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Results of selected ophthalmic diagnostic tests for clinically normal Syrian hamsters (Mesocricetus auratus)

  • Negah Veterinary Centre
  • Iranian Pet Hospital


OBJECTIVE To determine values for tear production, horizontal palpebral fissure length (HPFL), eye blink frequency, and intraocular pressure (IOP) in healthy Syrian hamsters (Mesocricetus auratus). ANIMALS 40 healthy adult Syrian hamsters (80 eyes). PROCEDURES Tear production was measured with the phenol red thread test (PRTT), modified Schirmer tear test (mSTT), and endodontic absorbent paper points tear test (EAPPTT). The IOP was measured by use of rebound tonometry. Correlations between test results and body weight were evaluated. RESULTS Mean ± SD values for the IOP, PRTT, EAPPTT, mSTT, HPFL, and blink frequency for all 80 eyes were 4.55 ± 1.33 mm Hg, 5.57 ± 1.51 mm/15 s, 4.52 ± 1.55 mm/min, 2.07 ± 0.97 mm/min, 5.84 ± 0.45 mm, and 1.68 ± 0.43 blinks/min, respectively. For all variables, values did not differ significantly between the right and left eyes or between males and females. There was no correlation between measured variables and body weight. CONCLUSIONS AND CLINICAL RELEVANCE Results for this study provided information on values for the IOP, PRTT, mSTT, EAPPTT, HPFL, and eye blink frequency in healthy Syrian hamsters. It was important to determine reference intervals for this species because they commonly are kept as pets or used as research animals.
72 AJVR • Vol 77 • No. 1 • January 2016
The tear film is vital to the physiologic function
of eyes and is essential for the maintenance of
corneal clarity. It serves as the cranial refracting sur-
face of the eye and provides nutrition for the corneal
The importance of tear film evaluation during as-
sessment of ocular health has long been recognized.
Tear film tests are categorized as quantitative tests
that are used to evaluate the volume of tear film or
qualitative tests that are used to assess quality of tear
film. Quantitative tests for the evaluation of tear film
include the STT, PRTT, and EAPPTT.
In clinical veterinary practice, quantitative clini-
cal evaluation of the precorneal tear film is most fre-
quently limited to use of the STT because published
standard values for the STT in domestic species are
accepted and clinically useful for the identification of
Results of selected ophthalmic diagnostic tests
for clinically normal Syrian hamsters
(Mesocricetus auratus)
Seyed Mehdi Rajaei dvm, dvsc
Maneli Ansari Mood dvm, dvsc
Reza Sadjadi dvm
David L. Williams ma, vetmd, phd
Received February 25, 2015.
Accepted May 6, 2015.
From the Department of Clinical Sciences, Faculty of
Specialized Veterinary Sciences, Science and Research
Branch, Islamic Azad University, Tehran, Iran (Rajaei,
Ansari Mood, Sadjadi); and the Department of Veterinary
Medicine, University of Cambridge, Cambridge, CB3
0ES, England (Williams). Dr. Rajaei’s present address is
Department of Clinical Sciences, College of Veterinary
Medicine, Karaj Branch, Islamic Azad University, Alborz,
Address correspondence to Dr. Rajaei (mehdi_13r@
To determine values for tear production, horizontal palpebral fissure length
(HPFL), eye blink frequency, and intraocular pressure (IOP) in healthy Syrian
hamsters (Mesocricetus auratus).
40 healthy adult Syrian hamsters (80 eyes).
Tear production was measured with the phenol red thread test (PRTT), modi-
fied Schirmer tear test (mSTT), and endodontic absorbent paper points tear
test (EAPPTT). The IOP was measured by use of rebound tonometry. Cor-
relations between test results and body weight were evaluated.
Mean ± SD values for the IOP, PRTT, EAPPTT, mSTT, HPFL, and blink fre-
quency for all 80 eyes were 4.55 ± 1.33 mm Hg, 5.57 ± 1.51 mm/15 s, 4.52 ±
1.55 mm/min, 2.07 ± 0.97 mm/min, 5.84 ± 0.45 mm, and 1.68 ± 0.43 blinks/
min, respectively. For all variables, values did not differ significantly between
the right and left eyes or between males and females. There was no correla-
tion between measured variables and body weight.
Results for this study provided information on values for the IOP, PRTT,
mSTT, EAPPTT, HPFL, and eye blink frequency in healthy Syrian hamsters.
It was important to determine reference intervals for this species because
they commonly are kept as pets or used as research animals. (Am J Vet Res
quantitative tear film deficiencies.2 Small domestic,
wild, and exotic animals have a small palpebral fissure
length; thus, narrow (2.5 and 4 mm wide) mSTT strips
have been recommended for measurement of tear
production in these animals.3
The PRTT was developed for use because of vari-
able results, poor repeatability, and low sensitivity of
the STT for detecting inadequate tear production in
humans.4 It is performed by placing a 75-mm-long cot-
ton thread impregnated with pH-sensitive phenol dye
(which changes from yellow to red when it absorbs
tears that are slightly alkaline) in the ventral fornix of
an eye for 15 seconds.2
The EAPPTT was proposed in 2012 as a new
method for tear film assessment.5 Standardized end-
odontic absorbent paper points are commonly used
in dentistry because their highly absorptive proper-
ties promote drying after irrigation, allow carriage
of medicants (eg, antiseptics and disinfectants), and
assist in collection of samples for microbiological
culture.5,6 They also can be used as an alternative
method for tear film measurement. For those mea-
surements, 1 standardized absorbent paper point is
inserted in the ventral conjunctival fornix of an eye
EAPPTT Endodontic absorbent paper points tear test
HPFL Horizontal palpebral fissure length
IOP Intraocular pressure
mSTT Modified Schirmer tear test
PRTT Phenol red thread test
STT Schirmer tear test
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AJVR • Vol 77 • No. 1 • January 2016 73
and allowed to remain there for 1 minute; the pa-
per point is then removed, and the wet portion is
measured by use of a digital calipers graduated in
Intraocular pressure is controlled and regulated
by the CNS, which maintains a balance between aque-
ous humor production and outflow.7,8 Assessment of
IOP is a critical component of a complete ophthalmic
examination because an abnormally high or low IOP
is evidence of ocular disease, such as glaucoma or
The purpose of the study reported here was to de-
termine tear secretion by use of the mSTT, PRTT, and
EAPPTT and to measure IOP by means of rebound to-
nometry in the eyes of healthy adult Syrian hamsters
(Mesocricetus auratus). Additionally, HPFL and eye
blink frequency were evaluated because these 2 vari-
ables could directly affect measurement of tear pro-
duction and spread of the tear film.10
Materials and Methods
The study population consisted of 40 healthy
adult Syrian hamsters (21 males and 19 females).
Animals were housed indoors beginning 7 days be-
fore the first day of testing; Syrian hamsters were
housed separately in labeled cages in an air-condi-
tioned room with a constant temperature (20° to
22°C) and relative humidity (50% to 55%). The light-
ing cycle consisted of 12 hours of light and 12 hours
of darkness. Animals were fed a commercial diet
formulated for hamsters, and water was available ad
libitum. The study was approved by the Iran Society
for Prevention of Cruelty to Animals in accordance
with the Iranian Ethical Code for Studies on Labora-
tory Animals.
A complete physical examination and ophthalmo-
scopic examination that included direct and indirect
ophthalmoscopy,a fluorescein staining,b and slit lamp
biomicroscopyc were performed. All the animals were
included in the study on the basis that no abnormali-
ties were detected during the physical and ophthal-
mic examinations.
A PRTT,d EAPPTT,e and STTf were performed.
Each test was produced by a single manufacturer and
was from the same batch with a single lot number. A
sequence of procedures was performed on each Syr-
ian hamster. Eye blink frequency and IOP were as-
sessed on day 1, the PRTT was performed on day 3, the
EAPPTT was performed on day 5, and the mSTT and
HPFL were assessed on day 7. On day 14, complete
physical and ophthalmoscopic examinations were
performed on all Syrian hamsters.
One investigator (SMR) conducted all ocular tests,
examinations, and measurements. All tests were con-
ducted between 4 pm and 6 pm to minimize possible
variations associated with diurnal changes.
Eye blink frequency was counted. Each animal
was placed in a cage that was made of clear plastic,
which was intended to provide familiar surroundings.
Syrian hamsters were not restrained or handled dur-
ing counting. Two investigators (SMR, MAM), 1 located
on each side of the cage, counted the number of eye
blinks during a 5-minute period. The mean value for
the 2 investigators was calculated and used for statisti-
cal analysis.
For IOP measurement, animals were physically
restrained without any pressure applied to the eye-
lids or neck. One of the investigators grasped a Syrian
hamster by the nape of the neck between a thumb
and forefinger and simultaneously maintained a grip
on the tail and supported the animal’s body against
the palm of the other hand; a second investigator then
obtained IOP values. Protrusion of the eyeballs was
not observed during tonometry. A tonometerg with a
disposable probe was held horizontally perpendicular
at a distance of 4 to 5 mm from the central corneal sur-
face. The device was calibrated by use of the p setting.
Six consecutive measurements were obtained. The se-
ries of measurements was repeated until the tonom-
eter indicated that there was an acceptable SD for the
6 measurements. The procedure then was repeated for
the contralateral eye.
To measure the aqueous portion of the tear film,
the ventral eyelid of each Syrian hamster was everted.
A 3-mm folded head of a phenol red cotton thread was
placed into the ventral conjunctival fornix and allowed
to remain there for 15 seconds. The thread was then re-
moved, and the portion of the thread that had changed
from yellow to red was immediately measured.
To measure the aqueous tear volume with the
EAPPTT, 1 absorbent paper point was inserted in the
ventral conjunctival fornix of each eye and allowed to
remain there for 1 minute. Each paper point was then
removed, and the wet portion was immediately mea-
sured by use of a digital calipers.
The mSTT strips were obtained by longitudinal-
ly dividing standard (35 mm in length and 5 mm in
width) commercial STT strips aseptically with a scal-
pel blade and stainless steel ruler to yield 2 strips that
were 35 mm in length and 2.5 mm in width. Forceps
were used to insert an mSTT strip in the ventral con-
junctival fornix. Strips were allowed to remain in the
fornix for 1 minute. Strips then were removed, and
the wet portion was measured. Because of the small
amount of tears in most of the eyes, the notch of the
mSTT strip often was not reached; thus, the distance
from the end of a strip to the point at which the strip
was wet was measured, rather than measuring the
length of the wet strip beginning at the notch as is
conventional for other species.11
For measuring HPFL, the distance between the
inner end of the ocular caruncle and the temporal
canthus (termed the palpebral fissure length) was
measured. Measurements were obtained by use of a
waterproof digital caliper with a liquid-crystal display
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74 AJVR • Vol 77 • No. 1 • January 2016
Statistical analysis
Statistical analysis was performed by use of a sta-
tistical software program.i A 1-sample Kolmogorov–
Smirnov test was used to assess data normality. Paired
sample t tests were used to compare IOP, PRTT,
EAPPTT, mSTT, and HPFL values obtained for the right
and left eyes. Mean and SD were calculated for all the
eyes and for right and left eyes separately. An inde-
pendent sample t test was used to compare mean
IOP, PRTT, EAPPTT, and mSTT values for sex and body
weight. A Pearson correlation analysis was used to
evaluate the relationship between body weight and
mean IOP, PRTT, EAPPTT, mSTT, and HPFL. Values were
considered significant at P < 0.05.
Ocular discomfort was not observed in any of the
Syrian hamsters for up to 7 hours after measurements
were obtained during the study. No signs of conjuncti-
vitis, keratitis, blepharitis, corneal ulcers, or intraocular
disease were detected in any of the Syrian hamsters.
All the continuous numeric data obtained for the
study were normally distributed as determined by use
of the 1-sample Kolmogorov-Smirnov test (P > 0.2).
Mean ± SD body weight for all Syrian hamsters was
83.40 ± 18.20 g (range, 42.2 to 122.0 g). Mean body
weight of females and males was 83.13 ± 15.61 g and
83.81 ± 20.76 g, respectively (Table 1). Mean values
for IOP, PRTT, EAPPTT, and mSTT for all 80 eyes were
4.55 ± 1.33 mm Hg, 5.57 ± 1.51 mm/15 seconds, 4.52
± 1.55 mm/min, and 2.07 ± 0.97 mm/min, respectively.
We did not detect significant differences in values be-
tween the right and left eyes or between males and
A correlation (r = 0.541; P = 0.014) was detected
between PRTT and EAPPTT values but not between
PRTT and mSTT values or between EAPPTT and
mSTT values. Moreover, there was no correlation be-
tween the measured variables and body weight of the
Syrian hamsters.
A paucity of information exists on ocular variables
for wild and exotic animals because of the large num-
ber of species involved.10 Some wild and exotic spe-
cies are maintained as pets, whereas others are used as
research animals. Regardless of their use, good veteri-
nary care must be provided for each species, and refer-
ence intervals need to be determined for physiologic
variables before diagnosis of abnormal conditions
is possible. This is particularly true for ophthalmic
Syrian hamsters are desert-dwelling species. Low
tear production may be a fluid conservation mecha-
nism for animals living in arid areas.12 Nevertheless,
low tear production by Syrian hamsters is adequate to
protect the ocular surface.13 In contrast to results of
a previous study13 on tear production by Syrian ham-
sters in which investigators found a significantly in-
creased PRTT value for male animals, compared with
results for female animals, no significant difference
was found between PRTT values of the males and fe-
males in the present study.
The mean ± SD EAPPTT for Wistar rats (Rattus
norvegicus) and Swiss Webster mice (Mus musculus)
is 6.18 ± 2.06 mm/min and 4.39 ± 1.45 mm/min, re-
spectively.10 The mean EAPPTT for Syrian hamsters in
the present study was slightly higher, compared with
values for the mice of that other study.10
Another alternative quantitative tear test is the
mSTT, which has been used in dogs,14,15 birds,16 rhe-
sus monkeys (Macaca mulatta),17 black-tufted mar-
mosets (Callithrix penicillata),5 and red-ear sliders
(Trachemys scripta elegans).18 In the present study,
STT values for Syrian hamsters were exceptionally
low, which made it difficult to evaluate tear produc-
tion by use of this method. A more precise measure-
ment was possible with the mSTT. The mSTT has been
used in birds16; however, the strips used in that study16
were only 2 mm wide.
During STT measurement, the filter paper strip ab-
sorbs all the tears produced as well as those compris-
ing the tear film. Once the tear film has been absorbed,
tear uptake by the test strip equals tear production by
the lacrimal and Harderian glands.19
In the present study, results for the PRTT and
EAPPTT were positively correlated, and volume of
fluid measured by use of the PRTT and EAPPTT was
small. We postulate that the PRTT and EAPPTT were
measuring tear volume in the conjunctival sac rather
Mean ± SD Range
Male Female Male Female
Variable All (n = 40) (n = 21) (n = 19) All (n = 40) (n = 21) (n = 19)
IOP (mm Hg) 4.55 ± 1.33 4.90 ± 1.41 4.20 ± 1.22 2–8 2–8 2–7
mSTT (mm/min) 2.07 ± 0.97 2.09 ± 1.15 2.05 ± 0.76 0–5 0–5 0–4
PRTT (mm/15 s) 5.57 ± 1.51 5.15 ± 1.56 6.00 ± 1.41 3.0–10.0 3.0–7.5 4.5–8.5
EAPPTT (mm/min) 4.52 ± 1.55 4.40 ± 1.48 4.65 ± 1.68 2–7 3–7 2–7
HPFL (mm) 5.84 ± 0.10 5.87 ± 0.49 5.81 ± 0.50 5.16–6.72 5.32–6.70 5.16–6.72
EBF (blinks/min) 1.68 ± 0.43 1.66 ± 0.53 1.70 ± 0.35 1.2–2.4 1.2–2.4 1.4–2.4
Body weight (g) 83.40 ± 18.20 83.81 ± 20.76 83.13 ± 15.61 42.2–122.0 42.2–122.0 51.0–105.0
EBF = Eye blink frequency.
Table 1—Mean ± SD and range for ophthalmic variables measured in both eyes of each of 40 Syrian hamsters (Mesocricetus
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AJVR • Vol 77 • No. 1 • January 2016 75
than assessing de novo tear production by the lac-
rimal glands.
The HPFL for Wistar rats and Swiss Webster mice is
6.45 ± 0.09 mm and 3.59 ± 0.27 mm, respectively.10 Adult
Syrian hamsters of the present study had a larger HPFL
than did mice of similar body weight. It is worth men-
tioning that the ease with which globes prolapse with
handling of hamsters is related to the longer lid aperture.
Measurement of IOP is important for evalu-
ation of ocular health. Reference IOP values for
mice and rats have been obtained with a rebound
tonometer.j Mean ± SD IOP of conscious rats is 18.4 ±
0.1 mm Hg.20 Mean IOP differs among strains of
mice (10.6 ± 0.6 mm Hg for Balb/c mice, 13.3 ±
0.3 mm Hg for C57-BL/6 mice, and 16.4 ± 0.3 mm Hg for
CBA mice).20 Mean IOP determined by use of a rebound
tonometerg in New Zealand White rabbits is 9.51 ±
2.62 mm Hg.21 The mean IOP of 4.55 ± 1.33 mm Hg for
Syrian hamsters of the present study was significantly
lower than values measured in mice, rats, and rabbits.
Differences in handling and restraint of animals, time of
day, and position of the body or head could have been
responsible for the difference between IOP of Syrian
hamsters and IOP of other rodents; however, in the au-
thors’ opinion, such factors are unlikely to result in such
a marked difference. The low IOP in Syrian hamsters
requires further evaluation.
A comparison of 2 types of rebound tonometersg,j
has been performed for chinchillas22 and red-ear slid-
ers.23 The rebound tonometerj for laboratory animals
may be more accurate than the veterinary rebound
tonometerb used for red-ear sliders.23 However, no sig-
nificant differences were observed in IOP of chinchil-
las for the various models of rebound tonometer.22 In
the present study, IOP was obtained by use of a veteri-
nary rebound tonometerg with the device calibrated
by use of the p setting. Use of a veterinary rebound
tonometerg would appear to be most appropriate
owing to its widespread availability as a diagnostic de-
vice in veterinary clinics.
Contact between the cornea and probe rarely
causes a corneal reflex in dogs.24 Similar to results for
Hermann’s tortoises (Testudo hermanni),25 impact of
the probe invariably induced a blink reflex in the Syr-
ian hamsters during the study reported here. Although
this discrepancy may be attributed to the size of the
ocular globe of Syrian hamsters, interspecies differ-
ences in corneal innervation cannot be excluded.25
Eye blink frequency of Syrian hamsters in the
present study ranged from 1.2 to 2.4 blinks/min. Eye
blink frequency of guinea pigs is 2 to 5 blinks/20 min-
utes.11 Eye blink frequency of dogs, cats, horses, cat-
tle, black-tufted marmosets, and pigs is 3 to 5 blinks/
min,26 1 to 5 blinks/5 minutes,26 5 to 25 blinks/min,26
5 blinks/min,26 3 to 5 blinks/min,5 and approximately
10 blinks/min,26 respectively. Blinking maintains the
physiologic thickness of the preocular surface by
spreading tears over the corneal surface.27
The study reported here provided reference val-
ues for ophthalmic examinations of adult Syrian ham-
sters. The IOP was measured by means of rebound to-
nometry, and tear production was assessed by use of a
number of tests.
The study was performed at the Faculty of Specialized Veteri-
nary Sciences, Science and Research Branch, Islamic Azad Univer-
sity, Tehran, Iran.
This research received no specific grant from any funding
agency in the public, commercial, or not-for-profit sectors. The
authors declare that they have no conflicts of interest.
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... An important feature of the rodent eye is the small tear volume, which hinders quantitative tear measurement by standard methods. 15 Tear production has been measured in other rodent species including chinchillas, 16 guinea pigs, 17,18 hamsters, 19,20 capybaras, 21 and lowland pacas. 22 In veterinary medicine, the most commonly used quantitative tear film assessment method is the Schirmer tear test. ...
Objective: To evaluate the effects of injectable dexmedetomidine-ketamine-midazolam (DKM) and isoflurane inhalation (ISO) anesthetic protocols on selected ocular variables in captive black-tailed prairie dogs (Cynomys ludovicianus; BTPDs). Animals: 9 zoo-kept BTPDs. Procedures: The BTPDs received dexmedetomidine hydrochloride (0.25 mg/kg, IM), ketamine hydrochloride (40 mg/kg, IM), and midazolam hydrochloride (1.5 mg/kg, IM) or inhalation of isoflurane and oxygen in a randomized complete crossover design (2-day interval between anesthetic episodes). Pupil size, globe position, tear production, and intraocular pressure measurements were recorded at 5, 30, and 45 minutes after induction of anesthesia. For each BTPD, a phenol red thread test was performed in one randomly selected eye and a modified Schirmer tear test I was performed in the other eye. Intraocular pressure was measured by rebound tonometry. Results: Compared with findings for the DKM protocol, pupil size was smaller at all time points when the BTPDs underwent the ISO protocol. Globe position remained central during anesthesia with the DKM protocol, whereas it varied among central, ventromedial, and ventrolateral positions during anesthesia with the ISO protocol. Tear production and intraocular pressure decreased significantly over time when the BTPDs underwent either protocol. Conclusions and clinical relevance: Results indicated that ophthalmic examination findings for anesthetized BTPDs can be influenced by the anesthetic protocol used. The DKM protocol may result in more consistent pupil size and globe position, compared with that achieved by use of the ISO protocol. Tear production and intraocular pressure measurements should be conducted promptly after induction of anesthesia to avoid the effect of anesthetic episode duration on these variables.
... A value close to that obtained in this species was also observed in Syrian hamster (Mesocricetus auratus), 5.57±1.51mm/15" (Rajaei et al. 2016a). ...
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The establishment of parameters for tear production in different species is important for better understanding eye´s health and is one of the components of the ophthalmic semiological technique. Particularities derived from the anatomophysiology of non-domestic species induce the search for more reliable methodologies. The aim was to evaluate and compare tear production of white-eared opossum (Didelphis albiventris) and Brazilian common opossum (Didelphis aurita) by three different methods. Fifteen individuals of each species, juveniles, healthy, of both sexes, with 60 to 90 days of life, were physically restrained. Phenol red thread test (PRTT), endodontic absorbent paper point tear test (EAPPTT) and modified -Schirmer tear test (mSTT) were performed. PRTT was the most difficult to perform because of the wire malleability, while EAPPTT was more feasible for both species. The median ± semi-quartile range for PRTT were 19.79±2.61mm/15 “and 5.22±2.92mm/15”, for EAPPTT were 16.25±1.82mm/min and 10.9±3.04mm/min, and for STTm were 0±1.63mm/min and 0±1.63mm/min for white-eared opossum and Brazilian common opossum respectively. There was no difference between the right and left eye neither sex. A significant difference was obtained for the same test to different species. No significant correlation was found between the tests for both species. The description of tear production parameters for juvenile white-eared opossum and Brazilian common opossum may be used as a tool, which will allow the early diagnosis of ocular diseases.
... 3 Normal ocular parameters such as tear production and intraocular pressure have been previously reported in Syrian hamsters. 4 Conjunctival aerobic flora of hamsters has not thus far been reported. ...
This study was performed to determine the normal aerobic bacterial flora of the cornea and conjunctiva in Syrian hamsters. Eleven healthy adult Syrian hamsters were used. Collection of specimens was performed using sterile micro-swab applicators. Immediately after sample collection, microbiologic aerobic culture was initiated. Fourteen eyes (63%) showed bacterial growth and a total number of 19 different species were isolated which belonged to 7 bacterial genera. Gram-positive bacteria were the most prominent with 83.3% (20/24) of isolates. The results of this study could help veterinarians in the diagnosis and therapeutic monitoring of surface ocular disease in this species.
... 10 In clinical practice, ketamine-diazepam and ketamine-xylazine combinations have been used for the induction of anesthesia in hamsters. 11 In a previous study 12 ...
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OBJECTIVE To determine effects of diurnal variation and anesthetic agents on intraocular pressure (IOP) in Syrian hamsters (Mesocricetus auratus). ANIMALS 90 healthy adult Syrian hamsters (45 males and 45 females). PROCEDURES IOP was measured with a rebound tonometer. In phase 1, IOP was measured in all hamsters 3 times during a 24-hour period (7 am, 3 pm, and 11 pm). In phase 2, hamsters were assigned to 5 groups (18 animals [9 males and 9 females]/group). Each group received an anesthetic agent or combination of anesthetic agents (ketamine hydrochloride, xylazine hydrochloride, diazepam, ketamine-diazepam [KD], or ketamine-xylazine [KX] groups) administered via the IP route. The IOP was measured before (time 0 [baseline]) and 10, 30, 60, 90, 120, and 150 minutes after administration of drugs. RESULTS Mean ± SD IOP values were 2.58 ± 0.87 mm Hg, 4.46 ± 1.58 mm Hg, and 5.96 ± 1.23 mm Hg at 7 am, 3 pm, and 11 pm, respectively. Mean baseline IOP was 6.25 ± 0.28 mm Hg, 6.12 ± 0.23 mm Hg, 5.75 ± 0.64 mm Hg, 5.12 ± 1.40 mm Hg, and 4.50 ± 1.30 mm Hg for the ketamine, xylazine, diazepam, KD, and KX groups, respectively. A significant decrease in IOP, compared with baseline IOP, was detected in only the KX group at 30, 60, and 90 minutes after drug administration. CONCLUSIONS AND CLINICAL RELEVANCE Maximum IOP in Syrian hamsters was detected at night. The ketamine-xylazine anesthetic combination significantly decreased IOP in Syrian hamsters.
... 5 Our previous published study was determined reference values for ophthalmic diagnostic tests including IOP in clinically normal Syrian hamsters. 6 In the present study our purpose was to determine the circadian IOP variation through the day in this nocturnal species. Also effects of anesthesia on intraocular pressure were assessed in clinically normal Syrian hamsters. ...
Conference Paper
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Purpose: This study was aimed to determined effects of anesthesia on intraocular pressure (IOP) in healthy Syrian hamsters (Mesocricetus auratus). Methods: Ninety healthy adult Syrian hamsters (45 males and 45 females) were used in this study. Hamsters were randomly assigned to five groups. Ketamine, xylazine, diazepam, ketamine-diazepam (KD) and ketamine-xylazine (KX) were administered by intraperitoneal route in each group. Ketamine, Xylazine and Diazepam were administered with the dose of 100 mg/kg, 5 mg/kg and 10 mg/kg, respectively. Ketamine and diazepam were administered with the dose of 40 mg/kg and 2mg/kg in KD group, respectively. 50 mg/kg of ketamine and 5 mg/kg of xylazine were administered in KX group. Baseline IOP was measured prior to the administration of anesthetic agents in both groups (T0). IOP measurements were then repeated at 10 min (T10), 30 min (T30), 60 min (T60), 90 min (T90), 120 min (T120), and 150 min (T150) following the administration of drugs. Results: Mean ± SD values of the baseline IOP for ketamine, xylazine, diazepam, KD and KX groups were 6.25 ± 0.28, 6.12 ± 0.23, 5.75 ± 0.64, 5.12 ± 1.40 and 4.50 ± 1.30 mm Hg, respectively. In ketamine, diazepam, xylazine and KD groups, there were no statistically significant changes in IOP. In KX group, a significant decrease in IOP was observed at T30, T60 and T90 (P30=0.001, P60=0.007 and P90=0.001). Conclusions: The present study demonstrating that ketamine-xylazine combinations decreased IOP significantly in Syrian hamsters while the other agents had no significant effect on IOP.
With over 2200 extant species, rodents (order Rodentia) represent the largest mammalian order and comprise 42% of global mammalian biodiversity (Donnelly et al. 2015). Rodents represent a diversity of morphological adaptations associated with their varied terrestrial and aquatic habitats, distributed throughout all continents except Antarctica. One common feature to all Rodentia is a powerful anatomical apparatus for chewing and gnawing, characterized by prominent rostral dentition and a large and often complex masseter muscle. The differing morphological characteristics and adaptations of the zygomasseteric apparatus are used to divide the Rodentia into five suborders including the Anomaluromorpha, Castorimorpha, Hystricomorpha, Sciuromorpha, and Myomorpha (Wilson and Reeder 2005).
Hamsters and gerbils are often presented on an emergent basis. Common presenting complaints include diarrhea, neurologic signs, ocular signs, respiratory distress, and trauma. Provided is an overview of these presenting complaints, with additional detail on underlying conditions. Unique species considerations are addressed, and an abbreviated formulary of anticonvulsant, antimicrobial, and antiparasitic agents is provided.
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.
Objective To provide reference values for ocular examination and diagnostics in ophthalmologically normal sugar gliders (Petaurus breviceps). To retrospectively determine the prevalence of ocular diseases in sugar gliders presenting to a single institution. Animals Ten client owned and 106 previously evaluated sugar gliders. Procedure A descriptive study evaluated sugar gliders presented to Colorado State University's Avian, Exotics, and Zoological Medicine Service (CSU‐AEZ) from August‐2019 to January‐2020. A complete ophthalmic examination including Schirmer tear test II (STT II), phenol red threat test (PRTT), intraocular pressure (IOP) via rebound tonometry, fluorescein, and rose bengal stain was performed under anesthesia. Conjunctival aerobic culture swabs and cytology were collected prior to ophthalmic evaluation. A retrospective review of medical records of sugar gliders presented to CSU‐AEZ from 2008 to 2018 for ocular disease was performed. Results Mean values ± standard deviation for selected diagnostics included the following: STT II: 2.2 ± 6.7 mm/min; PRTT: 0 ± 0 mm/15 s; IOP: 12 ± 2.6 mm Hg. Fluorescein and rose bengal staining highlighted corneal abrasions secondary to tear testing. The three most common conjunctival bacterial isolates cultured were Staphylococcus spp. (3/20, 15%), Coryneform spp. (3/20, 15%), and unidentified Gram‐positive cocci (3/20, 15%). Retrospective analysis revealed ocular diseases to be the third most common abnormality resulting in sugar glider presentations (13/106, 12.3%). Conclusion This descriptive study gives reference values for IOP, conjunctival microbiology, and cytology for sugar gliders. STT II and PRTT provide little clinical value in sugar gliders. The retrospective study revealed that ocular abnormalities, often secondary to dental disease, are a common reason for presentation.
Conference Paper
Purpose. The purpose of this study was to establish normal values for strip meniscometry (SM) as lacrimal function test and compare the results with schirmer tear test (STT) in dogs, cats and rabbits. Methods. sixty adult healthy dogs from thirteen different breeds (120 eyes), twenty adult healthy domestic shorthair cats (40 eyes) and eighteen adult healthy New Zealand white rabbits (36 eyes) were used in this study. Lacrimal function was tested by SM tube in all animals. 2 hours after meniscometry tear production was measured using Schirmer tear test (STT). Results. Mean SM and STT values for all the Dogs, Cats and rabbits were 9.66±2.15 mm/5 sec and 15.10±3.06 mm/min; 10.50±0.7 mm/5 sec and 11.00±1.41 mm/min; 4.72±1.20 mm/5 sec and 4.22±2.47 mm/min, respectively. There was a correlation (r = 0.281; P = 0.018) between SM and STT values in dogs, but no correlation in cats and rabbits (P = 0.61, P = 0.06) was observed. Also no correlation was found between age of animals and obtained SM values (P = 0.29). Sex has no effect on SM values in studied animals (P = 0.08). Conclusions. Result of this study provided the reference values for strip meniscometry (SM) as lacrimal function test. Based on the results of this study SM can be used as a method of lacrimal function test in dogs because of positive linear correlation with schirmer tear test.
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PurposeTo perform a descriptive investigation of the red-eared slider turtle (Trachemys scripta elegans) eye, performing selected ophthalmic diagnostic tests with the aim of establishing normal reference values for this species.Method Thirty adult healthy red-eared slider turtles were used to establish normal ophthalmic test values in this investigation. Selected ophthalmic tests included: collection of material for bacterial culture analysis, esthesiometry, intraocular pressure (IOP), A- and B-mode ultrasonic biometry, fundus photography, and central corneal thickness (CCT).Results and discussionNormal parameters found for the ocular diagnostic tests were: esthesiometry: 5.84 ± 0.48 cm; IOP: 5.42 ± 1.70 mmHg; CCT: 154.5 ± 0.14 μm; palpebral fissure length: 9.71 ± 0.55 mm; modified Schirmer tear test: 2.55 ± 3.4 mm; globe axial length: 7.60 ± 0.23 mm; anterior chamber depth: 0.76 ± 0.23 mm; lens axial length: 2.45 ± 0.28 mm; vitreous chamber depth: 4.31 ± 0.42 mm. An avascular retinal pattern with nerve fibers radiating from the small white circular optic disk was observed. None of the animals had a conus papillaris. The most frequent bacteria found were Bacillus spp. (33.33%) followed by Proteus vulgaris (20.69%) and Staphylococcus aureus (18.39%). No significant differences between left and right eyes or genders were found for any of the results. Reference data and morphologic observations obtained in this investigation might help veterinary ophthalmologists to diagnose ocular diseases in the red-eared slider turtle.
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Objective: To determine intraocular pressure (IOP) in healthy Hermann's tortoises (Testudo hermanni). Animals: 26 outdoor-housed Hermann's tortoises (13 males and 13 females); body weight ranged from 255 to 2,310 g, and age ranged from 4 to > 50 years. Procedures: After a preliminary ophthalmic evaluation was performed, IOP was measured by means of a rebound tonometer in both eyes of each tortoise. Three measurements were obtained for each eye; successive measurements were obtained from alternate eyes. Each measurement was based on the mean of 6 values automatically provided by the rebound tonometer. Statistical analysis was used to evaluate correlations between variables and to identify sex- or size-related IOP variations, and changes in IOP over multiple measurements. Results: Mean ± SEM IOP of the 52 eyes was 15.74 ± 0.20 mm Hg (range, 9 to 22 mm Hg). Results for t tests did not reveal significant differences in IOP between the right and left eyes or between males and females. A significant moderate negative correlation (r = -0.41; r(2) = 0.169) between IOP and body weight was detected. Results of repeated-measures ANOVA revealed a significant increase in IOP over multiple measurements. Conclusions and clinical relevance: Rebound tonometry was a practical and rapid means of determining IOP in small- to medium-sized tortoises that required minimal manual restraint of the animals. Establishing IOP values in healthy Hermann's tortoises will provide a reference frame for use during complete ophthalmic examinations, thus allowing clinicians to diagnose a broader spectrum of ocular pathological conditions in tortoises.
In this paper the use of the Phenol Red Thread (PRT) tear test is compared to the Schirmer tear test (STT) to establish normal values in the cat. The thread is 75 mm long and is impregnated with phenol red, a pH-sensitive indicator A 3 mm indentation at the end of the thread is inserted into the inferior conjunctival sac for 15 seconds. The slightly alkaline tears are absorbed and turn the pale yellow thread red. Tear production is measured in millimeters. Mean length of absorption for the PRT tear test was 23.04 mm +/- 2.23 mm/15 seconds. Due to little sensation of the thread while in the inferior conjunctival sac, the PRT tear test is theorized to accurately measure rears in the inferior conjunctival sac without the foreign body stimulus of the Schirmer tear test. We found the PRT tear test to be a simple, effective and rapid diagnostic tool for use in cats. The PRT tear rest values in cats are compared to previously established PRT tear test values in dogs.
Objective To evaluate feasibility and accuracy of intraocular pressure (IOP) measurement by rebound tonometry in adult red-eared slider turtles and determine the effects of manual and chemical restraint on IOP. Animal studiedSeventeen adult red-eared slider turtles. ProceduresIntraocular pressure was measured with TonoLab® and TonoVet® tonometers in conscious, unrestrained turtles. To evaluate the effects of manual restraint, turtles were restrained by digital pressure on the rostral head or proximal neck. The effect of two chemical restraint protocols (dexmedetomidine, ketamine, midazolam [DKM] and dexmedetomidine, ketamine [DK] subcutaneously) on IOP was evaluated. Triplicate TonoLab® and TonoVet® readings were compared with direct manometry in three ex vivo turtle eyes. ResultsTonoLab® correlated better with manometry at IOPs < 45 mmHg than TonoVet® (linear regression slopes of 0.89 and 0.30, respectively). Mean (±SD) IOP in unrestrained conscious turtles was significantly lower (P < 0.01) with TonoLab® (10.02 ± 0.66 mmHg) than with TonoVet® (11.32 ± 1.57 mmHg). Manual neck restraint caused a significant increase in IOP (+6.31 ± 5.59 mmHg), while manual rostral head restraint did not. Both chemical restraint protocols significantly reduced IOP (DKM: −1.0 ± 0.76 mmHg; DK: −1.79 ± 1.17) compared with measurements in conscious unrestrained turtles. Conclusions Chemical and manual neck restraint affected IOP. Rostral head restraint had no significant effect on IOP and is, therefore, recommended as the appropriate restraint technique in red-eared slider turtles. TonoLab® measurements estimated actual IOP more accurately, within physiologic range, than measurements obtained using the TonoVet®.
The aqueous fraction of the tear film and the horizontal palpebral fissure length (HPFL) were measured in exotic and laboratory animals, specifically saffron finches (Sicalis flaveola), chestnut-bellied seed-finches (Sporophila angolensis), red-eared sliders (Trachemys scripta elegans), rats (Rattus norvegicus) and mice (Mus musculus). These species possess small eyes making it difficult to perform the typical Schirmer tear test. Measurement of the aqueous fraction of the tear was performed using the standardized endodontic absorbent paper point tear test (PPTT), accomplished with manual restraint by a single operator. The following results were obtained: saffron finches (n = 42)-HPFL (4.46 ± 0.09 mm) and PPTT (5.10 ± 0.26 mm); chestnut-bellied seed-finches (n = 38)-HPFL (4.77 ± 0.05 mm) and PPTT (4.11 ± 0.34 mm); red-eared sliders (n = 56)-HPFL (8.59 ± 0.08 mm) and PPTT (8.79 ± 0.38 mm); rats (n = 60)-HPFL (6.45 ± 0.09 mm) and PTT (6.18 ± 2.06 mm); and mice (n = 22)-HPFL (3.59 ± 0.27 mm) and PPTT (4.39 ± 1.45 mm).
To determine the normal reference range for phenol red thread test (PRTT) values in clinically normal Syrian hamsters (Mesocricetus auratus). Sixteen healthy adult Syrian hamsters (eight males and eight females) were used in this study. Ophthalmic examinations 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. No statistically significant differences between right and left eyes were found for any of the results. The mean ± SD PRTT values for the study population were 6.8 ± 2.5 mm/15 s with a range from 3 to 11.5 mm/15 s. Mean PRTTs in male animals were 5.1 ± 1.2 mm/15 s, whereas mean PRTTs in female hamsters were 8.5 ± 2.3 mm/15 s. Comparison between mean PRTT values in males and females showed a significant difference (P = 0.004). Mean weights for males and females were 80.9 ± 4.8 and 90.6 ± 8.5 g, respectively. No linear relationship between mean PRTT and body weight was found in female (P = 0.46) and male (P = 0.92) hamsters. This study provides novel data for normal reference ranges of PRTT values in healthy Syrian hamsters. Results of this study may assist veterinarians in the diagnosis of ocular surface disease and syndromes affecting the tear film in these species.