Use of phenol red thread tests to evaluate tear production in clinically normal Amazon parrots and comparison with Schirmer tear test findings

Development and validation of a method to generate phenol red thread tests

PURPOSE

The aim of this study was to develop and validate a method to generate phenol red thread tests (PRTT) due to the lack of availability of commercial PRTT.

METHODS

White cotton thread was dyed with phenol red (pH indicator) for 48 h, dried, cut, and sterilized. To validate its wicking ability, the thread was inserted into solutions of varying pH, flanking the pH of healthy tears, for different time intervals. To assess its diagnostic utility, PRTTs were performed in vivo on wildtype and a murine model of evaporative dry eye, acyl-coA: wax alcohol acyltransferase 2 knockout (Awat2 KO) mice.

RESULTS

Two batches of PRTT were produced that had a similar appearance and function to the commercial product. In vitro testing revealed no significant differences in the wicking kinetics at any time point across the pH solutions for batch 1 and only one difference for batch 2 (pH 7.4 vs 7.8 at 5 s, P = 0.029). When comparing both batches, similar wicking kinetics were found with only two significant differences identified (pH 7.6 at 40 s and pH 7.8 at 35 s, P < 0.01). In vivo, our PRTT yielded similar measurements to the commercial PRTT in wildtype and Awat2 KO mice and detected a significant increase in aqueous tear volume in the Awat2 KO mice (commercial: P = 0.015, our PRTT: P = 0.002).

CONCLUSION

Our method provides a reproducible diagnostic test that performs similarly to its commercial counterpart in a relevant dry eye model indicating that it can serve as a valid and reliable replacement.

Ocular diagnostics, ophthalmic findings, and conjunctival microbiome in the Chilean flamingo (Phoenicopterus chilensis)

OBJECTIVE

To establish normative data for selected ocular diagnostic tests and commensal conjunctival microflora and describe the incidence of ocular pathology in Chilean flamingos.

ANIMALS STUDIED

A total of 41 Chilean flamingos were examined at the Blank Park Zoo in Des Moines, Iowa.

PROCEDURES

In 20 flamingos, blink rate was assessed undisturbed in their exhibit, then gentle manual restraint was used to assess palpebral fissure length (PFL), aqueous tear production (phenol red thread test [PRTT] in one eye, endodontic absorbent paper point tear test [EAPPTT] in the other), intraocular pressure (IOP; rebound tonometry), and fluorescein staining. Twenty-one other flamingos were brought to a darkened area for neuro-ophthalmic examination, slit lamp biomicroscopy, and indirect ophthalmoscopy. Swabs from seven flamingos were used for ocular microbiome evaluation.

RESULTS

Results are presented as mean ± standard deviation (range). Flamingos comprised 23 females/18 males, aged 11 ± 9.1 (0.7-40) years. Test results: blink rate, 3.7 ± 2 (1-9) blinks/min; PFL, 11.2 ± 1.2 (9-14) mm; IOP, 14 ± 3.2 (10-22) mmHg; EAPPT, 10.2 ± 2.8 (9-14) mm/min; PRTT, 6.8 ± 2.5 (3-13) mm/15 s. Dazzle reflex was positive in four birds examined. Pathologies included cataracts (n = 7 birds), corneal fibrosis (n = 3), endothelial pigment (n = 2), uveal cysts (n = 1), lens luxation (n = 1), and uveitis (n = 1). Ocular microbiome showed high diversity of taxa.

CONCLUSIONS

Baseline ocular parameters and incidence of ophthalmic pathology assist veterinarians with disease screening for Chilean flamingos, while the ocular microbiome showed high diversity.

Characterization of ophthalmic lesions and normal ocular parameters in a flock of captive MacQueen's (houbara) bustards (Chlamydotis macqueenii)

OBJECTIVES

To determine normal ocular parameters of the MacQueen's bustard (Chlamydotis macqueenii) and describe ophthalmic lesions in a captive bred population.

ANIMALS STUDIED

Captive breeding population of 257 Macqueen's bustards.

METHODS

All birds were screened for ocular abnormalities using direct ophthalmoscopy. Abnormalities were photographed. Normative values for Schirmer tear test-1 (STT-1), applanation tonometry, aerobic and anaerobic bacterial culture, fungal culture, and transcorneal ocular ultrasonography were derived from multiple cohorts of clinically normal adult birds. Five birds with ocular pathology also underwent transcorneal ultrasonography. Statistical comparisons for normative values between OD and OS, and males and females were made using a paired t-test or Mann-Whitney U-test, with a significance level of p < .05.

RESULTS

Mean tear production based on Schirmer tear test 1 (STT-1) was 10.16 ± 4.61 mm/min (3-21 mm/min). Mean intraocular pressure (IOP) was 12.42 ± 4.94 mm Hg (5-26 mm Hg). Staphylococcus species were the most isolated bacteria from the conjunctival surfaces of normal birds (85%). Significant differences were found in transcorneal ultrasonographic measurements between males and females for axial globe length (p = .032), vitreous body depth (p = .049) and lens thickness (p = .0428). Corneal fibrosis was the most observed ocular abnormality amongst eyes with pathological changes (39%).

CONCLUSIONS

Schirmer tear testing, tonometry and transcorneal ultrasound can easily be utilized in MacQueen's bustards and provide reproducible results. Normal parameters for these tests were determined, and common pathological ocular changes were described in this species.

Determination of reference values for tear production and intraocular pressure in Pygoscelis penguins of the Antarctic Peninsula

BACKGROUND

According to the literature review, this is the first study investigating tear production (TP) and intraocular pressure (IOP) in the Pygoscelis penguins living in their natural habitat. The study aimed to establish normal values for standard ocular tests in the genus Pygoscelis, namely, the Adélie (Pygoscelis adeliae), gentoo (Pygoscelis papua), and chinstrap (Pygoscelis antarctica) penguins, in four different islands of Antarctica. Sampling was made by specifically using the left eye of the penguins. The Schirmer's tear test type I (STT-I) and the Tonovet® (rebound tonometer) were used to measure the TP and the IOP, respectively.

RESULTS

The mean TP and IOP values of 129 Adélie, chinstrap, gentoo, and 120 adult Adélie, gentoo penguins were determined as 10.2 ± 4.0 mm/min and 38.9 ± 13.2 mmHg, respectively. No statistical difference was detected between the penguin species for the mean IOP values, while the difference was determined in all the locations. However, statistical differences in the mean TP values were determined between all locations.

CONCLUSION

The results of this study provide a reference range of Schirmer's tear test (STT) and IOP values in Pygoscelis penguins and show that the IOP is significantly affected by locations. This result can be attributed to the harsh climatic conditions of the Antarctic Peninsula that change very quickly. The described data may help diagnose clinical pathological findings in Pygoscelis penguins. The STT and rebound tonometry appears to be safe and reproducible methods in Pygoscelis penguins, as the results were obtained quickly and were well tolerated by the birds. Based on our results, we propose that similar studies can be initiated in crowded colonies of three penguin species of this genus on the Antarctic Peninsula, the southern Shetland Islands, and other frequently visited islands in Antarctica.

Clinical ophthalmic parameters of the Quaker parrot (Myiopsitta monachus)

PURPOSE

Ophthalmic diagnosis in many avian species remains hindered by a lack of normative values. This study aimed to establish normal ophthalmic parameters for select diagnostic tests in clinically normal Quaker parrots.

METHODS

Ninety-six captive Quaker parrots aged 8-18 years underwent ophthalmic examination to include assessment of neuro-ophthalmic reflexes, phenol red thread test, rebound tonometry, fluorescein staining, palpebral fissure length measurements, slit lamp biomicroscopy, indirect ophthalmoscopy, and ocular ultrasound biometry.

RESULTS

Menace response, dazzle reflex, and direct pupillary light reflex were present for all Quaker parrots. Tear production (mean ± SD) was 13.3 ± 4.0 mm/15 s and intraocular pressure (IOP, mean ± SD) was 10.6 ± 1.4 and 6.0 ± 1.3 mmHg in the D and P rebound tonometer calibration settings, respectively. For IOP measurement, D and P calibration settings were not interchangeable, with the lesser variation of the D setting preferred in the absence of a gold standard. Ultrasound measurement of the anterior chamber depth increased with age and males had longer axial globe and vitreous lengths. Incidental adnexal and ocular lesions, identified in 36/96 (37.5%) of Quaker parrots, did not statistically affect the created reference data.

CONCLUSIONS

This work provides reference values and clinical findings to assist with monitoring the health of wild populations and maintaining the health of captive Quaker parrots.

Tear Production, Intraocular Pressure, Ultrasound Biometric Features and Conjunctival Flora Identification in Clinically Normal Eyes of Two Italian Breeds of Chicken (Gallus gallus domesticus)

Simple Summary

In Italy, chickens are used for egg production and as courtyard/domestic animals and consequently veterinarians need to know their general and specialist characteristics. One key area is normal ocular measurements in order to understand any pathological changes affecting the eyes. For an accurate diagnosis and better management of ophthalmic diseases in chickens, this paper describes the normal values for the evaluation of ocular tear production, intraocular pressure, and biometric measurements of the eyes and on the microbial and cultural flora normally present in the conjunctival sac in two Italian chicken breeds.

Abstract

Given the abundance of chickens in Italy, it is important for veterinarians to know the normal state of chickens’ eyes in order to identify any ophthalmic pathological changes. The aim of this study was to determine the normal values of select ocular parameters and to evaluate conjunctival microflora in two Italian chicken breeds. Sixty-six healthy chickens underwent a complete ophthalmic examination, which included a phenol red thread test (PRTT) for the evaluation of tear production and the assessment of intraocular pressure by rebound tonometry. B-mode ultrasound biometric measurements and conjunctival microflora identification were also performed in twenty-seven chickens. Mean PRTT was 23.77 ± 2.99 mm/15 s in the Livorno breed and 19.95 ± 2.81 mm/15 s in the Siciliana breed. Mean intraocular pressure was 14.3 ± 1.17 mmHg in the Livorno breed and 14.06 ± 1.15 mmHg in the Siciliana breed. Reference ranges for morphometric parameters were reported in the two breeds. Twenty-three chickens (85.18%) were bacteriologically positive. Chlamydia spp. antigen was detected in 14.81% of chickens. No positive cultures were obtained for fungi. Normal reference range values for selected ophthalmic parameters were obtained in clinically healthy chickens, which could facilitate accurate diagnosis and better management of ophthalmic diseases in these animals.

Ocular Examinations and Investigation of Intraocular Pressure, Tear Production, Central Corneal Thickness, and Corneal Touch Threshold in a Captive Flock of Atlantic Puffins (Fratercula arctica)

Ocular examinations were completed on a group of 10 Atlantic puffins (Fratercula arctica), 5 males and 5 females that ranged in age from 8 months to older than 30 years. The exams consisted of intraocular pressure/rebound tonometry, tear production/phenol red thread test, central corneal thickness/ultrasound pachymetry, and corneal sensitivity/esthesiometry. On ocular examination, there were no corneal abnormalities observed. Bilateral cataracts were diagnosed in 8 puffins, 6 of which were considered incipient, focal subcapsular opacities. One bird had hypermature cataracts and was removed from the study and excluded from data analysis; the other birds had no evidence of ophthalmic pathology that would interfere with diagnostic results (n = 9). All results for 9 birds were included in the study, with the exception of 1 puffin's tear production, which was too low for accurate assessment and was excluded from data analysis. There were no significant differences between right and left eye measurements for intraocular pressure, corneal thickness, and corneal sensitivity. The median intraocular pressure for both eyes (OU) was 13 mm Hg with an interquartile range [IQR] of 12-15 mm Hg. The median corneal thickness OU was 241 µm, IQR 233-248 µm. The median corneal sensitivity OU was 1.13 cm, IQR 0.81-1.50 cm. There was a significant difference between right and left eye measurements for tear production (right eye median, 7.5 mm/15 s, IQR 6.5-9.3 mm/15 s; and left eye median, 5.0 mm/15 s, IQR 4.0-7.3 mm/15 s) (P= .03), with the right eye producing more tears than the left. However, 1 puffin was determined to be an outlier, and when removed, there was no longer a significant difference (OU median, 7.0 mm/15 s, IQR 4.6-8.0 mm/15 s) (P = .38). There was no significant difference between sex and intraocular pressure, tear production, and corneal sensitivity. However, there was a significant difference between sex and corneal thickness (P = .02), with males (left eye median, 249 µm, IQR 241-249 µm) having thicker corneas than females (left eye median, 236 µm, 234-238 µm). Although sample size precluded statistical testing, there appeared to be an association between opacities and increasing age. There were no associations between age and intraocular pressure, tear production, or corneal thickness. There was a moderate correlation between age and corneal sensitivity, with older birds showing decreased corneal sensitivity (r = -0.57). Although the sample size of 9 birds was small, these findings provide preliminary ranges for ocular parameters of Atlantic puffins.

Tear fluid collection methods: Review of current techniques

Tear fluid, composed of lipid, aqueous, and mucin layers, contains electrolytes, water, proteins, peptides, and glycoproteins. Its components may serve as diagnostic indicators of local and systemic diseases. The aim of the study was to conduct literature review in order to identify the current methods of tear collection. The most commonly used method which was relatively easy to perform and allowed to obtain sufficient tear volume for further chemical and physical analysis was selected through PubMed database search for the following keywords: tear sampling, human tears, chemical analysis of tears, physical tear analysis, animal tear sampling. Final criteria of articles selection were: human tears, tear sample collection, chemical and physical analysis of tears. Time of publication of the articles not older than 1995. The analysis of 70 articles revealed that the most common tear fluid collection methods are Schirmer tear strips and capillary tubes. Thus, we recommend the use of Schirmer strips and microcapillary tubes as the cheapest and easiest methods for sampling of tear fluid for further chemical analysis.

Normative ocular data for juvenile and adult Japanese quail (Coturnix japonica)

OBJECTIVE

To obtain normative ocular data for Japanese quail as they mature from juveniles to adults.

ANIMALS STUDIED

Twenty-six captive Japanese quail comprising thirteen males and thirteen females, free of ocular disease, were included in the study.

PROCEDURES

Ophthalmic reference values were measured in both eyes at 1 and 5 months of age. A complete ophthalmic examination was performed, including neuro-ophthalmic reflexes, slit lamp biomicroscopy, phenol red thread test (PRTT), rebound tonometry, fluorescein staining, horizontal corneal diameter measurement, indirect ophthalmoscopy, and ocular ultrasound biometry. Ultrasound biomicroscopy measurements of axial globe length, lens thickness, vitreal chamber length, and pecten length were recorded. The depth of the anterior chamber was calculated by subtracting the lens thickness and vitreous length from the axial globe length. Measures of association and descriptive statistics were analyzed using STATA-14 and STATA-15.

RESULTS

Juvenile and adult females were heavier than age-matched males. Weight, intraocular pressure, horizontal corneal diameter, axial globe length, and lens thickness measurements increased with age. No statistically significant differences were found in the remainder of measurements among individuals in different sex or age-groups.

CONCLUSIONS

This work provides reference values and clinical findings that can be used in future research on quail and ocular disease.

Ophthalmic findings in cinereous vultures (Aegypius monachus)

OBJECTIVE

The aim of the present study was to provide ophthalmic reference values under normal physiological conditions for Aegypius monachus (cinereous vulture).

PROCEDURES

Thirty-two eyes of sixteen adult captive cinereous vultures were used for this study. Tear tests and tonometry in conscious and anesthetized states, neuro-ophthalmic tests, measurement of corneal diameter, slit-lamp biomicroscopy, ophthalmoscopy, and funduscopy were performed.

RESULTS

Schirmer tear test (STT) value was 11.4 ± 2.6 and 11.5 ± 2.8 mm/min in the right (OD) and left eye (OS), respectively. Phenol red thread test (PRT) values were 22.3 ± 2.1 mm/15 s OD and 22.8 ± 3.0 mm/15 s OS. The results showed a strong correlation between STT and PRT in both eyes. Intraocular pressure (IOP) values were 32.8 ± 6.9 mm Hg OD and 31.9 ± 7.1 mm Hg OS with TonoVet and 20.7 ± 4.5 mm Hg OD and 19.5 ± 4.1 mm Hg OS with Tono-Pen. There were significant differences in IOPs between rebound and applanation tonometry in both OD and OS. Tear production and IOP values showed significant reductions with general anesthesia in both tear tests and both tonometry (P < .001). Horizontal corneal diameter (mm) was 15.56 ± 0.96 OD and 15.56 ± 0.96 OS. Vertical diameter (mm) was 14.13 ± 0.96 OD and 14.06 ± 1.06 OS. The horizontal diameter was significantly longer than vertical diameter (P < .001).

CONCLUSIONS

Ocular morphologic information and normal reference range values for various ophthalmic measurements were obtained in clinically healthy cinereous vultures, which can facilitate accurate diagnosis and better management of ophthalmic diseases in cinereous vultures.

Trauma-Induced Uveitis and Free Air in the Anterior Chamber of Three Eastern Screech Owls (Megascops asio)

Unusual ocular abnormalities were documented in 3 wild eastern screech owls (Megascops asio) presented to a wildlife rehabilitation hospital after vehicular strike-induced trauma to the head. All 3 had anterior uveitis and free air bubbles in the anterior chamber, but none of the cases had any discernable corneal damage, either grossly or with fluorescein stain technique. Perforation of the globe at the level of the scleral ossicle was considered a possible cause. All 3 cases recovered with standard treatment for anterior uveitis, and the free air was absorbed within 10-14 days and did not appear to cause any lingering complications. The owls were later released back into the wild after demonstrating the ability to navigate obstacles in a flight cage and capture live prey.

A novel strip meniscometry method for measuring aqueous tear volume in dogs: Clinical correlations with the Schirmer tear and phenol red thread tests

OBJECTIVES

The strip meniscometry test (SMT) is a novel method for quantitative measurement of tear volume with only five seconds. We aimed to evaluate clinical correlations of SMT with the gold standard Schirmer tear test (STT) and phenol red thread test (PRT) in dogs, including normal and tear-deficient eyes.

ANIMALS STUDIED

Left eyes from 621 outpatient dogs with and without ocular disorders were evaluated.

PROCEDURES

Each subject underwent SMT, PRT, and STT without topical anesthesia in the described order with five-minute intervals. The total population was divided into four groups by classifying tear deficiency severity based on STT results: "severe" (0-5 mm/min), "moderate" (6-10 mm/min), "subclinical" (11-14 mm/min), and "normal" (15 or more mm/min).

RESULTS

The strongest correlation coefficient was found between SMT-STT (0.676), followed by PRT-STT (0.637) and SMT-PRT (0.600) pairs. Mean(SD) scores of SMT, PRT, and STT in total population were 9.47 (4.08) mm/5 s, 33.30 (8.52) mm/15 s, and 16.47 (7.01) mm/min. Significant differences were found among STT-classified groups, both using SMT and PRT results. Receiver operating characteristic (ROC) curves revealed that SMT better agreed with STT than PRT; agreement increased with increasing STT severity. A cutoff for SMT was identified at 10 mm/5 s to discriminate normal eyes from tear-deficient eyes, yielding high sensitivities and acceptable specificities.

CONCLUSIONS

SMT could be superior to PRT for discriminating tear-deficient eyes. The high sensitivity of SMT could be useful as an initial diagnostic tool to rule out normal eyes with the short testing time.

Schirmer's I, modified Schirmer's I, phenol red thread, and paper point tests: a comparative study for tear production measurement techniques in broiler chicks (Gallus gallus domesticus)

Problems with indoor husbandry and immunological challenges are some of the stressors that broilers may face which can affect production. Infectious diseases can compound the effects of excessive concentrations of ammonia causing respiratory and ocular inflammation and increased lacrimal production in broiler chickens. The objectives of this investigation were to establish normal values of tear production in chicks and compare the practicality of the different methods. Palpebral fissure length (PFL) and tear production were evaluated in Cobb 500 chicks at 5 d old and then at 5 d of age by the following methods: modified Schirmer's test I (mSTT1), phenol red cotton thread tear test (PRCTTT), and standardized endodontic absorbent paper point test (EAPPTT). Ten chicks at the age of 5 and 42 d were evaluated for each method. In addition, at 42 d, when the palpebral fissure permitted, a regular-sized Schirmer tear test I (STT1) was performed in another group of 10 chickens. Overall, PFL and the secretion of the aqueous phase of the tear film increased with age. Mean mSTT1 results were 5.00 ± 1.83 mm and 10.45 ± 2.58 mm for 5- and 42-d-old chicks, respectively. Mean PRCTTT results were 12.37 ± 1.80 mm and 25.58 ± 4.8 mm for 5- and 42-d-old chicks, respectively. Mean EAPPTT results were 7.13 ± 0.72 mm and 12.03 ± 0.92 mm for 5- and 42-d-old chicks, respectively. Mean STT1 for 42-d-old chicks was 11.40 ± 2.60 mm. Results obtained with endodontic paper points showed the lowest coefficient of variation and investigators found the test easier to perform. These values reported for broilers at different ages may be applied in poultry ophthalmology to help the diagnosis of lacrimal production disorders and to detect early disease symptoms that could cause economic losses in poultry production.

Tear production and intraocular pressure values in clinically normal eyes of whooper swans (Cygnus cygnus)

The objective of this study was to determine the normal range of tear production and values of intraocular pressure (IOP) in clinically normal eyes of whooper swans (Cygnus cygnus). A total of 86 birds: 81 cygnets (6-10 weeks old) and 5 moulting - adult swans (3-6 years old) were examined in this study. Both eyes of all birds underwent a complete ophthalmic examination, including evaluation of tear production with the phenol red thread test (PRTT) and the assessment of the IOP by rebound tonometry, employing the TonoVet^® device. The mean ± standard deviation of PRTT values were as follows: all cygnets (81) 22.59±3.48 mm/15s, male cygnets (45) 22.64±3.54 mm/15s, female cygnets (36) 22.53±3.44 mm/15s. IOP was as follows: all cygnets 11.30±3.55 mmHg, male cygnets 10.93±3.56 mmHg, female cygnets 11.74±3.50 mmHg. No statistically significant differences between right and left eye and between female and male cygnets were found for IOP and PRTT values. This study provides the reference values for the PRTT and IOP in healthy whooper swan cygnets, showing that PRTT determination of the tear production and rebound tonometry to evaluate the IOP methods are practical methods for ophthalmic examination in swans.

OCULAR FINDINGS AND SELECT OPHTHALMIC DIAGNOSTIC TESTS IN CAPTIVE AMERICAN WHITE PELICANS (PELECANUS ERYTHRORHYNCHOS)

The aim of this study was to establish normal ophthalmic parameters for select diagnostic tests in American white pelicans (Pelecanuserythrorhynchos). Twenty-one zoo-housed American white pelicans were manually restrained for noninvasive ocular diagnostic testing and complete ophthalmic examination. Tear production quantification using the phenol red thread test (PRTT), fluorescein staining, and intraocular pressure (IOP) evaluation were performed. In addition, conjunctival aerobic bacterial culture and culture-independent 16S rRNA amplicon sequencing were performed on select eyes. Normal variations and ocular abnormalities detected during complete ophthalmic examination were documented and photographed. Direct pupillary light reflex, menace response, and palpebral reflex were present in all birds. The value (mean ± SD) for PRRT and IOP was 14.9 ± 7.84 mm/15 sec and 9.0 ± 1.41 mm Hg oculus uterque, respectively. Conjunctival culture in nine birds revealed no growth for six birds and Staphylococcus aureus growth in three birds. A high relative abundance of Mycoplasma sp. was detected in all samples based on 16S rRNA sequencing. The normal pelican eye was found to have relative conjunctival hyperemia, absent filoplumes, iris color ranging from light blue to brown, and a subcircular vertically elongated pupil. Ophthalmic abnormalities were noted in 10 of 21 birds. Common findings included corneal fibrosis, cataracts, and asteroid hyalosis. The most common ophthalmic abnormality in this species was cataracts.

Modified Schirmer tear test and rebound tonometry in blue-fronted Amazon parrot (Amazona aestiva)

ABSTRACT: The aim of this study was to describe the modified Schirmer tear test (mSTT), intraocular pressure (IOP) by rebound tonometry and palpebral fissure length (PFL) in blue-fronted Amazon parrots (Amazona aestiva). Thirty-five healthy adult animals from a conservation breeding center in Brazil were used in this study. Modified Schirmer tear test, rebound tonometry and PFL measurements were performed in both eyes, with birds under physical restraint. Mean mSTT was 6.2±0.1mm/min and mean IOP was 6.4±0.1mmHg, while PFL was 10.1±0.1mm. A moderate correlation was seen between mSTT and PFL for OD (ρ=0.14) and OS (ρ=0.20). The results provide ophthalmic tests reference values for A. aestiva.

Measurement of tear production and intraocular pressure in ducks and geese

OBJECTIVES

The purpose of this study was to establish a reference value of tear production and intraocular pressure in clinically normal ducks and geese.

ANIMAL STUDIED

The study population consisted of forty-eight ducks (24 males and 24 females) and fifty-two geese (26 males and 26 females).

PROCEDURES

Birds were gently physically restrained in dorsoventral position without any pressure to the head and neck. Tear secretion and intraocular pressure were measured using 5-mm-wide Schirmer tear test strips and TonoVet^® rebound tonometer, respectively.

RESULTS

Overall mean ± 2SD STT and IOP values of all eyes were 6.2 ± 2.2 mm/min and 10.2 ± 2.2 mmHg, respectively, for the ducks; 5.5 ± 2.6 mm/min and 9.1 ± 2.0 mmHg, respectively, for the geese. There was no statistically significant difference in IOP between left eye and right eye or between males and females in ducks (P = 0.56, P = 0.63) and geese (P = 0.23, P = 0.22). Analysis of variance revealed that there were no significant differences in the STT and IOP between the breeds in ducks (P = 0.49, P = 0.68) and geese (P = 0.14, P = 0.26).

CONCLUSIONS

Results of this study may be beneficial for the diagnosis and therapeutic monitoring of ducks and geese affected with Keratoconjunctivitis sicca, glaucoma, and uveitis.

Ophthalmic Diagnostic Tests and Ocular Findings in a Flock of Captive American Flamingos ( Phoenicopterus ruber ruber)

Seventeen adult captive American flamingos ( Phoenicopterus ruber ruber) (34 eyes) underwent a complete ocular examination, including assessment of menace response, pupillary light reflexes, dazzle reflex, palpebral and corneal reflexes, fluorescein staining, slit-lamp biomicroscopy, and direct ophthalmoscopy. Birds were randomly assigned to one of 2 groups for tear production and intraocular pressure measurements. Tear production was measured by modified Schirmer tear test I (n = 9 birds) or phenol red thread test (n = 8 birds), and intraocular pressure was measured indirectly by applanation (Tonopen-XL) (n = 9 birds) or rebound (TonoVet) (n = 8 birds) tonometry. Conjunctival swab samples were taken from one randomly selected eye of all 17 birds to identify surface ocular microbial flora via aerobic bacterial culture. Additionally, 3 of the 17 birds were anesthetized for bilateral B-mode ocular ultrasonography examination to obtain axial globe measurements. Results showed that the menace response and dazzle reflex were absent in all birds. Sixteen of the 17 birds were free of significant ocular disease; a small cataract and pigment on the anterior lens capsule were noted in one eye of one bird. Mean ± SD tear production was 12.3 ± 4.5 mm/min (range, 4-20 mm/min) for modified Schirmer tear test I and 24.2 ± 4.4 mm/15 s (range, 14-30 mm/15 s) for phenol red thread test. Modified Schirmer tear test I measurements were significantly lower than phenol red thread measurements (P < .001). Mean intraocular pressure was 16.1 ± 4.2 mm Hg (range, 7-22 mm Hg) for Tonopen and 9.5 ± 1.7 mm Hg (range, 7-13 mm Hg) for TonoVet. Tonopen measurements were significantly higher than TonoVet measurements (P < .001). An Enterococcus species (9/17 eyes; 53%) and a gram-positive coccus (7/17 eyes; 41%) were the bacteria most commonly isolated from conjunctival swab samples. Mean B-mode ultrasonographic globe measurements of 6 eyes (3 birds) were axial globe length, 13.8 ± 0.16 mm; anterior chamber depth, 1.75 ± 0.05 mm; lens thickness, 4.6 ± 0.06 mm; vitreous body depth, 6.95 ± 0.10 mm; and pecten dimensions, 5.1 ± 0.38 mm length, 2.2 ± 0.14 mm width. In summary, the prevalence of ocular lesions was low in this population of captive American flamingos. Results obtained from 2 types of tear and intraocular pressure measurement tests were significantly different, indicating that a single type of each diagnostic test should be consistently used. A modification of the standard Schirmer tear test or use of phenol red thread test is recommended due to the small flamingo eye.

Measurement of Tear Production Using the Phenol Red Thread Test in the Common Mynah ( Acridotheres tristis )

To evaluate tear production in the common mynah ( Acridotheres tristis ) using the phenol red thread test (PRTT) and to make a comparison of measurements with the PRTT placed in the fornices of lower and upper eyelids, tear production of both eyes in 22 healthy adult captive mynah birds was evaluated. After positioning of threads in the fornices of upper and lower eyelids, the PRTT values of the birds were 17.5 ± 3.1 mm/15 s and 19.2 ± 2.5 mm/15 s, respectively. A significant difference was found between PRTT values for upper eyelids and lower eyelids (P = 0.01). This study provides novel data for normal reference ranges of PRTT values in healthy common mynah birds and shows that a difference is found depending on where the PRTT thread is placed.

Measurement of tear secretion in healthy pigeons by using the phenol red thread test

The objectives of this study were to determine the applicability of the phenol red thread (PRT) test as a new method for the evaluation of tear secretion in healthy male and female pigeons, to establish normal physiologic reference values in these animals, and to compare seasonal variations in these values. Seventy-five pigeons of both sexes, with no ocular abnormalities, were included in the study. The phenol red impregnated thread was inserted into the recessus conjunctiva inferior for measuring tear secretion. After 15 seconds, the thread was removed and the wet portion of the thread was measured (in mm). The mean±sd PRT values were 23.02±2.98 mm/15 seconds and 24.04±2.60 mm/15 seconds for the April and June measurements, respectively. There were significant differences in the PRT between the two months, with a significant increase in June. Mean PRT values for males and females were, respectively, 23.30±3.35 and 22.79±2.65 mm/15 seconds in April, and 24.57±2.41 and 23.61±2.68 mm/15 seconds in June. There was no significant correlation (r=0.075, P>0.05) between bodyweight and tear production in both eyes of the male and female birds in April and June. The results indicated that seasonal variations have an effect on tear production. The PRT was a viable method for the measurement of tear production in pigeons and these measurements could be accepted as reference values for healthy pigeons.

Effects of short-term oral administration of trimethoprim-sulfamethoxazole on tear production in clinically normal Syrian hamsters

OBJECTIVE

To determine effects of 14 days of oral administration of trimethoprim-sulfamethoxazole on aqueous tear production in clinically normal Syrian hamsters.

ANIMAL STUDIED

Fifteen healthy adult Syrian hamsters.

PROCEDURE

Baseline phenol red thread test (PRTT) values were recorded 1 day prior to treatment. Eight hamsters in treated group received 15 mg/kg trimethoprim-sulfamethoxazole orally twice a day for 14 days. The remaining seven hamsters were used as untreated controls and received a placebo. All ophthalmic tests were performed without chemical restraint. PRTT values were evaluated in both eyes of all Syrian hamsters using a commercial PRTT strip of a single lot number.

RESULTS

The mean ± SD baseline PRTT values for treatment group and control group were 7.25 ± 1.3 mm/15 s and 5.42 ± 1.13 mm/15 s, respectively. After 14 days of drug administration, the mean ± SD PRTT values for treatment group and control group were 5.62 ± 1.5 and 5.64 ± 0.74, respectively. Significant decreases in the PRTT values, compared with baseline values, were observed in the treatment group on day 15 (P = 0.042).

CONCLUSIONS

Trimethoprim-sulfamethoxazole decreased tear production in the hamster in this study.

Ocular findings and reference values for selected ophthalmic diagnostic tests in the macaroni penguin (Eudyptes chrysolophus) and southern rockhopper penguin (Eudyptes chrysocome)

OBJECTIVE

To describe ophthalmic examination findings and standard diagnostic test results in 2 penguin species.

ANIMALS STUDIED

Macaroni & Southern Rockhopper Penguins.

PROCEDURE

Complete ophthalmic examinations including Schirmer tear test (STT), modified phenol red thread test (PTT), tonometry, and echobiometry were performed on penguins housed at the Detroit Zoo. Mean and standard deviation of ophthalmic tests are reported and compared for significance using two sample t-tests with significance set at P < 0.05. Correlations between variables were assessed using Pearson's correlation coefficient.

RESULTS

Cataracts were the most common finding, present in 64% of Macaroni Penguins, and 68% of Rockhopper Penguins. There were anterior segment anomalies in all eyes with cataracts consistent with lens-induced uveitis. The mean modified PTT for the Macaronis was 24.7 ± 6.37 mm/15 s and 25.1 ± 7.07 mm/15 s in the Rockhoppers. The mean STT value for the Macaronis was 12.1 ± 5.43 mm/min and 11.0 ± 3.96 mm/min in the Rockhoppers. Mean intraocular pressure (IOP) for the Macaronis was 21.9 ± 7.05 mmHg measured by applanation tonometry and 29.1 ± 7.16 mmHg using rebound tonometry. The Rockhoppers had a mean IOP of 20.0 ± 5.77 mmHg and 24.1 ± 5.09 mmHg for applanation and rebound tonometry, respectively. In both populations, there was a significant difference in IOP measurement between the two instruments. In the Macaroni penguins, the presence of cataracts correlated significantly with increased age and lower IOP readings. Anterior chamber distance and axial globe length were significantly greater in males than in females in both penguin species.

Differences in ocular parameters between diurnal and nocturnal raptors

OBJECTIVE

To establish and compare normal ocular parameters between and within diurnal and nocturnal raptor groups.

ANIMALS STUDIED

Eighty-eight ophthalmically normal raptors of six nocturnal and 11 diurnal species were studied.

PROCEDURE

Tear production was measured using Schirmer tear test (STT) and phenol red thread test (PRTT), and applanation tonometry was conducted. Ultrasonographic measurements of axial length (AL), mediolateral axis (ML), vitreous body (VB), and pecten length (PL) were recorded, and conjunctival cultures were obtained.

RESULTS

A weak correlation (R = 0.312, P = 0.006) was found between PRTT and STT. Tear production was significantly lower in nocturnal species (P < 0.001), but no difference was observed in intraocular pressure (IOP). VB and PL were significantly longer in diurnals (P < 0.001 and P = 0.021, respectively), and no significant difference was observed in AL and ML. When comparing results within these groups, there was a significant difference between most species for all parameters except IOP. Fifty-one percent of the examined raptors were positive for mycology or bacteriology, either on culture or PCR. The most common infectious agent isolated was Staphylococcus spp.

CONCLUSIONS

Phenol red thread test and STT are both valid methods to measure tear production; however, a separate baseline must be determined for each species using these methods, as the results of one method cannot be extrapolated to the other. Due to significant differences observed within diurnal and nocturnal species, it appears that a more intricate division should be used when comparing these parameters for raptors, and the classification of diurnal or nocturnal holds little significance in the baseline of these data.

O olho da coruja-orelhuda: observações morfológicas, biométricas e valores de referência para testes de diagnóstico oftálmico

Objetivou-se relatar características morfológicas do bulbo ocular e determinar valores de referência para testes oftálmicos selecionados em corujas-orelhudas (Asio clamator). Foram estudados 32 olhos de 16 corujas (Asio clamator), adultas e jovens, machos e fêmeas, de vida livre. Sendo compilados dados referentes a observações morfológicas do crânio, bulbo ocular e anexos, além de mensuração de testes oftálmicos, incluindo, Teste Lacrimal de Schirmer (TLS), cultura da microbiota normal da conjuntiva, estesiometria, pressão intraocular (PIO), espessura de córnea central (ECC), diâmetro horizontal da rima palpebral, diâmetro horizontal da córnea e oftalmoscopia indireta. Vinte e dois tipos de bactérias foram identificados em 12 corujas havendo predominância de microrganismos Gram-positivos. A média encontrada para o TLS foi de 5,03±3,28mm/min, para o diâmetro horizontal da rima palpebral em 16 corujas foi 21,24±1,17mm, e 15,7±2,74mm para o diâmetro horizontal da córnea. O valor médio para o teste de estesiometria foi de 0,80±0,59cm, a PIO média de 13,81±5,62mmHg e ECC média de 0,28±0,03cm. O estudo contribuiu para a caracterização da morfologia ocular e para o estabelecimento de valores de referências de testes diagnósticos oftálmicos em corujas-orelhudas, sendo necessário ainda o desenvolvimento de estudos complementares sobre histologia ocular desta espécie.

Schirmer tear test type I readings and intraocular pressure values assessed by applanation tonometry (Tonopen® XL) in normal eyes of four European species of birds of prey

OBJECTIVE

To determine normal values for Schirmer tear test I and intraocular pressure in four European species of birds of prey.

ANIMALS STUDIED

Twenty birds from each of the following species: Eurasian Tawny owl (Strix aluco), Little owl (Athene noctua), Common buzzard (Buteo buteo), and European kestrel (Falco tinnunculus).

PROCEDURES

Both eyes of all birds (80 eyes) underwent a complete ophthalmic examination, which included a Schirmer tear test type I (STT-I) performed with commercially available strips and the assessment of the intraocular pressure (IOP) by applanation tonometry, employing the Tonopen-XL(®) device. The animals, which had been taken to a rescue center, were examined for ocular lesions prior to their eventual release into the wild. STT-I readings and IOP values were expressed as means ± standard deviation.

RESULTS

Schirmer tear test type I readings were as follows: Eurasian Tawny owls: 3.12 ± 1.92 mm/min; Little owls: 3.5 ± 1.96 mm/min; Common buzzards: 12.47 ± 2.66 mm/min; European kestrels: 6.20 ± 3.67 mm/min. IOP values were as follows: Eurasian Tawny owls: 11.21 ± 3.12 mmHg; Little owls: 9.83 ± 3.41 mmHg; Common buzzards: 17.2 ± 3.53 mmHg; European kestrels: 8.53 ± 1.59 mmHg.

CONCLUSIONS

The results of this study give representative values for STT-I and IOP in four of the most common species of birds of prey in Europe.