Non-invasive optical coherence tomography angiography: A comparison with fluorescein and indocyanine green angiography in normal adult dogs and cats.

PURPOSE: While the retinal vasculature can be assessed by simple funduscopy, a more detailed assessment can be performed by conventional angiography using dyes such as fluorescein or indocyanine green. The development of optical coherence tomography angiography (OCT-A) allows a non-invasive detailed examination of posterior segment vasculature. The purpose of this prospective study was to compare imaging of posterior segment vasculature in normal dogs and cats using OCT-A, fluorescein angiography (FA), and indocyanine green angiography (ICGA). METHODS: Eight adult funduscopically normal dogs and 13 funduscopically normal cats were included in the study. Retinal vasculature was assessed by OCT-A followed by ICGA then FA. Regular fundus imaging was also performed. RESULTS: High-resolution images of the different vascular layers within the retina and choroid could be acquired using OCT-A in both dogs and cats. The technique provided more detail than obtained with FA/ICGA. However, artifacts/errors can occur during OCT-A image acquisition/analysis/interpretation and must be considered. Furthermore, OCT-A only allows for a limited field of view compared to FA/ICGA. CONCLUSIONS: Optical coherence tomography angiography is a new non-invasive posterior segment imaging technique that is complementary to traditional dye-based angiographic techniques. Detailed imaging of the dog and cat posterior segment can be achieved under general anesthesia. OCT-A provides additional detail of the vasculature and can clearly demonstrate the anatomical depth of the imaged vessels. There are, however, some limitations to this new technique that may be overcome by future technological advances.

Aqueous angiography in pre-glaucomatous and glaucomatous ADAMTS10-mutant canine eyes: A pilot study.

OBJECTIVE: To evaluate intravenous scleral and intracameral aqueous angiography in normotensive (n = 4) and hypertensive glaucomatous (n = 6) ADAMTS10-mutant canine eyes. ANIMALS STUDIED: Ten ADAMTS10-mutant dogs were used in this study. PROCEDURES: Dogs were sedated and one eye from each dog underwent scleral angiography following intravenous injection of 0.25% indocyanine green (ICG). After a 24-h recovery period, the same eye underwent aqueous angiography via intracameral administration of ICG. Imaging of identical scleral sectors from the same eye was performed using a Heidelberg Spectralis® Confocal Scanning Laser Ophthalmoscope. Intrascleral vessel depth and lumen diameters were measured using Heidelberg Spectralis® optical coherence tomography and computer software. RESULTS: Scleral angiography permitted visualization of vascular components associated with conventional aqueous humor outflow pathways with an average time from injection to fluorescence of 35.8 ± 10.6 s (mean ± SD). Two normotensive eyes (2/10;20%) demonstrated turbulent dye movement, while 4 hypertensive eyes (4/10;40%) exhibited laminar flow. Aqueous angiography demonstrated dye fluorescence within the post-trabecular conventional aqueous humor outflow pathways in all 10 eyes at 34.3 ± 11.0 s post-injection. Sectoral and dynamic outflow patterns were observed primarily within the superotemporal sector in nine eyes (9/10; 90%). Seven eyes (7/10; 70%) demonstrated pulsatile dye movement and five eyes (5/10; 50%) exhibited laminar flow. The degree of laminar movement of dye was greatest in hypertensive eyes. Vessel lumen diameters measured 133.85 ± 28.36 µm and 161.18 ± 6.02 µm in hypertensive and normotensive eyes, respectively. CONCLUSIONS: Aqueous angiography allowed for visualization of fluorescent dye in the superotemporal sclera. Laminar flow and smaller lumen vessels were observed mainly in hypertensive eyes.

Retinal structural and microvascular abnormalities in retinal dysplasia imaged by OCT and OCT angiography.

OBJECTIVE: To describe the in vivo structural characteristics of multifocal and geographic retinal dysplasia visualized with advanced retinal imaging including confocal scanning laser ophthalmoscopy (cSLO), optical coherence tomography (OCT), en face OCT, and the novel vascular imaging technique OCT angiography (OCTA). DOGS STUDIED AND PROCEDURES: Two dogs were diagnosed with unilateral multifocal or geographic retinal dysplasia and underwent advanced retinal imaging under general anesthesia at the Retinal Disease Studies Facility of the University of Pennsylvania. RESULTS: In both cases, the morphological pattern of the lesions was similar including outer retinal folds that invaginated and formed tubular retinal rosettes, surrounding a central inner retinal thickening (multifocal) or plaque (geographic). The two dogs had multiple vascular anomalies in the lesions such as increased tortuosity, abnormal change of vessel diameter including aneurysms and capillary network disruption. We also identified increased autofluorescence by AF cSLO with short wavelength light source (488 nm and barrier filter at 500 nm), and several areas of photoreceptor loss associated with the lesions. CONCLUSION: The use of OCTA allowed the identification of microvascular abnormalities associated with multifocal and geographic retinal dysplasia in two dogs. To our knowledge, this is the first report where the dye-free OCTA technique is used to study vascular lesions in canine retinas.

In vivo imaging comparison of unilateral circular retinal plaques in retriever dogs to dysplasia and detachment in the English Springer Spaniel.

PURPOSE: To compare the scanning laser ophthalmoscopy (SLO), optical coherence tomography (OCT), and fluorescein angiography (FA) findings in retrievers with a single unilateral circular retinal plaque to those of an English springer spaniel with bilateral retinal dysplasia. PROCEDURES: A retrospective record review identified three dogs with circular retinal plaques that underwent SLO and OCT; in two of the three dogs, FA was also completed. Morphologic changes, lesion measurements, and angiogram characteristics were documented. An English springer spaniel with bilateral retinal dysplasia that had undergone SLO, OCT, and FA was used for comparison. RESULTS: Scanning laser ophthalmoscopy of the retriever dogs revealed circular retinal plaques with a dark periphery located in the tapetal retina. OCT revealed a thickening of the nerve fiber layer corresponding to the circular pattern observed on SLO. Within the circular plaque, the retina was predominantly of normal architecture. FA revealed variable hypofluorescence of both the rim and the center of the circular lesion throughout the early angiogram phases. In the late recirculation phase, small multifocal areas of hyperfluorescence were observed. OCT of geographic retinal dysplasia in the English springer spaniel revealed disorganization of both inner and outer retinal layers, and retinal detachment. CONCLUSIONS: Circular plaques observed in the tapetal retina are predominantly formed by a thickening of inner retina, while retinal dysplasia has disorganization of both inner and outer retinal layers. Further etiologic research is needed, including pedigree mapping to determine whether retinal plaques are an acquired or inherited condition.

Evaluation of retinal morphology of canine sudden acquired retinal degeneration syndrome using optical coherence tomography and fluorescein angiography.

PURPOSE: To describe the optical coherence tomography (OCT) and fluorescein angiography changes in dogs with sudden acquired retinal degeneration syndrome (SARDS). METHODS: Retinal OCT was performed on 10 SARDS dogs and eight control dogs. Tomograms were collected in four quadrants around the optic nerve. Measurements were collected from the photoreceptor layer, the outer nuclear layer, the outer retina, the inner retina and the whole retina thickness in all quadrants. Sodium fluorescein was injected intravenously and serial fundic photographs were collected for a 5 minute period post-injection. RESULTS: In all quadrants, the outer nuclear layer (dorsal temporal P = 0.0000, dorsal nasal P = 0.0001, ventral temporal P = 0.0002, ventral nasal P = 0.000) and outer retina (dorsal temporal P = 0.0001, dorsal nasal P = 0.0002, ventral temporal P = 0.0054, ventral nasal P = 0.0084) measurements were significantly decreased in SARDS dogs. The whole retina thickness was significantly decreased in the dorsal temporal (P = 0.0082) and ventral temporal (P = 0.0428) retina. There were no significant differences in the photoreceptor layer thickness or inner retinal thickness between SARDS and control dogs. All SARDS dogs had a loss of definition of all of the photoreceptor bands on OCT. Two SARDS dogs had multifocal small retinal detachments and one of these dogs exhibited fluorescein leaking at the detachment sites. CONCLUSIONS: The significant reduction in the outer nuclear layer and the loss of band signals in the photoreceptor layers in dogs with SARDS identified on OCT support the previous histopathology findings. Small detachments may occasionally be detected on OCT and they may leak fluorescein.

Comparison of angiographic dyes and injection techniques for ocular anterior segment angiography in horses.

OBJECTIVE To assess and compare 2 injection techniques for conducting ocular anterior segment indocyanine green angiography (ASICGA) and sodium fluorescein (SF) angiography in horses. ANIMALS 3 healthy adult female horses (age range, 19 to 25 years). PROCEDURES Horses were sedated, jugular catheters were placed, and manual restraint was used to ensure proper positioning for the angiography procedure. Two injection techniques (IV and intra-arterial) were performed for each horse 1 week apart. Intravenous injections of 0.25% indocyanine green (ICG; 50 mg) and 10% SF (10 mg/kg) were administered via the jugular catheter. Intra-arterial injections of ICG (1 mg) and SF (1 mg/kg) were administered into the common carotid artery with ultrasound guidance. Angiography was performed by use of an adaptor system comprised of a modified digital single-lens reflex camera, camera adaptor, and lens. Imaging was performed at a rate of 3 images/s for 60 seconds immediately following ICG injection, then at 2, 3, 4, and 5 minutes after injection. The SF was injected 5 minutes thereafter. RESULTS ASICGA allowed visual identification of the arterial, capillary, and venous phases of angiography. Intra-arterial administration provided superior dye fluorescence, sharper contrast, and faster dye passage than IV administration. Visibility of the iris vasculature was limited with SF, and extravasation of SF was noted. No clinically important adverse events were detected. CONCLUSIONS AND CLINICAL RELEVANCE ASICGA images were obtainable with both injection techniques; however, visibility of the iris vasculature was better with intra-arterial administration of ICG. The ASICGA technique may serve as a viable ocular imaging modality for horses.

Snake spectacle vessel permeability to sodium fluorescein.

OBJECTIVE: Assess vascular permeability of the snake spectacle to sodium fluorescein during resting and shedding phases of the ecdysis cycle. ANIMAL STUDIED: Ball python (Python regius). PROCEDURES: The snake was anesthetized, and spectral domain optic coherence tomography was performed prior to angiographic procedures. An electronically controlled digital single-lens reflex camera with a dual-head flash equipped with filters suitable for fluorescein angiography was used to make images. Sodium fluorescein (10%) solution was administered by intracardiac injection. Angiographic images were made as fluorescein traversed the vasculature of the iris and spectacle. Individually acquired photographic frames were assessed and sequenced into pseudovideo image streams for further evaluation CONCLUSIONS: Fluorescein angiograms of the snake spectacle were readily obtained. Vascular permeability varied with the phase of ecdysis. Copious leakage of fluorescein occurred during the shedding phase. This angiographic method may provide diverse opportunities to investigate vascular aspects of snake spectacle ecdysis, dysecdysis, and the integument in general.

Comparison of indocyanine green and sodium fluorescein for anterior segment angiography of ophthalmically normal eyes of goats, sheep, and alpacas performed with a digital single-lens reflex camera adaptor.

OBJECTIVE To compare results of anterior segment angiography of ophthalmically normal eyes of goats, sheep, and alpacas performed by use of indocyanine green (ICG) and sodium fluorescein (SF). ANIMALS 10 female goats (mean ± SD age, 6.8 ± 1.7 years), 10 female sheep (3.0 ± 2.2 years), and 10 alpacas (7 females and 3 males; 6.8 ± 3.8 years). PROCEDURES A catheter was aseptically placed into a jugular vein. Each animal was anesthetized and properly positioned, and 0.25% ICG was administered. Images were obtained by use of an adaptor system consisting of a modified digital single-lens reflex camera, camera adaptor, and camera lens. Images were obtained at a rate of 3 images/s for the 60 seconds immediately after ICG administration and then at 2, 3, 4, and 5 minutes after administration. Ten minutes later, 10% SF was administered IV and images were obtained in a similar manner. RESULTS Angiography with ICG provided visual examination of the arterial, capillary, and venous phases in all species. Visual examination of the iris vasculature by use of SF was performed in goats and sheep but was not possible in the alpacas because of iridal pigmentation. Extravasation of SF was a common finding in sheep and alpacas but not in goats. No adverse events were detected. CONCLUSIONS AND CLINICAL RELEVANCE Quality angiographic images of the anterior segment were obtainable after IV administration of ICG to goats, sheep, and alpacas. This may provide a useful imaging modality for ocular research in these animal species.

Comparison between indocyanine green angiography and fluorescein angiography in normal cats.

OBJECTIVE: To study a new approach to indocyanine green (ICG) angiography for contrasting the ocular fundus in cats. ANIMALS STUDIED: Six healthy laboratory cats. PROCEDURES: Fluorescein (FLUO) and ICG angiography were performed using an infrared-sensitive charged coupled device-equipped fundus camera on sedated cats. RESULTS: At 12.3 ± 3.4 s after ICG administration, the choroidal arteries could be seen extending radially from the optic disk. The choroidal veins became apparent at 16.2 ± 4.1 s alongside the choroidal arteries. Gradual fading of the choroidal vessels began 5.8 ± 1.5 min postdye administration and diffuse fluorescence of the fundus appeared. Diffuse fluorescence of the optic disk faded at about 18.8 ± 2.9 min. Mean arterial blood pressure at 1 and 3 min after ICG administration showed no significant change when compared to pre-administration (P > 0.05). However, 5 min (P = 0.054) and 10 min (P < 0.05) postadministration, a significant drop in blood pressure occurred. The time lapse between FLUO administration and its appearance in the ocular fundus was 15.7 ± 3.8 s. Retinal veins became apparent at 22.0 ± 3.6 s alongside retinal arteries. At 31.2 ± 4.1 s, full venous fluorescence was visualized throughout the entire fundus. CONCLUSIONS: While FLUO angiography shows only the retinal vessels, ICG angiography enabled visualization of the choroidal vasculature. ICG angiography provides clear resolution while remaining reliable and simple; thus, a combination of ICG and FLUO angiography shows promise as a diagnostic aid for clinical evaluation of various chorioretinal diseases in cats.

Atypical chorioretinal coloboma in a Golden Retriever: a retinographic, fluoroangiographic, and optical coherence tomography study.

PURPOSE: To report a case of canine atypical chorioretinal coloboma where ophthalmoscopic, fluoroangiographic and optical coherence tomography characteristics are described. ANIMAL STUDIED: A 2-year-old Golden Retriever dog in which routine ophthalmoscopic examination allowed diagnosis of a posterior coloboma on the left eye. PROCEDURES: Retinography, fluorescein angiography, and optical coherence tomography were performed to characterize the lesion of the left fundus. RESULTS: Ophthalmoscopy revealed a pigmented circumscribed lesion dorsal to the optic nerve of the left fundus, surrounded by small areas of hyper-reflectivity and retinal vessels with an abnormal pattern. Fluoroangiography revealed a constant hypofluorescence of the defect and a complete altered vascular pattern associated with the coloboma. Optical coherence study demonstrated an important craterlike depression showing an atrophic neurosensory retina, and a lack of retinal pigment epithelium and choroidal tissue. CONCLUSIONS: Fluoroangiographic and optical coherence tomographic studies of an atypical chorioretinal coloboma in a dog are reported for the first time. Both imaging techniques are of great importance to characterize this type of congenital defects.

Use of indocyanine green and sodium fluorescein for anterior segment angiography in ophthalmologically normal cats.

OBJECTIVE: To assess and compare results of anterior segment angiography of ophthalmologically normal cats following IV injection with indocyanine green and sodium fluorescein dyes. ANIMALS: 10 client-owned cats. PROCEDURES: Anterior segment angiography was performed in anesthetized cats following administration of 0.25% indocyanine green (1.0 mg/kg, IV) or 10% sodium fluorescein (20 mg/kg, IV) solution. All cats received both treatments. Imaging (1 eye/cat) was performed with a full-spectrum digital single-lens reflex camera equipped with an adaptor (1 image/s for 30 seconds) immediately following IV dye injection and 1, 2, 3, 4, and 5 minutes after injection. Onset and duration of arterial, capillary, and venous phases of iris vasculature were identified and compared statistically between treatments. Degree of iridal pigmentation, leakage of dye from iris vasculature, and image quality were subjectively assessed. RESULTS: No differences were found in onset or duration of vascular phases between treatments. Visibility of the iris vasculature was not impaired by poor or moderate iridal pigmentation with either method. Indocyanine green provided subjectively better vascular detail and image contrast than sodium fluorescein. No vascular dye leakage was observed following indocyanine green administration. Leakage of dye from blood vessels in the stroma (in 10 cats) and presence of dye in the anterior chamber (in 5 cats) were detected after sodium fluorescein administration. CONCLUSIONS AND CLINICAL RELEVANCE: Images obtained with either fluorescent dye were considered to be of diagnostic quality. Lack of leakage following indocyanine green administration suggested this treatment may have better diagnostic utility for anterior segment angiography. The photographic equipment used provided a cost-effective alternative to existing imaging systems.

Fluorescein gonioangiography of the normal canine eye using a dSLR camera adaptor.

The purpose of this study was to describe fluorescein gonioangiography (FGA) of the normal canine eye using a digital single lens reflex (dSLR) camera adaptor. Dogs were anesthetized using intravenous propofol. Imaging was performed using a Lovac Barkan goniolens, dSLR camera, dSLR camera adaptor, camera lens, and accessory flash. Twelve dogs with a mean age of 2.0 +/- 0.8 years were imaged. No characteristic angiographic phases were observed. Leakage from the peri-limbal capillary network was a common finding and occurred 7.7 +/- 2.2 s post injection in 9 (75%) dogs. In 3 (25%) dogs, filling of the circumferential ciliary artery was observed 10.3 +/- 2.8 s post injection. Dye leakage within the iris base and into the aqueous humor was demonstrated in 4 (33%) and 6 dogs (50%) respectively. No adverse events were noted. This study demonstrates FGA findings in normal canine eyes using a cost effective dSLR camera adaptor.

ANGIOGRAPHIC ANATOMY OF THE MAJOR ABDOMINAL ARTERIAL BLOOD SUPPLY IN THE DOG.

Vascular-based interventional radiology (IR) procedures are being more regularly performed in veterinary patients for both diagnostic and therapeutic purposes. A complete description of the fluoroscopic arterial anatomy of the canine abdominal cavity has not been published. This information is essential for performance of IR procedures to allow for improved preparation before and during a particular procedure. The primary purpose of this study was to provide a fluoroscopic description of the vascular branching from the abdominal aorta in a ventro-dorsal projection with a secondary goal of producing pictorial reference images of the major abdominal arterial blood vessels. Five healthy female hound type dogs were enrolled and underwent fluoroscopic arteriography. During fluoroscopy, both nonselective and selective arteriography were performed. The nonselective arteriograms were obtained in the aorta at four locations: cranial to the celiac artery, cranial to the renal arteries, cranial to the caudal mesenteric artery, and cranial to the branching of the external iliac arteries. Selective arteriography was conducted by performing injections into the following arteries: celiac, splenic, common hepatic, cranial mesenteric, left and right renal, and caudal mesenteric. Fluoroscopic arteriography allowed for excellent characterization of the aortic ostia and the location of the lower order vascular branches. Future evaluation of vascular-based treatment options will likely increase as the understanding of the normal and pathologic anatomy improves.

Altered fundus appearance resulting from autofluorescence imaging with the confocal scanning laser ophthalmoscope (cSLO) in cats.

PURPOSE: This paper is to report that imaging the tapetal fundus of cats with the 488 nm laser of the Spectralis(®) HRA+OCT (Heidelberg Engineering Inc., Heidelberg, Germany) can result in a pale appearance of the imaged area. ANIMALS STUDIED AND PROCEDURES: Wild-type and Rdy kittens (CRX mutant heterozygotes-CRX(Rdy+/-) ) (8-20 weeks of age) and adult cats (1-4 years of age) were imaged by confocal scanning laser ophthalmoscope (cSLO) and spectral domain optical coherence tomography (SD-OCT) using the Spectralis(®) HRA+OCT. Color fundus photography (RetCam II(®) , Clarity Medical Systems, Inc., Pleasanton, CA) was performed after imaging using the Spectralis(®) HRA+OCT. RESULTS: Following retinal cSLO imaging using the 488 nm laser (autofluorescence imaging) in both wild-type kittens and adult cats, the imaged region appeared paler than the adjacent retina that had not been imaged. This change was probably due to retinal bleaching and was fully reversible. Imaging CRX(Rdy+/-) kittens or adults, which had very reduced levels of visual pigments, did not induce the altered fundus appearance. CONCLUSIONS: Those using autofluorescence imaging by cSLO should be aware that it can induce a characteristic pale appearance of the tapetal fundus in the imaged area of normal cats.

Towards a quantitative OCT image analysis.

BACKGROUND: Optical coherence tomography (OCT) is an invaluable diagnostic tool for the detection and follow-up of retinal pathology in patients and experimental disease models. However, as morphological structures and layering in health as well as their alterations in disease are complex, segmentation procedures have not yet reached a satisfactory level of performance. Therefore, raw images and qualitative data are commonly used in clinical and scientific reports. Here, we assess the value of OCT reflectivity profiles as a basis for a quantitative characterization of the retinal status in a cross-species comparative study. METHODS: Spectral-Domain Optical Coherence Tomography (OCT), confocal Scanning-Laser Ophthalmoscopy (SLO), and Fluorescein Angiography (FA) were performed in mice (Mus musculus), gerbils (Gerbillus perpadillus), and cynomolgus monkeys (Macaca fascicularis) using the Heidelberg Engineering Spectralis system, and additional SLOs and FAs were obtained with the HRA I (same manufacturer). Reflectivity profiles were extracted from 8-bit greyscale OCT images using the ImageJ software package (http://rsb.info.nih.gov/ij/). RESULTS: Reflectivity profiles obtained from OCT scans of all three animal species correlated well with ex vivo histomorphometric data. Each of the retinal layers showed a typical pattern that varied in relative size and degree of reflectivity across species. In general, plexiform layers showed a higher level of reflectivity than nuclear layers. A comparison of reflectivity profiles from specialized retinal regions (e.g. visual streak in gerbils, fovea in non-human primates) with respective regions of human retina revealed multiple similarities. In a model of Retinitis Pigmentosa (RP), the value of reflectivity profiles for the follow-up of therapeutic interventions was demonstrated. CONCLUSIONS: OCT reflectivity profiles provide a detailed, quantitative description of retinal layers and structures including specialized retinal regions. Our results highlight the potential of this approach in the long-term follow-up of therapeutic strategies.

Anterior segment angiography of the normal canine eye: a comparison between indocyanine green and sodium fluorescein.

The objective of this study was to assess and compare indocyanine green (IG) and sodium fluorescein (SF) angiographic findings in the normal canine anterior segment using a digital single lens reflex (dSLR) camera adaptor. Images were obtained from 10 brown-eyed Beagles, free of ocular and systemic disease. All animals received butorphanol (0.2 mg/kg IM), maropitant citrate (1.0 mg/kg SC) and diphenhydramine (2.0 mg/kg SC) 20 min prior to propofol (4 mg/kg IV bolus, 0.2 mg/kg/min continuous rate infusion). Standard color imaging was performed prior to the administration of 0.25% IG (1 mg/kg IV). Imaging was performed using a full spectrum dSLR camera, dSLR camera adaptor, camera lens (Canon 60 mm f/2.8 Macro) and an accessory flash. Images were obtained at a rate of 1/s immediately following IG bolus for 30 s, then at 1, 2, 3, 4 and 5 min. Ten minutes later, 10% SF (20 mg/kg IV) was administered. Imaging was repeated using the same adaptor system and imaging sequence protocol. Arterial, capillary and venous phases were identified during anterior segment IG angiography (ASIGA) and their time sequences were recorded. ASIGA offered improved visualization of the iris vasculature in heavily pigmented eyes compared to anterior segment SF angiography (ASSFA), since visualization of the vascular pattern during ASSFA was not possible due to pigment masking. Leakage of SF was noted in a total of six eyes. The use of IG and SF was not associated with any observed adverse events. The adaptor described here provides a cost-effective alternative to existing imaging systems.

Experimental infection with equine herpesvirus type 1 (EHV-1) induces chorioretinal lesions.

Equine herpesvirus myeloencephalitis (EHM) remains one of the most devastating manifestations of equine herpesvirus type 1 (EHV-1) infection but our understanding of its pathogenesis remains rudimentary, partly because of a lack of adequate experimental models. EHV-1 infection of the ocular vasculature may offer an alternative model as EHV-1-induced chorioretinopathy appears to occur in a significant number of horses, and the pathogenesis of EHM and ocular EHV-1 may be similar. To investigate the potential of ocular EHV-1 as a model for EHM, and to determine the frequency of ocular EHV-1, our goal was to study: (1) Dissemination of virus following acute infection, (2) Development and frequency of ocular lesions following infection, and (3) Utility of a GFP-expressing virus for localization of the virus in vivo. Viral antigen could be detected following acute infection in ocular tissues and the central nervous system (experiment 1). Furthermore, EHV-1 infection resulted in multifocal choroidal lesions in 90% (experiment 2) and 50% (experiment 3) of experimentally infected horses, however ocular lesions did not appear in vivo until between 3 weeks and 3 months post-infection. Taken together, the timing of the appearance of lesions and their ophthalmoscopic features suggest that their pathogenesis may involve ischemic injury to the chorioretina following viremic delivery of virus to the eye, mirroring the vascular events that result in EHM. In summary, we show that the frequency of ocular EHV-1 is 50-90% following experimental infection making this model attractive for testing future vaccines or therapeutics in an immunologically relevant age group.

Anterior segment fluorescein angiography of the normal feline eye using a dSLR camera adaptor.

PURPOSE: To describe anterior segment fluorescein angiography (ASFA) of the normal feline eye using a digital single-lens reflex (dSLR) camera adaptor. ANIMALS: Ten cats free of ocular and systemic disease were evaluated. METHODS: All cats received maropitant citrate (1.0 mg/kg SQ) and diphenhydramine (2.0 mg/kg SQ) 20 min prior to anesthesia using propofol (4 mg/kg IV bolus, 0.2 mg/kg/min CRI). Standard color and red-free images were obtained prior to the administration of 10% sodium fluorescein (20 mg/kg IV). Imaging was performed using a dSLR camera (Canon 7D), dSLR camera adaptor, camera lens (Canon EF-S 60 mm f/2.8 macro), and an accessory flash (Canon 580EXII). Imaging occurred at a rate of 1/second immediately following IV bolus of sodium fluorescein for a total of 30 s, then at 1, 2, 3, 4, 5, and 10 min. RESULTS: Ten cats with an average age of 3.7 ± 0.9 years and various iris colors were imaged. Arterial, capillary, and venous phases occurred 4.6, 7.8, and 8.9 s postinjection, respectively. Visibility of the vasculature was not impaired by the degree of iris pigmentation. Patency of a persistent pupillary membrane was noted in one cat. Vessel leakage was common, as well as, leakage into the aqueous humor. Proper patient positioning and restricted ocular movements were critical. No adverse events were noted. CONCLUSIONS: This study demonstrates ASFA findings in normal feline eyes using a cost-effective dSLR camera adaptor. Fluorescein leakage from vessels and into the aqueous humor was a common finding. Visibility of iris vasculature was not impaired by the degree of iris pigmentation.

Anterior segment fluorescein angiography of the normal canine eye using a dSLR camera adaptor.

PURPOSE: To describe anterior segment fluorescein angiography (ASFA) of the normal canine eye using two different sedation/anesthetic protocols and a digital single lens-reflex (dSLR) camera adaptor. METHODS: Dogs free of ocular and systemic disease were used for this study. Dogs received maropitant citrate (1.0 mg/kg SQ) and diphenhydramine (2.0mg/kg SQ) 20min prior to butorphanol [n = 6] (0.2 mg/kg IV) or propofol [n=6] (4 mg/kg IV bolus, 0.2 mg/kg/min CRI). Standard color and red-free images were obtained prior to administration of 10% sodium fluorescein (20 mg/kg IV). Image acquisition was performed using a dSLR camera (Canon 7D), dSLR camera adaptor, camera lens (Canon EF-S 60 mm f/2.8 macro), and an accessory flash (Canon 580EXII). Imaging occurred at a rate of 1/s immediately following bolus for a total of 30 s, then at 1, 2, 3, 4, 5, and 10 min. RESULTS: Twelve dogs with a combined mean age of 5.1 years and various iris colors were imaged. Arterial, capillary, and venous phases were identified and time sequences recorded. Visibility of the vascular pattern was inversely related to iris pigmentation. Complete masking of blood flow was noted with heavily pigmented irises. Vessel leakage was noted in some eyes. Proper patient positioning and restricted ocular movements were critical in acquiring quality images. No adverse events were noted. CONCLUSION: This study demonstrated that quality high resolution ASFA images were obtainable using a novel dSLR camera adaptor. ASFA of the normal canine eye is limited to irises, which are moderately to poorly pigmented. Use of general anesthesia produced higher quality images and is recommended for ASFA in the dog.

Detailed functional and structural characterization of a macular lesion in a rhesus macaque.

PURPOSE: Animal models are powerful tools to broaden our understanding of disease mechanisms and to develop future treatment strategies. Here we present detailed structural and functional findings of a rhesus macaque suffering from a naturally occurring bilateral macular dystrophy (BMD), partial optic atrophy and corresponding reduction of central V1 signals in visual fMRI experiments when compared to data in a healthy macaque (CTRL) of similar age. METHODS: Retinal imaging included infrared and autofluorescence recordings, fluorescein and indocyanine green angiography and spectral domain optical coherence tomography (OCT) on the Spectralis HRA + OCT platform. Electroretinography included multifocal and Ganzfeld-ERG recordings. Animals were killed and eyes analyzed by immunohistochemistry. RESULTS: Angiography showed reduced macular vascularization with significantly larger foveal avascular zones (FAZ) in the affected animal (FAZBMD = 8.85 mm(2) vs. FAZCTRL = 0.32 mm(2)). OCT showed bilateral thinning of the macula within the FAZ (total retinal thickness, TRTBMD = 174 ± 9 µm) and partial optic nerve atrophy when compared to control (TRTCTRL = 303 ± 45 µm). Segmentation analysis revealed that inner retinal layers were primarily affected (inner retinal thickness, IRTBMD = 33 ± 9 µm vs. IRTCTRL = 143 ± 45 µm), while the outer retina essentially maintained its thickness (ORTBMD = 141 ± 7 µm vs. ORTCTRL = 160 ± 11 µm). Altered macular morphology corresponded to a preferential reduction of central signals in the multifocal electroretinography and to a specific attenuation of cone-derived responses in the Ganzfeld electroretinography, while rod function remained normal. CONCLUSION: We provided detailed characterization of a primate macular disorder. This study aims to stimulate awareness and further investigation in primates with macular disorders eventually leading to the identification of a primate animal model and facilitating the preclinical development of therapeutic strategies.