Intersession repeatability of macular thickness measurements with the Humphrey 2000 OCT

PURPOSE: This study was designed to determine intersession repeatability of measurements of macular thickness made with a commercially available optical coherence tomography (OCT) system. The images that can be routinely acquired with the commercial instrument differ significantly in quality from the images in the literature, which have mostly been acquired on prototype systems. METHODS: Multiple OCT images of the nasal macula were obtained from the right eye during three independent measuring sessions, using the Humphrey 2000 OCT system (Humphrey, San Leandro, CA). Twenty-six volunteers with no history of ocular disease participated in this investigation. Eyes in all subjects were undilated during scan acquisition. Scans were horizontal, 3 mm long, and through the fovea. Five scans were used from each session, for a total of 15 scans per subject. Retinal boundaries were automatically detected using custom software. Statistical software was used to calculate intersession and intrasession repeatability. Manual correction was performed on the automatically detected boundaries, and a second analysis was performed using these boundaries. RESULTS: When no manual correction of boundaries was performed, there were no significant effects between different sessions (P = 0.529) or between different scans within the same session (P = 0.509). Average retinal thickness was found to be 274 +/- 17 microm for a 1-mm long region 0.75 mm from the fovea. Individual scan averages differed from overall patient averages by 0 +/- 4.3 microm (99% confidence interval, 11.2 microm). CONCLUSIONS: OCT measurements of macular thickness made with the Humphrey 2000 OCT system are repeatable over different sessions with an expected variation of less than 11 microm (99% confidence interval).     

Comparison of foveal thickness measured with the retinal thickness analyzer and optical coherence tomography.

PURPOSE: To assess and compare the reliability and reproducibility of retinal thickness measurements for the retinal thickness analyzer (RTA) and optical coherence tomography (OCT) in normal and edematous retina. METHODS: The authors measured the foveal thickness of 21 normal eyes and 9 eyes with macular edema with both methods in random order. With the RTA, the fovea was measured 10 times; with the OCT, six scans (one horizontal and five vertical cross-sections) of the fovea were obtained. RESULTS: Mean foveal thickness of normal eyes measured 153 microm with OCT and 181 microm with RTA (median for both methods 150 microm). Coefficients of variation (CV) within the same subjects were 10% (OCT) and 9% (RTA) reducing to 9% (OCT) and 7% (RTA) when scans were repeated only five times for both methods. The RTA, however, yielded an interpatient CV of 33% (OCT 17%), which was caused by several falsely high readings in normal individuals. In eyes with retinal thickening the OCT measured a mean of 324 microm with 15% intra- and 58% interpatient CV. The RTA yielded a mean of 403 microm with CV of 18% and 73%, respectively. CONCLUSION: Both methods yield reproducible measurements of foveal thickness in normal individuals and individuals with macular edema. However, falsely high measurements may occur with the RTA, reducing its reliability as compared to the OCT.     

Repeatability and reproducibility of corneal thickness measurements by optical coherence tomography

PURPOSE: To assess the repeatability and interoperator and intersession reproducibility of central corneal thickness (CCT) measurements made by a commercially available optical coherence tomography (OCT) system. METHODS: Intersession and interoperator reproducibility and repeatability were defined according to the guidelines of the British Standards Institution and examined in a control group of 14 normal subjects. An in-house computer program was used to evaluate central corneal thickness from these scans. RESULTS: The coefficient of interoperator reproducibility was 0.18%, whereas that for intersession reproducibility was 1.11%. Wilcoxon analysis (5% level of significance) showed that there was no statistically significant difference between scans acquired during different sessions or by different operators. Coefficients of repeatability were all less than 3%. The average CCT was 526 +/- 28 microm (SD) and the range of normal CCT between 5th and 95th percentiles was 498 to 576 microm. CONCLUSIONS: Although the commercially available OCT scanner was designed for retinal imaging, with a few minor modifications, the system may be used to image the anterior segment. Previous studies have shown that OCT measurements correlate well with those from conventional techniques, and it has the added advantage of being a noncontact technique. This study further demonstrates that the OCT measurements show a high degree of repeatability and reproducibility. Thus, OCT is emerging as a promising tool for evaluation of CCT in the clinical setting.     

Is quantitative spectral‐domain superior to time‐domain optical coherence tomography (OCT) in eyes with age‐related macular degeneration?

Purpose: The aim of this study was to determine the variability of macular map measurements, for two generations of optical coherence tomography (OCT) instruments, in eyes with wet age related macular degeneration (AMD) and low visual acuity. Methods: Patients were examined with Stratus OCT and Cirrus HD‐OCT. The macular thickness was assessed with the ‘macular thickness map scan’ and ‘fast protocol’ in Stratus and with the 512 × 128 and 200 × 200 cube protocols in Cirrus OCT. Two measurements were taken one directly after the other, at the first visit to analyse repeatability. Approximately 1 week later, a third measurement was taken to analyse reproducibility. In Cirrus OCT, a manual correction of foveal location was also performed. Repeatability and reproducibility were calculated as a coefficient of variance (CoV) and a coefficient of repeatability/reproducibility. Results: Repeatability for central macular thickness (expressed as CoV) was about three per cent for all protocols, and the coefficient of repeatability between 34 and 54 μm. Reproducibility (also expressed as CoV) was between four to seven per cent and coefficient of repeatability between 64 and 89 μm. After manual adjustment of foveal location in Cirrus OCT, the coefficient of repeatability improved to 12–18 μm, and the coefficient of reproducibility to 44–47 μm. Conclusions: In eyes affected by wet AMD, there were small differences in repeatability and reproducibility when comparing quantitative maps in Stratus and Cirrus OCT. However, when the software for manual correction of foveal position in Cirrus OCT was used, the variability decreased markedly, and the repeatability was close to what had been reported in normal eyes, demonstrating a significant, potential advantage of spectral‐domain over time‐domain OCT.     

Reproducibility of measurements of the peripapillary retinal nerve fibre layer thickness. Optical coherence tomography versus retinal thickness analyzer

PURPOSE: The aim of this study was to compare the intra- and inter-examiner reproducibility of measurements obtained by optical coherence tomography (OCT) and retinal thickness analyzer (RTA). PATIENTS AND METHODS: During a period of 2 months, 22 eyes of 16 patients and 6 healthy subjects were included. Two examiners (EMH, RK) successively performed three measurements of the peripapillary retinal nerve fibre layer (RNFL) thickness with RTA and OCT. The reproducibility of three individual measurements of one examiner (intra-examiner) as well as the reproducibility of the measurements between both examiners (inter-examiner) was evaluated using the Friedman test and sign test. RESULTS: The average thickness of the peripapillary RNFL was 154.4 microm for the first investigator (EMH) and 155.1 microm for the other investigator (RK) measured with RTA. The results obtained by OCT were 137.3 microm (EMH) and 138.9 microm (RK), respectively, generally indicating a threefold smaller range. Comparing the three measurements of one single examiner, no appreciable intra-observer dependency neither for RTA (EMH: p=0.19, RK: p=0.95) nor for OCT (EMH: p=0.51, RK: p=0.62) was observed. Inter-examiner analysis for RTA and OCT also revealed an acceptable reproducibility. CONCLUSIONS: Measurements of peripapillary RNFL thickness using RTA and OCT exhibited intra- and inter-observer agreement.     

Analysis of retinal nerve fiber layer and macular thickness measurements in healthy Taiwanese individuals using optical coherence tomography (Stratus OCT)

PURPOSE: To investigate the reproducibility of peripapillary retinal nerve fiber layer (RNFL) and macular thickness measurements in healthy Taiwanese subjects using optical coherence tomography (Stratus OCT). METHODS: Fifty-two eyes of 52 healthy Taiwanese subjects (32 females and 20 males) were enrolled in the cross-sectional study. A randomly chosen single eye from each healthy subject underwent thickness measurements using OCT, before and after pupillary dilation, by 3 trained and experienced operators. Average measurements of peripapillary RNFL and macular thickness were calculated. Comparisons of thickness measurements before and after pupillary dilation, and among the 3 operators were performed. RESULTS: The RNFL thickness measurements were higher in the inferior peripapillary area by RNFL scan (average: 107.4+/-17.8 microm) and the macular thickness measurements showed a ring-shaped hump in the 3 mm perifoveal area by macular scan (average: 252.8+/-8.9 microm). Comparing the peripapillary RNFL and macular thickness before and after pupillary dilation, there was no significant difference (P>0.05) in average, superior, inferior, temporal, or nasal peripapillary areas, in total macular volume and foveal thickness, nor in 1, 3, and 6-mm perifoveal areas, whether before or after pupillary dilation and irrespective of which operator performed the measurements. CONCLUSIONS: The inferior RNFL area and the 3-mm perifoveal area showed higher thickness measurements in the peripapillary region and macular region, respectively. The thickness measurements performed using OCT showed no significant differences before and after pupillary dilation, and showed good reproducibility.     

超长扫描深度的频域光学相干断层扫描在小鼠眼球生物学测量中的应用

目的 利用自行搭建的超长扫描深度的频域光学相干断层扫描（SD-OCT）活体测量小鼠眼球的眼轴长度、曲率等各眼内生物学参数,并评估其重复性和再现性。方法 实验研究。本研究自主研发的超长扫描深度SD-OCT扫描深度7.3 mm（空气中）,系统轴向扫描（A-Scan）速度28 kHz,轴向分辨率7.5 μm,横向分辨率19 μm。共有5只40日龄的C57BL/6小鼠（10眼）经历2天次的测量。第1天,由操作者1先执行测量步骤,连续拍摄2幅图后,由操作者2紧接着拍摄1幅图。在3次拍摄中,每次都保证前后拍摄的时间耽搁小于5 min。2 d以后,所有的小鼠再由操作者1拍摄1幅图,随后每只小鼠再进行1次时域OCT（TD-OCT）拍摄。所有测量都在下午2∶00到4∶00之间进行。测量的重复性和再现性评估都采用重复性系数、组内相关系数ICCs、Wilcoxon配对测试及绘制Bland-Altman图来综合分析。SD-OCT和TD-OCT的测量结果比较采用独立样本t检验。结果 用SD-OCT成功获得了清晰、高质量的小鼠眼球一次性成像。除角膜、前房外,其他数据接近于TD-OCT。前房、晶状体、玻璃体和眼轴的重复性/再现性系数均小于3%且对应的组内相关系数（ICCs）几乎都大于0.75,角膜和视网膜的重复性/再现性系数小于5%且对应的ICCs相对较小。除操作者1第1天获取的2组角膜数据之间差异有统计学意义外（Z=-2.310,P<0.05）,其余差异均无统计学意义。眼轴等生物学参数的Bland-Altman分析图显示所有的数据点都分布在95%可信区间内。各个曲率的重复性/再现性系数均小于5%。角膜前表面曲率半径和晶状体前、后表面曲率半径的ICCs基本大于0.75,而角膜后表面曲率半径的ICC大于0.45。Bland-Altman图显示曲率再现性的数据点约有5%分布在95%可信区间外。结论 利用SD-OCT,可获得高清晰的从小鼠角膜到视网膜的横断面切片图像,不仅能计算传统的眼轴等轴向生物学参数的长度,而且还能计算眼内各个成分的曲率半径,具有较好的重复性和再现性。     

Intraobserver variability in optical coherence tomography

PURPOSE: To assess the intraobserver variability of optical coherence tomography (OCT) in patients with clinically stable maculas. DESIGN: Retrospective, observational case series using a diagnostic instrument. METHODS: Retrospective study. setting. Private retina practice. patient population. Twenty-two eyes of 19 patients, each studied twice within 4 months. observation procedure. Optical coherence tomograph measurements of the macula obtained by two photographers. main outcome measures. Ordinary least products (OLP) and Bland-Altman analysis of OCT data. RESULTS: No fixed or proportional bias was detected in foveal zone thickness and total macular volume between measurements of either of the OCT operators. The coefficient of repeatability for foveal zone thickness was 37.0 microm for photographer 1 and 34.8 microm for photographer 2. The coefficient of repeatability for total macular volume was 0.29 mm(3) for photographer 1 and 0.10 mm(3) for photographer 2. CONCLUSION: Foveal zone thickness and total macular volume measurements show low intraobserver variability when analyzed by OLP and Bland-Altman techniques. Bounds are given for foveal zone thickness and total macular volume for which longitudinal OCT measurements by the same operator can be considered to reflect natural history or intervention effects rather than intraobserver variability.     

Noncontact optical coherence tomography for measurement of corneal flap and residual stromal bed thickness after laser in situ keratomileusis

PURPOSE: Studies show significant variability in the thickness of laser in situ keratomileusis (LASIK) corneal flaps cut by various microkeratomes. Most studies of corneal flap thickness are based on contact ultrasonic pachymetry measurements taken during the surgical procedure. This study reports a technique to obtain reproducible corneal flap thickness and residual stromal bed thickness measurements using noncontact optical coherence tomography (OCT) following LASIK. METHODS: The corneal flap thicknesses of 26 eyes of 15 patients were measured following LASIK in which the flap was created using the Amadeus microkeratome: 160-microm head, 9.5-mm ring, 4.0-mm/s translation speed, 8000 oscillations/m, and full vacuum. Zeiss Humphrey OCT-2 line scans were performed on postoperative days 1 and 7. The raw data from three scans for each eye and day were exported to Microsoft Excel for processing, averaging, and analysis. RESULTS: The OCT corneal flap thickness and residual stromal bed thickness measurements correlated well with ultrasonic pachymetry measurements performed during surgery (R2 = .92). The OCT technique yielded reproducible results, as the variance for repeated scans was only 2.5% of the variance between eyes. In bilateral cases a single blade was used for both eyes. The mean flap thickness of 15 first eyes was significantly greater than that of the 10 second eyes: 181 +/- 31 microm vs. 143 +/- 41 microm (P < .01). A positive correlation was found between the preoperative pachymetry and corneal flap thickness. CONCLUSIONS: The OCT scan averaging technique is a reproducible, noncontact postoperative method for measuring corneal flap and residual stromal bed thicknesses following LASIK.     

The repeatability of corneal and corneal epithelial thickness measurements using optical coherence tomography.

PURPOSE: The purpose of this study is to examine within and between session repeatability of clinical optical coherence tomography (OCT) imaging for anterior segment morphometry. METHODS: Images of the corneal apex of each eye in 18 subjects were obtained using a Humphrey Zeiss OCT imager. Subjects viewed a target positioned to ensure that scans were orthogonal to the ocular surface and each image, consisting of 100 adjacent sagittal scans, analyzed using custom software. Repeatability data were analyzed using intraclass correlation coefficients (ICCs), correlation coefficient of concordance (CCC, perfect test-retest agreement ICC or CCC = 1.0), and coefficients of repeatability (COR, 95% confidence interval of test-retest differences). To account for each eye, the multivariate repeatability statistic Iota was estimated. RESULTS: Mean central corneal and epithelial thickness of 32 eyes (OD and OS combined) is 536 +/- 26 microm (standard deviation [SD]) and 52 +/- 3 microm (SD) with 5th and 95th percentile thicknesses of 507 and 591 microm for central cornea and 48 and 57 microm for central epithelial. Worst case within session repeatability was defined as repeatability between images with greatest differences in mean thickness within a session. Corneal thickness worst case ICC was 0.95 and COR was +/- 9.98 microm. Epithelium worst case ICC was 0.36, CCC was 0.12, and COR was +/- 11.11 microm. First image between session corneal thickness had an ICC = 0.98 and a COR = 10.83 microm, whereas epithelium ICC = 0.38, CCC = 0.37, and COR was +/- 12.84 microm. When we compared the average of the first three tests with the first three retest images, corneal ICC was 0.98 and COR was +/- 10.64 microm and epithelium ICC = 0.73, CCC = 0.72, and COR was +/- 6.53 microm. Iota (multivariate repeatability, using eye as a factor) for the cornea was at least 0.96 (worst case) and increased to at least 0.98 when within-session image data were averaged. Iota for epithelium measures ranged from 0.29 when first images were compared with 0.57 when within-session image data were averaged. CONCLUSIONS: There is very good repeatability of corneal thickness measurement using OCT; even the worst case measurements are similar between sessions. On the other hand, this is not the case for epithelium measurements, and if multiple images within a session are acquired, the worst case results demonstrate how important it is to optimize each OCT scan and also average multiple scans to maximize intersession repeatability.     

Error correction and quantitative subanalysis of optical coherence tomography data using computer-assisted grading

PURPOSE: To demonstrate feature subanalysis and error correction of optical coherence tomography (OCT) data by using computer-assisted grading. METHODS: The raw exported StratusOCT (Carl Zeiss Meditec, Inc., Dublin, CA) scan data from 20 eyes of 20 patients were analyzed using custom software (termed OCTOR) designed to allow the user to define manually the retinal borders on each radial line scan. Measurements calculated by the software, including thickness of the nine standard macular subfields, foveal center point (FCP), and macular volume, were compared between two graders and with the automated Stratus analysis. Mean and range of differences for each parameter were calculated and assessed by Bland-Altman plots and Pearson correlation coefficients. Additional cases with clinically relevant subretinal findings were selected to demonstrate the capabilities of this system for quantitative feature subanalysis. RESULTS: Retinal thickness measurements for the various subfields and the FCP showed a mean difference of 1.7 mum (maximum, 7 microm) between OCTOR graders and a mean difference of 2.3 microm (maximum of 8 microm) between the OCTOR and Stratus analysis methods. Volume measurements between Stratus and OCTOR methods differed by a mean of 0.06 mm(3) (in reference to a mean macular volume of 6.81 mm(3)). The differences were not statistically significant, and the thicknesses correlated highly (R(2) > or = 0.98 for all parameters). CONCLUSIONS: Manual identification of the inner and outer retinal boundaries on OCT scans can produce retinal thickness measurements consistent with those derived from the automated StratusOCT analysis. Computer-assisted OCT grading may be useful for correcting thickness measurements in cases with errors of automated retinal boundary detection and may be useful for quantitative subanalysis of clinically relevant features, such as subretinal fluid volume or pigment epithelial detachment volume.     

Repeatability of stratus optical coherence tomography measures in neovascular age-related macular degeneration

PURPOSE: To determine the repeatability of Stratus optical coherence tomography (OCT) measures of retinal thickness and volume in patients with neovascular age-related macular degeneration (nAMD) METHOD: Fifty-one eyes of 51 consecutive patients with nAMD underwent an OCT imaging session in which two fast macular thickness map (FMTM) protocol scans sets were acquired by a single experienced operator certified for clinical trials work. Coefficients of repeatability for each of nine Early Treatment of Diabetic Retinopathy Study (ETDRS)-like regions, foveolar center-point retinal thickness (CPT) and total macular volume (TMV), were calculated. Scans were analyzed retrospectively for errors in retinal boundary placement by two observers, with revised coefficients of repeatability calculated after excluding any scan sets with significant segmentation error. RESULTS: The coefficient of repeatability for the central 1-mm macular subfield was 67 mum (23%) and was less than 75 mum for all macular subfields. There was much larger variability in the center-point thickness measure, with a coefficient of repeatability of 88 mum (32%) for the automated center-point thickness (ACPT). After excluding nine scan set pairs with significant segmentation error, the coefficient of repeatability for the central 1-mm macular subfield was reduced to 50 mum (19%). CONCLUSIONS: OCT-derived retinal thickness measurements are subject to considerable measurement variability in patients with nAMD. Changes in central macular thickness of more than 50 mum may better reflect true clinical change in scan sets without significant segmentation error and may be used to guide the retreatment of patients with nAMD in clinical trials and clinical practice.     

Wavelength independence and interdevice variability of optical coherence tomography.

BACKGROUND AND OBJECTIVE: Comparison of nerve fiber layer (NFL) thickness and macular retinal thickness measurements in two different commercial optical coherence tomography (OCT) machines with the same and different super luminescent diode lasers (SLDs). PATIENTS AND METHODS: Thirty eyes of 30 subjects were studied, with each eye scanned on two different OCT machines on the same day. Three 3.4-mm diameter circumpapillary NFL scans and six 6-mm radial scans centered on the fovea were obtained. Macular volumes were calculated from the central 3.45 mm of the 6 radial scans. RESULTS: The first study (identical SLDs of 850 nm) included 10 eyes of 10 subjects for mean NFL thickness and 6 eyes of 6 subjects for macular volume. There was no systematic difference between the measurements on the two machines for NFL (difference = 5.6 microm, standard error [SE] = 3.8, P= .18) or macular volume (difference = -0.003 mm3, SE = 0.064, P = .96). The second study (SLDs of 850 and 820 nm) included 20 eyes of 20 subjects. There was no significant difference between the two machines for mean NFL (difference = 3.4 microm, SE = 2.9, P= 0.26) or macular volume (difference = -.017 mm3, SE = 0.017, P= .33). For the smaller areas of the macular scan, several (including the outer ring) showed a significant systematic difference between measurements at the two wavelengths, but even these had at most 12% of the total variance attributable to the different wavelengths. CONCLUSION: Our study indicates that OCT measurements of NFL thickness do not differ much when the device or the wavelength of the SLD is changed. Some measurements of the macular thickness in specific areas may differ systematically for different wavelengths, but in most cases the difference is small.     

Correlation of optical coherence tomography pattern and visual recovery after vitrectomy with silicone oil for retinal detachment

PURPOSE: To assess prospectively the features of the macular surface in silicone oil-filled eyes after surgery by analyzing whether silicone oil affects optical coherence tomography (OCT) measurements and their reproducibility and whether a statistical correlation exists between postoperative best-corrected visual acuity (BCVA) and foveal thickness measured by OCT. METHODS: Twenty eyes of 20 patients underwent vitrectomy with silicone oil tamponade for retinal detachment. After vitrectomy, complete ophthalmic examination including determination of BCVA and OCT was performed to quantify the visual recovery and the foveal thickness. RESULTS: Ophthalmoscopy revealed that the retina appeared to be reattached in all 20 eyes at 3 months after surgery. BCVA ranged from 0.4 logMAR to 1.7 logMAR, and foveal thickness ranged from 80 microm to 500 microm. Postoperative foveal thickness and BCVA had a strong correlation (r = 0.93; P = 0.003). CONCLUSION: The presence of silicone oil in the vitreous chamber does not change the reproducibility of OCT measurements of foveal thickness (coefficient of reproducibility, 1.48%). This study showed high statistical correlation between BCVA and foveal thickness. Therefore, postoperative BCVA is affected by postoperative foveal thickness, and visual improvement is limited in eyes with increased or decreased foveal thickness.     

The Humphrey optical coherence tomography scanner: quantitative analysis and reproducibility study of the normal human retinal nerve fibre layer

BACKGROUND/AIMS: To determine the reproducibility of the Humphrey optical coherence tomography scanner (OCT), software version 5.0, for measurement of retinal nerve fibre layer (RNFL) thickness in normal subjects and to compare OCT measurements with published histological thickness of the human RNFL. METHODS: Three independent measurements were obtained at each session for one eye from 15 normal subjects with a mean age of 30.8 (SD 10.9) years. Scans were taken in the peripapillary retina using the default setting (1.74 mm radius from centre of the optic disc) and were repeated 1 week later. Additional scans were obtained at the optic nerve head (ONH) margin overlying the scleral rim, for comparison with available histological data on the human RNFL. RESULTS: For the 1.74 mm circular scan, the mean coefficient of variation (COV) for the global RNFL thickness measurement was 5% (SD 3%). This increased to 8% (3%) for quadrant measurements and to 9% (3%) with further subdivision into 12 segments. Significant differences (p<0.05) between sessions were only found when the data were divided into segments. The mean RNFL thickness for the 1.74 mm scan was 127.87 (9.81) microm. The RNFL was maximal at the superior disc pole, 161.44 microm (14.8), and minimal at the temporal pole, 83.1 (12.8) microm. Peak thickness values occurred superior temporal and inferior temporal to the vertical axis. RNFL thickness for every sector of the disc was greatest at the margin of the optic disc (mean 185.79 microm; SD 32.61). Although the variation in RNFL thickness around the disc follows published histology data, the OCT underestimates RNFL thickness by an average of 37% (SD 11; range 21-48%). CONCLUSION: The OCT provides reproducible measurement of the retinal structures that are consistent with the properties of the RNFL. However, comparison with available studies of RNFL thickness in the human suggests that in its present form, the OCT underestimates RNFL thickness. Further refinement of this technology is required to improve the accuracy with which the OCT measures retinal nerve fibre layer thickness.     

Reproducibility of and effect of magnification on optical coherence tomography measurements in children

PURPOSE: To determine the reproducibility of optical coherence tomography (OCT) measurements of macular thickness, peripapillary nerve fiber layer (NFL) thickness, and optic disk parameters and to investigate the effect of axial length and refractive error on these measurements in children with healthy eyes. DESIGN: Cross-sectional study. METHODS: The Sydney Childhood Eye Study examined 2,353 year 7 students (75.3% response) from a random cluster sample of 21 secondary schools across Sydney. A consecutive subsample of 120 children had OCT (StratusOCT, Carl Zeiss, Dublin, California, USA) performed by a single operator, which was repeated with a brief rest between the two sessions. Scans of the NFL, macula, and optic disk were performed. RESULTS: Intersubject variability of measurements of macular thickness, NFL thickness, and optic disk parameters assessed using intraclass correlation coefficients accounted for >85%, >62%, and >38% of total variability of measurements, respectively. Corresponding coefficients of variability were <5%, <8%, and <13%. Magnification effects attributable to axial length and refractive error on the measurement of these parameters were statistically not significant. CONCLUSION: The StratusOCT demonstrated reproducible measurements of macular and NFL thickness. Measurement of most optic disk parameters were also reproducible. Magnification attributable to axial length and refractive error had minimal impact on measurements of macular and NFL thickness.     

Reproducibility of retinal nerve fiber thickness measurements using the stratus OCT in normal and glaucomatous eyes

PURPOSE: To determine the reproducibility of Stratus Optical Coherence Tomography (OCT) retinal nerve fiber layer (RNFL) measurements around the optic nerve in normal and glaucomatous eyes. METHODS: One eye was chosen at random from 88 normal subjects and 59 glaucomatous subjects distributed among mild, moderate, and severe glaucoma, determined by visual field testing. Subjects underwent six RNFL thickness measurements performed by a single operator over a 30-minute period with a brief rest between sessions. Three scans were taken with the high-density Standard RNFL protocol, and three were taken with the Fast RNFL protocol, alternating between scan protocols. RESULTS: Reliability, as measured by intraclass correlation coefficient (ICC), was calculated for the overall mean RNFL thickness and for each quadrant. The ICC for the mean Standard RNFL thickness (and lower 95% confidence interval [CI]) in normal and glaucomatous eyes was 0.97 (0.96 CI) and 0.98 (0.97 CI), respectively. The ICC for the mean Fast RNFL thickness in normal and glaucomatous eyes was 0.95 (0.93 CI) and 0.97 (0.95 CI), respectively. Quadrant ICCs ranged between 0.79 and 0.97, with the nasal quadrant being the least reproducible of all four quadrants, using either the Standard or Fast RNFL program. The test-retest variability ranged from 3.5 microm for the average RNFL thickness measurements in normal eyes to 13.8 microm for the nasal quadrant measurements in glaucomatous eyes, which appeared to be the most variable. CONCLUSIONS: Reproducibility of RNFL measurements using the Stratus OCT is excellent in normal and glaucomatous eyes. The nasal quadrant appears to be the most variable measurement. Standard RNFL and Fast RNFL scans are equally reproducible and yield comparable measurements. These findings have implications for the diagnosis of glaucoma and glaucomatous progression.     

Diagnosis of macular pseudoholes and lamellar macular holes by optical coherence tomography

PURPOSE: To assess the usefulness of optical coherence tomography (OCT) for better differential diagnosis of macular pseudoholes (MPH) and lamellar macular holes (LMH). DESIGN: Observational case series. METHODS: setting: Institutional practice. patients: We reviewed the files of 71 eyes of 70 consecutive patients who were diagnosed as having a pseudohole or lamellar hole on OCT examination. All patients referred for suspected pseudohole or lamellar hole on biomicroscopy were evaluated by OCT. main outcome measures: Each eye underwent six radial 3-mm OCT scans centered on the macula, one 6-mm vertical and one 6-mm horizontal scan. Retinal thickness was measured at the foveal center and 750 microm from the center, vertically, and horizontally. The diameter of the macular contour was also measured on vertical and horizontal scans. RESULTS: In 40 cases, OCT showed a macular profile characteristic of MPH: a steepened foveal pit combined with thickened foveal edges and a small foveal pit diameter. Central foveal thickness was normal or slightly increased (167 +/- 42 microm). Mean perifoveal thickness was greater than normal (363 +/- 65 microm). In 29 other cases corresponding to LMH, OCT showed a profile characterized by a thin irregular foveal floor, split foveal edges, and near-normal perifoveal retinal thickness. Central foveolar thickness was thinner than normal (72 +/- 19 microm). Mean perifoveal thickness was near normal (283 +/- 36). Optical coherence tomography did not allow the classification of the remaining two cases. CONCLUSIONS: Optical coherence tomography is very useful in distinguishing MPH attributable to epiretinal membrane contraction from LMH because of partial opening of a macular cyst.     

Retinal thickness in diabetic retinopathy: a study using optical coherence tomography (OCT)

BACKGROUND AND OBJECTIVE: The authors conducted a controlled study to quantify macular retinal thickness in diabetic retinopathy using optical coherence tomography (OCT) as an objective and noninvasive tool. The relationship between retinal thickness and standard methods of evaluating macular edema was investigated. PATIENTS AND METHODS: A total of 136 patients in different stages of diabetic retinopathy were examined with OCT. In addition, fluorescein angiograms as well as standard eye examinations were conducted. The control group consisted of 30 individuals with a normal macula. RESULTS: In the controls, retinal thickness was 153 +/- 15 microm in the fovea, 249 +/- 19 microm in the temporal parafoveal region, and 268 +/- 20 microm in the nasal parafoveal region. In diabetic patients, retinal thickness was increased to 307 +/- 136 microm in the fovea, 337 +/- 88 microm in the temporal retina, and 353 +/- 95 microm in the nasal retina, respectively. The differences between diabetics and controls were highly significant (P < 0.001). Retinal thickening correlated with fluorescein leakage in the angiograms to some extent. There was an intermediate correlation between retinal thickness and visual acuity, particularly in patients without macular ischemia. Sensitivity of detecting clinically significant macular edema by measuring foveal retinal thickness was 89% and specificity was 96%. CONCLUSION: Optical coherence tomography allows us to quantify retinal thickness in diabetic retinopathy with excellent reproducibility. OCT is able to detect sight-threatening macular edema with great reliability.     

Optical coherence tomography in photodynamic therapy for subfoveal choroidal neovascularisation secondary to age related macular degeneration: a cross sectional study

AIMS: To introduce new terminology and validate its reliability for the analysis of optical coherence tomography (OCT) scans, compare clinical detection of cystoid macular oedema (CMO) and subretinal fluid (SRF) with OCT findings, and to study the effect of photodynamic therapy (PDT) on the foveal morphology. METHODS: Patients with subfoveal, predominantly classic choroidal neovascularisation (CNV) secondary to age related macular degeneration (AMD) undergoing PDT were evaluated with refraction protocol best corrected logMAR visual acuity (VA), slit lamp biomicroscopy, stereoscopic fluorescein angiography (FFA), and OCT. New terminologies introduced to interpret the OCT scans were: neuroretinal foveal thickness (NFT), bilaminar foveal thickness (BFT), outer high reflectivity band thickness (OHRBT), intraretinal fluid (IRF), subretinal fluid (oSRF), and vitreomacular hyaloid attachment (VMHA). RESULTS: Fifty six eyes of 53 patients were studied. VA was better in eyes with a thinner outer high reflectivity band (OHRBT) (p = 0.02) and BFT (p = 0.05). BFT was less in eyes that had undergone a greater number of PDT treatments (p = 0.04). There was poor agreement between OCT and clinical examination in the detection of CMO and subretinal fluid (kappa = 0.289 and kappa = 0.165 respectively). To validate the interpretation and measurements on OCT, two groups of 20 scans were analysed by two independent observers. There was good agreement between the observers in the detection of IRF, oSRF, and VMHA (p<0.001). Measurements of NFT and BFT had a high reproducibility, and of OHRBT reproducibility was low. CONCLUSIONS: New terminology has been introduced and tested. OCT appears to be superior to clinical examination and FFA in the detection of CMO. In this study, better vision was associated with a thinner OHRBT and/or the absence of SRF giving insight into the biological effect of PDT.