Jason Y. Zhang

Retinal Neovascularization Secondary to Proliferative Diabetic Retinopathy Characterized by Spectral Domain Optical Coherence Tomography

Purpose: The purpose of this study was to characterize diabetic retinal neovascularization (NV) and accompanying retinal and vitreal morphologic changes using high-resolution spectral domain optical coherence tomography. Methods: A cross-sectional retrospective analysis was performed on 16 eyes of 14 nonconsecutive subjects with proliferative diabetic retinopathy that were seen between August 2011 and December 2011 at the New England Eye Center, Boston, MA. Patients who had NV of the disk, NV elsewhere, and intraretinal microvascular abnormalities were scanned using optical coherence tomography directly over the region of the abnormal vessels. Results: Characteristic changes of the retinal vasculature, retina, and vitreous were seen in the 16 eyes with NV. This study describes optical coherence tomography characteristics of 1) NV of the disk, 2) NV elsewhere, 3) intraretinal microvascular abnormality, 4) NV causing traction without retinal detachment; and 5) NV causing traction with retinal detachment. The morphologic appearance of vitreous traction was found to be consistent with the previous histologic reports. Conclusion: It is possible to image diabetic NV using spectral domain optical coherence tomography and to visualize the spectrum of retinal, retinal vascular, and vitreal changes seen through these areas of abnormal retinal vasculature.

Analysis of the Morphology and Vascular Layers of the Choroid in Retinitis Pigmentosa Using Spectral-Domain OCT

BACKGROUND AND OBJECTIVE To analyze choroidal morphology and vascular layers in eyes with retinitis pigmentosa (RP) using spectral-domain optical coherence tomography. PATIENTS AND METHODS Cross-sectional, retrospective analysis of 14 patients (14 eyes) with RP and 33 healthy subjects (33 eyes) who underwent high-definition one-line raster scanning at a single center. Two independent raters evaluated the morphology, thickness, and vascular layers of the choroid in both groups. RESULTS The choroid had an irregular shape in 11 of 14 eyes (79%) with RP. The thickest point of choroid was not subfoveal as in healthy eyes, and exaggerated nasal thinning of the choroid was observed in nine of 14 eyes (65%) with RP. Mean subfoveal total choroidal thickness and large choroidal vessel layer thickness were significantly lower in eyes with RP (P = .04 and P = .02, respectively) than in healthy eyes. CONCLUSION Choroidal morphology is altered and an exaggerated thinning of the large choroidal vessel layer is observed in eyes with RP. Further studies involving correlation of disease stage and severity with choroidal changes may provide further insight into the involvement of choroid in RP and other inherited retinal dystrophies.

Use of Optical Coherence Tomography in the Diagnosis and Management of Uveitis

Uveitis is a challenging disease. It represents a major cause of ocular morbidity worldwide. More than half of all patients with uveitis develop sight threatening complications related to their disease, and up to 35% of patients suffer severe visual impairment 1, 2. Uveitis and its complications are responsible for 5% to 10% of all causes of legal blindness in developed countries 1, 3. The causes of uveitis are numerous, and include infectious conditions, autoimmune diseases, trauma and tumors (masquerade syndrome). To develop an accurate differential diagnosis, clinicians must consider all available information, including the patient history, anatomic location of the inflammation (anterior or posterior), character (granulomatous vs. non granulomatous), laterality, and chronicity of inflammation. Moreover, diagnostic tools, such as fluorescein angiography (FA), indocyanine green angiography (ICG), optical coherence tomography (OCT) and ultrasound, play an important role in the diagnosis and in the management of the uveitis 4. Until recently, fluorescein FA was the primary imaging modality used to detect macular edema and other features related with uveitis like choroidal neovascularization and serous retinal detachment. Although FA is useful for determining the presence of vascular leakage, this technique does not provide any three-dimensional anatomic information about the retinal layers, the retinal pigment epithelium (RPE) or the choroid. The development of OCT makes it possible to have high-resolution cross-sectional images of the retina or optic nerve. OCT is now proven to be an effective noninvasive method in detecting pathologic features in uveitis and is rapidly gaining popularity as an ancillary exam. It may be used to assist in the diagnosis of uveitis and may be repeated safely during follow-up to monitor response to any intervention 5, 6. Recently, the introduction of spectral domain OCT (SDOCT) has improved image quality. Spectral domain, a type of fourier domain detection, uses a high-speed spectrometer to measure light echoes from all time delays simultaneously enhancing OCT capabilities. The reference mirror does not require mechanical scanning. Improved sensitivity enables dramatic improvements in sampling speed and signal-to-noise ratio 7, 8. SD detection, coupled with improvements in light sources, achieves axial scanning speeds of greater than 20,000 A-scans per second with an axial resolution of 3 μm to 7 μm in the eye. Consequently SDOCT has the advantage of detecting small changes in the morphology of the retinal layers and subretinal space, allowing for precise anatomic detection of microstructural changes that may corresponds to progression or regression of chorioretinal lesions or complications secondary to uveitis6. In addition, SDOCT is also used for anterior segment imaging where it may illustrate features of anterior uveitis and its complications. This review focuses on SDOCT imaging in uveitis. It will first review OCT imaging in anterior uveitis; then, it will describe the image features observed in the posterior uveitis. OCT and Anterior Uveitis Anterior segment optical coherence tomography (ASOCT) allows the visualization of various features of the anterior segment, including iris thickness, anterior chamber (AC) depth, the extent of anterior synechiae, iris bowing, and angle lesions. In vivo cross-sectional imaging of the anterior segment from ASOCT is particularly useful in the presence of corneal opacity and ocular inflammation, where it is often difficult to use slit-lamp biomicroscopy to visualize the anterior segment. It can serve as an non-invasive method for assessment of anterior uveitis and its complications 9, and can detect features of uveitis such as inflammatory cells, keratic precipitates (Figure 1A), fibrin (Figure 1B), and corneal edema (Figure 1C). In addition, positive posterior segment findings on OCT (e.g. increased macular thickness, retinal edema) can often reinforce anterior uveitis findings and may suggest its manifestation as part of a panuveitis associated with systemic illnesses such as sarcoidosis and Vogt-Koyanagi-Harada syndrome 9, 10. Figure 1 Representative ASOCT images show different features of anterior uveitis (A) Keratic precipitates (arrow) on ASOCT; (B) Fibrin deposition (arrow); (C) Corneal edema (arrow); (D) Inflammatory cells in the anterior chamber, visualized as hyperreflective ... Anterior Chamber Inflammatory Cells on ASOCT Lowder et al. 11 used a high-speed prototype SDOCT (2,000 A-scan/sec, 1.3 micron wavelength) to characterize inflammatory and pigmented cells in the anterior chamber (AC) as hyperreflective spots. In 28 non-granulomatous anterior uveitic eyes, a significant correlation was found between the cell count on OCT and the clinical grading from slit-lamp biomicroscopy. Similarly, a significant correlation was found between 6 eyes with pigmentary particles on OCT and clinical grading. Another study by Agarwal et al 12, inflammatory cells in the AC were visualized on ASOCT as hyperreflective spots (Figure 1D) in eyes compromised AC visualization secondary to corneal edema or opacity. In their study of 62 eyes with AC inflammation, 91.6% of eyes with corneal edema (n=12) had identifiable hyperreflective spots consistent with AC cells on ASOCT, which were manually counted and graded using the standardization of uveitis nomenclature (SUN) criteria. At the same time, keratic precipitates (Figure 1A) were seen in 12 eyes as discrete hyperreflective spots attached to the cornea endothelium, and fibrinous membrane (Figure 1B) were detected in 4 eyes in the papillary area or endothelium of the cornea.

Optic disc edema from papilledema.

Papilledema, first described over 100 years ago, has captured the attention of clinical and experimental investigators throughout the world. The vast amount of literature on this subject has made it clear that there are anatomic, mechanical, vascular, and metabolic factors involved in the pathogenesis and etiology of papilledema. The multifactorial nature of papilledema has made it difficult to establish theories to account for its development and progression, whereas experimental models have been met with only limited success. This review will attempt to clarify the diagnosis of, interpretation of findings in, and explore common causes of papilledema. There exists some confusion among practicing physicians regarding what the definition and implications of papilledema are. Most neuroophthalmologists use the term ‘‘papilledema’’ to refer to swelling of the optic disc as a consequence of increased intracranial pressure (ICP) and use other terms such as ‘‘optic disc edema’’ and ‘‘edema of the optic nerve’’ to refer to disc swelling of other etiologies. As such, it can be helpful to think of papilledema as an optic neuropathy akin to ‘‘glaucoma of the brain,’’ where it is the elevated pressure that is the key pathogenic factor. It is also important to understand that the term papilledema implies interstitial edema of the optic nerves without functional axonal loss or disruption interfering with vision, at least at its onset. It is only after axoplasmic stasis leads to neuronal dysfunction that visual loss is thought to occur, with visual function often correlating to optic disc appearance in the acute setting. This distinction differentiates papilledema from conditions such as ‘‘papillitis’’ in which there is disc edema associated with a primary disorder of the nerve itself resulting in a loss of vision. Treatment typically involves medical therapy

Choroidal Vessel Diameters in Pseudoexfoliation and Pseudoexfoliation Glaucoma Analyzed Using Spectral-Domain Optical Coherence Tomography

Purpose of the Study: The purpose of the study was to analyze choroidal vessel diameters in pseudoexfoliation (PXF) and pseudoexfoliation glaucoma (PXFG) using spectral-domain optical coherence tomography (SD-OCT). Materials and Methods: Fifty patients (100 eyes) with PXF and PXFG who underwent high-definition 1-line raster SD-OCT imaging at New England Eye Center, Boston, were retrospectively identified and divided into unilateral PXFG (26 patients, 52 eyes), unilateral PXF (4 patients, 8 eyes), bilateral PXFG (4 patients, 8 eyes), and bilateral PXF (16 patients, 32 eyes). Eyes with concomitant chorioretinal pathology, history of shunting/filtering for glaucoma, and significant anisometropia were excluded. SD-OCT scans were divided into subfoveal, central, and peripheral zones and choroidal vessel diameters were measured. Results: In patients with unilateral PXFG, mean choroidal vessel diameter was 12.9 &mgr;m smaller in the affected eyes when compared with their contralateral eyes (45.7 vs. 58.6 &mgr;m; P<0.0001) with the greatest reduction (16.6 &mgr;m) in the subfoveal zone (49.0 vs. 65.6 &mgr;m; P<0.0001). In patients with unilateral PXF, the mean choroidal vascular diameter was 13.3 &mgr;m smaller in the affected eyes when compared with their contralateral eyes (42.8 vs. 56.1 &mgr;m; P=0.02). As expected, no significant difference was observed between the 2 eyes of patients with bilateral PXFG (45.5 vs. 45.7 &mgr;m; P=0.95) and bilateral PXF (51.4 vs. 50.2 &mgr;m; P=0.52). Conclusions: Choroidal vessel diameters are smaller in the affected eyes of patients with unilateral PXF and PXFG when compared with their contralateral unaffected eyes. These changes appear to be independent of the presence or absence of glaucoma. Future studies may identify the choroidal vascular changes and their relationship with the pathogenesis of these conditions.