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.

Evaluation of potential risk factors for development of primary angle-closure glaucoma in Bouviers des Flandres.

OBJECTIVE To evaluate potential risk factors for development of primary angle-closure glaucoma (PACG) in Bouviers des Flandres. DESIGN Prospective, observational study. ANIMALS 98 Bouviers des Flandres. PROCEDURES All dogs underwent slit-lamp biomicroscopy, indirect ophthalmoscopy, gonioscopy, applanation tonometry, streak retinoscopy, and A-scan, B-scan, and high-resolution ultrasonography. Iridocorneal angles and degree of pectinate ligament dysplasia sheeting were graded, and an angle index was mathematically derived for each eye on the basis of these values. Ciliary clefts evaluated by high-resolution ultrasonography were classified as open, narrow, or closed. Owners were contacted by telephone 7 to 9 years after the initial examination to determine whether dogs had a subsequent diagnosis of PACG. Relationships between previously recorded variables and the development of PACG were evaluated by logistic regression methods. Available pedigrees were reviewed to assess genetic relationships among affected dogs. RESULTS 9 of 92 (9.8%) dogs with follow-up information available developed PACG. An angle index < 1 and presence of a narrow or closed ciliary cleft in 1 or both eyes were each significantly associated with development of PACG. Odds of developing PACG for dogs with an angle index < 1 (indicating marked reduction in outflow capacity through the iridocorneal angle), a narrow or closed ciliary cleft in > 1 eye, or both findings were 13, 20, and 28 times those for dogs that did not have these findings, respectively. All dogs that developed PACG shared 1 common male sire or grandsire. CONCLUSIONS AND CLINICAL RELEVANCE Several anatomic factors were significant risk factors for development of PACG in this population of dogs. Results also suggested a genetic component for the disease.

Corneal sequestrum in a dog with chronic unilateral keratoconjunctivitis sicca.

CASE DESCRIPTION: A 14-year-old 8.2-kg (18.04-lb) castrated male Cairn Terrier with chronic keratoconjunctivitis sicca in the left eye was evaluated because of severe blepharospasm and a black plaque of 3 weeks' duration. CLINICAL FINDINGS: Abnormalities of the left eye included a decreased Schirmer tear test value and the presence of a brownish-black plaque in the center of the cornea. The plaque was surrounded by fibrovascular tissue except at the medial aspect where there was mild malacia of the adjacent corneal stroma. TREATMENT AND OUTCOME: The plaque was removed by superficial keratectomy, and a conjunctival graft was performed. Histologic evaluation of the plaque and surrounding cornea revealed ulceration, stromal necrosis, and chronic suppurative keratitis with fibrosis and neovascularization. Evaluation of plaque sections that were stained with Gram and Von-Kossa stains yielded negative results for bacteria and mineralization, respectively; examination of sections stained with periodic acid-Schiff stain revealed multiple intracytoplasmic inclusions in macrophages. Virus isolation and a PCR assay for canine herpesvirus yielded negative results. Transmission electron microscopy revealed collagen disruption with interspersed macrophages and apoptotic keratocytes; no viral particles or evidence of other infectious agents was observed. The graft healed without complication and was trimmed 2 weeks after surgery. Four months after surgery, the Schirmer tear test value remained decreased from reference limits despite topical tacrolimus treatment, and pigmentary keratopathy was present surrounding the graft. CLINICAL RELEVANCE: Corneal sequestra are rare in species other than cats. In this dog, it was possible that chronic keratoconjunctivitis sicca might have contributed to the development of the corneal sequestrum.