Biomedical subjects

D A Wilkie

Publications and source records attributed to D A Wilkie.

At least 19 recordsLinked to original sources

PubMed2002

Partial orbital rim resection, mesh skin expansion, and second intention healing combined with enucleation or exenteration for extensive periocular tumors in horses.

Ocular and periorbital sarcoids and squamous cell carcinoma are common in equine practice. Extensive involvement of periorbital tissues often necessitates removal of the globe if the function of the eyelids can not be maintained with tumor removal alone. This report describes a modification of the standard enucleation or exenteration technique for cases in which there is insufficient skin to achieve primary closure following complete surgical excision. The caudal portion of the dorsal orbital rim is protuberant; partial excision with an osteotome facilitates skin closure by decreasing the size of the wound. Mesh expansion of skin via multiple rows or parallel stab incisions can also be used as an adjunct to facilitate closure. Four horses underwent enucleation or exenteration using the orbital rim resection and mesh skin expansion techniques for extensive periocular tumors that were unresponsive to prior treatments. Follow-up intervals ranged from 6 to 42 months and no horses had tumor regrowth.

Animals↗

PubMed2001

Mineralized corneal sequestrum in a cat.

An 8-month-old 3-kg (6.6-lb) sexually intact male cat was evaluated for chronic refractory keratitis and a corneal plaque that developed after treatment with a corticosteroid-containing ophthalmic preparation. Pertinent ophthalmic findings included blepharospasm, conjunctivitis, corneal vascularization, and a tan raised corneal plaque with a dense and gritty composition. Lamellar keratectomy was performed to excise the plaque. The cornea healed with mild scarring. Histologic examination revealed extensive coagulation necrosis and mineralization of the corneal stroma with increased inflammatory cells, blood vessels, and fibrosis, which is compatible with a diagnosis of mineralized corneal sequestrum. The history suggested chronic feline herpesvirus-1 (FHV-1)-induced keratoconjunctivitis as the underlying cause. Topical corticosteroid administration may have potentiated the preexisting corneal necrosis and initiated mineralization. To our knowledge, mineralization of a corneal sequestrum in a cat has not been reported in a clinical case but has been reported in cats experimentally infected with FHV-1.

Adrenal Cortex Hormones↗

PubMed2001

Description of ciliary body anatomy and identification of sites for transscleral cyclophotocoagulation in the equine eye.

OBJECTIVE: To determine the most appropriate anatomical location for diode laser probe placement to accurately photoablate the equine ciliary body using a contact, transscleral approach. DESIGN: Original research. PROCEDURES: Forty-two freshly enucleated adult equine eyes were evaluated. The horizontal, medial vertical, central vertical, and lateral vertical lengths of the cornea were measured from limbus to limbus. Needles were inserted perpendicular to the sclera at specific distances posterior to the external limbus at the 1, 2, 4, 5, 6, 7, 8, 10, 11 and 12 o'clock positions. The per cent frequency that needles penetrated internal anatomical regions (lens, lens zonules, pars plicata, anterior, middle, and posterior pars plana, ora ciliaris retinae, or retina), when inserted at 2, 4, 6, and 8 mm posterior to the limbus, were calculated for all eyes combined, for right vs. left, for males vs. females, and for three age groups. The internal distance from the limbus to the anterior pars plana, and from the anterior pars plana to the ora ciliaris retinae were also measured in six of the horses (12 eyes). Mean distances and standard deviations were computed for all parameters. RESULTS: Average corneal sizes and standard deviations were: 30.24 mm +/- 1.53 (horizontal); 24.69 mm +/- 1.52 (central vertical); 22.79 mm +/- 1.49 (medial vertical); and 19.79 mm +/- 1.55 (lateral vertical). Internal distances of the pars plicatas ranged from 5.33 mm +/- 0.49 to 10.67 mm +/- 1.15. Internal distances of the pars planas ranged from 0.33 mm +/- 0.49 to 3.17 mm +/- 0.39. High probabilities of penetrating the pars plicata correspond to positions 4 mm posterior to the external limbus dorsotemporal 10, 11 o'clock (OD), and 1, 2 o'clock (OS), dorsonasal 1 o'clock (OD) and 11 o'clock (OS), and ventrotemporal 5-7 o'clock (OU). Low probabilities of penetrating the pars plicata correspond to positions ventronasal 4 o'clock (OD), 8 o'clock (OS) and dorsonasal 2 o'clock (OD), 10 o'clock (OS) at 4 and 6 mm posterior to the external limbus as well as ventrotemporal 4 o'clock (OS), 8 o'clock (OD) at 6 mm posterior to the external limbus. CONCLUSIONS: Transscleral cyclophotocoagulation may be a viable alternative to medical therapy for control of intraocular pressure in horses with glaucoma. Overall, the most accurate anatomical position on the sclera for cyclophotocoagulation of the equine eye is 4-6 mm posterior to the limbus, avoiding the nasal quadrants. Accurate transscleral cyclophotocoagulation should optimize the therapeutic outcome and minimize potential side-effects such as retinal detachment and cataract formation.

Animals↗

PubMed2001

Ocular oncology.

Neoplasia can affect all ocular tissues. The clinical appearance of ocular neoplasia can vary considerably depending on the specific tissue involved. Intraocular neoplasia may mimic or incite ocular inflammatory disease in addition to causing hyphema or secondary glaucoma. Intraocular neoplasms can be primary tumors or may be secondary to metastatic disease or systemic neoplasia. Primary neoplasms, metastatic tumors, tumors extending from adjacent structures, and systemic neoplasms can also affect the adnexal tissues. Many ophthalmic tumors are histologically benign but are locally invasive and, within the confined space of the eye or orbit, can produce significant tissue distortion. Certain ocular neoplasms, such as many canine eyelid tumors, are amenable to simple excision and can be adequately managed in general practice. The evaluation and treatment of other ophthalmic neoplasms, however, may require the additional equipment available only in larger specialty practices, such as computed tomography and radiation therapy. Early diagnosis of ocular neoplasia is an important aspect of successful management.

Animals↗

PubMed2001

Use of an intravitreal sustained-release cyclosporine delivery device for treatment of equine recurrent uveitis.

OBJECTIVE: To evaluate the use of an intravitreal sustained-release cyclosporine (CsA) delivery device for treatment of horses with naturally occurring recurrent uveitis. ANIMALS: 16 horses with recurrent uveitis. PROCEDURES: Horses with frequent recurrent episodes of uveitis or with disease that was progressing despite appropriate medication were selected for this study. Additional inclusion criteria included adequate retinal function as determined by use of electroretinography, lack of severe cataract formation, and no vision-threatening ocular complications (eg, retinal detachment, severe retinal degeneration, and posterior synechia). Sustained-release CsA delivery devices (4 microg of CsA/d) were implanted into the vitreous through a sclerotomy at the pars plana. Reexaminations were performed 1, 3, 6, and 12 months after implantation, then continued annually. Ophthalmic changes, number of recurrent episodes of uveitis, and vision were recorded. RESULTS: The rate of recurrent episodes after device implantation (0.36 episodes/y) was less than prior to surgery (75 episodes/y). In addition, only 3 horses developed episodes of recurrent uveitis after surgery. Vision was detected in 14 of 16 affected eyes at a mean follow-up time of 13.8 months (range, 6 to 24 months). CONCLUSIONS AND CLINICAL RELEVANCE: This intravitreal sustained-release CsA delivery device may be a safe and important tool for long-term treatment of horses with chronic recurrent uveitis.

Animals↗

PubMed2001

Effect of topical administration of 2% dorzlamide hydrochloride or 2% dorzlamide hydrochloride-0.5% timolol maleate on intraocular pressure in clinically normal horses.

OBJECTIVE: To evaluate the effect of topical administration of 2% dorzolamide hydrochloride or 2% dorzolamide hydrochloride-0.5% timolol maleate on intraocular pressure (IOP) in clinically normal horses. ANIMALS: 18 healthy adult horses without ocular abnormalities. PROCEDURE: The IOP was measured at 5 time points (7 AM, 9 AM, 11 AM, 3 PM, 7 PM) over 11 days. On days 1 and 2, baseline values were established. On days 3 through 5, horses received 2% dorzolamide HCI (group D, n = 9) or 2% dorzolamide HCl-0.5% timolol maleate (group DT, 9) in 1 randomly assigned eye every 24 hours immediately following each daily 7 AM IOP measurement. On days 6 through 9, each drug was given every 12 hours (7 AM and 7 PM) in the treated eye. Measurements on days 10 and 11 assessed return to baseline. Mixed linear regression models compared mean IOP difference for each drug at each time period. RESULTS: Mean IOP decreased significantly in all eyes during the 2 dose/d period, compared with the baseline, 1 dose/d, and follow-up periods. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of either drug every 24 hours for short-term treatment does not reduce IOP significantly. Administering either drug every 12 hours induced a significant reduction of IOP; however, controlling for all variables, the reduction was less than 2 mm Hg.

Administration, Topical↗

PubMed2000

Boron neutron capture therapy of brain tumors: functional and neuropathologic effects of blood-brain barrier disruption and intracarotid injection of sodium borocaptate and boronophenylalanine.

Sodium borocaptate (BSH) and boronophenylalanine (BPA) are two drugs that have been used clinically for boron neutron capture therapy (BNCT) of brain tumors. We previously have reported that hyperosmotic mannitol-induced disruption of the blood-brain barrier (BBB-D), followed by intracarotid (i.c.) administration of BPA or BSH, either individually or in combination, significantly enhanced tumor boron delivery and the efficacy of BNCT in F98 glioma bearing rats. The purpose of the present study was to determine the short-term neuropathologic consequences of this treatment and the long-term effects on motor and cognitive function, as well as the neuropathologic sequelae 1 year following neutron capture irradiation. BBB-D was carried out in non-tumor bearing Fischer rats by infusing a 25% solution of mannitol i.c. followed by i.c. injection of BPA or BSH, either individually or in combination, immediately thereafter. Animals were euthanized 2 days after compound administration, and their brains were processed for neuropathologic examination, which revealed sporadic, mild, focal neuronal degeneration, hemorrhage, and necrosis. To assess the long-term effects of such treatment followed by neutron capture irradiation, non-tumor bearing rats were subjected to BBB-D after which they were injected i.c. with BPA (25 mg B/kg body weight (b.w)) or BSH (30 mg B/kg b.w.) either individually or in combination (BPA 12.5 mg and BSH 14 mg B/kg b.w.). Two and a half hours later they were irradiated at the Medical Research Reactor, Brookhaven National Laboratory, Upton, NY, with the same physical radiation doses (5.79, 8.10 or 10.06 Gy), delivered to the brain, as those that previously had been used for our therapy experiments. The animals tolerated this procedure well, after which they were returned to Columbus, Ohio where their clinical status was monitored weekly. After 1 year, motor function was assessed using a sensitive and reliable locomotor rating scale for open field testing in rats and cognitive function was evaluated by their performance in the Morris water maze, the results of which were similar to those obtained with age matched controls. After functional evaluation, the rats were euthanized, their brains were removed, and then processed for neuropathologic examination. Subtle histopathologic changes were seen in the choroid plexuses of irradiated animals that had received BPA, BSH or saline. Radiation related ocular changes consisting of keratitis, blepharitis, conjunctivitis and cataract formation were seen with similar frequency in most rats in each treatment group. Based on these observations, and the previously reported significant therapeutic gain associated with BBB-D and i.c. injection of BSH and BPA, the present observations establish its safety in rats and suggest that further studies in large animals and humans are warranted.

Animals↗

PubMed2000

Evaluation of intraocular pressure in eyes of clinically normal llamas and alpacas.

OBJECTIVE: To estimate intraocular pressure (IOP) in eyes of healthy camelids, using applanation tonometry. ANIMALS: The eyes of 34 camelids (16 llamas [Lama glamal and 18 alpacas [L. pacos]) that did not have major abnormalities of the ocular surface or intraocular abnormalities. PROCEDURE: Tonometry measurements were obtained from each eye 3 times during a 24-hour period. Each measurement was the mean of several corneal applanations obtained by use of an applanation tonometer. Data were analyzed, using an ANOVA for a repeated-measures design. RESULTS: Mean (+/- SEM) IOP of llamas and alpacas was 13.10+/-0.35 and 14.85+/-0.45 mm Hg, respectively. Range of IOP was 7 to 18 mm Hg for llamas and 11 to 21 mm Hg for alpacas. Mean IOP of llamas was significantly less than the mean IOP of alpacas. Significant differences in IOP were not detected between the right and left eye of animals. Significant differences in IOP were not attributed to sex, age, or time of measurement within llamas or alpacas. CONCLUSIONS AND CLINICAL RELEVANCE: Establishing the mean and range of IOP of clinically normal llamas and alpacas provides a frame of reference that is important for use in a complete ophthalmic examination of camelids, which can assist clinicians in the diagnosis of glaucoma and uveitis. Reasons for the difference in mean IOP between llamas and alpacas are unknown. Although the difference may be unimportant clinically, this finding reiterates the fact that caution must be used when extrapolating IOP among species.

Animals↗

PubMed1998

Normal variation in, and effect of 2% pilocarpine on, intraocular pressure and pupil size in female horses.

OBJECTIVE: To determine normal variation in, and effect of 2% pilocarpine hydrochloride on, intraocular pressure (IOP) and pupil size in female horses during a specified period. ANIMALS: 10 female horses with normotensive eyes. PROCEDURE: IOP and horizontal and vertical pupil size were measured on a single day between 8 AM and 8 PM at hours 0, 0.5, 1, 2, 4, 6, 8, 10, and 12. Measurements were repeated after single- dose application of 2% pilocarpine to both eyes. IOP and pupil size were measured at 8 AM and noon in a 5-day experiment of twice-daily application of 2% pilocarpine. RESULTS: Variation in IOP and pupil size was not significant between 8 AM and 8 PM. Change in IOP or pupil size after a single dose of 2% pilocarpine also was not significant. In the multiple-dose experiment, the IOP at noon on the fifth day was significantly higher than the IOP in the morning on the first and second days. The IOP in the morning on the fifth day was significantly higher than the IOP in the morning and at noon on the first and second days. The IOP at noon on the fourth day was significantly higher than the morning IOP on the first and second days and at noon on the first day. The decrease in vertical pupil size was significant. CONCLUSIONS: Between 8 AM and 8 PM, variation in IOP and pupil size in normotensive eyes of horses is not significant. Two percent pilocarpine does not significantly change IOP between 8 AM and 8 PM in clinically normal horses after a single dose or multiple twice-daily applications. After multiple twice-daily applications, a trend toward an increase in IOP was seen, and the decrease in vertical pupil size was significant.

Animals↗

PubMed1997

Surgical treatment of dacryocystitis caused by cystic dilatation of the nasolacrimal system in three dogs.

A 4-year-old castrated male Golden Retriever was referred for evaluation of intermittent purulent discharge from the right eye of 4-months' duration. A radiolucent area in the maxillary bone was detected on examination of skull radiographs. Dacryocystorhinography revealed pooling of contrast material in the radiolucent area. A rhinotomy was performed, and a large opening between the cystic structure of the nasolacrimal system and the nasal cavity was created. Epiphora resolved after surgery and had not recurred by 9 months after surgery. Two other dogs had cystic structures of the nasolacrimal system and were treated surgically to allow drainage into the nasal cavity.

Animals↗

PubMed1997

Surgery of the cornea.

Corneal surgery is a common and essential part of veterinary ophthalmology and ranges from simple linear keratotomy for indolent ulcers to penetrating keratoplasty for restoration of optical clarity. Success in corneal surgery relies on an understanding of corneal anatomy, physiology and wound healing, meticulous attention to detail, microsurgical equipment and techniques, and use of appropriate preoperative, intraoperative, and postoperative medications. Surgical management of corneal disease is indicated for corneal ulceration, excision of a mass lesion, reconstructive procedures, therapeutic indications, optical restoration, and cosmetic purposes.

Animals↗

PubMed1996

Eosinophilic keratoconjunctivitis in seven horses.

Eosinophilic keratoconjunctivitis was diagnosed in 7 horses at The Ohio State University between 1976 and 1994. All horses had moderate-to-severe blepharospasm, chemosis, and conjunctival hyperemia; epiphora; and extensive yellow-to-white caseous mucoid discharge. Corneal ulcers associated with this disease were perilimbal and extended centrally. All ulcers were covered with a white necrotic plaque firmly attached to the underlying cornea. Other ophthalmic abnormalities were not detected. Corneal scrapings examined cytologically contained numerous eosinophils interspersed between epithelial cells, few mast cells, and neutrophils. Microbial organism were not seen. Bacterial and fungal cultures were negative for ocular pathogens. The initial diagnosis of eosinophilic keratoconjunctivitis was made on the basis of clinical and cytologic findings. In 5 horses, the condition completely resolved after topical treatment with corticosteroid (0.05% dexamethasone) and triple antibiotic ointments. However, the duration of treatment was prolonged, with a mean treatment time of 64 days (range, 45 to 106 days). All corneal ulcers remained superficial, and despite the prolonged duration of treatment, none of the horses developed secondary bacterial or fungal keratitis. One horse underwent superficial keratectomy and had the shortest resolution time (14 days).

Administration, Topical↗

PubMed1996

Penetrating keratoplasty for treatment of recurrent squamous cell carcinoma of the cornea in a horse.

Squamous cell carcinoma involving the cornea and conjunctiva of the left eye in a 14-year-old horse was treated by superficial keratectomy in combination with beta-radiation and radiofrequency hyperthermia. The tumor recurred 4 months later in the central cornea at the edge of the previous keratectomy site. Penetrating keratoplasty was performed in an effort to remove the tumor and retain a visual eye. The eye was visual 13 months after surgery. Mild fibrosis and vascularization were observed in the area of the penetrating keratoplasty.

Animals↗

PubMed1995

Traumatic ocular proptoses in dogs and cats: 84 cases (1980-1993).

Eighteen eyes of 66 dogs were visual on reevaluation of traumatic proptosis. Twenty-one eyes were enucleated, and 4 dogs were euthanatized. In 18 cats, no eyes regained vision after traumatic proptosis: 12 cats had the affected eye enucleated, 2 had an eye that was considered blind, and 4 cats were euthanatized. Affected eyes of 45 dogs and 2 cats underwent surgical replacement and temporary tarsorrhaphy. Favorable prognostic indicators for eyes undergoing surgical replacement included proptosis in a brachycephalic dog, positive direct or consensual pupillary light response, normal findings on posterior segment examination, and a proptosed eye that had vision on initial examination. Unfavorable prognostic indicators included proptosis in a nonbrachycephalic dog, proptosis in cats, hyphema, no visible pupil, facial fractures, optic nerve damage, and avulsion of 3 or more extraocular muscles.

Animals↗

PubMed1995

Cellular immunity in dogs with keratoconjunctivitis sicca before and after treatment with topical 2% cyclosporine.

Peripheral cellular immunity of ten dogs with keratoconjunctivitis sicca (KCS) that had not been treated with topical corticosteroids or cyclosporine was evaluated (by use of in vitro lymphocyte proliferation assays and CD4+/CD8+ lymphocyte subset analysis) before and after 1 and 3 months of treatment with topical ocular 2% cyclosporine (CsA). In vitro lymphocyte proliferation and CD4+/CD8+ lymphocyte subset analysis was done in eight normal dogs at the 0, 1 and 3 month time periods to use for comparison. There was no significant difference in lymphocyte proliferation or numbers of CD4+ or CD8+ lymphocytes in dogs with KCS and normal dogs prior to CsA treatment. However, by 1 month's time, lymphocyte proliferation had decreased in the CsA-treated Dogs with KCS, and by 3 months there was a significant difference (P < 0.0001) from the normal dogs. These results suggest that dogs with KCS may not have altered peripheral cellular immunity and that use of topical 2% cyclosporine for treatment of KCS causes a suppression of lymphocyte proliferation after 1 to 3 months of use.

Administration, Topical↗

PubMed1995

[Ultrasonography in veterinary ophthalmology].

Ophthalmic examination evaluates ocular structures in both the anterior and the posterior segments of the eye. In the eye without opacities of the transmitting media, this is accomplished through biomicroscopy, direct and indirect ophthalmoscopy. However, in eyes with media opacities, evaluation, especially of the posterior segment, is difficult or impossible by these routine methods. Further, evaluation of retrobulbar tissues has been limited to radiography and blind aspirate, or surgical exploration. Ultrasound is a noninvasive, safe procedure that allows evaluation of the intraocular and retrobulbar tissues without sedation or general anesthesia.

Animals↗

PubMed1995

Effect of auriculopalpebral nerve block and intravenous administration of xylazine on intraocular pressure and corneal thickness in horses.

Intraocular pressure (IOP) was measured, using applanation tonometry, in both eyes of 20 horses after topical application of 0.5% proparacaine to the cornea. Ultrasonic pachymetry was used to measure central, mid-peripheral, and peripheral corneal thickness (CT) in all 4 quadrants of both eyes of 25 horses. All measurements were repeated after auriculopalpebral nerve block, sedation by IV administration of xylazine, or combination of nerve block and sedation. Mean IOP after topical anesthesia of the cornea was 20.6 +/- 4.7 mm of Hg for the left eye and 20.35 +/- 3.7 mm of Hg for the right eye. Mean central CT was 793.2 +/- 42.3 microns. The peripheral part of the cornea was significantly (P < 0.05) thicker, on average, than the central part of the cornea. Auriculopalpebral nerve block had no significant effect on IOP or CT. Intravenous administration of xylazine resulted in a significant (P < 0.05) decrease in IOP, but had no effect on CT.

Animals↗

PubMed1994

Radiation effects of boron neutron capture therapy on brain, skin, and eye of rats.

PURPOSE: The present study was carried out to evaluate the radiation effects of boron neutron capture therapy (BNCT) on the brain, skin, and eyes of nude rats following systemic administration of boronophenylalanine (BPA) and neutron irradiation to the head. METHODS AND MATERIALS: A solution containing 120 mg of 10B-enriched-L-BPA complexed with fructose was administered IP to nude rats. Boron concentrations were approximately 8.4, 9.4, 10.0, and 11.0 micrograms/g in the brain, blood, skin, and eyes, respectively, at 6 h when the animals were irradiated at the Brookhaven Medical Research Reactor (BMRR). As determined in a study carried out in parallel with this one, the BNCT radiation doses were sufficient to cause tumor regression in nude rats carrying intracerebral implants of the human melanoma cell line MRA 27. RESULTS: Mild to moderate increases in loose fibrous tissue were observed in the choroid plexus at estimated physical doses to the brain and blood that ranged from 4.3-7.1 Gy and 4.6-7.7 Gy, respectively, and these appeared to be dose and time dependent. Other changes in the choroid plexus included occasional infiltrates of macrophages and polymorphonuclear leukocytes and vacuolation of epithelial cells. Dose-dependent moist desquamation of the skin was observed in all rats, but this had healed by 28 days following irradiation. Cataracts and keratitis developed in the eyes of most animals, and these were dose dependent. CONCLUSION: The minimal histopathological changes seen in the brain at doses that were sufficient to eradicate intracerebral melanoma indicates that BNCT has the potential to cure a tumor bearing host without producing the normal brain injury usually associated with conventional external beam radiation therapy. Studies in canines, which currently are in progress, should further define the dose-effect relationships of BNCT on critical neuroanatomic structures within the brain.

Animals↗