Neuropharmacological lesion localization in idiopathic Horner's syndrome in Golden Retrievers and dogs of other breeds.

OBJECTIVE: To investigate whether idiopathic Horner's syndrome (HS) in Golden Retrievers is an exclusively preganglionic disorder based on denervation hypersensitivity pharmacological testing with phenylephrine. ANIMALS STUDIED: Medical records of dogs presented with HS between 2000 and 2012. Dogs presented with additional ocular or systemic signs were excluded. PROCEDURES: Clinical data examined included age, sex, duration of clinical signs, ancillary diagnostic test results, and time to mydriasis on topical ocular application of 1% phenylephrine. Lesions were diagnosed as postganglionic (mydriasis within 20 min) or preganglionic (mydriasis between 20 and 45 min). RESULTS: Medical records of 21 dogs of nine different breeds were included. An etiopathogenesis for Horner's syndrome was determined in five dogs, none of which were Golden Retrievers. All diagnoses correlated with pharmacological lesion localization. Ten Golden Retrievers were included (eight male and two female) with a mean age of 8.5 years (range: 4-13). Lesion localization was diagnosed as postganglionic in eight (mean: 10 min [range: 6-18]) and preganglionic in two Golden Retrievers (20 and 24 min). All cases were unilateral and had completely resolved within 15 weeks (range: 11-20). Recurrence was not reported in any of the patients. CONCLUSIONS: Idiopathic postganglionic HS was diagnosed in eight of 10 Golden Retrievers contradicting previous reports of a purely preganglionic localization. Etiopathogenesis of canine idiopathic HS remains to be determined; nevertheless, a vascular etiology cannot be excluded. Future studies using magnetic resonance angiography may aid in clarifying the pathogenesis.

Effects of an intravenous bolus of alfaxalone versus propofol on intraocular pressure in sheep.

The objective of this prospective study was to determine the effects of a single intravenous bolus of alfaxalone in 2-hydroxypropyl-ß-cyclodextrin and propofol on the intraocular pressure (IOP) in sheep. Ten Ripollesa sheep with a bodyweight of 48.5 (6.8) kg (mean [sd]) were used in the study. Twenty-four hours before the experimental procedure, a complete ophthalmic examination was performed in all animals. The day of the study, intravenous alfaxalone (2 mg/kg) or propofol (6 mg/kg) was randomly administered in a cross-over design, with a washout period of two weeks. Measurements of IOP, globe position and pupil size were obtained at basal time, before induction (time 0) and at two, five, 10, 15, 20, 30, 45, 60, 90 and 120 minutes after drug administration. Occasional side effects and time to standing were also noted. Intravenous administration of alfaxalone and propofol in sheep resulted in no alteration of IOP. Nevertheless, a decrease in the pupil size was observed in both groups. This present study shows that alfaxalone and propofol, administrated as a single intravenous bolus, are good options for maintaining IOP during anaesthesia in sheep, although marked miosis was observed after administration.

Ocular effects of topical 0.03% bimatoprost solution in normotensive feline eyes.

OBJECTIVE: The current study was undertaken to evaluate the effects of topically applied bimatoprost, an ocular hypotensive lipid, on intraocular pressure (IOP) and pupil size (PS) in healthy cats. ANIMAL STUDIED: Nine European Shorthair cats free from clinically relevant ocular abnormalities were used in the study. PROCEDURES: Pretreatment baseline measurements of IOP and PS were obtained bilaterally at 8 am, 2 pm, and 8 pm for five consecutive days (days 1 to 5). Then the cats received one drop twice daily (10 am and 6 pm) of bimatoprost ophthalmic solution 0.03% (Lumigantrade mark, Allergan Inc., Irvine, CA USA), in one randomly selected eye and one drop of artificial tears in the fellow eye (control eye) for 5 days (days 6 to 10). Values for IOP and PS were obtained under the same conditions as in the pretreatment phase. The potential for ocular irritation following bimatoprost application was also evaluated. RESULTS: During the pretreatment period, the mean IOP and mean PS were not significantly different between the eyes subsequently treated with bimatoprost and those subsequently determined as controls. During the treatment period, the mean IOP in bimatoprost-treated eyes was not significantly lower than in control eyes (14.2+/-2.3 vs. 14.5+/-2.8 mmHg). Mean IOP in control eyes was not significantly changed at any time during the study period. A marked reduction of PS was seen in all bimatoprost-treated eyes, but no other clinically relevant side effects were observed. CONCLUSION: Twice daily topical applications of bimatoprost produced miosis but had no significant effect on IOP in healthy cats.

Effects of 0.005% latanoprost solution on intraocular pressure in healthy dogs and cats.

OBJECTIVE: To evaluate effects of daily topical ocular administration of latanoprost solution on intraocular pressure (IOP) in healthy cats and dogs. ANIMALS: 9 domestic shorthair cats and 14 dogs. PROCEDURE: Latanoprost solution (0.005%) was administered topically to 1 eye (treated) and vehicle to the other eye (control) of all animals once daily in the morning for 8 days. Intraocular pressure was measured twice daily for the 5 days preceding treatment, and IOP, pupillary diameter, conjunctival hyperemia, and blepharospasm were measured 0, 1, 6, and 12 hours after the first 4 treatments and 0 and 12 hours after the final 4 treatments. Measurements continued twice a day for 5 days after treatment was discontinued. Aqueous flare was measured once daily during and for 5 days after the treatment period. RESULTS: Intraocular pressure and pupillary diameter were significantly decreased in the treated eye of dogs, compared with the control eye. Mild conjunctival hyperemia was also detected, but severity did not differ significantly between eyes. Blepharospasm and aqueous flare were not detected in either eye. Intraocular pressure in cats was not significantly affected by treatment with latanoprost. However, pupillary diameter was significantly decreased in the treated eye, compared with the control eye. Conjunctival hyperemia, aqueous flare, and blepharospasm were not detected in either eye. CONCLUSIONS AND CLINICAL RELEVANCE: Once-daily topical ocular administration of latanoprost solution (0.005%) reduced IOP in healthy dogs without inducing adverse effects but did not affect IOP in healthy cats. Latanoprost may be useful for treating glaucoma in dogs.

The effect of intravenous medetomidine on pupil size and intraocular pressure in normotensive dogs.

Medetomidine, a highly specific alpha-2 adrenergic agonist, has been demonstrated to lower intraocular pressure (IOP) in rabbits and cats when applied topically. The purpose of this study was to assess the influence of intravenously injected medetomidine on the pupil size (PS) and the IOP of non glaucomatous dogs. IOP was measured by applanation tonometry and PS was measured using Jameson calipers at t=0 (or time of IV injection of medetomidine (Domitor; Orion) at the dose of 1500 microg/m2 body surface area) and again after 5 minutes (t=5). The IV administration of medetomidine caused miosis in all 14 dogs. The mean PS decreased from 9.0 to 4.0 mm (p<0.001). The IOP was lowered in 10 dogs and in 4 dogs there was a rise in IOP. The mean IOP (mmHg) decreased from 22 to 21 (p>0.2). The data presented above confirm that medetomidine at a dose of 1500 microg/m2 body surface area produces miosis in non glaucomatous dogs, without influencing the IOP.

Effect of topical pilocarpine treatment on tear production in dogs.

Tear production, evaluated every 2 hours from 8 AM to 8 PM by use of the Schirmer tear test over a 3-day period, was not significantly different between left and right eyes in 12 dogs. However, a significant diurnal pattern was evident. Tear production was lowest at midday and highest in the late afternoon/early evening. After pilocarpine HCl ophthalmic solution (0.25, 1.0, or 2.0%; 1 drop) was administered topically to the left eye of each dog at 7 AM on days 4, 6, and 8, respectively, tear production was determined for both eyes every 2 hours from 8 AM to 8 PM on the day of treatment. Analysis of tear values between eyes and between each eye's treatment and pretreatment values did not reveal significant change for the treated eye, but tear production was significantly less in the untreated eye, compared with its pretreatment values and with values in the treated eye. On day 10 (48 hours after the last treatment), tear production values were not significantly different between left and right eyes, and for both eyes, were not significantly different from the mean pretreatment tear production values. Topical application of 0.25, 1.0, or 2.0% pilocarpine HCl consistently caused blepharospasm, conjunctival hyperemia, and miosis of the treated eye, without significant increase in tear production. We concluded that topical application of pilocarpine, at the concentrations used, may have little value in treating disorders involving reduced tear production.

Effects of topical administration of timolol maleate on intraocular pressure and pupil size in cats.

Effects of topical administration of a single dose of timolol maleate, a nonselective beta-adrenergic blocking agent, on intraocular pressure (IOP) and pupil diameter were evaluated in the normotensive eyes of 10 clinically normal cats over 12 hours. Mean (+/- SEM) normal IOP was 17.1 (+/- 1.1) mm of Hg and diurnal fluctuation was observed, with the highest IOP seen in the evening. Mean (+/- SEM) normal pupil diameter was 10.1 (+/- 0.5) mm. Topical treatment with 0.5% timolol resulted in reduction of IOP in treated and nontreated eyes. This effect was time-dependent and was first observed at 6 hours after treatment. Mean reduction of IOP was 22.3% in the treated eye and 16.3% in the nontreated eye. The treated eye had reduced pupil diameter at 30 minutes after treatment, and miosis persisted throughout the 12 hours of the study. Mean reduction of pupil diameter was 38.7%. A contralateral effect on pupil diameter was not seen in the nontreated eye. Topical administration of timolol maleate results in a reduction of IOP in treated and contralateral eyes, which supports the use of timolol for treatment of glaucoma in cats. In addition, the treated eye becomes miotic. This effect may indicate beta-adrenergic inhibition or alpha-adrenergic activation of the iris sphincter muscle. beta-Adrenergic blockade would then result in miosis.

Effects of topical administration of 2.0% pilocarpine on intraocular pressure and pupil size in cats.

Effects of topical administration of a single dose of 2% pilocarpine on intraocular pressure (IOP) and pupil diameter were evaluated in normotensive eyes of 10 clinically normal cats over 12 hours. Mean (+/- SEM) normal IOP was 17.1 (+/- 1.1) mm of Hg and, diurnal fluctuation was observed, with the highest IOP seen in the evening. Mean (+/- SEM) normal pupil diameter was found to be 10.1 (+/- 0.5) mm. Topical treatment with pilocarpine resulted in reduction of IOP in treated and nontreated eyes. This effect was time-dependent and was first observed at 4 hours after treatment. Mean reduction of IOP was 15.2% in the treated eye and 9.3% in the nontreated eye. The treated eye had reduced pupil diameter at 30 minutes after treatment, and miosis persisted throughout the 12 hours of the study. Mean reduction in pupil diameter was 28.5% in the treated eye and 14.2% in the nontreated eye. Topically administered pilocarpine results in reduction of IOP and pupil diameter in treated and contralateral eyes, which supports the use of pilocarpine for treatment of glaucoma in cats.

Horner's syndrome in the horse: a clinical, experimental and morphological study.

A clinical case of Horner's syndrome is described in a Standardbred horse, and the various symptoms of cranial sympathetic denervation are studied in two ponies after experimental transection of the left cervical sympathetic trunk and vagosympathetic trunk, respectively. The most prominent symptoms of equine Horner's syndrome were ptosis, local sweating and increased cutaneous temperature in the denervated area. Enophthalmos, miosis and increased lacrimation were also observed but these symptoms were mild, variable and difficult to ascertain. Prolapse of the third eyelid was not noticed. Concomitant laryngeal hemiplegia was present in the clinical case and was provoked experimentally in one pony by transection of the left vagosympathetic trunk. The aetiology of each of these symptoms is discussed by comparing the results of pharmacological tests and histological findings in the three horses with the data from the literature.