Nonhypotensive autonomic agents in veterinary ophthalmology

Static anisocoria in cats and dogs with naturally occurring tick paralysis (Ixodes holocyclus)

OBJECTIVE

To characterise the novel occurrence and neuro-ophthalmological features of static anisocoria in cats and dogs with tick paralysis (TP) (Ixodes holocyclus) due to a single tick located remote from the head and neck.

DESIGN

Observational case series with retrospective analysis.

METHODS

Medical records were reviewed from 69 cats and 169 dogs treated for TP from a suburban veterinary hospital in Newcastle, New South Whales, between September 2005 and October 2021.

RESULTS

Anisocoria was observed in 2/18 (11.1%) cats and 3/30 (10.0%) dogs with a single tick located remote from the head and neck. These proportions were not different when compared within species to 4 of 28 (14.3%) cats and 16 of 98 (16.3%) dogs with aniscocoria with a single tick located on the head and neck region (P = 1 and 0.56 respectively). Anisocoria arose from pupillary efferent dysfunction and included unilateral oculoparasympathetic dysfunction (internal ophthalmoplegia) in one dog, unilateral oculosympathetic dysfunction (Horner's syndrome) in one cat and one dog, and a combination of bilateral, but asymmetric, oculosympathetic and oculoparasympathetic dysfunction in one cat and one dog.

CONCLUSION

It is proposed that anisocoria in cases of TP with a tick located remote from the head and neck is due to an intrinsic latent asymmetry in the safety factor for pupillary efferent function that is unmasked by a systemically distributed holocyclotoxin inhibiting neural transmission within this system, and this is the prevailing pathomechanism, rather than a direct local effect, underscoring anisocoria with a tick located on the head or neck.

Long-lasting otic medications may be a rare cause of neurogenic keratoconjunctivitis sicca in dogs

OBJECTIVE

To characterize the clinical course and long-term prognosis of a suspected novel cause of neurogenic keratoconjunctivitis sicca (nKCS) secondary to florfenicol, terbinafine hydrochloride, mometasone furoate (Claro and Neptra) or florfenicol, terbinafine, betamethasone acetate (Osurnia).

ANIMALS

29 client-owned dogs.

PROCEDURES

Online survey and word-of-mouth recruitment were conducted to identify dogs that developed clinical signs of nKCS after application of otitis externa medication containing terbinafine and florfenicol. A retrospective analysis of medical records of dogs meeting inclusion criteria was then conducted. Included dogs had onset of clinical signs of nKCS within 1 day after application of otitis externa medications containing terbinafine and florfenicol and had documentation of low Schirmer tear test value (< 15 mm/min) of affected eyes.

RESULTS

29 dogs with medical records available for review met the inclusion criteria. Documented return of clinically normal tear production was identified in 24 of 29 dogs, with a median time from application of ear medication to documented return of clinically normal tear production of 86 days (range, 19 to 482 days). A corneal ulcer was diagnosed in 68% (20/29). Multivariable Cox regression analysis showed being referred to an ophthalmologist (P = .03) and having a deep ulcer (P = .02) were associated with a longer time to documentation of Schirmer tear test ≥ 15 mm/min.

CLINICAL RELEVANCE

Dogs that developed nKCS within 1 day after application of otitis externa medications containing terbinafine and florfenicol had a good prognosis for return of normal tear production within 1 year.

Corneal Emergencies

Corneal emergencies can be due to a number of different causes and may be vision threatening if left untreated. In an attempt to stabilize the cornea, it is of benefit to place an Elizabethan collar on the patient to prevent further corneal damage. This article discusses the diagnosis, prognosis, and management of corneal emergencies in dogs and cats.

Examination techniques and therapeutic regimens for the ruminant and camelid eye

A step-wise procedure and necessary equipment for examination of the ruminant and camelid eye are detailed. Restraint techniques and usage of local anesthetics to facilitate examination are described. Common examination findings and their significance are discussed. Finally, therapeutic options for keratoconjunctivitis and uveitis are explored. A complete ocular examination of ruminants is often not performed in the field because of lack of time, lack of appropriate facilities, and/or lack of equipment. Although individual ophthalmic examinations are not frequently performed as part of a herd health program, they can be of value in select cases. Ocular manifestations of systemic diseases may assist the clinician in establishing a diagnosis on the farm and for little additional cost. For patients with a specific ocular complaint, a complete ophthalmic examination is critical. After completion of the examination and arrival at a diagnosis, one must also be cognizant of the therapeutic regimens that are appropriate for use in ruminants, particularly animals that may be used for meat or milk.

Mydriasis associated with local dysfunction of parasympathetic nerves in two dogs

In clinical practice, photophobia resulting from persistent mydriasis may be associated with dysfunction of ocular parasympathetic nerves or primary iris lesions. We encountered a 5-year-old Miniature Dachshund and a 7-year-old Shih Tzu with mydriasis, abnormal pupillary light reflexes, and photophobia. Except for sustained mydriasis and photophobia, no abnormalities were detected on general physical examination or ocular examination of either dog. We performed pharmacological examinations using 0.1% and 2% pilocarpine to evaluate and diagnose parasympathetic denervation of the affected pupillary sphincter muscles. On the basis of the results, we diagnosed a pupillary abnormality due to parasympathetic dysfunction and not to overt primary iris lesions. The test revealed that neuroanatomic localization of the lesion was postciliary ganglionic in the first dog.

Asymmetrical focal neurological deficits in dogs and cats with naturally occurring tick paralysis (Ixodes holocyclus): 27 cases (1999-2006)

OBJECTIVE

To describe basic epidemiological features, clinical characteristics and outcomes of asymmetrical focal neurological deficits identified in dogs and cats with naturally occurring tick paralysis (Ixodes holocyclus).

DESIGN

A retrospective study.

PROCEDURE

Computer records were reviewed for all dogs and cats treated for tick paralysis between July 1999 and June 2006 at a suburban veterinary hospital in Newcastle, New South Wales.

RESULTS

Neurological deficits were identified in 17/197 dogs and 10/89 cats and included unilateral facial paralysis (14 dogs; 2 cats), anisocoria (4 dogs; 7 cats), unilateral loss of the cutaneous trunci reflex (1 dog; 1 cat) and Horner's syndrome in 2 cats with anisocoria. Occurrence of deficits was not linked to season, severity of tick paralysis, breed, age, sex or body weight. With facial paralysis and anisocoria, the site of tick attachment was invariably on the head or neck and always ipsilateral to the facial paralysis. By contrast, with anisocoria alone, no consistent relationship was noted between any one pupillary dimension and the side of tick attachment. With cutaneous trunci deficits the site of tick attachment was the ipsilateral caudal axilla. Compared with recovery times from generalised signs of tick paralysis, those for facial paralysis were significantly longer (days to weeks; P < 0.001), those for anisocoria showed no significant difference (P = 0.25) and those for cutaneous trunci deficits lagged by 6 and 7 days.

CONCLUSIONS

Asymmetrical focal neurological deficits are a consistent finding in a proportion of dogs and cats with naturally occurring tick paralysis due to I. holocylcus.

Canine and feline uveitis

The clinical signs of uveitis occur as a result of inflammation within the vascular coat of the eye, which causes breakdown of the blood-aqueous barrier and blood-retinal barrier. Many infectious and noninfectious causes can incite episodes of uveitis. Although a complete diagnostic evaluation is highly recommended to identify any underlying etiologic agent, many cases remain idiopathic in nature. The goals of therapy are preserving vision, minimizing pain, and halting inflammation.