Faculty Bibliography

PURPOSE: To report the frequency of optical coherence tomography (OCT) scan artifacts and to compare macular thickness measurements, interscan reproducibility, and interdevice agreeability across 3 spectral-domain (SD) OCT (also known as Fourier domain; Cirrus HD-OCT, RTVue-100, and Topcon 3D-OCT 1000) devices and 1 time-domain (TD) OCT (Stratus OCT) device. DESIGN: Prospective, noncomparative, noninterventional case series. PARTICIPANTS: Fifty-two patients seen at the New England Eye Center, Tufts Medical Center Retina Service, between February and August 2008. METHODS: Two scans were performed for each of the SD OCT protocols: Cirrus macular cube 512 x 128 (software version 3.0; Carl Zeiss Meditec, Inc., Dublin, CA), RTVue (E)MM5 and MM6 (software version 3.5; Optovue, Inc., Fremont, CA), Topcon 3D Macular and Radial (software version 2.12; Topcon, Inc., Paramus, NJ), in addition to 1 TD OCT scan via Stratus macular thickness protocol (software version 4.0; Carl Zeiss Meditec, Inc.). Scans were inspected for 6 types of OCT scan artifacts and were analyzed. Interscan reproducibility and interdevice agreeability were assessed by intraclass correlation coefficients (ICCs) and Bland-Altman plots, respectively. MAIN OUTCOME MEASURES: Optical coherence tomography image artifacts, macular thickness, reproducibility, and agreeability. RESULTS: Time-domain OCT scans contained a significantly higher percentage of clinically significant improper central foveal thickness (IFT) after manual correction (11-mum change or more) compared with SD OCT scans. Cirrus HD-OCT had a significantly lower percentage of clinically significant IFT (11.1%) compared with the other SD OCT devices (Topcon 3D, 20.4%; Topcon Radial, 29.6%; RTVue (E)MM5, 42.6%; RTVue MM6, 24.1%; P = 0.001). All 3 SD OCT devices had central foveal subfield thicknesses that were significantly more than that of TD OCT after manual correction (P<0.0001). All 3 SD OCT devices demonstrated a high degree of reproducibility in the central foveal region (ICCs, 0.92-0.97). Bland-Altman plots showed low agreeability between TD and SD OCT scans. CONCLUSIONS: Out of all OCT devices analyzed, cirrus HD-OCT scans exhibited the lowest occurrence of any artifacts (68.5%), IFT (40.7%), and clinically significant IFT (11.1%), whereas Stratus OCT scans exhibited the highest occurrence of clinically significant IFT. Further work on improving segmentation algorithm to decrease artifacts is warranted.

BACKGROUND/AIMS: To investigate retinal nerve fibre layer (RNFL) thickness measurement reproducibility using conventional time-domain optical coherence tomography (TD-OCT) and spectral-domain OCT (SD-OCT), and to evaluate two methods defining the optic nerve head (ONH) centring: Centred Each Time (CET) vs Centred Once (CO), in terms of RNFL thickness measurement variability on SD-OCT. METHODS: Twenty-seven eyes (14 healthy subjects) had three circumpapillary scans with TD-OCT and three raster scans (three-dimensional or 3D image data) around ONH with SD-OCT. SD-OCT images were analysed in two ways: (1) CET: ONH centre was defined on each image separately and (2) CO: ONH centre was defined on one image and exported to other images after scan registration. After defining the ONH centre, a 3.4 mm diameter virtual circular OCT was resampled on SD-OCT images to mimic the conventional circumpapillary RNFL thickness measurements taken with TD-OCT. RESULTS: CET and CO showed statistically significantly better reproducibility than TD-OCT except for 11:00 with CET. CET and CO methods showed similar reproducibility. CONCLUSIONS: SD-OCT 3D cube data generally showed better RNFL measurement reproducibility than TD-OCT. The choice of ONH centring methods did not affect RNFL measurement reproducibility.

PURPOSE: To determine the effects of age on global and sectoral peripapillary retinal nerve fiber layer (RNFL), macular thicknesses, and optic nerve head (ONH) parameters in healthy subjects using optical coherence tomography (OCT). DESIGN: Retrospective, cross-sectional observational study. PARTICIPANTS: A total of 226 eyes from 124 healthy subjects were included. METHODS: Healthy subjects were scanned using the Fast RNFL, Fast Macula, and Fast ONH scan patterns on a Stratus OCT (Carl Zeiss Meditec, Dublin, CA). All global and sectoral RNFL and macular parameters and global ONH parameters were modeled in terms of age using linear mixed effects models. Normalized slopes were also calculated by dividing the slopes by the mean value of the OCT parameter for interparameter comparison. MAIN OUTCOME MEASURES: Slope of each OCT parameter across age. RESULTS: All global and sectoral RNFL thickness parameters statistically significantly decreased with increasing age, except for the temporal quadrant and clock hours 8 to 10, which were not statistically different from a slope of zero. Highest absolute slopes were in the inferior and superior quadrant RNFL and clock hour 1 (superior nasal). Normalized slopes showed a similar rate in all sectors except for the temporal clock hours (8-10). All macular thickness parameters statistically significantly decreased with increasing age, except for the central fovea sector, which had a slight positive slope that was not statistically significant. The nasal outer sector had the greatest absolute slope. Normalized macular slope in the outer ring was similar to the normalized slopes in the RNFL. Normalized inner ring had shallower slope than the outer ring with a similar rate in all quadrants. Disc area remained nearly constant across the ages, but cup area increased and rim area decreased with age, both of which were statistically significant. CONCLUSIONS: Global and regional changes caused by the effects of age on RNFL, macula, and ONH OCT measurements should be considered when assessing eyes over time. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.

OBJECTIVE: To evaluate intraretinal anatomy in patients with exudative age-related macular degeneration (AMD) using high-speed ultrahigh resolution optical coherence tomography (hsUHR-OCT) before and 1 month after intravitreal injection of ranibizumab. DESIGN: Retrospective case series. PARTICIPANTS: Twelve eyes of 12 patients. METHODS: A broad bandwidth superluminescent diode laser light source and spectral/Fourier domain signal detection were used to create a prototype hsUHR-OCT instrument with 3.5 mum axial image resolution and approximately 25,000 lines/second acquisition speed. Twelve eyes of 12 patients with exudative AMD were imaged with hsUHR-OCT before and 1 month after intravitreal ranibizumab injection. High pixel density and raster-scanned 3-dimensional (3D) OCT data sets were generated. Three-dimensional imaging software was used to calculate subretinal/retinal pigment epithelium fluid volume and volume of the fibrovascular lesion. MAIN OUTCOME MEASURES: Qualitative and quantitative analysis of hsUHR-OCT images and 3D data sets. RESULTS: All eyes had some degree of normalization of macular contour after intravitreal ranibizumab. The inner/outer photoreceptor segment junction visualized on hsUHR-OCT was discontinuous, overlying the fibrovascular lesion in all 12 of 12 eyes both before and after treatment; 9 of 12 eyes had focal areas of thinning of the outer nuclear layer, which remained after treatment. Volumetric measurements were possible in 8 of 12 eyes with 3D-rendering software. Fibrovascular lesion volume did not change significantly after treatment. CONCLUSIONS: hsUHR-OCT is capable of unprecedented imaging speed and resolution, making it a valuable instrument in measuring in vivo intraretinal pathology. All 12 eyes had some normalization of macular contour. Fibrovascular lesion volume did not change significantly 1 month after treatment, suggesting that ranibizumab does not cause much initial regression of preexisting neovascular tissue. Photoreceptor abnormalities remained in all patients after treatment of wet AMD, suggesting that although ranibizumab improves overall retinal architecture, some photoreceptor damage may be irreversible. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.

AIMS: To demonstrate ultrahigh-resolution, three-dimensional optical coherence tomography (3D-OCT) and projection OCT fundus imaging for enhanced visualisation of outer retinal pathology in non-exudative age-related macular degeneration (AMD). METHODS: A high-speed, 3.5 mum resolution OCT prototype instrument was developed for the ophthalmic clinic. Eighty-three patients with non-exudative AMD were imaged. Projection OCT fundus images were generated from 3D-OCT data by selectively summing different retinal depth levels. Results were compared with standard ophthalmic examination, including fundus photography and fluorescein angiography, when indicated. RESULTS: Projection OCT fundus imaging enhanced the visualisation of outer retinal pathology in non-exudative AMD. Different types of drusen exhibited distinct features in projection OCT images. Photoreceptor disruption was indicated by loss of the photoreceptor inner/outer segment (IS/OS) boundary and external limiting membrane (ELM). RPE atrophy can be assessed using choroid-level projection OCT images. CONCLUSIONS: Projection OCT fundus imaging facilities rapid interpretation of large 3D-OCT data sets. Projection OCT enhances contrast and visualises outer retinal pathology not visible with standard fundus imaging or OCT fundus imaging. Projection OCT fundus images enable registration with standard ophthalmic diagnostics and cross-sectional OCT images. Outer retinal alterations can be assessed and drusen morphology, photoreceptor impairment and pigmentary abnormalities identified.

Optical coherence tomography has allowed unprecedented visualization of ocular structures, but the identity of some visible objects within slices remains unknown. This study reconstructs a number of those objects in 3D space, allowing their identification by observation of their 3D morphology. In the case mottling deep within image slices through the optic disc, C-mode imaging provided visualization of the appearance and distribution of laminar pores. In the case of white spots and streaks sometimes observed in image slices through the cornea, C-mode imaging contoured to the path of those white spots allowed their visual identification as nerves extending radially into the cornea from the limbus. White spots observed in ultra-high resolution retinal image slices were identified as blood within retinal capillaries. C-mode contour-corrected imaging of three dimensional structures provided the identification of previously unidentified structures visible in cross-sectional image slices.

The Optical Society (OSA) is pleased to present this special issue of Optics Express on "Optical Coherence Tomography (OCT) in Ophthalmology" as part of the new Interactive Science Publishing (ISP) project. The project is being performed in collaboration with the National Library of Medicine and represents a new paradigm for the publication of digital image and large dataset information.

Ultrahigh resolution optical coherence tomography (OCT) enhances the ability to visualize different intra retinal layers. In age-related macular degeneration (AMD), pathological changes in individual retinal layers, including photoreceptor inner and outer segments and retinal pigment epithelium, can be detected. OCT using spectral / Fourier domain detection enables high speed, volumetric imaging of the macula, which provides comprehensive three-dimensional tomographic and morphologic information. We present a case series of AMD patients, from mild drusen to more advanced geographic atrophy and exudative AMD. Patients were imaged with a research prototype, ultrahigh resolution spectral / Fourier domain OCT instrument with 3.5 microm axial image resolution operating at 25,000 axial scans per second. These cases provide representative volumetric datasets of well-documented AMD pathologies which could be used for the development of visualization and imaging processing methods and algorithms.

PURPOSE: To develop a semiautomated method to visualize structures of interest (SoIs) along their contour within three-dimensional, spectral domain optical coherence tomography (3D SD-OCT) data, without the need for segmentation. METHODS: With the use of two SD-OCT devices, the authors obtained 3D SD-OCT data within 6 x 6 x 1.4-mm and 6 x 6 x 2-mm volumes, respectively, centered on the fovea in healthy eyes and in eyes with retinal pathology. C-mode images were generated by sampling a variable thickness plane semiautomatically modeled to fit the contour of the SoI. Unlike published and commercialized methods, this method did not require retinal layer segmentation, which is known to fail frequently in the presence of retinal pathology. Four SoIs were visualized for healthy eyes: striation of retinal nerve fiber (RNF), retinal capillary network (RCN), choroidal capillary network (CCN), and major choroidal vasculature (CV). Various SoIs were visualized for eyes with retinal pathology. RESULTS: Seven healthy eyes and seven eyes with retinal pathology (cystoid macular edema, central serous retinopathy, vitreoretinal traction, and age-related macular degeneration) were imaged. CCN and CV were successfully visualized in all eyes, whereas RNF and RCN were visualized in all healthy eyes and in 42.8% of eyes with pathologies. Various SoIs were successfully visualized in all eyes with retinal pathology. CONCLUSIONS: The proposed C-mode contour modeling may provide clinically useful images of SoIs even in eyes with severe pathologic changes in which segmentation algorithms fail.