Tear clearance rate in dogs: Measurement using anterior segment optical coherence tomography.

OBJECTIVE: The tear clearance rate (TCR), determined using anterior segment optical coherence tomography (AS-OCT) images, and its correlation with ocular surface parameters, including blink rate, Schirmer tear test-1 (STT-1) and tear film breakup time (TFBUT), were evaluated. ANIMALS STUDIED: Left eyes of 20 client-owned dogs with no ocular disease symptoms. PROCEDURES: The tear meniscus height (TMH) was evaluated using AS-OCT images before the instillation of 5 µL saline (TMHbase ), immediately post-instillation (TMH0 ), 30-s post-instillation (TMH0.5 ) and at 1 min intervals for 5 min post-instillation (TMH1 , TMH2 , TMH3 , TMH4 and TMH5 ). The TCR was calculated using the formula [(TMH0  - TMH0.5 )/TMH0 ]×100 (%). The eyes were classified into two groups with the median: 'High TMHbase ' (n = 10) and 'Low TMHbase ' (n = 10). Eyes with STT-1 values ≥15 mm/min and TFBUT ≥ 12 s were assigned to the 'Satisfied' subgroup, whereas eyes not satisfying these criteria were assigned to the 'Not satisfied' subgroup. RESULTS: TMH0 was higher than TMH0.5 (p = 0.02), wherein TMH0.5 to TMH5 did not differ significantly. The TCR and blink rate were negatively correlated (p = 0.02). The 'Not satisfied' subgroup in the low TMHbase group had a lower TCR (p = 0.02) and higher blink rate (p = 0.04) than the 'Satisfied' subgroup. CONCLUSIONS: TCR can be evaluated using AS-OCT in dogs. Eyes with a lower TCR blink more frequently. TMH merits studying to understand ocular surface health.

Clinical parameters obtained during tear film examination in domestic rabbits.

BACKGROUND: One of the contributing factors to ocular surface health is a stable precorneal tear film. Considering the increasing interest in rabbits as pets and the limited literature available on domestic rabbit tearing, the aim of this study was to establish normative data for examination of the tear film in domestic rabbits. RESULTS: The study included 75 client-owned domestic Holland Lop rabbits (150 eyes). The following examinations were performed in each eye: Schirmer tear test-1, tear osmometry, interferometry, tear meniscus height measurement and meibography (quantifying meibomian gland loss as a percentage). The resulting median (95% central range) values were 10.0 (5.0-17.3) mm/min for the Schirmer tear test-1, 345.0 (280.5-376.1) mOsm/L for tear osmolarity, grade 2 (1-4) of interferometry, 0.28 (0.20-0.47) mm for tear meniscus height and 0.0 (0.0-67.6) % meibomian gland loss. A significant association was found between tear osmolarity and age, with an estimated decrease of - 4.0 mOsm/L with each additional year of age (p < 0.001). The distributions of interferometry grades were significantly different between males and females (p < 0.001), with grade 1 and grade 2 being the most frequent in females and males, respectively. A weak negative correlation was also observed between interferometry grade and the percentage of meibomian gland loss (r = - 0.22, p = 0.006). CONCLUSIONS: This is an original study that documents extensive tear film parameters in healthy Holland Lop rabbits. The results can be used as normative data for the examination of the tear film in this lagomorph breed.

Schirmer Tear Test Value and Corneal Lesions' Incidence during General Anesthesia for Non-Ophthalmic Surgery in Non-Brachycephalic Dogs: A Pilot Study Comparing Three Different Lubricant Eye Drop Formulations.

Aim of this blinded, prospective, randomized clinical study was to compare three different lubricant eye drops (LED) in healthy adult dogs undergoing general anaesthesia (GA) for non-ophthalmic surgery. Tear production rate was monitored by means of Schirmer tear test-1 (STT-1), and incidence of post-operative corneal abrasions/ulcerations was detected by corneal staining. A complete ophthalmic examination was performed before premedication, at extubation time and 24 h after GA in twenty-five non-brachycephalic dogs (fifty eyes) undergoing elective orthopaedic or spinal surgery procedures. Dogs were randomly allocated to one of three groups receiving as prophylactic LED either carmellose sodium (GC), or 1% hyaluronic acid (GH), or 0.25% hyaluronic acid (GL). In each eye STT-1 was repeated every hour during GA, before instilling one drop of the assigned LED. In all groups STT-1 values drastically decreased during GA, while 24 h later nine eyes (18%) had STT-1 values lower than 15 mm/minute. All of the three formulations tested were fully effective in preventing corneal ulceration (0% in all groups), while 10% of eyes reported superficial de-epithelialization. Fluorescein staining demonstrated that hourly prophylactic LED application prevented exposure keratopathy during general anesthesia in 90% of the eyes in non-brachycephalic dogs.

A prospective study of the prevalence of corneal surface disease in dogs receiving prophylactic topical lubrication under general anesthesia.

OBJECTIVE: To identify the prevalence of corneal ulceration in dogs receiving prophylactic gel lubrication under general anesthesia (GA). MATERIALS AND METHODS: An ophthalmic examination was performed before premedication and 24 h after GA in 100 dogs (199 eyes) undergoing nonophthalmic procedures. Individuals with known pre-existing ocular surface conditions were excluded. An ocular lubricating gel containing carmellose sodium was applied by the anesthetist at induction and every 2-4 h until extubation. Logistic regression analysis was used to calculate risk factors for ulcerative disease, including signalment, length of GA, patient position, procedure performed, pre-, and post-GA ophthalmic examination findings and admitting service. A Wilcoxon rank sum test compared pre- and post-GA Schirmer tear test-1 (STT-1) values. RESULTS: One dog (0.5% of total eyes) developed fluorescein stain uptake consistent with superficial corneal ulceration that resolved within 48 h with supportive treatment. Twenty-five (18.6% of total eyes) developed a faint, patchy corneal uptake of stain in the axial cornea that was consistent with epithelial erosion. All erosions resolved with lubrication 24 h later. The decrease in STT-1 readings at 24 h post-GA was statistically significant from those pre-GA (P < 0.001). No significant risk factors for corneal erosion/ulceration were identified. CONCLUSIONS: The results of this study show that a basic protocol of prophylactic lubrication during GA was associated with a low prevalence of corneal ulceration but a higher prevalence of epithelial erosion. In addition, the study supports the need for post-GA corneal examination.

Intraocular pressure and tear secretion in Saanen goats with different ages / Pressão intraocular e produção lacrimal em cabras da raça Saanen com diferentes idades

This study aimed to compare the normal intraocular pressure (IOP) and tear secretion, by means of applanation tonometry and the Schirmer tear test-1 (STT-1), in goats of the Saanen breed with different ages, and at different time points. Thirty six goats, free of ocular abnormalities, were grouped into three different age categories (n=12), animals with 45, 180 and 549 days of age. STT-1 and IOP measurements were carried out always at 9:00am and 7:00pm, during three consecutive days. Results were evaluated statistically (P<0.05). Regarding the time of the day, overall IOP values were significantly lower at 7:00 pm (P<0.001) in individuals with 45 days of age; whereas STT-1 values were significantly higher at 7:00pm (P=0.004) in goats with 549 days of age. Considering the sum of three days, both parameters were significantly lower in individuals with 45 days of age (P<0.001). Intraocular pressure and tear secretion values increase until 180 days of age in the Saanen breed of goats.

Objetivou-se comparar os valores normais de pressão intraocular (PIO) e de produção lacrimal, através de tonometria de aplanação e do teste da lágrima de Schirmer-1 (TLS-1) em cabras da raça Saanen, com diferentes idades e momentos. Trinta e seis cabras da raça Saanen, livres de afecções oculares, foram agrupadas em três categorias etárias (n=12), compreendendo animais com 45, 180 e 549 dias de idade. O TLS-1 e a PIO foram aferidos sempre às 9:00 e às 19:00, durante três dias consecutivos. Os resultados foram avaliados estatisticamente (p<0,05). Relativamente ao horário do dia, a PIO foi significativamente menor às 19:00 (p<0,001) nos animais com 45 dias de idade; os valores do TLS-1 foram significativamente maiores às 19:00 (p=0,004) nas cabras com 549 dias de idade. Considerando-se a somatória dos três dias, ambos os parâmetros foram significativamente menores nos indivíduos com 45 dias de idade (p<0,001). A pressão intraocular e a produção lacrimal em cabras da raça Saanen se elevam de forma significativa até os 180 dias de idade.