John E. Legarreta

Three-Dimensional Spectral-Domain Optical Coherence Tomography Images of the Retina in the Presence of Epiretinal Membranes

PURPOSE To study the inner surface of the retina in the presence of epiretinal membranes (ERMs) using a prototype spectral-domain optical coherence tomography (SD-OCT) device. DESIGN Small case series, performed in the Department of Ophthalmology, Bascom Palmer Eye Institute, Miller School of Medicine, University of Miami, from August 2005 through December 2006. METHOD An 8-microm axial-resolution SD-OCT instrument was used to scan the eyes of patients diagnosed with ERM. The ERM and the internal limiting membrane (ILM) were segmented separately to evaluate the traction caused by the ERM on the retina. It was then possible to reconstruct the ILM and ERM surfaces in 3-dimensional space and to obtain corresponding retinal thickness maps. RESULTS SD-OCT B scans showed the points of attachment of the ERM to the ILM. Segmented surface maps of the ERM produced very smooth sheets, whereas those of the ILM presented wrinkles under and around the ERM. CONCLUSIONS SD-OCT revealed the geometry of retinal traction in eyes with ERM and may be useful in understanding further the pathologic features of these lesions.

SWEPT SOURCE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF NEOVASCULAR MACULAR TELANGIECTASIA TYPE 2.

Background/Purpose: To image subretinal neovascularization in proliferative macular telangiectasia Type 2 (MacTel2) using swept source optical coherence tomography based microangiography (OMAG). Methods: Patients with macular telangiectasia Type 2 were enrolled in a prospective, observational study known as the MacTel Project and evaluated using a high-speed 1,050 nm swept-source OCT prototype system. The OMAG algorithm generated en face flow images from three retinal layers, and the region bounded by the outer retina and Bruch membrane, the choriocapillaris, and the remaining choroidal vasculature. The en face OMAG images were compared with images from fluorescein angiography and indocyanine green angiography. Results: Three eyes with neovascular macular telangiectasia Type 2 were imaged. The neovascularization was best identified from the en face OMAG images that included a layer between the outer retinal boundary and Bruch membrane. Optical coherence tomography based microangiography images identified these abnormal vessels better than fluorescein angiography and were comparable to the images obtained using indocyanine green angiography. In all 3 cases, OMAG identified choroidal vessels communicating with the neovascularization, and these choroidal vessels were evident in the 2 cases with indocyanine green angiography imaging. In 1 case, monthly injections of bevacizumab reduced the microvascular complexity of the neovascularization, and the telangiectatic changes within the retinal microvasculature. In another case, less frequent bevacizumab therapy was associated with growth of the subretinal neovascular complex. Conclusion: Optical coherence tomography based microangiography imaging provided detailed, depth-resolved information about subretinal neovascularization in macular telangiectasia Type 2 eyes demonstrating superiority to fluorescein angiography imaging, and similarities to indocyanine green angiography imaging for documenting the retinal microvascular changes, the size and extent of the neovascular complex, the communications between the neovascular complex and the choroidal circulation, and the response to monthly bevacizumab therapy.

Widefield En Face Optical Coherence Tomography Imaging of Subretinal Drusenoid Deposits

BACKGROUND AND OBJECTIVE To determine whether subretinal drusenoid deposits (SDD) can be detected on widefield en face slab images derived from spectral-domain (SD) and swept-source (SS) optical coherence tomography (OCT) volume scans. PATIENTS AND METHODS Retrospective study of patients with dry age-related macular degeneration (AMD) enrolled prospectively in an OCT imaging study using SD-OCT (Cirrus HD-OCT; Carl Zeiss Meditec, Dublin, CA) with a central wavelength of 840 nm, and a prototype 100-kHz SS-OCT instrument (Carl Zeiss Meditec) with a central wavelength of 1,050 nm. Seven en face slabs were evaluated with thicknesses from 20 to 55 µm and positioned at distances up to 55 µm above the retinal pigment epithelium (RPE). A montage of 6 × 6 mm SD-OCT en face images of the posterior pole from each patient was compared with a 9 × 12 mm SS-OCT single en face slab image and with color, autofluorescence, and infrared reflectance images. RESULTS A total of 160 patients (256 eyes) underwent scanning with both OCT instruments; 57 patients (95 eyes) also underwent multimodal fundus imaging. Of 95 eyes, 32 (34%) were diagnosed with reticular pseudodrusen (RPD) using multimodal imaging. All eyes with RPD demonstrated a pattern of SDD on widefield en face OCT similar to that observed for RPD. The en face slab image that consistently identified SDD was the 20-µm thick slab with boundaries from 35 to 55 µm above the RPE. CONCLUSION Widefield en face slab imaging with SD-OCT and SS-OCT can detect SDD and could replace multimodal imaging for the diagnosis of RPD in the future.

En-Face Imaging of Microcysts in Macular Teleangiectasia Type 2 Using Minimum- and Mean-Intensity Projections

PURPOSE We characterized mitochondrial respiration and glycolysis activity of human corneal endothelium, and compared metabolic activity between central and peripheral regions. METHODS Endothelial keratoplasty-suitable corneas were obtained from donors aged 50 to 75 years. The endothelium-Descemet membrane complex (EDM) was isolated, and 3-mm punches were obtained from central and peripheral regions. Endothelium-Descemet membrane punches were assayed for mitochondrial respiration (oxygen consumption) and glycolysis (extracellular acidification) using an extracellular flux analyzer. Enzymatic (citrate synthase, glucose hexokinase) and mitochondrial density (MitoTracker) assays also were performed. RESULTS Ten corneas were analyzed per assay. Metabolic activity for mitochondrial respiration and glycolysis showed expected changes to assay compounds (P < 0.01, all pairwise comparisons). Basal mitochondrial respiration and glycolysis activity did not differ between regions (P > 0.99). Similarly, central versus peripheral activity after assay compound treatment showed no significant differences (P > 0.99, all time points). The intracorneal coefficient of variation for basal readings between two and four peripheral punches was 18.5% of the mean. Although peripheral samples displayed greater enzymatic activity than central samples (P < 0.05), similar to extracellular flux results, mitochondrial density did not differ between regions (P = 0.78). CONCLUSIONS Extracellular flux analysis of oxygen and pH is a valid technique for characterizing metabolic activity of human corneal endothelium. This technique demonstrates high reproducibility, allows quantification of metabolic parameters using small quantities of live cells, and permits estimation of overall metabolic output. Neither oxygen consumption nor extracellular acidification differed between central and peripheral regions of transplant suitable corneas in this series. Our results show that endothelial cell health can be quantified biochemically in transplant suitable corneas.

Proliferative Diabetic Retinopathy

Proliferative diabetic retinopathy (PDR) is characterized by neovascularization of the disk (NVD) or neovascularization elsewhere (NVE).

Nonproliferative Diabetic Retinopathy

Nonproliferative diabetic retinopathy (NPDR) is characterized by dot/blot hemorrhages, flame-shaped hemorrhages, microaneurysms, hard exudates, cotton wool spots, venous beading, venous loops, and IRMA.

Diabetic Macular Edema

Diabetic macular edema is characterized by retinal thickening in the macula and the ETDRS defined clinically significant macular edema (CSME) as the following:

Nonexudative Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is characterized by drusen, disruption of retinal pigment epithelium or geographic atrophy of the central macula.

Clinical Trials in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a leading cause of blindness in elderly adults in the United States and other developed countries across the world. Exudative or “wet” AMD remains the leading cause of AMD-related blindness. Clinical trials in AMD are reviewed.