Tear production and intraocular pressure in canine eyes with corneal ulceration

Ophthalmic findings associated with Australian tick paralysis (holocyclotoxicity) in hospitalized domestic dogs and cats

OBJECTIVE

To describe ophthalmic findings in hospitalized canine and feline patients with tick paralysis (TP) and investigate possible predisposing factors.

ANIMALS STUDIED

Forty-seven dogs and 28 cats hospitalized with TP assessed with an ophthalmic examination performed by an ABVO resident.

METHODS

Dogs and cats were hospitalized with TP from October 2021 to January 2022 and had an ophthalmic examination performed by an ABVO resident. Patient signalment data, information regarding tick number and location, hospitalization duration, medications used, and patient paralysis grades were recorded. Statistical analysis was performed to correlate findings.

RESULTS

Corneal ulcers developed in up to 34.8% of dogs and up to 42.9% of cats hospitalized with TP. An absent palpebral reflex ipsilaterally increased the odds of a concurrent corneal ulcer being present by 14.7× in dogs and 20.1× in cats (p < .0001). Palpebral reflexes were absent in 38.3% of dogs and 35.7% of cats hospitalized with TP and were correlated with more severe gait paralysis (p = .01) and respiratory paralysis (p = .005) in dogs, and respiratory paralysis in cats (p = .041). STT-1 findings <10 mm/min were present in 27.7% of dogs and 57.1% of cats examined and were associated with increasing gait paralysis (p = .017) and respiratory paralysis (p = .007) in dogs, and increasing gait paralysis in cats (p = .017).

CONCLUSIONS

Simple corneal ulcers, loss of a complete palpebral reflex, and reduced STT-1 scores frequently occurred in dogs and cats hospitalized for TP. The frequency of these findings increased as the degree of patient paralysis increased.

Diagnostic Tests Used During the Ocular Examination

This article provides a review of the required ocular tests during the ophthalmologic examinations of canine and feline patients. Knowledge of medications affecting ocular parameters and awareness of available instrumentation and test materials is essential for accurate diagnoses.

Comparative study of healing time of canine non-infectious deep ulcerative keratitis between medical therapy alone and combined treatment with medical therapy and a nictitating membrane flap: A retrospective study

Background

Canine non-infectious deep ulcerative keratitis is considered a severe ocular disorder that possibly can progress to perforation. Immediate treatment should be directed to stimulate corneal wound healing, control infection, and minimize self-trauma while eliminating the underlying causes.

Aim

This retrospective study was aimed to compare the difference in non-infectious deep corneal wound healing time between cases treated with medical therapy alone and those treated with medical therapy combined with a nictitating membrane flap.

Methods

The medical records at the Ophthalmology Clinic, Small Animal Teaching Hospital, Faculty of Veterinary Science, Chulalongkorn University between January 2018 and March 2020 were retrospectively reviewed. Sixty-six eyes (from 65 dogs) diagnosed with non-infectious deep ulcerative keratitis from the medical treatment group (n = 34) and the combined treatment group (n = 32) were included. The combined treatment group was prescribed the same conservative medical administrations plus a surgical nictitating membrane flap for 14 days.

Results

Healing time was defined as the duration of time from the day that the dog had been diagnosed with deep ulcerative keratitis by a fluorescein staining test to the day that the corneal fluorescein stain was negative. Overall, the mean age of dogs with deep ulcerative keratitis was 10.49 ± 4.7 years. The disease was commonly evident in females more than males. Shih Tzu was the most prevalent dog breed. The corneal healing time between dogs receiving medical therapy alone and those receiving combined treatment was not statistically significant (p = 0.386). Healing times were not significantly different between sex and breed (p = 0.41). The median corneal healing time for dogs older than 10 years in the combined treatments group (29.5 days; ranging from 20 to 46 days) was longer than for those receiving medical therapy alone (21 days; ranging from 9.5 to 30.5 days).

Conclusion

Supportive therapy including a nictitating membrane flap is suggested in dogs prone to deep corneal ulcers not involving infection. Even though the healing time is not statistically significant, a nictitating membrane flap acts as a tissue bandage to reduce friction over the cornea, and it also alleviates the healing process by moistening the ocular surface.

Effect of Topical Cyclopentolate 1% on Ocular Ultrasonographic Features, Intraocular Pressure, Tear Production, and Pupil Size in Normal Donkeys (Equus Asinus)

This study was performed to investigate the effects of cyclopentolate on ultrasonographic parameters of eye structures, intraocular pressure (IOP), tear production, and pupil size in normal donkeys. Sixteen eyes of eight clinically healthy adult donkeys (2-2.5 years old) weighing 295 ± 34 kg (mean ± standard deviation) were used in this study. Cyclopentolate hydrochloride 1% was instilled in a randomly selected eye and the other eye received normal saline drops as a control. The effect of cyclopentolate was evaluated by ultrasonography. Additionally, changes in IOP and tear production were evaluated for 2 hours post-instillation by tonometry and Schirmer tear test (STT), respectively. Vertical and horizontal pupil diameters were recorded pre-instillation (0), and 15, 30-, 45-, 60-, and 120-minutes post-instillation. After cyclopentolate 1% instillation, iridocorneal angle and width of the entry of ciliary cleft were significantly increased as observed by ultrasonography. IOP was significantly increased starting from 30 minutes till 60 minutes post-instillation of cyclopentolate 1%. Non-significant alteration in the STT was observed in the cyclopentolate-treated eyes compared to the control eyes. Both vertical and horizontal pupil diameters began to significantly increase 30 minutes after cyclopentolate 1% instillation compared to the control saline group. In conclusion, cyclopentolate 1% could be used as a potent cycloplegic drug in donkeys without systemic or ocular side effects.

Breed prevalence of canine ulcerative keratitis according to depth of corneal involvement

OBJECTIVE

To investigate the breed prevalence of canine ulcerative keratitis (UK) according to the depth of corneal involvement.

PROCEDURES

Dogs diagnosed with ulcerative keratitis from 2008 to 2017 at the Triangle Animal Eye Clinic were included in this study. Only breeds with more than 20 eyes affected were selected. UK lesions were classified as superficial (Grade 1), stromal (Grade 2) or descemetoceles and perforations (Grade 3) and compared between brachycephalic (BC) and non-BC dog breeds.

RESULTS

Of 8877 dogs evaluated at Triangle Animal Eye Clinic from 2008 to 2017, 1109 eyes of 1018 dogs (male, 326 eyes; neutered male, 253 eyes; female, 211 eyes; spayed female, 316 eyes; and unknown sex, 3 eyes) aged between 0.1 and 19.2 years (mean ± standard deviation [SD], 8.33 ± 4.24 years) were diagnosed with UK. The number of eyes that was classified as Grade 1 was 359 eyes (187 non-BC and 172 BC), Grade 2 was 373 eyes (60 non-BC and 313 BC) and Grade 3 was 377 eyes (47 non-BC and 330 BC). Significant differences were observed between BC and non-BC dogs for all grades of UK. BC dogs were significantly more frequently affected by Grades 2 and 3 and less frequently by Grade 1 UK (P < .01). French bulldogs are more likely to be affected with Grade 1.

CONCLUSIONS

Brachycephalic dogs are more likely to have deeper corneal involvement in UK. This study provides novel data on the prevalence of superficial UK, which was low in BC dogs and high in non-BC breeds.

Impact of acute conjunctivitis on ocular surface homeostasis in dogs

OBJECTIVE

To investigate the effects of acute conjunctivitis on tear film characteristics and corneal sensitivity in dogs.

ANIMALS STUDIED

Eight female spayed Beagle dogs (1.5-2 years old, 7.5-10 kg).

PROCEDURES

On two consecutive days, one randomly selected eye in each dog received 1 or 375 mg/mL histamine solution to induce mild or severe conjunctivitis, while the contralateral eye served as control. Diagnostic tests were performed in the following order: fluorescein instillation and repeated tear collection over 20 minutes (to determine tear volume [TV] and turnover rate [TTR] by fluorophotometry), Schirmer tear test-1 (STT-1), tear ferning, corneal esthesiometry, and tear film breakup time (TFBUT).

RESULTS

Results are presented as median values for severe conjunctivitis, mild conjunctivitis, and control eyes. Eyes with severe conjunctivitis had significantly higher STT-1 (24, 19.5, 17.5 mm/min; P = .002) and significantly lower TFBUT (10.5, 13.5, 15.5 s; P = .002), but no changes were noted in corneal tactile sensation (2, 2.5, 2.5 cm) or tear ferning (grades 2, 2, 2.5). Severe conjunctivitis significantly increased TV by nearly 10-fold (631, 97, 65 µL) initially (reflex tearing), although basal TV returned rapidly (<5 minutes) in all eyes (46, 58, 48 µL). Finally, there was a nonsignificant trend for higher reflex TTR in the conjunctivitis vs control eyes (68, 58, 43%/min).

CONCLUSIONS

Experimentally induced conjunctivitis increases tear quantity and decreases tear quality in dogs, but has no impact on corneal sensitivity. Changes in tear film dynamics could affect ocular pharmacology (eg, precorneal retention time), although homeostasis of lacrimal volume and drainage is rapidly restored.