Biomedical subjects
Publications and source records attributed to K P Barrie.
One to five weeks after cataract removal, retinal detachments due to retinal breaks (rhegmatogenous detachments) were detected in 4 dogs. Surgical repair of the detachments, using a scleral buckling procedure, was successful in 3 of the 4 dogs.
In uveoscleral outflow, aqueous humor leaves the anterior chamber and passes caudally through the trabecular meshwork and the sclerociliary cleft to enter the supraciliary and suprachoroidal spaces. The fluid is then absorbed by choroidal and scleral circulations. Using 3H-labeled dextran, uveoscleral outflow was quantitated in normotensive and glaucomatous Beagles under general anesthesia. The intrascleral plexus was isolated and 3H-labeled dextran was injected into the anterior chamber. Intrascleral plexus contents were sampled every 5 minutes over a 30- to 60-minute period. The eyes were enucleated, sectioned, and prepared for scintillation counting. Uveoscleral outflow accounted for 15% and 3% of the total aqueous humor outflow in the normotensive dogs and in the advanced glaucomatous dogs, respectively. In the advanced glaucomatous Beagle, conventional and uveoscleral outflow pathways were reduced and contributed to the etiopathogenesis of glaucoma.
Aqueous humor leaves the anterior chamber through 2 pathways: the trabecular meshwork of the iridocorneal angle and the unconventional uveoscleral route. In the latter route, aqueous humor leaves the anterior chamber, passes caudally through the trabecular meshwork and sclerociliary cleft to enter the supraciliary and suprachoroidal spaces. The fluid is absorbed by the choroidal and scleral circulation. Fluorescein-labeled dextran was slowly infused into the posterior chamber of healthy and glaucomatous Beagles for 30 minutes. The eyes were fixed in a mixture of 70% alcohol and formalin, placed in epoxy resin for histologic evaluation, and examined by fluorescent microscopy. Fluorescence was detected in the healthy dogs throughout the uveoscleral pathway. In the glaucomatous dogs, the uveoscleral outflow was decreased or completely absent.
Forty-two Miniature Schnauzer pups and adults with congenital cataracts and microphthalmia were evaluated by serial ophthalmic examinations, slit lamp biomicroscopic photography, and A-scan ultrasonography. The cataracts were evident when the eyelids opened at 2 weeks, affecting predominantly the lens nucleus and posterior cortex. Lenticonus was evident in 19% of the cataractous lenses. Progression of the cataracts was variable and related to involvement of the equatorial and posterior cortices. Lens-induced uveitis developed in some adult dogs with advanced hypermature cataracts. The globe and lens were smaller than normal in the cataractous eyes, as ascertained by A-scan ultrasonography. Age-matched comparisons of clear lens carrier Miniature Schnauzers and normal Beagles with the cataractous Miniature Schnauzers indicated affected globes and cataractous lenses were reduced 10% to 20% in their anteroposterior lengths. The microphthalmia appeared related to the congenital microphakic cataract.
Congenital cataracts and microphthalmia in the Miniature Schnauzer were inherited as an autosomal recessive trait. Eighteen matings of affected X affected Miniature Schnauzers resulted in 87 offspring with congenital cataracts and microphthalmia (49 males/38 females). Two matings of congenital cataractous and microphthalmic Miniature Schnauzers (2 females) X a normal Miniature Schnauzer (1 male) yielded 11 clinically normal Miniature Schnauzers (7 males/4 females). Eighteen matings of congenital cataractous and microphthalmic Miniature Schnauzers (6 males) X carrier Miniature Schnauzers (9 females) produced 81 offspring; 39 exhibited congenital cataracts and microphthalmia (20 males/19 females) and 42 had clinically normal eyes (17 males/25 females).
Injection of 150, 500, or 750 U of alpha chymotrypsin into the posterior chamber of clinically normal Beagles resulted in changes in intraocular pressure and iridocyclitis. In the 6 eyes treated with 500 or 750 U, lens subluxation occurred in 4 eyes, retinal detachment in 1 eye, retinal degeneration in 1 eye, and optic nerve degeneration in 6 eyes. Scanning electron microscopic changes included dose-related zonulolysis and zonulary remnants within the aqueous humor outflow pathways. Ultrastructural changes by transmission microscopy of the optic nerve degeneration revealed loss of axoplasm and organelles and disruption of the myelin sheaths. Retinal and optic nerve changes may represent the direct toxic effects of alpha chymotrypsin and/or the indirect effects of increased intraocular pressure.
The Mackay-Marg, pneumatonograph, and EMT-20 tonometers were evaluated in the eyes of glaucomatous beagles. Tonometric scale readings were compared to the manometric recordings from the anterior chamber. Tonometry was performed with manometric system closed and open to the reservoir column. The Mackay-Marg tonometer evaluated in the closed and open manometric systems was highly reliable (goodness of fit [r2] = 0.852 and 0.816, respectively) with intraocular pressures up to 50 mm Hg and somewhat lower (r2 = 0.818 and 0.740, respectively) with intraocular pressures up to 100 mm Hg. The pneumatonograph also exhibited high reliability (r2 = 0.892 [closed] and 0.806 [open]) at pressures up to 50 mm Hg and (r2 = 0.796 [closed] and 0.75 [open]) at pressures up to 100 mm Hg. The EMT-20 tonometer was the least satisfactory for the glaucomatous globe, with r2 ranging from 0.235 to 0.654.
The base and pupillary zones of the iris were exposed for 10 s to a -79 C cryoprobe (iridocryothermy). The resultant iritis lasted 7 to 10 days as evidenced by aqueous flare, hypotony, and miosis. At 21 days, the iris was depigmented and had an irregular pupil. The initial histopathologic changes after iridocryothermy were iridic intrastromal hemorrhage, exudation, and neutrophil infiltration. The iridic pigmented epithelium was lyzed, and the melanin granules were liberated into the iridic stroma, posterior, and anterior chambers. Irides frozen at the pupillary zone exhibited sphincter muscle degeneration. By 21 days after iridocryothermy, the irides were depigmented and atrophic.
Cataracts developed in 13 of 27 related Chesapeake Bay Retrievers. The posterior pole, "Y" sutures, and equatorial cortices of the lens were predominantly affected. In one affected dog, the cataracts had progressed to hypermaturity, permitting restoration of vision. The trait was believed to be dominant, with incomplete penetrance.
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Unilateral chorioretinitis caused by ophthalmomyiasis interna posterior in a 5-month-old, female spayed Dachshund is reported. Larva removal by pars plana vitrectomy was performed after an unsuccessful photocoagulation of the organism. The larva was intact after surgical removal and was identified as a first stage instar Cuterebra spp. larva. The eye remains visual and comfortable with no signs of residual or recurrent inflammation postoperatively. This report describes, for the first time, the successful surgical retrieval of an intravitreal fly larva in a dog using vitrectomy techniques without sacrificing either the globe or vision, and taxonomic identification of the parasite.
OBJECTIVE: The purpose of this study was to evaluate the usefulness and effectiveness of permanent amniotic membrane transplantation as an adjunctive treatment to superficial keratectomy alone or combined with strontium-90 irradiation for treatment of equine corneolimbal squamous cell carcinoma (SCC) to decrease corneal scarring and recurrence rate. STUDY: The retrospective case study included 11 horses (n = 12 eyes) diagnosed and treated for ocular SCC that involved the limbus and cornea. Nine of those horses (n = 9 eyes) were treated between 2002 and 2006, with superficial lamellar keratectomy alone or combined with strontium-90 irradiation and followed by placement of a permanent amniotic membrane graft in the surgical defect. The level of scarring (i.e. the clarity of the cornea) resulting with the use of amniotic membrane was subjectively compared to cases where a permanent bulbar conjunctival graft was performed following keratectomy combined with strontium-90 irradiation or cryotherapy (n = 3 eyes). Recurrence was defined as the postoperative and postirradiation regrowth of SCC in the same site and globe. RESULTS: The nine horses that received an amniotic membrane graft after keratectomy alone or combined with irradiation showed a minimal level of scarring in a cornea that regained a greater transparency in comparison to the horses that were treated with a bulbar conjunctival graft. All of the horses that received an amniotic membrane graft had 226 +/- 218 days of follow-up without tumor recurrence (mean +/- SD), ranging from 21 days to 778 days. CONCLUSIONS: The combination of superficial keratectomy alone or associated with beta-irradiation and permanent amniotic membrane transplantation is an effective treatment of corneal or corneolimbal SCC in horses. The placement of an amniotic membrane material represents an alternative surgical procedure to bulbar conjunctival grafts, especially if there is a lack of bulbar conjunctiva tissue available after tumor resection or if a particularly large corneal resection is necessary. The amniotic membrane is incorporated into the corneal defect and seems to create noticeably much less scarring than a corneal defect covered by bulbar conjunctiva.