Fig. 3.1
A SuperQuad 160 lens (left, Volk Optical, Mentor, OH) and an Ocular Staurenghi 230 SLO Retina Lens (right, Ocular Instruments, Bellevue, WA). Both contact lenses can be used for wide-field imaging . Note the relative bulk of the Staurenghi lens
The two predominant non-contact systems are the Heidelberg ultra-wide-field non-contact module and the various products from Optos PLC. The Heidelberg non-contact module (Heidelberg Engineering, Heidelberg, Germany) is an accessory that can be purchased to expand the functionality of a Heidelberg confocal scanning laser ophthalmoscope (cSLO) . The Heidelberg system can be used for both FA and ICGA, and it offers the advantage of high-speed video angiography. Images capture up to 120° of the ocular fundus. Optos PLC, on the other hand, markets wide-field cSLO devices that are stand-alone machines, although an Optos unit also is capable of obtaining high-resolution images of the posterior pole. There are several Optos products with a variety of capabilities, including pseudocolor (red and green channels) fundus imaging, autofluorescence, FA, and ICGA. Detection of some types of uveitis pathology is more difficult with Optos pseudocolor fundus imaging compared to traditional fundus camera imaging (Fig. 3.2). On the other hand, the multispectral imaging available with Optos wide-field ophthalmoscopy may help differentiate retinal and choroidal pathology since images obtained with the 532 nm laser preferentially show retinal/retinal pigment epithelium (RPE) structure and retinal vasculature, while imaging with the 635 nm laser better shows choroidal structure and vasculature [9]. Optos images are as wide as 200°, and at present Optos predominates the wide-field imaging literature.
Fig. 3.2
Comparison of Optos color (a), Optos simulated white light (b), and fundus camera montage (c) images taken on the same day in a patient with birdshot retinochoroidopathy. The inferonasal and superonasal birdshot lesions are more apparent on the fundus camera montage image
Utility of Wide-Field Fluorescein Angiography in Uveitis
Several studies have demonstrated the utility of wide-field FA techniques for detection of peripheral pathology in uveitis. Wide-field FA , in which both the posterior pole and periphery are seen through the various phases of the angiogram, allows for improved characterization of peripheral vascular pathology and peripheral staining, blocking, and leakage patterns. The area of fluorescein leakage in a series of uveitis patients imaged with the Optos was a median 22.5 mm2 compared with just 4.8 mm2 (P < 0.0001) with fundus camera montage images [5]. The Optos was noted to capture 50% more retinal area in this series when compared with standard montage imaging (Fig. 3.3). This study also suggested that the Optos revealed more posterior pole leakage than the fundus camera, presumably because of the optical advantages of a cSLO system. Some clinicians use the term “Optos leakage” to describe mild leakage that is seen with the Optos system that likely would not be apparent in traditional FA images (Fig. 3.4). The clinical significance of this mild leakage as well as more substantial peripheral vascular leakage (Fig. 3.5) remains to be determined.
Fig. 3.3
Fundus camera and Optos FA images of the same eye during the same sitting. The image on the left is a montage of images taken with a fundus camera. The patient was then moved to the Optos machine to obtain the image on the right. More retinal area is captured in the Optos image, allowing visualization of temporal vascular leakage with the Optos system but not the fundus camera montage image. Additionally, the superonasal and superotemporal areas of retinal nonperfusion are better defined on the Optos image
Fig. 3.4
Optos FA image showing mild vascular leakage in a patient with non-granulomatous anterior uveitis
Fig. 3.5
Optos FA images showing extensive peripheral vascular leakage OU in a patient with idiopathic retinal vasculitis. The areas of leakage are too peripheral to be captured reliably by traditional fundus camera images.
Campbell and colleagues prospectively evaluated Optos FA in uveitis and compared the wide-field images with cropped 30° and 60° images that simulated standard FA images [4]. They noted that treating physicians reported making management changes more frequently with the use of wide-field angiography than they would have with only standard FA and clinical examination. In their initial series of 43 subjects, disease activity was more likely to be detected using wide-field FA (63% active with Optos FA vs. 51% active with clinical exam ± simulated standard FA), but the difference was not statistically significant. A subsequent larger study of 71 visits from the same group found similar activity detection rates (68% active with Optos FA vs. 45% active with clinical exam ± simulated standard FA, P = 0.0095), though this difference was statistically significant [10].
Optos FA findings have been described in a variety of specific conditions. Optos FA appears to be useful in Behcet retinal vasculitis for the detection of peripheral vasculitis (present in 25/33 eyes with active vasculitis) and peripheral non-perfusion (present in 22/33 eyes) [11]. Optos images were used to guide sectoral panretinal photocoagulation in this series. Hong and colleagues showed that even the posterior extent of active retinal vasculitis may be missed with conventional FA [12]. They also demonstrated the usefulness of serial wide-field angiograms to follow treatment responses. Wide-field imaging was especially important in a case in which the posterior edge of retinal vasculitis receded into the periphery with treatment.
Other reported applications of Optos FA include imaging of peripheral periphlebitis in intermediate uveitis [13, 14], lupus retinal vasculitis [5, 13], sarcoid uveitis [5, 10, 14], acute posterior multifocal placoid pigment epitheliopathy [13], Vogt-Koyanagi-Harada (VKH) disease [5], birdshot chorioretinopathy [5], ampiginous chorioretinopathy [5], cytomegalovirus retinitis [13], granulomatosis with polyangiitis [10], and acute retinal necrosis [5].
Optos images are relatively easily obtained in eyes with small pupils, and the illumination may be more comfortable for photophobic patients when compared with flash photography [3]. Optos fluorescein angiography has in our hands been helpful in following pediatric uveitis, and Tsui and colleagues documented a variety of potential uses in children [2]. For example, a 9-year-old female with juvenile rheumatoid arthritis and an unremarkable exam was found to have peripheral retinal vascular leakage. The group was able to document peripheral periphlebitis in two children with pars planitis and an inactive peripheral toxoplasmosis scar in a 6-year-old.
One disadvantage of wide-field imaging compared to traditional fundus imaging is the lower image resolution. A patient with birdshot retinochoroidopathy presented to our clinic with severe rod and cone dysfunction by electroretinography . Though there was no apparent clinical activity or leakage on FA, fundus camera FA images clearly show diffuse capillary non-perfusion (Fig. 3.6) that may not be as apparent on wide-field FA imaging without additional magnification.
Fig. 3.6
Fundus camera FA image showing extensive retinal capillary non-perfusion in a patient with birdshot retinochoroidopathy
The Staurenghi contact lens also has been studied for wide-field angiography in posterior uveitis, and it is thought to have similar diagnostic advantages when compared with standard FA (Fig. 3.7). As with the Optos, Staurenghi images have been used to guide peripheral sectoral laser treatment [15]. In the same study, the Staurenghi images were noted to be of value even in the presence of significant vitritis. No corneal abrasions occurred in this series, but the authors note that there was a learning curve for use of the lens and that a second person held the lens so that the photographer could concentrate on image quality. The Staurenghi lens costs less than an Optos system with FA capability, and it may be a reasonable alternative in practices that have a Heidelberg retinal angiograph (HRA) . The Heidelberg wide-field lens is another less costly alternative to the Optos. To our knowledge, no studies of this lens in uveitis have been published, but our clinical experience suggests that it provides similar advantages over traditional FA in conditions such as retinal vasculitis (Fig. 3.8).
Fig. 3.7
An FA image of an eye with inactive posterior uveitis taken with the Heidelberg retinal angiograph camera and a Staurenghi lens . The wider field of view documents filling defects in peripheral venules and extensive peripheral window defects
Fig. 3.8
An FA image taken with the Heidelberg non-contact wide-field lens in an eye with active peripheral retinal vasculitis . In this case, disease activity may not have been detected with traditional 50° imaging
Overall, studies of wide-field FA in uveitis are few in number, and they provide mostly qualitative data. Some are entirely non-comparative, and there are no treatment trials that have specifically addressed the role of wide-field angiography in uveitis. The literature presently suggests three benefits of wide-field FA over traditional angiography: (1) clearer delineation of peripheral pathology, (2) easier monitoring of disease progression or response to therapy in eyes with peripheral disease, and (3) guidance of peripheral laser treatment. The impact of these benefits on treatment strategies and patient outcomes remains to be determined.
Wide-Field Fluorescein Angiography: Principles from Non-uveitic Applications
Studies of wide-field FA in non-uveitic entities have suggested a variety of advantages that might in some instances be applicable in uveitis. These studies naturally demonstrate the increased width of field versus standard photography and the related enhanced detection of peripheral neovascularization and non-perfusion. In addition, sectoral peripheral laser that is guided by wide-field angiographic findings may help to treat retinal neovascularization. Wide-field FA has been particularly well-studied in diabetic retinopathy, vein occlusion, and other retinal vascular disorders including sickle retinopathy.
Several general principles of wide-field imaging have been shown in studies of diabetic retinopathy and retinal vein occlusion. For example, a study in diabetic retinopathy quantified the retinal area imaged with a seven standard field pattern and with the Optos. The Optos image captured 3.2× the retinal area, 3.9× more non-perfusion, and 1.9× more neovascularization [16]. In this study, there was a significant relationship between the presence of Optos-defined retinal ischemia and the presence of diabetic macular edema (DME) , although the extent of ischemia did not appear to be related to the severity of DME. Another study suggests that peripheral ischemia and DME are related in untreated eyes only [17]. Targeted laser treatment to areas of peripheral ischemia can cause regression of neovascularization in proliferative diabetic retinopathy [18].
In central retinal vein occlusion (CRVO) , peripheral non-perfusion as seen with wide-field FA is associated with neovascularization and macular edema [19]. Targeted peripheral laser may not have any effect on the clinical course of CRVO-associated macular edema [20], although this finding has been challenged in a paper describing peripheral laser treatment to areas of both reversible and nonreversible retinal ischemia [21]. Peripheral retinal ischemia may be partially reversible with anti-vascular endothelial growth factor treatment. Wide-field FA has been shown to be adequate not only for peripheral imaging but also for reliable detection of macular leakage in vein occlusion [22].
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