Pilot study supporting the existence of novel lymphatic channels within the canine anterior uveal tract using Lyve-1 and CD31.

OBJECTIVE: To demonstrate the existence of lymphatics in the canine anterior uvea using lymphatic-specific markers Lyve-1, Prox-1, and podoplanin, the endothelial cell marker CD31, and basement membrane matrix marker collagen IV. DESIGN: Prospective Study. ANIMALS: Eight normal globes from animals euthanized for unrelated health problems. PROCEDURES: Sagittally cut serial sections of six normal canine eyes were immunofluorescence double-stained with Lyve-1 and CD31 and single-stained with colorimetric Prox-1 and collagen IV. Three serial sections from 2 additional eyes were cut in the coronal plane at the level of the ciliary body and immunofluorescence double-stained with Lyve-1 and CD31 to map lymphatic channel distribution. Lymphatics from normal canine lymph nodes were used for validation of podoplanin. RESULTS: Four of 6 of the sagitally sectioned eyes had Lyve-1-positive lymphatic-like structures that were distinct from CD31-positive blood vessels in the iris base and ciliary body. Both of the coronally sectioned globes had Lyve-1-positive lymphatic-like structures in the ciliary body. The location of these structures was evaluated and found to be diffusely present circumferentially around the ciliary body. CONCLUSION AND CLINICAL RELEVANCE: These results support the existence of lymphatic channels in the anterior uveal tract of the canine eye. This could indicate the presence of a novel uveolymphatic outflow pathway, which may play a role in aqueous humor outflow. Future studies are needed to confirm the existence and elucidate the role of this proposed uveolymphatic outflow pathway and potentially develop novel treatment options for managing glaucoma.

Canine anterior uveitis.

Canine anterior uveitis can be a debilitating, painful, vision-threatening disease. Several local and systemic diseases can cause anterior uveitis. Because the eye is limited in its ability to respond to injury, different diseases produce similar clinical signs, making an etiologic diagnosis difficult but imperative to improve the likelihood of a successful outcome. A thorough history and complete ocular and physical evaluations are necessary to ensure timely and accurate diagnosis. This article reviews the pathophysiology, most common causes, diagnostic recommendations, current therapeutic options, potential complications, and prognosis for canine anterior uveitis.

Identification of lymphatics in the ciliary body of the human eye: a novel "uveolymphatic" outflow pathway.

Impaired aqueous humor flow from the eye may lead to elevated intraocular pressure and glaucoma. Drainage of aqueous fluid from the eye occurs through established routes that include conventional outflow via the trabecular meshwork, and an unconventional or uveoscleral outflow pathway involving the ciliary body. Based on the assumption that the eye lacks a lymphatic circulation, the possible role of lymphatics in the less well defined uveoscleral pathway has been largely ignored. Advances in lymphatic research have identified specific lymphatic markers such as podoplanin, a transmembrane mucin-type glycoprotein, and lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1). Lymphatic channels were identified in the human ciliary body using immunofluorescence with D2-40 antibody for podoplanin, and LYVE-1 antibody. In keeping with the criteria for lymphatic vessels in conjunctiva used as positive control, D2-40 and LYVE-1-positive lymphatic channels in the ciliary body had a distinct lumen, were negative for blood vessel endothelial cell marker CD34, and were surrounded by either discontinuous or no collagen IV-positive basement membrane. Cryo-immunogold electron microscopy confirmed the presence D2-40-immunoreactivity in lymphatic endothelium in the human ciliary body. Fluorescent nanospheres injected into the anterior chamber of the sheep eye were detected in LYVE-1-positive channels of the ciliary body 15, 30, and 45 min following injection. Four hours following intracameral injection, Iodine-125 radio-labeled human serum albumin injected into the sheep eye (n = 5) was drained preferentially into cervical, retropharyngeal, submandibular and preauricular lymph nodes in the head and neck region compared to reference popliteal lymph nodes (P < 0.05). These findings collectively indicate the presence of distinct lymphatic channels in the human ciliary body, and that fluid and solutes flow at least partially through this system. The discovery of a uveolymphatic pathway in the eye is novel and highly relevant to studies of glaucoma and other eye diseases.

Uveítis anterior

La uveítis anterior o iridociclitis es la inflamación intraocular más frecuente. Afecta al iris y al cuerpo ciliar, que aunque responden como un todo ante la inflamación, son dos estructuras anatómicas y funcionalmente diferenciadas. En este artículo se revisa la anatomía de la zona para adentrarnos después en un complejo repertorio de síntomas y signos oculares que pueden ser producidos por la uveítis anterior, tanto los más frecuentes como los producidos por las complicaciones de la inflamación (AU)

[Equine recurrent uveitis]. / Zur equinen rezidivierenden Uveitis (ERU).

Equine recurrent uveitis is an important ocular disease and the most common cause for blindness in horses and mules worldwide. The anatomy, physiology, immunology and inflammatory reactions of the uveal tract are discussed. Possible etiologies and the clinical signs are described. A detailed description of possible therapies is given and the prognosis is discussed.

Refractive state, corneal curvature, accommodative range and ocular anatomy of the Asian elephant (Elephas maximus).

The resting refractive state of six mature, female, Asian elephants (Elephas maximus) was determined using streak retinoscopy and neutralizing video retinoscopy. The amplitude of accommodation was also measured by neutralizing video retinoscopy of two animals and the corneal curvatures of three animals was measured by photokeratoscopy. The net spherical refraction was found to be +0.23 D. No difference was observed between cyclopleged and non-cyclopleged eyes (data from three animals), nor was there any difference between right and left eyes. Nine of the twelve eyes refracted had > or = 0.5 D astigmatism. The mean corneal power, as measured by photokeratometry was 21.3 D (SD = 1.8 D). There was a tendency towards with-the-rule corneal astigmatism in our sample (mean value: 1.2 D), though it did not reach statistical significance (P = 0.06). Two elephants were examined using neutralizing video photoretinoscopy. They were able to accommodate through 3 D. Three fixed eyes from three different elephants were obtained for gross and microscopic examination. The mean axial length of the eye was 38.75 mm and the lens had an axial diameter of approx. 10 mm. The posterior sclera was thick (8.0-8.5 mm). Histologically, the cornea was comprised of five distinct layers. A thin, meridionally oriented smooth ciliary muscle was identified. Individual muscle fibers were also observed associated with the posterior trabeculae of the uveal meshwork.

Effects of intracameral injection of chondroitinase ABC in vivo.

A glycosaminoglycan-degrading enzyme, chondroitinase ABC, was introduced into the anterior chamber of three cynomolgus monkeys. Following the injection, the intraocular pressure decreased in the experimental eyes. Depending on the monkey, the intraocular pressure was lowered for 5, 7, or 14 days before it returned to the normal level. Repeated injections produced a similar response. Structurally, the intertrabecular spaces appeared widened, and marked ballooning of the juxtacanalicular tissue was observed. The outer trabecular beams and the inner wall of Schlemm's canal were greatly disorganized. Considerable loss of the juxtacanalicular tissue was noted even 2 months after the enzyme was injected into the anterior chamber. These observations suggest that chondroitinase ABC digested the trabecular glycosaminoglycans, triggering intraocular pressure reduction and causing disorganization of the extracellular matrices of the disorganized trabecular beams, especially in areas near Schlemm's canal.

Microfibril-microvessel connections in the uvea and optic nerve of the mammalian eye.

Light- and electron-microscopic examination of arterioles, venules and capillaries of the eyes of several mammalian species has shown that the microfibrils of ocular elastic tissue attach to microvascular basement membranes throughout the uvea (iris, ciliary body, choroid) and optic nerve. Although described sporadically in prior investigations, this report shows that the connections are a common feature of the mammalian eye. The connections appear most numerous at venules and capillaries and are sparse at arterioles. The connections may provide a mechanism by which perivascular elastic tissue influences microvascular function, e.g. the control of blood pressure in them or their response to changes in intraocular pressure.

Uveitis associated with juvenile rheumatoid arthritis.

Chronic nongranulomatous uveitis associated with JRA, a distinctive clinical entity occurring almost exclusively in the pediatric age group, represents an important cause of visual impairment in children. Despite continuing clarification of the clinical manifestations of this disorder, the etiology of uveitis associated with JRA remains unknown and the pathophysiology is still poorly understood. Further study of uveitis-associated JRA, by the application of improved immunologic theories and techniques, should aid in developing more effective therapeutic and preventive strategies.

Age-related changes in the trabecular meshwork of the normal human eye.

Specimens from 17 human eyes, ranging in age from 3 to 80 years, were subjected to morphometric studies using light microscope, transmission electron microscope and scanning electron microscope, in order to clarify the age-related changes in the normal trabecular tissue. Statistical analyses showed that the cellularity in the various regions of the trabecular meshwork significantly declined with age. The spaces corresponding to the aqueous outflow pathway in each region of the meshwork also significantly decreased with age. On the other hand, extracellular materials significantly increased in amount with age in all regions of the trabecular meshwork. However, the decrease in the cellularity and the outflow pathway spaces did not show any statistically significant regional difference. These results suggest that general narrowing of the outflow pathway spaces due to the accumulation of extracellular materials with age is the cause of the increase in aqueous outflow resistance with age, and that each region of the trabecular meshwork is equally responsible for the increased resistance.

Aqueous outflow in the beagle. I. Postnatal morphologic development of the iridocorneal angle: pectinate ligament and uveal trabecular meshwork.

The present study examined the postnatal development of the pectinate ligaments and uveal trabecular meshwork of the normal canine chamber angle of the Beagle breed at one day, one through ten weeks, three, four and six months, and one and two years of age. Angle tissue was prepared and examined by standard techniques for light microscopy and scanning and transmission electron microscopy. Developmentally, pectinate ligaments matured by the third week although areas continued to develop through the eighth week. Each primary pectinate ligament possessed a large, posterior extracellular space at its iridal attachment. The uveal meshwork, which developed by rarefaction, was not formed at birth and did not appear adult-like until the end of the second month. Adult trabecular cells were ultrastructurally identical throughout the angle, having been characterized by having cilia and "special" rough endoplasmic reticulum.

Elastic and precursor fibres in the normal human eye.

Completely formed elastic fibres consist of a core of amorphous elastin within a mantle of microfibrils. The fibrillar component may occur as isolated bundles (oxytalan) or may be randomly intermingled with variable amounts of elastin (elaunin). The distribution of both mature elastic and incomplete oxytalan and elaunin fibres in the different parts of 53 human eyes from foetal life to old age is described, as evaluated by light microscopy of histochemical preparations. In general elastic tissue was most evident in the collagenous structures save the adult cornea in which incomplete elastic fibres occur rarely and then late in life. Precursor forms predominate in early childhood and show a limited and slow capacity for maturation. The suspensory zonular fibres of the lens appear to be composed largely of oxytalan throughout life. There is also evidence that corneal epithelium and endothelium, irideal smooth muscle and, less certainly, retinal pigment epithelium can synthesise the fibrillar component, although not elastin, of elastic tissue.

Ophthalmic anatomy.

A brief review of the anatomy of the eye, the eyelid, and the lacrimal system provides reference material for the articles that follow in this issue. Pathologic changes in the normal anatomy that can help the physician diagnose an ophthalmic or systemic problem are highlighted.