Tomey EM-3000,SP3000P (A) and SP3000P ( M ) respectively.The 95％ confidence intervals were ( - 100.8 - 306.8 ),( 162.6 - 617.4 ),( 109.9-494.1 ) and ( -0.6 - 132.6 ) cell/mm2 for between SP02 and Tomey EM-3000,SP3000P ( A ) and SP02,SP3000P(A) and Tomey EM-3000,SP3000P(A) and SP 3000P(M) respectively.ConclusionsSP02,Tomey EM-3000 and SP3000P(A) have good repeatability in the measurement of corneal endothelial cell density,however the outcome is different.Therefore,it is not interchangeable for the detection of corneal endothelial cell density.The differences of corneal endothelial cell density obtained from these instruments shall be paid high attention for their differences.SP3000P(A) and SP3000P(M) can be used interehangeably and SP3000P(A) is a preferable choice due to its convenience and quickness.
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Background Biometry of the anterior ocular segment parameter is very important for the diagnosis and treatment of glaucoma and ocular injury as well as measurement of intraocular lens(IOL).Objective This study was to compare the differences in the anterior chamber depth(ACD) and the central corneal thickness (CCT) between Sirius and Pentacam and evaluate the agreement of these two measurement methods.Methods The ACD and the CCT of 38 right eyes from 38 health volunteers aged 23- 32 years were measured with both Pentacam and Sirius.Three times of measurement were pedormed on each eye for each method to obtain the average values.The repeatability and agreement from each method were assessed as intraclass correlation coefficient( ICC ) and coefficient of variation(CV) and the agreement between these two methods were evaluated using Bland-Altman mode.ResultsThe mean ACD value was( 3.18±0.21 ) mm from Pentacam with the ICC 0.995 and CV 0.066.The mean ACD value from Sirius was (3.22 ±0.21 )mm with the ICC 0.996 and CV 0.065.The difference value in ACD between two methods was 0.04 mm,showing a significant difference( t =-6.225,P＜0.05 ) and a positive correlation (r=0.977) between two methods.The 95％ limit of agreement was( -0.04-0.13)mm within 1 standard difference (SD) of the mean value( ±0.21mm),which was acceptable for clinical measurement.The CCT was( 535±33 )μm from Pentacam with the ICC 0.994 and CV 0.062.The CCT was(537±36)pm from Sirius with the ICC 0.999 and CV 0.067.The difference value in the CCT between two methods was about 2 μm,presenting a in significant difference ( t =1.771,P＞0.05 ) and positive correlation ( r =0.985 ).The 95 ％ limit of agreement was ( - 11.64-15.65 ) μm within 1 SD of the mean value( ±34.27 pm),which was acceptable for clinical measurement.ConclusionsSirius and Pentacam show good agreement in the measurement of ACD and CCT.The two methods offer an alternative choice for the biological measurement of the anterior ocular segment.
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Background Axial length and anterior chamber depth are important parameters for the calculation of diopter of intraocular lens ( IOL ). Objective This study was to investigate and compare the measuring outcomes of axial length and anterior chamber depth with IOLMaster,Axis- Ⅱ A-scan and ODM 1000A sonograph.Methods This a observational study.Axial length and anterior chamber depth were measured in 83 eyes of 48 patients with IOLMaster,Axis-Ⅱ A-scan and ODM 1000A sonograph by the same operator.The measuring results were compared among the three methods.Results The axial length were(25.79±0.85) mm,(25.72± 0.82 )mm and ( 26.00 ±0.83 )mm respectively with Axis- Ⅱ,ODM 1000A sonograph and IOLMaster.The difference between Axis-Ⅱ and DM 1000A sonograph was (0.07 ± 0.35 )mm without statistical difference between them (t=1.711,P =0.091 ).The difference of axial length between IOLMaster and DM 1000A sonograph was ( 0.27 ±0.29) mm with a statistical difference between them ( t =-8.570,P =0.000 ).The difference between IOLMaster and Axis- Ⅱ was (0.21 ±0.32 ) mm and showed a statistical difference ( t =- 5.931,P ＜ 0.01 ).The positive correlations were found in the axial length values by the each other comparison among the three instruments( r=0.916,0.938,0.928,P＜0.01 ).The anterior chamber depth values were ( 3.81 ±0.21 ) mm,( 3.84 ±0.25 ) mm and ( 3.83 ±0.18 )mm respectively with Axis-Ⅱ,0DM 1000A sonograph and IOLMaster.The difference of anterior chamber depth between Axis- Ⅱ and DM 1000A was (0.03 ±0.17 ) mm without statistical difference between them ( t =- 1.324,P =0.189 ).The difference in the anterior chamber depth between IOLMaster and DM 1000A was (0.01 ±0.15 ) mm and that between IOLMaster and Axis-Ⅱ was( 0.01 ±0.12)mm without any statistical differences among them (t =0.815,P=0.417 ;t=-0.900,P=0.371 ).The high correlation between anterior chamber depth measurements were found by the each other comparison in the three instruments ( r =0.735,0.813,0.823,P ＜ 0.01 ).Conclusions ODM 1000A sonograph can provide precise axial length and anterior chamber depth values.However,ODM 1000Asonograph can not substitute for IOLMaster in the measurement of the anterior chamber depth and axial length.