Comparison of clinically relevant findings from high-speed fourier-domain and conventional time-domain optical coherence tomography

A Review of Optical Interferometry for High-Precision Length Measurement

Optical interferometry has emerged as a cornerstone technology for high-precision length measurement, offering unparalleled accuracy in various scientific and industrial applications. This review provides a comprehensive overview of the latest advancements in optical interferometry, with a focus on grating and laser interferometries. For grating interferometry, systems configurations ranging from single-degree- to multi-degree-of-freedom are introduced. For laser interferometry, different measurement methods are presented and compared according to their respective characteristics, including homodyne, heterodyne, white light interferometry, etc. With the rise of the optical frequency comb, its unique spectral properties have greatly expanded the length measurement capabilities of laser interferometry, achieving an unprecedented leap in both measurement range and accuracy. With regard to discussion on enhancement of measurement precision, special attention is given to periodic nonlinear errors and phase demodulation methods. This review offers insights into current challenges and potential future directions for improving interferometric measurement systems, and also emphasizes the role of innovative technologies in advancing precision metrology technology.

Does corneal epithelial thickness show the severity of psoriasis? SD-OCT study

BACKGROUND

Previous studies have generally focused on dry eye test abnormalities and ocular involvements such as uveitis, and blepharitis in psoriasis. Psoriasis area severity ındex (PASI), which is used to assess psoriasis severity, is a time-consuming and complex tool.

OBJECTIVE

To evaluate the relationship between disease severity and central corneal epithelial thickness (CCET) in psoriasis.

METHODS

175 eyes of 175 psoriasis patients and 57 eyes of 57 healthy individuals as a control group was included in this study. Psoriasis patients were divided into three subgroups according to PASI score as < 10 mild, 10‒20 moderate and > 20 severe. CCET was measured by spectral domain-optical coherence tomography (SD-OCT), and mean values were recorded. Mean CCET values were compared between the psoriasis groups and the control group. Additionally, the relationship between PASI score and CCET was examined.

RESULTS

The mean CCET value was 58.06±3.1μm in the mild group, 60.10±5.0μm in the moderate group, 65.75±6.3μm in the severe group and 56.16±3.1μm in the control group. It was determined that the mean CCET value was significantly higher in all psoriasis groups compared to the control group (p<0.001). The mean CCET value was significantly higher in the moderate psoriasis group than in the mild psoriasis group (p=0.018), and in the severe psoriasis group compared to the moderate psoriasis group (p<0.001). There was a strong positive correlation between PASI score and CCET (p<0.001, r=0.519).

STUDY LIMITATIONS

Cross-sectional design and a relatively small number of participants.

CONCLUSIONS

There is a strong positive correlation between psoriasis severity and CCET. Contactless measurement of CCET by SD-OCT can be an indicator of psoriasis severity.

Lamellar macular holes: monitoring and management strategies

Lamellar macular holes are a vitreoretinal condition characterized by abnormalities in foveal contour with splitting of the neuroepithelium and often an intact photoreceptor layer. Recent developments in high-resolution imaging have increased our ability to study the details of the vitreoretinal interface and to distinguish between different forms of lamellar holes. A new classification is needed to help clinicians in the management of lamellar macular holes. Some clinicians prefer to observe these clinical entities, especially when visual acuity is maintained or alterations of the photoreceptor layer are present. Nevertheless, lamellar holes may sometimes progress, and visual acuity can deteriorate. On the other hand, surgical treatment may lead to positive anatomical and functional outcomes, but not without risks. This review provides a critical overview of the available data on lamellar macular holes, focusing on diagnosis and managing options.

Focal choroidal excavation complicated with choroidal neovascularization in young and middle aged patients

AIM

To investigate the clinical and optical coherence tomography (OCT) features of focal choroidal excavation (FCE) complicated with choroidal neovascularization (CNV) in young and middle aged patients.

METHODS

We performed a retrospective review of 26 patients with FCE accompanied by CNV. All patients underwent a complete ophthalmic examination. We analyzed the clinical characteristics of patients, focusing on the spectral-domain OCT features. All patients received intravitreal injection of anti-vascular endothelial growth factor (anti-VEGF) agents. And we assessed the changes of central retinal thickness and best-corrected visual acuity (BCVA) after anti-VEGF therapy.

RESULTS

The mean age of 26 patients was 35.5±7.3y (range, 21-48y). Of the 26 FCE lesions, 11 were located subfoveal, 6 were parafoveal, and 9 were extrafoveal. The mean FCE depth was 129.8±50.3 µm, and the mean width was 901.3±306.0 µm. The FCE depth was correlated positively with the width, but not correlated with age or refractive error. CNV was located within the excavation (19 eyes) or adjacent to the excavation (7 eyes). After anti-VEGF therapy, the central retinal thickness was significantly reduced and the BCVA was significantly improved. In the absorption process of subretinal fluid, we found that the fluid in the excavations needed to be absorbed at the last. A small amount of residual fluid could still be seen in a few deep excavations even after a long-term follow-up.

CONCLUSION

FCE may be an important reason to cause CNV. Especially in young patients with idiopathic CNV, we should pay attention to the use of OCT to check the presence of FCE. Anti-VEGF therapy is generally effective for CNV associated with FCE.

Development of a new algorithm based on FDT Matrix perimetry and SD-OCT to improve early glaucoma detection in primary care

Purpose

The purpose of this study was to develop an objective algorithm to discriminate the earliest stages of glaucoma using frequency doubling technology (FDT) Matrix perimetry and spectral domain-optical coherence tomography (OCT) technology to improve primary care detection.

Materials and methods

Three hundred six eyes (mean age 58.67±15.12) from 161 patients were included and classified in the following three groups: 101 nonglaucoma (GI-NG), 100 glaucoma suspect (GII-SG), and 105 open-angle glaucoma (GIII-OAG). All participants underwent a visual field exploration using the Humphrey Matrix visual field instrument and retinal nerve fiber layer evaluation using the Topcon 3D OCT-2000. Pattern deviation plot was divided into 19 areas and five aggrupation or quadrants and ranked with a value between 0 and 4 according to its likelihood of normality, and differences among three groups were analyzed. Principal component analysis (PCA) was also used to extract the most notable features of FDT and OCT, and a logistic regression analysis was applied to obtain the classification rules.

Results

Only area numbers 7 and 12 and the central zone of FDT Matrix showed statistical differences (P<0.05) between GI-NG and GII-SG. The classification rules were estimated by the four PCA obtained from FDT Matrix and 3D OCT-2000 in a separate and combined use. Area under the receiver operating characteristic curve was 78.88% with FDT-PCA, 82.09% with OCT-PCA, and 94.27% with combined use of FDT and OCT-PCA to discriminate GI-NG and GII-SG.

Conclusion

The predictive rules based on FDT-PCA or OCT-PCA provide a high sensitivity and specificity to detect the earliest stages of glaucoma and even better in combined use. These predictive rules may help the future development of software for FDT Matrix perimetry and 3D OCT-2000, which will greatly improve their diagnostic ability, making them useful in daily practice in a primary care setting.

Accuracy of Alcon WaveLight® EX500 optical pachymetry during LASIK

Purpose

To study the accuracy and reliability of optical pachymetry using the Alcon WaveLight EX500 during laser-assisted in situ keratomileusis (LASIK).

Materials and methods

This was a retrospective chart review of 90 eyes from 45 patients who had undergone LASIK (mean age 35.2±8.2 years; 19 males, 26 females). The WaveLight FS200 femtosecond laser was programmed to cut LASIK flaps at a desired depth of 120 μm. Optical low-coherence reflectometry (WaveLight EX500) was used to measure central corneal thickness prior to lifting the flap, and the residual stromal bed immediately after excimer ablation. Flap thickness (FT) was calculated using simple subtraction. Optical coherence tomography (OCT) was used to measure central corneal thickness, flap thickness, and residual stromal bed in the postoperative period and the results compared to intraoperative measurements.

Results

Mean programmed FS200 FT was 119 μm. Mean FT using EX500 optical pachymetry was 109 μm. The difference between FS200- programmed and EX500-measured FT was 9 μm (P<0.001). There was also a significant difference between the EX500 and OCT FT (109 μm vs 119 μm, respectively; P<0.001).

Conclusion

FT values calculated using intraoperative EX500 optical pachymetry were significantly lower than programmed FS200 values or OCT measurements.

Corneal Epithelial Remodeling and Its Effect on Corneal Asphericity after Transepithelial Photorefractive Keratectomy for Myopia

Purpose. To evaluate the changes in epithelial thickness profile following transepithelial photorefractive keratectomy (T-PRK) for myopia and to investigate the effect of epithelial remodeling on corneal asphericity. Methods. Forty-four patients (44 right eyes) who underwent T-PRK were retrospectively evaluated. Epithelial thickness was measured using spectral-domain optical coherence tomography at different corneal zones (central, 2 mm; paracentral, 2–5 mm; and mid-peripheral, 5-6 mm) preoperatively and at 1 week and 1, 3, and 6 months postoperatively. The correlation between the changes in corneal epithelial thickness (ΔCET) and postoperative Q-value changes (ΔQ) was analyzed 6 months postoperatively. Results. Epithelial thickness at 6 months showed a negative meniscus-like lenticular pattern with less central thickening, which increased progressively toward the mid-periphery (3.69 ± 4.2, 5.19 ± 3.8, and 6.23 ± 3.9 μm at the center, paracenter, and mid-periphery, resp., P < 0.01). A significant positive relationship was observed between epithelial thickening and ΔQ 6 months postoperatively (r = 0.438, 0.580, and 0.504, resp., P < 0.01). Conclusions. Significant epithelial thickening was observed after T-PRK and showed a lenticular change with more thickening mid-peripherally, resulting in increased oblateness postoperatively. Epithelial remodeling may modify the epithelial thickness profile after surface ablation refractive surgery for myopia.

Focal choroidal excavation: a preliminary interpretation based on clinic and review

AIM

To describe the clinical and imaging characteristics associated with focal choroidal excavation (FCE), analyze the possible complication, and interpret its probable etiopathogenesis.

METHODS

Retrospective descriptive case series of 37 eyes of 32 patients with FCE. Findings of spectral-domain optical coherence tomography (SD-OCT), fluorescein angiography, indocyanine green angiography, and clinical features were analyzed.

RESULTS

All patients were Chinese. Five patients (15.6%) were bilaterally involved. Patients' ages ranged from 7 to 66y. Refractive error ranged between +2.0 D and -11.0 D. Mean best-corrected visual acuity was 0.6 (range, 0.1 to 1.2). Fundus examinations exhibited mild-moderate localized pigmentary disturbances in the corresponding area of 17 eyes. Fluorescein angiography performed in 18 patients showed varying degrees of hyperfluorescence and hypofluorescence related to a range of retinal pigment epithelium (RPE) alterations. Indocyanine green angiography performed in 7 patients showed hypofluorescence at the excavation. SD-OCT demonstrated choroidal excavation in all 37 eyes. Twenty-nine eyes showed a single lesion of FCE, and three eyes showed 2-3 separated lesions. Fifteen eyes showed separation between the photoreceptor tips and RPE consistent with nonconforming FCE. Central serous chorioretinopathy (CSC, n=1) and choroidal neovascularization (CNV, n=1) developed during follow-up.

CONCLUSION

FCE could be interpreted as congenital focal choroidal dysplasia involving the RPE, choriocapillaris, and photoreceptor associated with the faulty anatomy. The abnormal anatomy of FCE was similar to anatomy at risk of CSC and CNV.

The diagnostic accuracy of spectral-domain optical coherence tomography for neovascular age-related macular degeneration: a comparison with fundus fluorescein angiography

PURPOSE

To evaluate the diagnostic accuracy of spectral-domain optical coherence tomography (SD-OCT) for neovascular age-related macular degeneration (nAMD): a comparison against fundus fluorescein angiography (FFA).

METHODS

A retrospective review of SD-OCT, colour fundus photographs (FP), and FFA of 411 consecutive patients referred to a rapid access Macular Clinic over a 4-year period was performed. FFA images were reviewed non-stereoscopically. SD-OCT images were acquired using the Topcon 3D OCT-1000 instrument. All FFA and OCT images were graded by at least two ophthalmologists independently. Side-by-side grading took place with immediate open discussion and adjudication. If there was disagreement between the two grading ophthalmologists or they were not 90% confident of their assigned grade, then adjudication by a third ophthalmologist was performed.

RESULTS

A total of 278 eyes were graded as having choroidal neovascularisation (CNV) with SD-OCT and 231 diagnosed with FFA. The main diagnostic CNV classifications on FFA were: classic no occult in 27 eyes, predominantly classic in 16, minimally classic in 50, occult in 129, and 9 peripapillary membranes. There were a total of 47 false positives with SD-OCT: a rate of 16.9%. The sensitivity and specificity of SD-OCT alone for detecting CNV was 100 and 80.8%, respectively.

CONCLUSION

Our study confirms SD-OCT in comparison to the reference standard of non-stereoscopic FFA is highly sensitive at detecting newly presenting nAMD in the setting of a specialist AMD clinic where the investigations are interpreted by trained specialists. However, it does not seem accurate enough to replace FFA in the diagnosis on nAMD in current practice.

Strategies for improving early detection and diagnosis of neovascular age-related macular degeneration

Treatment of the neovascular form of age-related macular degeneration (AMD) has been revolutionized by the introduction of such agents as ranibizumab, bevacizumab, and aflibercept. As a result, the incidence of legal blindness occurring secondary to AMD has fallen dramatically in recent years in many countries. While these agents have undoubtedly been successful in reducing visual impairment and blindness, patients with neovascular AMD typically lose some vision over time, and often lose the ability to read, drive, or perform other important activities of daily living. Efforts are therefore under way to develop strategies that allow for earlier detection and treatment of this disease. In this review, we begin by providing an overview of the rationale for, and the benefits of, early detection and treatment of neovascular AMD. To achieve this, we begin by providing an overview of the pathophysiology and natural history of choroidal neovascularization, before reviewing the evidence from both clinical trials and “real-world” outcome studies. We continue by highlighting an area that is often overlooked: the importance of patient education and awareness for early AMD detection. We conclude the review by reviewing an array of both established and emerging technologies for early detection of choroidal neovascularization, ranging from Amsler chart testing, to hyperacuity testing, to advanced imaging techniques, such as optical coherence tomography.

Repeatability of retinal thickness and volume metrics in neovascular age-related macular degeneration using the Topcon 3DOCT-1000

Introduction:

Optical coherence tomography (OCT) is a commonly used imaging modality that provides detailed cross-sectional retinal images. This has revolutionised management of neovascular age-related macular degeneration. The need for repeated anti-vascular endothelial growth factor injections has led to therapy being delivered using OCT-guided retreatment strategies with both qualitative OCT features of disease activity (e.g. macular fluid) and changes in retinal thickness as triggers for retreatment The purpose of this study is to determine the intra-session repeatability of retinal thickness and volume measurements using the Topcon 3DOCT-1000 spectral-domain optical coherence tomography (SDOCT) device in patients with neovascular age-related macular degeneration (nAMD). This is the largest study to date looking specifically at the Topcon 3DOCT-1000.

Materials and Methods:

Two SDOCT raster scans were performed by the same blinded observer in the same sitting in consecutive patients attending for nAMD treatment as part of standard validation of a new device. Retrospective analysis was undertaken, with retinal thickness and volume measurements automatically calculated by the onboard software for each Early Treatment of Diabetic Retinopathy Study subfield for each scan. Bland-Altman methods of analysis were used to assess repeatability.

Results:

Data from the 73 patients were analyzed with a mean age of 78 years (standard deviation 8). The 95% coefficient of repeatability (CR) was 64 μm and 0.050 mm³ for retinal thickness and volume respectively in the central 1 mm macular subfield. The CR did not exceed 85 μm (0.30 mm³) in any subfield. The revised CR for retinal thickness and volume for the subgroup of 37 patients with no segmentation error in the central 1 mm subfield was 53 μm and 0.050 mm³ respectively.

Discussion:

We report relatively modest intra-sessional repeatability of SDOCT retinal thickness and volume metrics in patients with nAMD in a clinical setting. Though useful in detecting clinical change from measurement variability in clinical practice, these results suggest the precision of macular thickness measurement does not approach the theoretical resolution of SDOCT.

Spectral-domain optical coherence tomography epithelial and flap thickness mapping in femtosecond laser-assisted in situ keratomileusis

PURPOSE

To evaluate the change of epithelial and flap thickness after femtosecond laser-assisted in situ keratomileusis (LASIK) using spectral-domain optical coherence tomography (SD OCT) in correlation with the spherical equivalent refraction treated and clinical outcomes.

DESIGN

Prospective, randomized, contralateral-eye study.

METHODS

Forty myopic eyes underwent LASIK using an excimer laser with refraction ranging from -1.00 to -7.25 diopters (mean -3.25±1.9). Flap creation was randomized between eyes, using the IntraLASE FS60 laser (IL) in 1 eye and WaveLight FS200 laser (FS) in the contralateral eye. SD OCT was used to evaluate the epithelial and flap thickness profiles and corneal power preoperatively and at 1 week and 1, 3, and 9 months postoperatively. Manifest and wavefront refractions were performed at each postoperative visit.

RESULTS

Statistically significant epithelial thickening was observed in both IL and FS groups as early as 1 month postoperatively (P=.033 and P=.042), but this stabilized between 3 (P=.042 and P=.035) and 9 months (P=.043 and P=.041). Femtosecond-LASIK flaps were thicker in the IL group in comparison to the FS group at 3 and 9 months postoperatively (P=.003 and P=.005, respectively). There was a statistically significant correlation between the magnitude of preoperative myopic refraction and the central epithelial thickness at 1, 3, and 9 months (Pearson correlation coefficients 0.485, 0.587 and 0.576) (P=.0021, P=.0010, and P=.0011), respectively. SD OCT corneal power maps showed steepening at 3 and 9 months along with mild myopic shift.

CONCLUSION

Progressive epithelial and flap thickening with increased corneal power were observed after femtosecond laser-assisted in situ keratomileusis for myopia with consequent stabilization between 3 to 9 months postoperatively. The magnitude of epithelial and flap thickness remodeling correlated to the preoperative myopic refractive error.

Epithelial and stromal remodeling after corneal collagen cross-linking evaluated by spectral-domain OCT

PURPOSE

To evaluate changes in corneal epithelial and stromal thickness after corneal collagen cross-linking (CXL) in eyes with keratoconus and postoperative corneal ectasia using spectral-domain optical coherence tomography (SD-OCT).

METHODS

Anterior segment SD-OCT (RTVue-100; Optovue, Inc., Fremont, CA) was used to compare regional corneal epithelial and stromal thickness in eyes with keratoconus and ectasia before CXL and 1 and 3 months after CXL. The anterior surface of the cornea, epithelium-Bowman's layer interface, and posterior reflective surface were used as anatomical landmarks to measure epithelial and stromal thickness, respectively. Regional thickness was assessed centrally and at 21 points 0.5 mm apart across the central 6 mm of the corneal vertex in the horizontal and vertical meridians.

RESULTS

Thirty-one eyes from 30 patients were evaluated, including 17 eyes (17 patients) with keratoconus and 14 eyes (13 patients) with ectasia. Preoperatively, a highly irregular epithelial thickness profile and distribution was observed in both groups. After CXL, epithelial thickness was significantly thinner 2.5 and 2 mm below and 1.5 mm above the corneal apex (49.26 ± 5.69 μm; range: 43 to 62 μm), and 2.5 and 1 mm nasal and 2 mm temporal to the corneal apex (46.66 ± 4.53 μm; range: 39 to 57 μm) compared to preoperative values (P < .05 for all measurements). Epithelial thickness standard deviations were significantly lower (by 3 to 6 μm) 3 months after CXL, compared to ranges before CXL in both the vertical and horizontal meridians for keratoconus and ectasia (P = .048). No significant differences were found between epithelial remodeling in keratoconus and corneal ectasia (P = .98). No significant or consistent stromal changes were found for either group.

CONCLUSIONS

Significant epithelial remodeling occurs after CXL in eyes with keratoconus and corneal ectasia, creating a similar, more regularized thickness profile in all meridians in the early postoperative period. This pattern of remodeling may facilitate interpretation of corneal curvature and thickness changes after CXL and may be related to visual acuity after CXL.

Agreement of two different spectral domain optical coherence tomography instruments for retinal nerve fiber layer measurements

PURPOSE

To determine the agreement between Spectralis and Cirrus spectral domain optical coherence tomography (SD-OCT) measurements of peripapillary retinal nerve fiber layer (RNFL) thickness.

METHODS

Suspected or confirmed cases of glaucoma who met the inclusion criteria underwent peripapillary RNFL thickness measurement using both the Spectralis and Cirrus on the same day within a few minutes.

RESULTS

Measurements were performed on 103 eyes of 103 patients with mean age of 50.4±17.7 years. Mean RNFL thickness was 89.22±15.87 versus 84.54±13.68 µm using Spectralis and Cirrus, respectively. The difference between measurements and the average of paired measurements with the two devices showed a significant linear relationship. Bland-Altman plots demonstrated that Spectralis thickness values were systematically larger than that of Cirrus.

CONCLUSION

Spectralis OCT generates higher peripapillary RNFL thickness readings as compared to Cirrus OCT; this should be kept in mind when values obtained with different instruments are compared during follow-up.

Different phenotypes of the appearance of the outer plexiform layer on optical coherence tomography

PURPOSE

To present a selected case series of different phenotypes of the normal outer plexiform layer (OPL) visualized by optical coherence tomography (OCT).

METHODS

Five cases were selected to represent the spectrum of appearances of the OPL in this case series. Categorical descriptions of each manifestation were then developed. Additional SD-OCT scans were obtained from a normal volunteer to further support the hypothesis.

RESULTS

The inner one-third of the OPL typically appears hyperreflective on OCT, while the outer two-thirds (Henle fiber layer) may have a more varied appearance. Six different phenotypes of Henle fiber layer reflectivity were noted in this series, and classified as: bright, columnar, dentate, delimited, indistinct, and dark. The brightness of the Henle fiber layer appears to depend on the geometric angle between the OCT light beam and the axonal fibers in this portion of the OPL. This angle appears to be a function of the natural orientation of the Henle fiber layer tissue (θN), the existence of subretinal pathology that alters the angle of the neurosensory retina (θ(P)), and the tilt angle of the tissue on the B-scan (θ(T)) due to decentered OCT acquisition.

CONCLUSIONS

Since accurate interpretation of the OPL/ONL boundary is of vital importance to study the thickness of ONL, location of cystoid lesions, hyperreflective crescents over drusen, et al., our case series may aid better understanding of the OPL appearance in SD-OCT. In the absence of clear delineation, it may be most correct to refer to indistinct OPL and ONL together as the photoreceptor nuclear axonal complex (PNAC).

Grading of Age-Related Macular Degeneration: Comparison between Color Fundus Photography, Fluorescein Angiography, and Spectral Domain Optical Coherence Tomography

Purpose. To compare color fundus photography (FP), fluorescein angiography (FA), and spectral domain optical coherence tomography (SDOCT) for the detection of age-related macular degeneration (AMD), choroidal neovascularisation (CNV), and CNV activity. Methods. FPs, FAs, and SDOCT volume scans from 120 eyes of 66 AMD and control patients were randomly collected. Control eyes were required to show no AMD, but other retinal pathology was allowed. The presence of drusen, pigmentary changes, CNV, and signs for CNV activity was independently analyzed for all imaging modalities. Results. AMD was diagnosed based on FP in 75 eyes. SDOCT and FA showed sensitivity (specificity) of 89% (76%) and 92% (82%), respectively. CNV was present on FA in 68 eyes. Sensitivity (specificity) was 78% (100%) for FP and 94% (98%) for SDOCT. CNV activity was detected by SDOCT or FA in 60 eyes with an agreement in 46 eyes. Sensitivity was 88% for SDOCT and 88% for FA. FP showed sensitivity of 38% and specificity of 98%. Conclusions. CNV lesions and activity may be missed by FP alone, but FP may help identifying drusen and pigmentary changes. SDOCT is highly sensitive for the detection of AMD, CNV, and CNV activity; however, it cannot fully replace FA.

Optical coherence tomography grading reproducibility during the Comparison of Age-related Macular Degeneration Treatments Trials

OBJECTIVE

To report reading center reproducibility during grading of Stratus optical coherence tomography (OCT) (Carl Zeiss Meditec, Dublin, CA) images obtained during the Comparison of Age-Related Macular Degeneration Treatments Trials (CATT).

DESIGN

Prospective, clinical trial.

PARTICIPANTS

Independent reading teams reevaluated 270 OCT scans randomly sampled from the first 2 years of CATT enrollment. To assess temporal drift, a cohort of 23 scans submitted during the initial portion of the CATT study was longitudinally followed with serial reproducibility analysis.

INTERVENTION

The CATT readers performed standardized grading of OCT images. A reader team, composed of 2 independent readers and a senior reader, evaluated each scan. Grading included the CATT OCT end points of total thickness at the foveal center point and intraretinal fluid (IRF), subretinal fluid (SRF), and subretinal pigment epithelium (RPE) fluid. Independent reading teams masked to the results of initial grading reevaluated scans to determine the reproducibility of qualitative grading and measurements.

MAIN OUTCOME MEASURES

Categorical grading agreement was reported using percent agreement and kappa statistic, and measurement agreement was reported using intraclass correlations and paired differences.

RESULTS

Reading center teams reproducibly graded IRF (percent agreement = 73%, kappa = 0.48; 95% confidence interval [CI], 0.38-0.58), SRF (percent agreement = 90%; kappa = 0.80; 95% CI, 0.73-0.87), and sub-RPE fluid (percent agreement 88%; kappa = 0.75; 95% CI, 0.67-0.83). For independent reading center team measurements of total thickness at the foveal center point, the intraclass correlation was 0.99 (95% CI, 0.99-0.99), and the mean paired difference between reading center teams was 4 μm (95% limits of agreement, -55 to 47 μm). There was no qualitative or quantitative grading drift.

CONCLUSIONS

The standardized protocols used to evaluate OCT scans from the CATT study were reproducible. The methods used are suitable to monitor OCT imaging data from a large, neovascular age-related macular degeneration, interventional, multicenter study.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Impact of scanning density on spectral domain optical coherence tomography assessments in neovascular age-related macular degeneration

PURPOSE

To determine the effect of optical coherence tomography (OCT) B-scan density on the qualitative assessment of neovascular age-related macular degeneration (AMD).

METHODS

Data were collected from 59 patients imaged with Topcon 3D OCT-1000 (128 B-scans × 512 A-scans). Custom software was used to generate less dense subsets of scans: 1/16 (eight B-scans), 1/8 (16 B-scans), 1/4 (32 B-scans) and 1/2 (64 B-scans). At each B-scan density, scans were assessed for cystoid spaces, subretinal fluid (SRF), subretinal tissue (SRT) and pigment epithelium detachment (PED). For each sampling density, sensitivity, specificity and predictive values were calculated using the full volume scan (128 B-scans) as the reference standard.

RESULTS

For cystoid spaces, the detection sensitivity was 76.3% at 1/16 density; this rose to 89.5% with a 1/4 density. For SRF, the detection sensitivity was 75.0% at a 1/16 density; this increased to 91.1% with 1/4 density. For PED, even at the lowest sampling density (1/16) the detection sensitivity was 86.4%; this rose to 94.9% at 1/4 density. For SRT, detection sensitivity at a 1/16 density was 64.7% and only rose above 90% with the densest sampling subset (1/2).

CONCLUSIONS

Use of scanning protocols with reduced sampling densities resulted in decreased detection of key features of neovascular AMD; despite this, a sampling density reduced to 1/4 appeared to allow accurate assessment for most features. Current management of neovascular AMD is dependent on qualitative assessment of OCT images; with the recent proliferation of OCT systems, optimization and standardization of scanning protocols may be of value.

Spectral domain OCT versus time domain OCT in the evaluation of macular features related to wet age-related macular degeneration

Background

The aim of this study was to compare the agreement between spectral domain optical coherence tomography (SD OCT) and time domain stratus OCT (TD OCT) in evaluating macular morphology alterations in wet age-related macular degeneration (AMD).

Methods

This retrospective study was performed on 77 eyes of 77 patients with primary or recurring subfoveal choroidal neovascularization secondary to AMD. All patients underwent OCT examination using Zeiss Stratus OCT 3 (Carl Zeiss Meditec Inc, Dublin, CA) and Opko OTI Spectral SLO/OCT (Ophthalmic Technologies Inc, Toronto, Canada). In all radial line scans, the presence of intraretinal edema (IRE), serous pigment epithelium detachment (sPED), neurosensory serous retinal detachment (NSRD), epiretinal membrane (EM), inner limiting membrane thickening (ILMT), and hard exudates (HE) were evaluated. The degree of matching was quantified by Kappa measure of agreement.

Results

The percentage distribution of TD OCT findings versus SD OCT findings was: IRE 36.3% versus 77.9%, sPED 57.1% versus 85.7%, NSRD 38.9% versus 53.2%, EM 10.5% versus 26.3%, ILMT 3.8% versus 32.4%, and HE 6.4% versus 54.5%. The agreement was as follows: sPED: kappa value 0.15; NSRD: kappa value 0.61; IRE: kappa value 0.18; EM: kappa value 0.41; ILMT: kappa value 0.02; HE: kappa value 0.06.

Conclusion

The agreement in the evaluation of macular lesions between the two techniques is poor and depends on the lesion considered. SD OCT allows better detection of the alterations typically related to choroidal neovascularization such as IRE, PED, ILM thickening, and HE. Consequently its use should be strongly considered in patients with wet AMD.

Analysis of microkeratome thin flap architecture using Fourier-domain optical coherence tomography

PURPOSE

To assess the corneal architecture and reproducibility of LASIK flap thickness created by the Amadeus II mechanical microkeratome (Ziemer Ophthalmic Systems AG) using Fourier-domain optical coherence tomography (OCT; Optovue Inc).

METHODS

Anterior segment Fourier-domain OCT was used to analyze the morphology of 58 LASIK flaps from 30 patients created with the Amadeus II microkeratome 140-μm head and ML7090CLB blades (Med-Logics Inc) at 2 weeks postoperatively. Flap thickness was assessed at 10 points across the central 6 mm of the cornea (horizontal and vertical meridians). Postoperative central corneal flap thickness measured by Fourier-domain OCT was compared with intraoperative ultrasound pachymetry measurements.

RESULTS

No significant difference was noted between central flap thickness measured by intraoperative pachymetry (107.2 ± 14 μm) and postoperative OCT (111.7 ± 11 μm; P=.07, correlation coefficient=0.86). Fourier-domain OCT measurements demonstrated functionally planar flap architecture (standard deviation [SD] of thickness across the flap=4.9 μm, SD range across the flap=2 to 9 μm) for the microkeratome flaps.

CONCLUSIONS

The Amadeus II microkeratome with Med-Logics blades created thin, reproducible, functionally planar flaps as measured by Fourier-domain OCT. Central flap thickness measured by intraoperative ultrasound pachymetry was equivalent to that measured 2 weeks postoperatively by OCT.

Macular changes detected by Fourier-domain optical coherence tomography in patients with hypotony without clinical maculopathy

PURPOSE

To investigate macular changes in eyes with postoperative hypotony without clinical maculopathy using high-resolution Fourier-domain optical coherence tomography (FD-OCT).

METHODS

Fourteen eyes of 12 patients with postoperative intraocular pressure (IOP) ￡ 6 mmHg for at least 4 weeks but with no detectable clinical features associated with hypotony maculopathy were imaged by FD-OCT prospectively. Images were analysed by two retina specialists masked to clinical findings.

RESULTS

Most patients were female (83%) and myopic (75%) with a mean age of 65 ± 17 [standard deviation (SD)] years (range 2–86 years). Mean central corneal thickness was 519 ± 34 lm [95% confidence interval (CI) 502–537] and mean IOP before surgery was 20 ± 8 mmHg (95% CI 15–24). During the period of hypotony (mean 15 ± 6 weeks), the average mean IOP was 4 ± 1 mmHg (95% CI 3–5). Abnormal FD-OCT findings (retinal folds and ⁄ or intraretinal fluid) were present in eight eyes. These patients had a higher rate of visual symptoms (75% versus 17%), visual acuity loss (‡ 2 lines; 63% versus 17%) and increased mean foveal thickness (250 ± 26 versus 210 ± 12 lm; p < 0.01, Mann–Whitney U-test) compared with those with normal FD-OCT.

CONCLUSION

FD-OCT identified subclinical macular abnormalities in over half of the eyes with postoperative hypotony. These findings were accompanied by visual disturbances and central macular thickening. FD-OCT can be an important diagnostic tool for this disorder when clinical features are absent.

Spectral-domain versus time domain optical coherence tomography before and after ranibizumab for age-related macular degeneration

PURPOSE

To study the ability to appreciate qualitative features that indicate disease activity in patients with neovascular age-related macular degeneration (AMD) and to analyze the differences in automated retinal thickness measurement, using 1 time domain optical coherence tomography (TD-OCT) and 2 different spectral-domain OCT (SD-OCT) machines.

METHODS

Thirty-three consecutive naïve patients with neovascular AMD underwent Stratus TD-OCT, Cirrus SD-OCT and Spectralis SD-OCT, at baseline, 1 h, 1 day, 1 week and 1 month after intravitreal ranibizumab injection.

RESULTS

As regards the ability to detect retinal cysts, subretinal fluid and pigment epithelium detachment, at each follow-up visit, there was a significant correlation among all 3 OCT devices (p < 0.05), even though Cirrus SD-OCT and Spectralis SD-OCT showed the highest level of intermachine agreement. At each follow-up visit, automated retinal thickness measurements showed a greater mean central macular thickness (CMT) for both Spectralis SD-OCT and Cirrus SD-OCT, compared with Stratus TD-OCT. However, the mean paired differences in CMT among the 3 OCT devices were not statistically significant (p > 0.05). Overall, Cirrus SD-CT showed fewer segmentation errors, compared with both Spectralis SD-OCT and Stratus TD-OCT.

CONCLUSION

SD-OCT showed a greater ability to evaluate qualitative features indicating disease activity and fewer errors in automated segmentation. However, differences in CMT changes were similar between TD-OCT and SD-OCT systems during follow-up.

Spectral-domain optical coherence tomography in patients with congenital nystagmus

AIM

To study macular features in patients with congenital nystagmus and to assess the utility of spectral-domain optical coherence tomography (SD-OCT) in nystagmus.

METHODS

The macular areas of 51 outpatients with congenital nystagmus were examined using SD-OCT. Morphological changes in the retinal layers of the macular area were analysed.

RESULTS

Macular images were successfully obtained with SD-OCT from 50 (98%) patients. Patients with ocular albinism mainly have macular hypoplasia, abnormal foveal depression, and increased foveal thickness with persistence of an inner nuclear layer, an inner plexiform layer, a ganglion cell layer and a nerve fiber layer. Macular morphology similar to albinism was observed in three patients with idiopathic macular hypoplasia. The OCT findings of cone dystrophy included unclear, disrupted or invisible photoreceptor outer segment/inner segment in the fovea; fusion, thickening and uneven reflection of the outer segment/inner segment with external limiting membrane. Some patients with congenital idiopathic nystagmus showed normal macular morphology and structure, and others showed indistinct macular external limiting membrane reflection.

CONCLUSION

SD-OCT is an effective and reliable method to detect the macular morphology of congenital nystagmus patients. This technique has diagnostic value in particular for patients with macular hypoplasia and cone cell dystrophy with no distinct abnormality on fundoscopy.

Detection of cystoid macular edema with three-dimensional optical coherence tomography versus fluorescein angiography

PURPOSE

To compare the sensitivity and reproducibility of three-dimensional optical coherence tomography (3D-OCT) and fluorescein angiography (FA) for the detection of cystoid macular edema (CME).

METHODS

Data were retrospectively collected from all patients who underwent digital FA and 512 × 128 horizontal raster 3D-OCT scans on the same day in a retina subspecialty clinic. Images were reviewed independently by four reading center graders and adjudicated as a group to render a single result for each eye and each imaging modality. The κ statistic was used to determine the level of agreement between graders for each modality. The sensitivity of each imaging modality for CME detection was calculated by using the presence of CME on either modality as the ground truth; subgroup analysis was performed according to disease diagnosis and lens status.

RESULTS

Four hundred thirteen eyes of 207 patients were included in the analysis. Intergrader agreement was higher for 3D-OCT than for FA both before (κ(OCT) = 0.61, κ(FA) = 0.43) and after adjudication (κ(OCT) = 0.74, κ(FA) = 0.58).The sensitivity for detection of definite CME was higher for 3D-OCT (95%, 144/151 cases) than for FA (44%, 67/151 cases). Definite FA (+) 3D-OCT (-) CME was identified in 1 eye (0.2%), whereas definite FA (-) 3D-OCT (+) CME was identified in 40 eyes (10%). No significant associations between CME detection and lens examination or disease diagnosis were observed.

CONCLUSIONS

In this study, 3D-OCT was more sensitive and had better intergrader agreement than did FA for the detection of CME.

Effects of retinal morphology on contrast sensitivity and reading ability in neovascular age-related macular degeneration

PURPOSE

To investigate the effect of changes in retinal morphology on contrast sensitivity and reading ability in patients with neovascular age-related macular degeneration (AMD) in the Avastin (bevacizumab; Genentech, South San Francisco, CA) for choroidal neovascularization (ABC) Trial.

METHODS

Contrast sensitivity obtained with Pelli-Robson charts, reading ability assessed with Minnesota Reading charts, and Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity (VA) obtained by protocol refraction, were recorded. Raw Stratus optical coherence tomography (OCT; Carl Zeiss Meditec, Inc., Dublin, CA) images were analyzed with the publicly available software OCTOR, which allows precise delineation of any retinal compartment of interest. Thickness and volume were calculated for neurosensory retina, subretinal fluid (SRF), subretinal tissue, and pigment epithelium detachment, and the resulting measurements were correlated with each visual function parameter.

RESULTS

One hundred twenty-two patients with newly diagnosed neovascular AMD and enrolled in the ABC Trial, were evaluated. Increased subretinal tissue volume correlated with decreased contrast sensitivity (Pearson's correlation coefficient, r = -0.4944, P = 0.001). A modest correlation was detected between SRF volume and contrast sensitivity (r = -0.2562, P = 0.004). Increased retinal thickness at the foveal center also correlated with decreased visual function (ETDRS VA: r = -0.4530, P < 0.001).

CONCLUSIONS

The strongest correlation detected between the functional parameters assessed and any of the OCT-derived morphologic parameters was that between decreased contrast sensitivity and increased subretinal tissue. In the future, assessment of contrast sensitivity and reading ability, in combination with quantitative subanalysis of retinal compartments, may lead to the identification of parameters relevant to functional improvement and ultimate prognosis in patients with newly diagnosed neovascular AMD (www.controlled-trials.com number, ISRCTN83325075).

Foveomacular schisis in juvenile X-linked retinoschisis: an optical coherence tomography study

PURPOSE

To explore the structural features of juvenile X-linked retinoschisis using spectral-domain optical coherence tomography (OCT).

DESIGN

Retrospective, observational cross-sectional study.

METHODS

Eighteen male patients (34 eyes) who were diagnosed with juvenile X-linked retinoschisis at the Eye & ENT Hospital of Fudan University over an 18-month period were included. Their OCT images, which were obtained using spectral-domain OCT (Cirrus HD-OCT; Carl Zeiss Meditec), were analyzed. The anatomic location of the schisis cavity in juvenile X-linked retinoschisis was characterized by direct inspection of OCT images.

RESULTS

On OCT, the schisis cavity was visible at the fovea in all 34 eyes, and it was associated with increased retinal thickness. Schisis was present at the retinal nerve fiber layer in 4 eyes, at the inner nuclear layer in 29 eyes, and at the outer nuclear layer/outer plexiform layer in 22 eyes. In most cases, widespread foveomacular schisis was detected using OCT; however, in 9 eyes (6 patients), the schisis was confined to the fovea. Schisis of the inner nuclear layer and outer nuclear layer/outer plexiform layer almost always involved the foveal center, but retinal nerve fiber layer schisis was seen only in the parafoveal area.

CONCLUSIONS

Despite conventional wisdom, in patients with X-linked retinoschisis, the schisis cavity can occur in a number of different layers of the neurosensory retina (retinal nerve fiber layer, inner nuclear layer, and outer nuclear layer/outer plexiform layer). In addition, different forms of schisis may affect different locations in the macula (foveal vs parafoveal), and, in most eyes, the schisis involves the entire foveomacular region.

Agreement of time-domain and spectral-domain optical coherence tomography with fluorescein leakage from choroidal neovascularization

PURPOSE

To compare fluorescein leakage from choroidal neovascularization (CNV) with signs of intraretinal or subretinal fluid on time-domain optical coherence tomography (TD-OCT) and spectral-domain optical coherence tomography (SD-OCT) in patients receiving anti-vascular endothelial growth factor (anti-VEGF) therapy for CNV caused by age-related macular degeneration (AMD).

DESIGN

Retrospective, consecutive case series.

PARTICIPANTS

Fifty-nine eyes of 56 patients with neovascular AMD receiving anti-VEGF therapy.

METHODS

All patients were imaged with fluorescein angiography (FA), TD-OCT (Stratus, Carl Zeiss Meditec, Inc., Dublin, CA), and SD-OCT (Cirrus, Carl Zeiss Meditec, Inc). All images were analyzed by an experienced reading center grader masked to all clinical data. Fluorescein leakage from CNV and OCT abnormalities (presence of interstitial fluid, retinal cystoid abnormalities, and subretinal fluid) were documented for each visit.

MAIN OUTCOME MEASURES

Agreement of OCT findings with presence or absence of fluorescein leakage from CNV.

RESULTS

For TD-OCT, the sensitivity, specificity, positive predictive value, and negative predicative value (and 95% confidence intervals) for OCT abnormalities were 59% (46-72), 63% (50-75%), 61% (49-73), and 61% (48-74), respectively. For SD-OCT, the sensitivity, specificity, positive predictive value, and negative predictive value (and 95% confidence intervals) for OCT abnormalities were 90% (82-98), 47% (34-60), 62% (49-75), and 82% (72-92), respectively.

CONCLUSIONS

Spectral-domain optical coherence tomography seems more likely than TD-OCT to detect abnormalities when fluorescein leakage from CNV is detected after anti-VEGF therapy. However, SD-OCT also seems to detect abnormalities frequently in the absence of fluorescein leakage from CNV. Whether treatment decisions based on any of these modalities result in visual acuity outcomes that are similar or superior to monthly treatments without such evaluations is unknown, but this study provides information that may assist in the design of studies to evaluate the role of OCT and FA in the management of CNV.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Imaging chorioretinal vascular disease

Since its first description more than 40 years ago, fluorescein angiography had a crucial role in the diagnosis and management of chorioretinal vascular disorders such as neovascular age-related macular degeneration. Although fluorescein angiography permits visualization of the retinal microcirculation in exquisite detail, visualization of the choroidal circulation is more limited. Moreover, fluorescein angiography provides only minimal information regarding the functional consequences of vascular disease and allows, at best, only semi-quantitative assessment of retinal thickness. In recent years, the development of other chorioretinal imaging modalities, such as indocyanine green angiography, fundus autofluorescence, and optical coherence tomography (OCT), has addressed many of these issues. In particular, OCT has become an integral tool for vitreoretinal specialists as it allows high-resolution cross-sectional images of the neurosensory retina to be obtained in a non-invasive manner. The latest generation of commercial OCT technology-spectral domain OCT-offers high-speed scanning that allows complete coverage of the macular area, generation of three-dimensional retinal reconstructions, and precise image registration for inter-visit comparisons. The high speed of spectral domain OCT also facilitates B-scan averaging, which reduces speckle noise artefact and allows unparalleled visualization of the outer retina and choroid. In the near future, further advances in OCT technology (eg Doppler OCT) are likely to dramatically enhance the diagnosis and management of patients with chorioretinal vascular disease.

Impact of scanning density on measurements from spectral domain optical coherence tomography

PURPOSE

To investigate the relationship between B-scan density and retinal thickness measurements obtained by spectral domain optical coherence tomography (SDOCT) in eyes with retinal disease.

METHODS

Data were collected from 115 patients who underwent volume OCT imaging with Cirrus HD-OCT using the 512 x 128 horizontal raster protocol. Raw OCT data, including the location of the automated retinal boundaries, were exported from the Cirrus HD-OCT instrument and imported into the Doheny Image Reading Center (DIRC) OCT viewing and grading software, termed "3D-OCTOR." For each case, retinal thickness maps similar to those produced by Cirrus HD-OCT were generated using all 128 B-scans, as well as using less dense subsets of scans, ranging from every other scan to every 16th scan. Retinal thickness measurements derived using only a subset of scans were compared to measurements using all 128 B-scans, and differences for the foveal central subfield (FCS) and total macular volume were computed.

RESULTS

The mean error in FCS retinal thickness measurement increased as the density of B-scans decreased, but the error was small (<2 microm), except at the sparsest densities evaluated. The maximum error at a density of every fourth scan (32 scans spaced 188 microm apart) was <1%.

CONCLUSIONS

B-scan density in volume SDOCT acquisitions can be reduced to 32 horizontal B-scans (spaced 188 microm apart) with minimal change in calculated retinal thickness measurements. This information may be of value in design of scanning protocols for SDOCT for use in future clinical trials.