Spectral Domain Optical Coherence Tomography of Vogt-Koyanagi-Harada Disease: Novel Findings and New Insights into the Pathogenesis

Objective To provide novel spectral domain optical coherence tomography (SD OCT) findings of Vogt-Koyanagi-Harada (VKH) disease as well as new insights into the pathogenesis of this disease. Methods Detailed SD OCT and fluorescein angiography (FA) findings of 18 consecutive VKH patients (11 women and 7 men) from December 2007 to April 2009 who were in acute uveitic stage at presentation were reviewed. All the patients had been followed up for at least 6 months with reevaluation(s) of SD OCT performed in 10 patients. Results Intraretinal cysts were found to be located in various layers of the outer retina. In addition to the photoreceptor layer, they could also be found between the outer plexiform layer and the outer nuclear layer, or spanning the external limiting membrane. On FA, intraretinal cysts could be hypofluorescent, normofluorescent, or hyperfluorescent. Some intraretinal cysts had a characteristic FA pattern, in which a small round hypofluorescent area was surrounded by a ring of hyperfluorescence (donut-shaped dye pooling). Subretinal fibrinoid deposit appeared in acute uveitic stage in two severe VKH patients and seemed to develop from subretinal exudates and evolved into typical subretinal fibrosis. Gradual transfiguration/migration and progressive proliferation/pigmentation of the subretinal fibrinoid deposit/subretinal fibrosis was observed in one patient. Conclusions Intraretinal cysts could form in various layers of the outer retina and may result from extension of choroidal inflammation. Subretinal fibrosis may develop from subretinal exudates in VKH patients and may cause substantial visual impairment.

Spectral domain optical coherence tomography crosssectional image of optic nerve head during intraocular pressure elevation

AIM: To analyze changes of the optic nerve head(ONH) and peripapillary region during intraocular pressure(IOP) elevation in patients using spectral domain optical coherence tomography(SD-OCT).METHODS: Both an optic disc 200×200 cube scan and a high-definition 5-line raster scan were obtained from open angle glaucoma patients presented with monocular elevation of IOP(≥30 mm Hg) using SD-OCT. Additional baseline characteristics included age, gender, diagnosis,best-corrected visual acuity, refractive error, findings of slit lamp biomicroscopy, findings of dilated stereoscopic examination of the ONH and fundus, IOP, pachymetry findings, and the results of visual field.RESULTS: The 24 patients were selected and divided into two groups: group 1 patients had no history of IOP elevation or glaucoma(n =14), and group 2 patients did have history of IOP elevation or glaucoma(n =10). In each patient, the study eye with elevated IOP was classified into group H(high), and the fellow eye was classified into group L(low). The mean deviation(MD)differed significantly between groups H and L when all eyes were considered(P =0.047) and in group 2(P =0.042), not in group 1(P =0.893). Retinal nerve fiber layer(RNFL) average thickness(P =0.050), rim area(P =0.015),vertical cup/disc ratio(P =0.011), cup volume(P =0.028),inferior quadrant RNFL thickness(P =0.017), and clockhour(1, 5, and 6) RNFL thicknesses(P =0.050, 0.012, and0.018, respectively), cup depth(P =0.008), central prelaminar layer thickness(P =0.023), mid-inferior prelaminar layer thickness(P =0.023), and nasal retinal slope(P =0.034)were significantly different between the eyes with groups H and L.CONCLUSION:RNFLaveragethickness,rim area,vertical cup/disc ratio, cup volume, inferior quadrant RNFL thickness, and clock-hour(1, 5, and 6) RNFL thicknesses significantly changed during acute IOP elevation.

Systematic review of macular ganglion cell complex analysis using spectral domain optical coherence tomography for glaucoma assessment

AIM: To review the use of spectral domain optical coherence tomography(SD-OCT) for macular retinal ganglion cells(RGC) and ganglion cell complex(GCC) measurement in glaucoma assessment, specifically for early detection and detection of disease progression. METHODS: A systematic review was performed by searching Pub Med, Medline, and Web of Science for articles published in English through July 2014 describing the various macular SD-OCT scanning strategies developed for glaucoma assessment. The review focused on papers evaluating the use of macular RGC/GCC SDOCT to detect early glaucoma and its progression. The search included keywords corresponding to the index test(macular ganglion cell/RGC/GCC/Spectral domain OCT), the target condition(glaucoma), and diagnostic performance. The RGC/GCC SD-OCT scanning strategies used to assess glaucoma of most commonly used SD-OCT instruments were described and compared. These included the Cirrus high definition-OCT(Carl Zeiss Meditec, Inc., Dublin, CA, United States), RTVue(Optovue, Inc., Fremont, CA, United States), Spectralis(Heidelberg Engineering, Heidelberg, Germany) and the 3D OCT 2000(Topcon Corporation, Tokyo, Japan). Studies focusing on the ability of RGC/GCC SD-OCT to detect early glaucomatous damage and on the correlation between glaucomatous progression and RGC/GCC measurement by SD-OCT were reviewed.RESULTS: According to the literature, macular RGC/GCC SD-OCT has high diagnostic power of preperimetric glaucoma, reliable discrimination ability to differentiate between healthy eyes and glaucomatous eyes, with good correlation with visual filed damage. The current data suggests that it may serve as a sensitive detection tool for glaucomatous structural progression even with mild functional progression as the rate of change of RGC/GCC thickness was found to be significantly higher in progressing than in stable eyes. Glaucoma assessment with RGC/GCC SD-OCT was comparable with and sometimes better than circumpapillary retinal nerve fiber layer thickness measurement.CONCLUSION: An increasing body of evidence supports using macular RGC/GCC thickness as an indicator for early glaucoma. This might be a useful tool for monitoring disease progression.

Microperimetry and spectral domain optical coherence tomography in myelinated retinal nerve fibers

Dear Sir,I write to present the correlation between microperimetric （MP） values and the density of myelinated retinal nerve fibers （MNFs） in optical coherence tomography （OCT） imaging.

Comment on “The diurnal variation pattern of choroidal thickness in macular region of young healthy female individuals using spectral domain optical coherence tomography”

Dear Editor,We have read and reviewed the article entitled＂The diurnal variation pattern of choroidal thickness in macular region of young healthy female individuals using spectral domain optical coherence tomography＂by Zhao et al^（[1]）with great interest.

Comparison of central macular thickness between two spectral-domain optical coherence tomography in elderly non-mydriatic eyes

AIM: To compare central macular thickness (CMT) measurements obtained by two spectral-domain optical coherence tomography (SD-OCT) exams, and to evaluate measurement reproducibility and agreement between these two exams, and to investigate the relationship between CMT and possible influencing factors such as age, sex, eye (OD/OS), and operators in elderly non-mydriatic eyes. METHODS: Seventy-two normal subjects were included. Every subject underwent CMT measurement twice using one of two SD-OCT (OSE-2000, Moptim, Shenzhen, China & 3-D OCT-1000, Topcon, Tokyo, Japan) instruments respectively where we randomly chose one eye in each patient for the test; these exams were performed by two operators over an hour period with a brief rest between sessions. Comparison of the OSE-2000 and 3-D OCT-1000 CMT measurements was based on paired- t test The mean difference between the CMT measurements was calculated. General linear model analyzed the relationships among eye (OD/OS), operator, sex, and CMT values using age as co-variant. All tests were considered statistically significant at P <0.05. The main outcome measures included CMT. RESULTS: When evaluated with general linear model analysis, CMT measurements were found to have high reproducibility across the two instruments between the two operators for the OSE-2000 single line scan and 3-D OCT-1000 macular scans (P=0.731; P=0.443). There was statistically significant difference in CMT values between the two instruments (P<0.001) and the mean difference was -46.83 mu m at 95% confidence limits (-49.15,-44.51). Age was positively correlated with CMT (beta coefficient =0.516, P=0.001; beta coefficient=0.453, P =0.009) and sex was correlated with CMT from the OSE-2000 (P=0.021) but not with the 3-D OCT-1000 (P=0.056). According to the actual thickness measurements, the CMT of the male was thicker than the female's but there was no statistical difference. There was interaction between sex and eye in OSE-2000 and not in 3-D OCT-1000 (P=0.02; P =0.374). No significant correlation was found between CMT and the influencing factor of eye in both of the instruments (P=0.884; P=0.492). CONCLUSION: Reproducibility of CMT measurement using the two SD-OCTs is excellent in normal eyes according to the operator factor analysis. OSE-2000 has a different posterior retinal boundary of CMT measurement, which results in the CMT value differences, compared with the 3-D OCT-1000. Age is positively correlated with CMT measurement while sex is correlated with CMT in the OSE-2000 but not in the 3-D OCT-1000 and eye (OD/OS) had no correlation with CMT values. Mydriatic drops may not be necessary for CMT measurement using high scan rate SD-OCT in normal eyes in dark room.

Choroidal Analysis of Polypoidal Choroidal Vasculopathy by Spectral Domain Optical Coherence Tomography

Purpose: This study was designed to measure the changes in the subfoveal choroidal thickness(SFCT) and choroidal maximal vessel diameter(MVD) of the affected and unaffected fellow eyes in patients with polypoidal choroidal vasculopathy(PCV) and compare them to healthy controls.Methods: In this cross-sectional observational clinical study,SFCT and MVD were measured in both eyes of 53 patients with unilateral PCV. PCV eyes were subgrouped into group A and unaffected fellow eyes into group B. All patients were diagnosed with PCV by fundus fluorescein angiography.(FFA)and indocyanine green angiography.(ICGA). Sixty age- and gender-matched healthy subjects were enrolled in the control group(group C).Results: No statistical difference was observed among groups in age and gender. Overall, SFCT was correlated with MVD in all subjects(P <0.001; correlation coefficient: 0.759). P values were < 0.001 with a correlation coefficient of 0.686,0.801, and 0.808 in groups A, B, and C, respectively. No statistical significance was noted in SFCT among groups A(266.45±99.51 μm),B(269.57 ± 105.10 μm),and C(243.83±99.68 μm)(P =0.335). However, the MVD in group A was(202.55±72.45 μm), significantly larger than that in group C(166.45 ±56.18 μm,P =0.008), while the MVD in group B(194.75±85.27 μm) was equally significantly greater than that in group C(166.45 ± 56.18 μm)(P=0.038).Conclusion: For both PCV patients and healthy subjects,SFCT was positively correlated with MVD. No statistical significance was noted in SFCT between PCV eyes and unaffected fellow / normal eyes. However, MVD was significantly larger in the PCV affected eyes than in unaffected fellow or normal control eyes, suggesting that MVD could be considered as a sensitive indicator to evaluate choroidal perfusion in PCV patients.

1310 nm Source Spectral-Domain Optical Coherence Tomography for Chinese Pigment and Jadeite Research

Optical Coherence Tomography (OCT) technique is a nondestructive optical detection technology based on low-coherence interferometer and it has become an attractive cultural heritage research method. A 1310 nm source spectral-domain optical coherence tomography (SD-OCT) system based on optical fiber Michelson interferometer and optical spectrum analyzer is proposed and demonstrated for Chinese cultural heritage research. The cross-section OCT images of Chinese pigment samples and jadeite samples can provide a lot of valuable microstructure information for the Chinese cultural heritage research and identification works.

Comparison of Ziemer FEMTO LDV "Classic" and " Crystal Line" femtosecond laser flap quality by Fourierdomain optical coherence tomography

AIM:To compare the regularity and accuracy of laser in situ keratomileusis(LASIK) flaps created by the Ziemer FEMTO LDV 'Classic'(Ziemer 'Classic') and Ziemer FEMTO LDV Crystal Line femtosecond laser(Ziemer Crystal Line). METHODS:Fourier-domain optical coherence tomography(RTVue OCT) was used to measure the morphology of 200 LASIK flaps of 100 consecutive patients created with the Ziemer Classic(100 flaps) or the Ziemer Crystal Line(100 flaps) at one week postoperatively.Flap thickness was evaluated at 36 specified measurement points on each flap.For all procedures with both lasers,the nominal flap thickness was 110μm.RESULTS:The mean flap thickness of the Ziemer Crystal Line group(102.49±2.68μm) was thinner than that of the Ziemer Classic group(107.65±5.09μm)(P【0.01).Average thickness of all flaps was uniform within 4μm at all measurement points.The flaps in the Ziemer Crystal Line group were more regular than those in the Ziemer Classic group when measured from the center to the periphery.The maximum deviation from the nominal 110μm of 36 measurements was 8μm in the Ziemer Classic group,while in the Ziemer Crystal Line group it was 9μm.Within the 3 600 measurements on the 100 eyes,differences greater than 20μm were observed 0.14% in the Ziemer Classic group,and 0.04% in the Ziemer Crystal Line group. CONCLUSION:The flaps created with the Ziemer FEMTO LDV Crystal Line femtosecond laser are more uniform and thinner than those created by the Ziemer FEMTO LDV Classic femtosecond laser.

Central choroidal thickness in children and adolescents with anxiety disorders:enhanced depth imaging optical coherence tomography findings

AIM:To measure the central choroidal thickness(ChT)in children and adolescents with anxiety disorders.METHODS:Totally 41 anxiety patients(8-16 y)and 35 healthy controls(age-matched)were evaluated.Complete ophthalmic examination was performed.Inclusion criteria were best corrected visual acuity≥20/20,normal intraocular pressure(IOP;10-21 mm Hg),and no systemic or ocular diseases according to history.The diagnosis of psychiatric disorders was determined using Schedule for Affective Disorders and Schizophrenia for School Aged Children Present-Lifetime Version(K-SADS-PL).Enhanced depth imaging optical coherence tomography(EDI-OCT)was used to measure the central ChT.RESULTS:The mean age was 12.18±3.24 y in the patient group and 12.86±3.15 y in the control group.Age and gender distribution of the two groups was similar.Central ChT mean value was 353.26±31.9μm in anxiety patients while 318.75±60.9μm in the control group.Mean central ChT was statistically significantly higher in the children and adolescents with anxiety disorders than healthy controls(P=0.002).CONCLUSION:The children and adolescents with anxiety disorders have significantly thicker central ChT than controls.In the larger sample,longitudinal studies will contribute to the use of choroidal differences as a clinical marker for monitoring anxiety disorders.

BINARY TISSUE CLASSIFICATION STUDIES ON RESECTED HUMAN BREAST TISSUES USING OPTICAL COHERENCE TOMOGRAPHY IMAGES

We report the results of a comparative study of Fourier domain analysis(FDA)and texture analysis(TA)of optical coherence tomography(OCT)images of resected human breast tissues for binary classification between normal
abnormal classes and benign
malignant classes.With the incorporation of Fisher linear discriminant analysis(FLDA)in TA for feature extraction,the TA-based algorithm provided improved diagnostic performance as compared to the FDAbased algorithm in discriminating OCT images corresponding to breast tissues with three different pathologies.The specificity and sensitivity values obtained for normal
abnormal classification were both 100%,whereas they were 90% and 85%,respectively for benign
malignant classification.

WAVELENGTH PROBING OPTICAL COHERENCE TOMOGRAPHY

In swept-source optical coherence tomography(SSOCT),the swept-source stimulates system by a series of wavelengths in time sequence;a photo detector then collects all reflected/backscattered light from testing sample as the components of Fourier series.Due to the nature of the SSOCT,the processing in spectral domain can merge multiple swept-sources with different central wavelengths,which greatly increases the resolution of the OCT imaging.In the wavelength probing OCT,a standard broadband SSOCT system is used to extract the internal structure of the sample,and another narrow band light can be used to probe the spectral feature of the sample at the probing wavelength.

Renal function and choroidal thickness using swept-source optical coherence tomography in diabetic patients

AIM: To assess the relationship between choroidal thickness and renal function in diabetic patients. METHODS: Cross-sectional retrospective clinical study of 42 eyes of 21 ocular treatment-na?ve diabetic patients. Demographic data included: age, sex, type and course of diabetes. Ocular data included: severity of diabetic retinopathy;retinal thickness at the central macular region, as well as choroidal thickness at the central and paracentral quadrants, using automatically generated maps by swept-source optical coherence tomography;presence of cystic macular edema;and ocular axial length(AXL). Lab-test parameters included: glycated hemoglobin(HbA1c), albuminuria, albumin/creatinine ratio in urine, and glomerular filtration rate. RESULTS: A significant negative correlation was mainly observed between several choroidal thicknesses, age(P<0.020) and ocular AXL(P<0.030). On the contrary, a significant positive correlation was found between all choroidal thicknesses, HbA1 c(P<0.035) and albuminuria(P<0.040). CONCLUSION: Choroidal thickness can represent an additional tool to help clinicians predicting the renal status in ocular treatment-na?ve diabetic patients.

Angle-to-angle and spur-to-spur distance analysis with high-resolution optical coherence tomography

Background:To measure angle-to-angle(ATA)and spur-to-spur(STS)distances along six meridians using highresolution swept-source optical coherence tomography(SS-OCT)and to compare those values with horizontal white-to-white(WTW)distance.Methods:Sixty-eight eyes from 68 patients were quantitatively assessed with the Anterion SS-OCT(Heidelberg Engineering,Heidelberg,Germany).ATA and STS distances were measured with the SS-OCT B-scan in six cross-sectional images corresponding to the vertical(6-12 o'clock),1-7 o'clock,2-8 o'clock,horizontal(3-9 o'clock),4-10 o'clock and 5-11 o'clock meridians.WTW was measured horizontally with the device's infrared camera.A Pearson correlation analysis was carried out to compare ATA and STS distances with WTW.Results:The largest values were found for the vertical meridian and the shortest for the 2-8 o'clock meridian,both for ATA and STS distances.No statistically significant differences were found between WTW,ATA and STS along the horizontal meridian(P>0.1).However,ATA and STS showed statistically significant differences elsewhere,except for the horizontal and the 2-8 o'clock meridians(P>0.05).Moreover,we found that ATA and STS varied significantly depending on the meridian being assessed,except for ATA at 4-10 versus 3-9 o'clock and for STS at 4-10 versus 3-9 o'clock and at 3-9 versus 2-8 o'clock(P>0.1).R2 values ranged from 0.49 to 0.75 for ATA and STS at the different meridians,showing the best correlation at 3-9 o'clock meridian(0.64 and 0.75,respectively)and the worst at 6-12 o'clock meridian(R2=0.49 for both ATA and STS).Conclusions:ATA and STS distances vary radially,thus showing that the anterior chamber is vertically oval.Therefore,it is advisable to measure these two distances along the meridian to be used.

Numerical Study on Spectral Domain Optical Coherence Tomography Spectral Calibration and Re-Sampling Importance

A spectral calibration technique, a data processing method and the importance of calibration and re-sampling methods for the spectral domain optical coherence tomography system were numerically studied, targeted to optical coherence tomography （OCT） signal processing implementation under graphics processing unit （GPU） architecture. Accurately, assigning the wavelength to each pixel of the detector is of paramount importance to obtain high quality images and increase signal to noise ratio （SNR）. High quality imaging can be achieved by proper calibration methods, here performed by phase calibration and interpolation. SNR was assessed employing two approaches, single spectrum moving window averaging and consecutive spectra data averaging, to investigate the optimized method and factor for background noise reduction. It was demonstrated that the consecutive spectra averaging had better SNR performance.

Comparing imaging capabilities of spectral domain and swept source optical coherence tomography angiography in healthy subjects and central serous retinopathy

Background:There are two forms of system implementation of optical coherence tomography angiography(OCTA)in ophthalmic imaging,i.e.,spectral domain(SD-)and swept source OCTA(SS-OCTA).The purpose of this paper is to compare the SD-OCTA and SS-OCTA for elucidating structural and vascular features associated with central serous retinopathy(CSR),and to evaluate the effects of CSR on SD-and SS-OCTA’s imaging capabilities.Methods:Normal subjects and CSR patients were imaged by SD-and SS-OCTA using 3×3 mm and 6×6 mm scan patterns.OCT signal strengths at the superficial retina,deep retina,Sattler’s layer and Haller’s layer were used to compare the ability of SD-and SS-OCTA to image structural features.In addition,the ability to acquire angiograms were discussed by evaluating retinal vessel density.Central serous volume(CSV)was measured and it was correlated with difference in signal strengths(ΔS)between two OCTA devices.Results:Seven normal eyes and seven diseased eyes were recruited.Results showed no significant differences between SD-and SS-OCT in detecting structural features of the retinal layer according to the paired t-test.However,when imaging the Sattler’s layer for normal eyes,a significant difference is found between SD-and SS-OCT(p<0.0001 for 3×3 mm scan,and p=0.0002 for 6×6 mm);while for CSR eyes,the corresponding values were p<0.0001 and p=0.0003,respectively.At Haller’s layer for normal eyes,the corresponding values were p=0.0004 and p=0.0014;and for CSR eyes,p=0.0004 and p<0.0001,respectively.A strong correlation betweenΔS and CSV was observed in the Sattler’s layer(3×3 mm–p=0.0031 and R^(2)=0.951;6×6 mm–p=0.0075 and R^(2)=0.911)and Haller’s layer(3×3 mm–p=0.0026 and R^(2)=0.955;6×6 mm–p=0.0013 and R^(2)=0.972).Conclusions:The results suggest no differences between SD-and SS-OCTA for imaging the retinal layers however,when imaging beyond retinal layers,SS-OCTA appears advantageous in detecting returning signals.In CSR cases,the CSV may have an impact on sub-CSR tissue imaging and appears to have more impact on SD-than SS-OCTA.

SD-OCT检测Nd∶YAG激光周边虹膜切除术后黄斑区视网膜厚度变化

目的:探讨Nd∶YAG激光周边虹膜切除术(LPI)对原发性闭角型青光眼(PACG)患者黄斑区视网膜厚度的影响。方法:前瞻性研究。选取2019-10/2021-10我院PACG患者30例30眼为PACG组,同期健康体检者20名20眼为正常对照组(随机选取一眼)。PACG组患者接受LPI治疗,术后随访1mo。两组受试者均行最佳矫正视力(BCVA)、眼压、角膜内皮细胞、IOL Master 500光学测量仪测量前房深度(ACD)及眼轴长度(AL)、频域光学相干断层扫描(SD-OCT)检查黄斑区视网膜厚度。比较两组受试者及PACG组患者LPI前后ACD、眼压、AL和黄斑区视网膜厚度,并行相关性分析。结果:PACG组患者术后1wk, 1mo ACD较术前变深(均P<0.05)。PACG组患者手术前后眼压和AL均无差异(均P>0.05)。PACG组患者术前黄斑中心区,内外环上方、颞侧、下方、鼻侧,共9个区域视网膜厚度分别为243.50±13.24、324.50±13.46、308.83±15.94、310.00±14.24、314.50±16.29、300.67±19.95、290.17±12.58、302.40±16.37、307.33±14.84μm,正常对照组相应部位分别为266.14±16.16、342.67±15.86、327.95±16.41、337.85±13.03、341.24±15.58、313.76±17.59、290.24±16.29、303.81±13.91、323.01±14.80μm,两组间中心区、内环上方、颞侧、下方、鼻侧比较均有差异(均P<0.05)。PACG组术后1wk黄斑区9个区域视网膜厚度分别与术前相比均增加,术后1mo接近术前水平,但手术前后各分区比较均无差异(均P>0.05)。结论:与正常受试者比较,PACG患者黄斑区视网膜厚度较薄。PACG患者LPI术后早期黄斑区视网膜可变厚。

Graves眼病视网膜厚度改变的SD-OCT检测研究

目的观察Graves眼病(GO)患者黄斑区视网膜厚度(RT)的变化。方法横断面研究。采集Graves眼病患者及正常对照组的视力、眼压(IOP)、裂隙灯、眼底、眼轴、眼球突出度等检查,并根据临床活动性评分(CAS)评分将GO患者分为活动性和非活动性两组。视网膜厚度检查使用频域相干光层析成像术(SD-OCT)设备检测。采用单因素方差分析以及非配对t检验对各组患者视网膜厚度、眼压、眼球突出度、眼轴等进行比较。结果本研究最终纳入66例(132只眼),其中非活动性GO 22例(44只眼),活动性GO 22例(44只眼),对照组22例(44只眼)。活动性GO与对照组、非活动性GO组相比较,眼球突出度增加,差异均有统计学意义(均P<0.001)。各组比较,眼压差异无统计学意义(P=0.142)。活动性GO的患者的颞侧1 mm,3 mm处视网膜厚度较对照组薄,差异均有统计学意义(P值分别为0.016、0.013)。结论活动性GO患者的颞侧视网膜厚度明显低于正常对照,视网膜厚度可作为评估GO患者早期视网膜病变以及疾病活动性的一种潜在的生物学指标。

Comparison of central corneal thickness measurements with three new optical devices and a standard ultrasonic pachymeter

AIM:To compare the RTVue spectral optical coherence tomography(SD-OCT),Sirius Scheimpflug-Placido topographer,Lenstar optical low coherence reflectometry(OLCR)and ultrasound pachymetry(USP)devices in terms of their agreement and repeatability of measuring central corneal thickness(CCT).METHODS:In this prospective study,50 eyes of 50patients were included.Three repeated measures were obtained using SD-OCT,Scheimpflug-Placido topographer and USP and five measurements were determined with the OLCR.Bland-Altman plots were used to assess agreement among the instruments,and 95%limits of agreement(LoA)for each comparison were calculated.Intra-examiner repeatability was assessed using intraclass correlation coefficients(ICCs).RESULTS:The mean CCT by SD-OCT,ScheimpflugPlacido topographer,OLCR,and USP were 525.90±34.08μm,525.92±34.10μm,530.30±35.62μm,and543.50±37.11μm respectively.All 4 modalities of CCT measurements correlated closely with each other,with Pearson correlation coefficients ranging from 0.977 to0.995.The mean differences(and upper/lower LoA)for CCT measurements were-0.05±6.77μm(13.3/-13.3)between SD-OCT and Scheimpflug-Placido topographer,4.38±3.79μm(11.8/-3.1)between OLCR and SD-OCT,4.38±6.03μm(16.2/-7.5)between OLCR and ScheimpflugPlacido topographer,13.20±6.46μm(25.9/0.5)between USP and OLCR,17.59±6.76μm(30.8/4.3)between USP and SD-OCT,and 17.58±8.13μm(33.5/1.6)between USP and Scheimpflug-Placido topographer.Intra-examiner repeatability was excellent for all devices with ICCs】0.98.CONCLUSION:For most practical purposes,CCT measurements with the RTVue,Sirius and Lenstar can be used interchangeably.Although highly correlated,CCTmeasurement differences between USP and these 3optical instruments can be significant depending on the clinical situation.

Diagnostic capability of Fourier-Domain optical coherence tomography in early primary open angle glaucoma

Background Optical coherence tomography （OCT） is a high resolution noncontact imaging modality which can quantitatively detect the optic disc and retinal structure.This study was designed to evaluate the diagnostic capability of parameters of the optic disc, retinal nerve fiber layer thickness, and ganglion cell complex （GCC） using a new technology called Fourier-domain OCT （FD-OCT） for early primary open angle glaucoma （POAG） patients.Methods Two groups of patients, early perimetric damage POAG and normal subjects were included in this observational cross-sectional study.All patients underwent FD-OCT and visual field examination in addition to full ophthalmic examinations.Receiver operating characteristic curves （ROC） were studied for all parameters.The sensitivity and specificity for distinguishing between normal and early glaucomatous eyes, the areas under the receiver operating characteristic curves （AROC） and positive, negative likelihood ratios were evaluated for all the single parameters and selected combined parameters using arbitrary cutoffs.Results Thirty-four eyes of 34 early POAG patients and 42 eyes of 42 normal subjects were analyzed.Cup/disc （C/D）vertical ratio presented the best sensitivity and positive likelihood ratio for selected specificities （95% and 85%） which were 79.4% and 88.2%, 33.4 and 7.4, respectively.Among all single parameters, the C/D vertical ratio demonstrated the highest AROC which was at 0.930.The average thickness of circumpapillary RNFL on 3.45 mm showed the highest AROC among all of the peripapillary RNFL parameters.The sensitivity at selected specificity and AROC of GCC were not as high as C/D vertical ratio and RNFL AT on 3.45 mm.When the C/D vertical ratio, RNFL AT on 3.45 mm, and rim area were combined using a logistical diagnostic model, the AROC was raised to 0.949 but not significantly different from the top single parameter, C/D vertical ratio.Conclusions The key parameters obtained by FD-OCT were able to show the significant differences of optic discs,thickness of RNFL and GCC between POAG patients and normal subjects.According to sensitivity, specificity, likelihood ratio and AROC, the top three parameters from FD-OCT for early diagnosis of POAG were C/D vertical ratio, RNFL AT on 3.45 mm, and the rim area.