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Biomedical subjects

J Dziezyc

Publications and source records attributed to J Dziezyc.

At least 19 recordsLinked to original sources
PubMed2005

Redistribution of strain and curvature in the porcine anterior lens capsule following a continuous circular capsulorhexis.

Cataract surgery is the most commonly performed surgical procedure in the US, it consists of three steps: introduction of a hole into the lens capsule, removal of the clouded lens through this access hole, and insertion of an artificial lens. We hypothesize that errant behavior by the residual epithelial cells of the lens capsule following surgery are due, in part, to surgically-induced changes of the native stress and strain fields in the lens capsule. Because the capsular bag can be regarded mechanically as a membrane, here we study changes in curvature and strains due to the most common means of introducing the initial access hole: a continuous circular capsulorhexis (CCC). We show that a modest sized CCC increases circumferential strains and decreases meridional strains by up to approximately 20% and that curvatures change by up to approximately 13%, particularly near the edge of the CCC. We submit that such changes can induce mechanobiological responses that are responsible, in part, for some of the long-term complications following cataract surgery.

Animals↗
PubMed2005

Multiaxial mechanical behavior of the porcine anterior lens capsule.

The biomechanics of the lens capsule of the eye is important both in physiologic processes such as accommodation and clinical treatments such as cataract surgery. Although the lens capsule experiences multiaxial stresses in vivo, there have been no measurements of its multiaxial properties or possible regional heterogeneities. Rather all prior mechanical data have come from 1-D pressure-volume or uniaxial force-length tests. Here, we report a new experimental approach to study in situ the regional, multiaxial mechanical behavior of the lens capsule. Moreover, we report multiaxial data suggesting that the porcine anterior lens capsule exhibits a typical nonlinear pseudo-elastic behavior over finite strains, that the in situ state is pre-stressed multi-axially, and that the meridional and circumferential directions are principal directions of strain, which is nearly equi-biaxial at the pole but less so towards the equator. Such data are fundamental to much needed constitutive formulations.

Animals↗
PubMed2000

Canine systemic bacterial infections.

Although systemic bacterial diseases are an uncommon cause of uveitis in dogs, they should be included in the differential diagnoses for uveitis. A work-up for uveitis should include tests for B. canis and B. burgdorferi. If an aqueous centesis is performed, Leptospira titers or PCR can be performed on the aqueous humor and the serum. Better documentation of the role of Leptospira and B. burgdorferi in uveitis in the dog is needed. Any suspected cases should be worked-up thoroughly. If the dog does prove to be positive for the organism, the case should be submitted to a peer-reviewed journal.

Animals↗
PubMed1995

Ocular Halicephalobus (syn. Micronema) deletrix in a horse.

Ocular contents from a horse with a 4-week history of severe unilateral uveitis were submitted for histopathologic examination. A severe unilateral granulomatous chorioretinitis with intralesional Halicephalobus deletrix was diagnosed. The horse developed progressive neurologic signs several days following the surgery to remove ocular contents and implant a prosthesis and was subsequently euthanatized. A severe multifocal granulomatous encephalitis with intralesional H. deletrix, localized primarily to the optic chiasm, thalamus, and brain stem, was diagnosed from tissues acquired at necropsy. The other eye was not affected. This is the first report of ocular parasitism by H. deletrix and suggests possible systemic dissemination from a primary site in the eye.

Animals↗
PubMed1993

A possible feline model for human blepharospasm.

'Benign essential blepharospasm' is a human eyelid disorder of unknown aetiology characterized by involuntary, bilateral, and disabling spasmodic contracture of the orbicularis oculi muscle. Treatments are frequently disappointing. Here we report what might be a first step toward developing an animal model for exploring mechanisms of the disorder and potential treatments. We surgically implanted stimulating electrodes into brain areas known to supply input to the lateral division of the facial nerve nucleus to induce blinking by electrical stimulation. Single-pulse stimuli at or near the facial, parabrachial, red, and interstitial nuclei produced consistent stimulus-induced eyelid contractions. Responses were ipsilateral to stimulation, except for the interstitial nucleus where contralateral responses occurred. Little or no other movements of the face, head, or body occurred at eye-blink threshold voltages. When these sites were stimulated with pulse trains, eyelid closures followed stimulus frequency and tended to fuse into constant closure. Thresholds at each stimulus site remained constant during three days of testing. Drug treatments produced no consistent effect on eye-blink threshold from any stimulation site, even when general behaviour was affected. We conclude that these input pathways to the facial nucleus may contribute to blepharospasm and that future neurochemical and electrophysiological study of these pathways may produce a suitable animal model for understanding this disorder.

Animals↗
PubMed1992

Comparison of applanation tonometers in dogs and horses.

Two Mackay-Marg tonometers and 2 Tono-Pen tonometers were evaluated in eyes in which intraocular pressure (IOP) had been altered and measured by use of a manometer. Eyes of anesthetized dogs and enucleated horse eyes were used. Compared with the manometer, none of the tonometers accurately measured IOP over the range between 0 and 100 mm of Hg. However at manometer measurements from 0 to 30 mm of Hg, several of the tonometers accurately measured IOP. In addition, significant differences were observed when the measurement accuracy of one tonometer was compared with that of another, especially at high IOP. Coefficient of determination (r2) values for a linear model ranged from 0.979 to 0.991 in dogs, and from 0.982 to 0.996 in horse eyes.

Animals↗
PubMed1992

Insect defensive spray-induced keratitis in a dog.

Ulcerative keratitis was seen in a dog after it had been sprayed in the face by the larger striped walking stick, Anisomorpha buprestoides. This insect has defensive glands from which it can spray a secretion that is lachrymogenic and irritating.

Aerosols↗
PubMed1992

Innervation of the feline eyelids.

The innervation of the eyelids is incompletely understood. This is a particular problem for those who wish to develop animal models of eyelid dysfunction in humans. Blepharospasm, for example, is a disease of uncontrolled eyelid spasm that is difficult to manage clinically because the aetiology is not understood. The anatomical literature on eyelid innervation is sparse and even conflicting. We attempted to study eyelid innervation, both sensory and motor, with injection of horseradish peroxidase (HRP) into the superior eyelid, inferior eyelid, and bulbar conjunctiva. We used 13 anesthetized weanling cats. Shape and structure of the facial nucleus varied along its rostrocaudal extent, but there was a clear demarcation of lateral and medial division. HRP-filled facial nucleus cells were ipsilateral to the injection site, and label appeared throughout the rostrocaudal length. All injection sites, including bulbar conjunctiva, labelled facial nucleus neurons located with overlapping distribution, predominantly in the dorsal part of the lateral division. Likewise, heavy labelling occurred throughout the entire ipsilateral cranial cervical ganglion and the trigeminal ganglion in all kittens. Injection of upper or lower eyelids caused some labelling in the second through the fourth cervical spinal ganglia.

Animals↗
PubMed1992

Effects of prostaglandin F2 alpha and leukotriene D4 on pupil size, intraocular pressure, and blood-aqueous barrier in dogs.

In each of 5 groups of dogs, 0.05 ml of 1 of the following solutions was injected into the anterior chamber of both eyes: phosphate-buffered saline solution, 0.001 microgram of prostaglandin F2 alpha (PGF2 alpha), 0.01 microgram of PGF2 alpha, 0.1 microgram of leukotriene D4 (LTD4), and 1 microgram of LTD4. A 10% solution of sodium fluorescein was injected IV (14 mg/kg of body weight) at the same time, and pupil size, intraocular pressure, and anterior chamber fluorescence were measured for 1 hour after injections. In a dose-dependent manner, PGF2 alpha was a potent miotic. A significant effect on intraocular pressure was not detected when the groups given PGF2 alpha were compared with the control group. When compared with LTD4, PGF2 alpha significantly (P less than 0.05) increased the breakdown of the blood-aqueous barrier, as evidenced by increased fluorescein leakage into the anterior chamber. Leukotriene D4 caused a decrease in pupil size only at 5 minutes, compared with that of the control group. Intraocular pressure was greater (but not significantly) in the group given 1 microgram of LTD4.

Animals↗
PubMed1992

Comparison of prednisolone and RMI-1068 in the ocular irritative response in dogs.

Ocular inflammation was induced in 36 dogs by performing an anterior capsulotomy with a Nd:YAG laser. All dogs were pretreated with topical atropine. Dogs were then divided into three groups: (1) control, with no other pretreatment; (2) pretreatment with the topical dual cyclooxygenase/lipoxygenase inhibitor RMI-1068; and (3) pretreatment with topical prednisolone acetate. Dogs were studied 1-3 hours after lasering. RMI-1068 maintained mydriasis and raised intraocular pressure compared to the control and prednisolone groups. An ocular fluorophotometer used to measure anterior chamber fluorescence after IV injection of sodium fluorescein showed that RMI-1068 decreased anterior chamber fluorescein concentration compared to the control and prednisolone groups. RMI-1068 decreased PGF2 alpha concentrations in the aqueous at 1 and 3 hours compared to the control and prednisolone groups. Prednisolone decreased PGF2 alpha concentrations compared to the control group at 1 h. Concentrations of LTB4 in the aqueous at 1 hour were lower in the RMI-1068 group than in the control and prednisolone groups.

Animals↗
PubMed1991

Use of phacofragmentation for cataract removal in horses: 12 cases (1985-1989).

The medical records of 12 horses that had cataracts removed by use of phacofragmentation were reviewed. Cataracts were removed from 16 eyes in horses ranging in age from 2 months to 15 years. Complications after surgery included corneal ulcers in 13 eyes, diffuse corneal edema in 5 eyes, and uncontrollable uveitis in 3 eyes. Follow-up information was obtained in all horses from 1 month to 3.5 years after surgery. Visual results were judged good by owners or veterinarians in 10 of the horses.

Animals↗
PubMed1991

Acute effects of anti-inflammatory drugs on neodymium:yttrium aluminum garnet laser-induced uveitis in dogs.

Dogs were treated with flunixin meglumine, a cyclooxygenase inhibitor; L-651,896, a 5-lipoxygenase inhibitor; and matrine, a herbal anti-inflammatory drug. Acute inflammation was induced in the eyes by disruption of the anterior lens capsule, using a neodymium:yttrium aluminum garnet laser. Intraocular pressure, pupil diameter, and eicosanoid production in the aqueous humor were measured. Statistically significant effects were seen in the eyes of flunixin meglumine-treated dogs where mydriasis was maintained and aqueous prostaglandin E2 concentration was reduced.

Alkaloids↗
PubMed1991

Effect of flurbiprofen on facility of aqueous outflow in the eyes of dogs.

Aqueous outflow from cannulated canine eyes was determined, using a constant-pressure perfusion technique. The effect of topically applied flurbiprofen, a cyclo-oxygenase inhibitor, on outflow in eyes with or without neodymium:yttrium aluminum garnet laser-induced inflammation was measured. Flurbiprofen caused decrease in aqueous outflow that was more marked in the inflamed eyes.

Animals↗
PubMed1991

Comparison of flunixin meglumine and flurbiprofen for control of ocular irritative response in dogs.

Dogs were treated with the cyclo-oxygenase inhibitors flunixin meglumine IV or flurbiprofen topically. Acute inflammation was induced in the eyes by disruption of the anterior lens capsule, using a neodymium:yttrium aluminum garnet laser. Pupil diameter and intraocular pressure were measured before and after inducing ocular inflammation. Both drugs maintained mydriasis and increased intraocular pressure in the inflamed eyes, compared with untreated controls.

Animals↗
PubMed1990

Nonulcerative keratouveitis in five horses.

Five horses with severe nonulcerative keratouveitis had corneal lesions characterized by a pink stromal infiltrate that initially appeared in the stroma near the limbus. Unremitting iridocyclitis also was evident. In 3 horses, microscopic lesions consisted of marked corneal stromal fibrosis, with mild to severe inflammatory cellular infiltration. Corticosteroids and mydriatic/cycloplegics applied topically and corticosteroids and nonsteroidal anti-inflammatory medications administered parenterally were used with varying degrees of success to control pain and retain vision.

Animals↗
PubMed1990

Cataract surgery. Current approaches.

Cataract surgery in the dog can be a highly successful and rewarding technique for restoring vision to the cataract patient. Coexisting ocular conditions can complicate cataract surgery or be a contraindication for lens removal; these include KCS, uveitis, glaucoma, lens subluxation, and retinal disease. Techniques for cataract surgery include intracapsular cataract extraction, extracapsular cataract extraction, and phacofragmentation, both extracapsular and endocapsular (intercapsular). Phacofragmentation is probably the most successful technique in the dog at this time. Postoperative complications include uveitis, hyphema, glaucoma, capsular opacities, corneal endothelial damage, and retinal detachments. Newer methods of dealing with these problems include the use of viscoelastic materials and IOL implants intraoperatively and the use of the Nd:YAG laser for posterior capsulotomies postoperatively.

Animals↗