Objective: To demonstrate optical coherence tomography for high-resolution, noninvasive imaging of the human retina. Optical coherence tomography is a new imaging technique analogous to ultrasound B scan that can provide cross-sectional images of the retina with micrometer-scale resolution. Design: Survey optical coherence tomographic examination of the retina, including the macula and optic nerve head in normal human subjects. Settings Research laboratory. Participants: Convenience sample of normal human subjects. Main Outcome Measures: Correlation of optical coherence retinal tomographs with known normal retinal anatomy. Results: Optical coherence tomographs can discriminate the cross-sectional morphologic features of the fovea and optic disc, the layered structure of the retina, and normal anatomic variations in retinal and retinal nerve fiber layer thicknesses with 10- μm depth resolution. Conclusion: Optical coherence tomography is a potentially useful technique for high depth resolution, cross-sectional examination of the fundus.

Optical Coherence Tomography of the Human Retina

AIM To evaluate the outcomes of ≥6y ranibizumab therapy in neovascular age-related macular degeneration (AMD). METHODS HELIX was a retrospective, observational effectiveness study using medical records of patients treated in three clinics in Belgium. Patients had neovascular AMD and were initially treated with intravitreal ranibizumab (0.5 mg) between November 1, 2007 and October 31, 2008, had ≥6y of data available, and were treated on an ongoing, as-needed basis. Outcomes included best-corrected visual acuity (BCVA) and central retinal thickness (CRT). RESULTS The sample consisted of 88 eyes from 69 patients. Mean age was 76.4±6.5y, most patients were female (62.3%). Most eyes (62.5%) were treatment-naive, 33 previously treated eyes had received predominantly other anti-vascular endothelial growth factor agents and verteporfin. Mean baseline BCVA was 57.4±12.7 ETDRS letters and CRT was 291.5±86.1 μm. On average, patients received 20.6±11.9 ranibizumab injections over the ≥6y. Intervals between injections were on average 12.7±16.1wk. Mean change in BCVA from baseline to last observation for the sample was less than one letter (-0.9±17.3 letters), with an average loss of -3.2±15.6 letters in previously treated eyes versus a gain of 0.6±18.4 letters in treatment-naive eyes. When considering a loss of <15 letters over 6y as stabilization of disease, 75.9% of all eyes showed a positive (improvement or stabilization) outcome. Mean change in CRT from baseline to last observation for the sample was -26.9±148.4 μm with the greatest reduction observed in treatment-naive eyes. CONCLUSION This retrospective study of 69 neovascular AMD patients treated for ≥6y with ranibizumab demonstrates long-term visual stabilization. In light of the natural evolution of the disease, these data confirm that ranibizumab is effective long-term under real-world conditions of heterogeneity of patients, clinicians, and centers.

Six-year outcomes in neovascular age-related macular degeneration with ranibizumab

Optical coherence tomography (OCT) is widely used in ophthalmology for viewing the morphology of the retina, which is important for disease detection and assessing therapeutic effect. The diagnosis of retinal diseases is based primarily on the subjective analysis of OCT images by trained ophthalmologists. This paper describes an OCT images automatic analysis method for computer-aided disease diagnosis and it is a critical part of the eye fundus diagnosis. This study analyzed 300 OCT images acquired by Optovue Avanti RTVue XR (Optovue Corp., Fremont, CA). Firstly, the normal retinal reference model based on retinal boundaries was presented. Subsequently, two kinds of quantitative methods based on geometric features and morphological features were proposed. This paper put forward a retinal abnormal grading decision-making method which was used in actual analysis and evaluation of multiple OCT images. This paper showed detailed analysis process by four retinal OCT images with different abnormal degrees. The final grading results verified that the analysis method can distinguish abnormal severity and lesion regions. This paper presented the simulation of the 150 test images, where the results of analysis of retinal status showed that the sensitivity was 0.94 and specificity was 0.92.The proposed method can speed up diagnostic process and objectively evaluate the retinal status. This paper aims on studies of retinal status automatic analysis method based on feature extraction and quantitative grading in OCT images. The proposed method can obtain the parameters and the features that are associated with retinal morphology. Quantitative analysis and evaluation of these features are combined with reference model which can realize the target image abnormal judgment and provide a reference for disease diagnosis.

/pdf/retinal-status-analysis-method-based-on-feature-extraction-2nkwb9p0n3.pdf

Retinal status analysis method based on feature extraction and quantitative grading in OCT images.

PURPOSE The aim of this study was to investigate the pathogenic role of obesity on blinding eye diseases in a population of severely obese patients with no history of eye diseases, and to verify whether weight loss induced by bariatric surgery may have a protective effect. METHODS This was a pilot, monocentric, prospective, and open label study conducted at the University Hospital of Pisa. Fifty-seven severely obese patients with a mean body mass index value of 44.1 ± 6 kg/m2 were consecutively recruited and received a complete ophthalmological evaluation and optical coherence tomography. Twenty-nine patients who underwent gastric bypass were evaluated also 3 months, and 1 year after surgery. RESULTS At baseline, blood pressure value were directly and significantly related to intraocular pressure values (p<0.05, R = 0.35). Blood pressure values were also significantly and inversely related to retinal nerve fiber layer thickness, particularly in the temporal sector (RE p<0.05 r-0.30; LE p<0.01, R = -0.43). Moreover, minimum foveal thickness values were significantly and inversely associated with body mass index (RE p<0.02, R = -0.40; LE p<0.02, R = -0.30). A significant reduction of body mass index (p<0.05) and a significant (p<0.05) improvement of blood pressure was observed three months and one year after gastric bypass, which were significantly associated with an increase in retinal nerve fiber layer thickness and minimum foveal thickness values in both eyes (p<0.05). CONCLUSIONS The results of this study suggest that obese patients may have a greater susceptibility to develop glaucomatous optic nerve head damage and age-related macular degeneration. Moreover, weight reduction and improvement of comorbidities obtained by bariatric surgery may be effective in preventing eye disease development by improving retinal nerve fiber layer and foveal thickness.

Ophthalmologic evaluation of severely obese patients undergoing bariatric surgery: A pilot, monocentric, prospective, open-label study.

PURPOSE To evaluate the alterations in mean central choroidal, central macular, and disk retinal nerve fiber layer (RNFL) thickness measured by optical coherence tomography (OCT) during Valsalva maneuver among patients with high refractive errors. METHODS A total of 60 high myopic (≥-6.0 D) and 50 high hyperopic (≥ + 3.0 D) eyes of 58 patients aged 19-65 years with visual acuity of 20/20 and without any ophthalmologic or systemic diseases were evaluated by OCT before and after the Valsalva maneuver. The choroidal thickness was measured with enhanced depth imaging OCT method. Central macular thickness, disk RNFL thickness, and axial length were also assessed. RESULTS Mean choroidal thickness increased significantly from 275.0 ± 27.2 μm at rest to 279.8 ± 31.6 μm after Valsalva maneuver in high myopic patients, and from 308.2 ± 27.3 μm to 313.6 ± 28.5 μm in high hyperopic patients (p<0.01 for each). A significant negative correlation of the choroidal thickness was noted with axial length (r = -0.509, p<0.01) and age (r = -0.224, p = 0.01) in the overall study population. Mean central macular thickness was 242.9 ± 44.4 μm and 254.0 ± 22.8 μm, while mean disk RNFL thickness was 81.6 ± 12.4 μm and 98.4 ± 13.3 μm in high myopic and hyperopic patients, respectively. Valsalva maneuver was not associated with significant change in central macular or disk RNFL thickness. CONCLUSIONS Significant association of Valsalva maneuver with an increase in choroidal thickness was noted among patients with high degree of myopia and hyperopia. Our findings emphasize the likelihood of increase in choroidal volume due to venous distension to be responsible for the increase observed in choroidal thickness after Valsalva maneuver.

Impact of Valsalva maneuver on central choroid, central macula, and disk fiber layer thickness among high myopic and hyperopic patients.

Optical coherence tomography (OCT) is the most common imaging tool used to examine the macula, as it is the only instrument that provides direct visualization of the in vivo retinal structure [1]. The traditional OCT technique involves time-domain OCT (TD-OCT) [2-5], where retinal depth information is obtained with a reference arm after longitudinal translation over time [6]. Good reproducibility of retinal thickness measurements by Stratus OCT (Carl Zeiss Meditec, Dublin, CA, USA) has been demonstrated [7,8]. However, since the time-domain method samples only one point at a time, a relatively long period of time is needed to obtain A- and B-scan images, resulting in lower image resolution compared to spectral domain-OCT (SD-OCT) [9].

Newer SD-OCT offers improved image resolution of less than 5 to 7 µm, dramatically faster acquisition speeds (18,000 to 40,000 A-scans/second), and detailed views of the intraretinal microstructures as well as three-dimensional images of the retina [8,10-12]. In SD-OCT, light beams returning from the sample and reference paths are combined at the detector, and then a spectrometer resolves the interference signals throughout the depth of each A-scan without varying the length of the reference path [9]. This allows the acquisition of retinal images approximately 50 times faster with SD-OCT than with TD-OCT [13] and results in improved resolution of the B-scan images and better delineation of the retinal layers, including the retinal pigment epithelium (RPE)-Bruch's membrane choriocapillaris complex [14,15].

Numerous studies and clinical trials have used foveal thickness (FT) values that are measured by Stratus OCT for the determination of macular lesions, such as those in exudative age-related macular degeneration (AMD) and macular edema, and for the assessment of treatment response and guidelines for retreatment [16-18]. In order to use the known treatment and follow-up guidelines that are proposed in numerous clinical studies, it is essential to match the thickness parameters of different OCT devices, especially between TD-OCT and SD-OCT. A recent study on normal subjects demonstrated that Spectralis OCT (Heidelberg Engineering Inc., Heidelberg, Germany) obtained retinal thickness measurements that were increased by approximately 65 to 70 µm compared to Stratus OCT measurements [19].

However, studies have reported discrepancies in FT values measured by TD-OCT and SD-OCT in eyes with various retinal diseases [20-23]. Stratus OCT defines retinal thickness from the internal limiting membrane (ILM) to the complex of the inner and outer segments (IS/OS) of the photoreceptor junction and RPE layer, while Spectralis OCT selects images from the ILM to the RPE-Bruch's membrane choriocapillaris complex [12]. Because the segmentation algorithm for each OCT instrument is different, the measured FT should also be different for each. One study using Stratus and Spectralis OCT reported that the mean foveal thickness differences (FTD) in eyes with choroidal neovascularization (CNV) and AMD were significantly greater than those in normal eyes and in other retinal diseases [20]. Conversion equations and their application to TD-OCT and SD-OCT for the examination of eyes with diabetic macular edema [22] and with AMD [23] have been previously reported. However, no studies have compared the distribution of FTDs in various retinal diseases or constructed conversion formulas that predict TD-OCT-measured FT on the basis of SD-OCT-measured FT across different retinal diseases. In addition, the association between the amount of FTD and the disease severity indicated by FT has not yet been investigated.

The purpose of this study was to compare the measurement values obtained using TD-OCT (Stratus) and SD-OCT (Spectralis) devices in normal and diseased retinas in order to construct conversion formulas in normal eyes and eyes with various retinal diseases. These conversion formulas must be as accurate as possible in order to predict the FT provided by Stratus OCT on the basis of data obtained using Spectralis OCT. The accuracy of these formulas must also be verified to ensure minimal errors in clinical application.

/pdf/foveal-thickness-between-stratus-and-spectralis-optical-2m4r48kolk.pdf

Foveal Thickness between Stratus and Spectralis Optical Coherence Tomography in Retinal Diseases

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Foveal Thickness between Stratus and Spectralis Optical Coherence Tomography in Retinal Diseases