Tono-Pen Vet Research Articles

Variation of intraocular pressure comparing rebound (TONOVET Plus®) and applanation (TONO-PEN VET®) tonometry in New Zealand rabbits treated with Amlodipine®

Rabbits have played an important role in ophthalmological research processes, however in the environment there has been a deficiency of sensitive equipment in measurement of intraocular pressure for this species. To compare intraocular pressure (IOP) measured with rebound (TONOVET Plus®) and applanation (TONO-PEN VET®) tonometry in healthy New Zealand rabbits treated with Amlodipine. Twelve healthy male New Zealand white rabbits, 5 months old; two groups with 6 individuals were used in this study. The experimental group was given Amlodipine® at a dose of 5 mg/kg, once a day for a month. Blood pressure and intraocular pressure were measurement before treatment and 6 h after treatment in a period of one month. A trend is noted where the group of animals treated with amlodipine® presents lower values than the control group, both in systolic and diastolic pressure. The systolic pressure of the control group showed an average of 116.5 ± 7.9 mmHg and 117.4 ± 8.9 mmHg and the treatment group showed an average of 113.6 ± 7.9 mmHg and 111.8 ± 10.0 mmHg (pretreatment and posttreatment respectively). Tonometry: the values obtained using the TONOVET Plus® (19 ± 3 mmHg) are on average higher than the values obtained using the TONO-PEN VET® (17 ± 3 mmHg). It was possible to demonstrate the relationship between systemic blood pressure and intraocular pressure in New Zealand white rabbits. Rebound tonometry showed less variability in results than applanation tonometry. This study confirmed that both tonometers are reliable for measuring IOP in rabbits.

Effect of four local anesthetics (tetracaine, bupivacaine, lidocaine and proparacaine) on intraocular pressure in rabbits- Comparison of an applanation and a rebound tonometer

The type of device used, the type of local anesthetic agents, and the animal species may affect the intraocular pressure(IOP). Therefore, in order to determine these issues, the effects of four local anesthetics were investigated in 10 adult rabbits by ICare TA01i and Tono-Pen Vet tonometers. In the right eye of half of the rabbits and in the left eye of the other half of the rabbits, one drop of tetracaine was instilled. The IOP in each rabbit was measured using two tonometers, ICare and Tono-Pen Vet, before and each 5 minutes until 40 minutes later. The effects of other drugs were also studied at least with one-week interval. Based on the results of ICare tonometer, tetracaine significantly reduced the IOP immediately and 25 minutes after instillation. IOP changes after instillation of bupivacaine, lidocaine and proparacaine were not significant at any time compared to baseline values (p > 0.05). Based on the results of Tono-Pen Vet tonometer, all drugs reduced the IOP immediately after use; however, the effects of bupivacaine and lidocaine on IOP were much lower than that of tetracaine and proparacaine. The average duration of corneal anesthesia were 20, 15.5, 7.5 and 21 minutes for tetracaine, bupivacaine, lidocaine, and proparacaine, respectively. It is concluded that IOP reduction by local anesthetics when Tono-Pen Vet is used is much greater than the ICare tonometer measurements. Also, the reduction of IOP with each of the devices when tetracaine or proparacaine is used is greater than when bupivacaine or lidocaine is used.

Effects of sex, eye-side, diurnal variation on intraocular pressure in calves.

The aim of this study was to determine the effects of factors such as sex, eye-side and diurnal variation on intraocular pressure (IOP) values measured by Tono-Pen Vet® in healthy calves. Twenty four (12 males, 12 females) calves were used in this study. IOP measurements were per- formed in the morning (6:00 a.m.) and at night (8:00 p.m). Average IOP values in all calves were measured as 17.67±2.64 mmHg in the morning and 15.52±2.05 at night and the difference between these two time points was found to be statistically significant (p⟨0.0001). Average IOP values were measured as 16.04±2.82 mmHg in males and 17.15±2.23 mmHg in females with a statistically significant (p⟨0.05=0.023) difference between them. Average IOP values were 16.81±2.85 mmHg in right eyes and 16.37±2.23 mmHg in left eyes and the difference between these values were statistically insignificant (p>0.05). At the end of study, overall average IOP in all calves was measured as 16.59±2.59 mmHg. The present data showed a significant difference in terms of sex and diurnal variations and a non-significant difference in eye-side. In addition, this study is the first research article in which the intraocular pressure in calves was measured by Tono-Pen Vet®.

Evaluation of Intraocular Pressure (IOP) Regarding Circadian Rhythm, Age, Sex and Eye Side in Awassi Sheep

Measurement of intraocular pressure (IOP) in domestic animals has become a part of routine eye examination with advent of applanation tonometer. Delayed control of high IOP may lead to permanent blindness due to retinal ganglion cells dysfunction and optic nerve degeneration. This study aimed at evaluating IOP of Awassi sheep with respect to circadian rhythm, age, sex and eye sides and finally to establish a reference (baseline, normal) IOP value for this particular species. A total of 24 healthy sheep with different ages and sexes were used. The animals were divided into 2 equal groups, <1 (6 male, 6 female, n = 12) and ≥1 (6 male, 6 female, n = 12) years old. IOP measurements were performed twice, in the morning (6:00 a.m.) and in the evening (8:00 p.m.) with Tono-pen Vet® applanation tonometer. Mean IOP in the animals decreased from 16.21 mmHg in the morning to 12.65 mmHg in the evening with an approximately rate of 22% (P <0.0001). Comparison of mean IOP values of right eyes (n=12) to the left (n=12), male (n=48) to female (n=48), and ages < 1 (n=48) to ≥ 1 (n=48) showed no difference (P >0.05). The reference IOP for this animal was calculated as 14.43±2.72 mmHg notwithstanding any variable. It was concluded that in this breed IOP values can vary significantly as far as circadian rhythm is concerned and Tono-pen Vet® can be used for sheep IOP measurement as an alternative to other applanation tonometry.

Comparison of Intraocular Pressure Measurement with Schiotz Tonometer and Tono-Pen Vet Tonometer in Healthy Dogs.

IntroductionMeasurement of intraocular pressure (IOP) in dogs has high diagnostic value because of the possibility of detecting ocular and systemic diseases. Various types of tonometers are available for this measurement in small animal practice. The aim of the study was to compare the IOP values measured with Schiotz and Tono-Pen Vet tonometers in healthy dogs. Clinical diagnostic usefulness of both models was also evaluated.Material and MethodsThe examination was performed in 62 eyes in 31 clinically healthy dogs of different races, gender, and ages.ResultsThe values for intraocular pressure obtained with Schiotz tonometer were in the range of 12 to 24 mmHg, with the mean of 16.3 ± 2.1 mmHg. The intraocular pressure measured with Tono-Pen Vet tonometer was in the range of 11–25 mmHg, with a mean of 18.1 ± 3.8 mmHg. The mean results of measurements taken using the two tonometers differed statistically significantly, the difference being 1.79 mmHg and the higher values being read from the Tono-Pen Vet tonometer.ConclusionCorrelation coefficients calculated for the results obtained in the right and left eyes using two tonometers indicated highly correlative relationships between the results. The study shows that both tonometers can be advantageously used in clinical practice to measure intraocular pressure in dogs.

Measurement of intraocular pressure in clinically normal Turkish Shepherd Dogs with the rebound tonometer (TonoVet®) and the applanation tonometer (Tono-Pen Vet®)

The current study was undertaken to establish reference values of intraocular pressure in clinically normal Turkish Shepherd Dogs with the rebound tonometer (TonoVet®) and the applanation tonometer (Tono-Pen Vet®). Twenty-eight dogs (14 male and 14 female, aged 9 months-9 years, 56 eyes) were used in this study. All animals were healthy and showed no abnormalities in ophthalmic examinations, which consisted of the Schirmer tear test, slit lamp bio-microscopy, and fluorescein staining. The animals were restrained manually without using systemic anesthetics or tranquilizers. IOP was measured in both eyes with a TonoVet® and a Tono-Pen Vet®. In normal dogs, the mean IOP values for all eyes were 17.63±3.34 mmHg according to the TonoVet® and 14.95±2.92 mmHg according to the Tono-Pen Vet®. There was no effect of sex, age, or eye side (right vs. left) on the results obtained with either the TonoVet® or the Tono-Pen Vet®. The mean IOP obtained with the rebound tonometer was 2-3 mmHg higher than that measured with the applanation tonometer. The reference data obtained in the present study may assist in diagnostic testing for ophthalmic diseases in Turkish Shepherd Dogs and may promote further studies in this area..

ASSESSMENT OF INTRAOCULAR PRESSURE BY APPLANATION AND REBOUND TONOMETRY IN GUINEA PIGS OF DIFFERENT AGES

Fifty-two guinea pigs (Cavia porcellus) with normal ophthalmic examinations were included in this study to determine whether there are differences in the intraocular pressure (IOP) according to age, while assessing the clinical usefulness of 2 different tonometry methods for this species. The animals were divided into 2 groups according to age: young (4 weeks old, 29 animals) and adult (3 to 36 months, 23 animals). Tonometry was performed oculus utro (OU) in the central cornea according to the manufacturer’s recommendations. Only measurements with low standard deviation (SD < 5%) were included. Rebound tonometry was performed first OU; following topical anesthesia, applanation tonometry was then performed OU. The time required to obtain an IOP value was recorded for each eye. Descriptive statistics were calculated and Lin Concordance Coefficient (LCC) was performed to describe concordance between methods. Mean TonoVet IOP readings were 8.53 ± 1.28mmHg and 13.20 ± 1.28mmHg for young and adult animals, respectively (p < 0.05). Tono-Pen VET readings could not be obtained in young animals, but yielded a mean of 10.93 ± 3.61mmHg in adults. No differences were found between the left and right eyes (p > 0.05) nor between sexes (p > 0.05). TonoVet readings were obtained faster than Tono-Pen VET readings (less than 1min vs 3.38 ± 1.27min, respectively [p < 0.05]). Lin Concordance Coefficient between methods was 0.37 (95% CI: 0.19 to 0.53), documenting a poor concordance between the 2 methods. This study found that normal IOP values are lower in young animals compared with adult animals. Moreover, the results obtained from this investigation demonstrated that TonoVet tonometry is a rapid and well-tolerated procedure when performed on guinea pigs of any age, whereas Tono-Pen VET tonometry is a more time-consuming technique that can only be used on guinea pigs older than 3 months.

Determination of reference values for intraocular pressure and Schirmer tear test results in clinically normal domestic donkeys (Equus asinus)

This study was conducted to establish normal reference range for the Schirmer tear test (STT) and intraocular pressure (IOP) in clinically normal donkeys for use in clinical practice. Sixteen adult...

Effect of body position on intraocular pressure in clinically normal cats.

Objectives The objective of this study was to investigate the effect of body position on intraocular pressure in clinically normal cats. Methods Sixteen clinically normal cats without any ocular abnormalities were used in this study. Cats were sequentially placed in three different recumbency positions (sternal recumbency, right lateral recumbency and dorsal position). For each of the three body positions, intraocular pressure (IOP) was recorded in the left eye using a Tono-Pen Vet tonometer (Reichert). Results Mean IOP readings in cats in the sternal recumbency, right lateral recumbency and dorsal positions were 15.6 ± 4.1, 16.6 ± 6.4 and 18.6 ± 6.8 mmHg, respectively. A significant increase was observed in IOP in cats in the dorsal position compared with the IOP observed in cats in sternal recumbency ( P = 0.01) and right lateral recumbency ( P = 0.04). There was no significant difference between the IOP recorded in the lateral recumbency and sternal recumbency ( P = 0.17) positions. Conclusions and relevance Body position has a significant effect on the IOP of cats. IOP increases when cats are placed in dorsal recumbency.

THE ADVANTAGES OF USING THE TONO-PEN VET TONOMETER IN THE MEASUREMENT OF IOP IN VETERINARY PRACTICE

Objective The aim of this study was to evaluate and to validate the accuracy of the Tono-Pen Vet applanation tonometer in the measurement of IOP in dogs and to observe the advantages and disadvantages of using the Tono-Pen Vet tonometer in clinical practice.Animals Both eyes of 41 conscious and healthy dogs were evaluated.Procedure Readings of IOP were taken using tonometry (measured with a Tono-Pen Vet applanation tonometer). The IOP measurement with Tono-Pen Vet tonometer in conscious dogs was accomplished by instillation of 0,5% Alcaine eye drops.Results The mean IOP readings with the Tono-Pen Vet were 18,5 ± 3,7 mmHg (range 11,5 – 24,5 mmHg).The correlation coefficient (r²) between both eyes was 0,26826 in dogs.Conclusion Mean values measured by Tono-Pen Vet where in the correct range for dogs, but we conclude in comparison with the data of other studies, that values measured with a Tono-Pen Vet could be 5-6 mmHg higher than measured by another tonometers, like Perkins or TonoVet.The advantages of using the Tono-Pen Vet tonometer include the ease of taking the IOP measurement reading, ease of visualization of measurement readings, ease of disinfecting and long-term battery life. The disadvantages include frequent calibration, reduced accuracy and underestimation of true IOP compared to manometry and cost of the Tono-Pen Vet is higher, than for example Schiotz Tonometer or Perkins.

Clinical comparison of theTonoVet®rebound tonometer and theTono‐PenVet®applanation tonometer in dogs and cats with ocular disease: glaucoma or corneal pathology

To compare the TonoVet(®) rebound tonometer with the Tono-Pen Vet(®) applanation tonometer in a larger number of glaucomatous eyes and to evaluate the effect of different corneal pathologies on both tonometers. In 26 eyes with clinical signs of glaucoma, intraocular pressure (IOP) was measured using the TonoVet(®) followed by the Tono-Pen Vet(®) . In 29 eyes with focal corneal pathology (e.g., corneal scarring, edema, pigmentation), both tonometers were used successively to measure IOP in one unaffected area of the cornea, as well as on the lesion itself. Impact on measurement results was assessed comparing the deviation in IOP readings of each tonometer between the two localizations. Statistical data analysis included paired t-tests and regression analysis using sas software (version 9.2; SAS Institute, Cary, NC). In glaucomatous eyes, the TonoVet(®) consistently yielded higher values of IOP than the Tono-Pen Vet(®) as can be quantified by the regression equation IOP (TonoVet(®) ) [mmHg] = 1.12 * IOP (Tono-Pen Vet(®) ) [mmHg] + 11.5 with R(2) = 0.91 and P < 0.0001. Depending on the type and degree of corneal pathology, the deviation in IOP resulting from measurements on altered cornea ranged from -6 to 16 mmHg for the TonoVet(®) and -7 to 20 mmHg for the Tono-Pen Vet(®) , respectively. On average, the effect of corneal disease on IOP measurements was lower for the TonoVet(®) by 1.14 mmHg. Rebound tonometry appears to be a valuable alternative to established applanation tonometry in patients with ocular disease such as glaucoma and corneal disorders. In patients suffering from glaucoma, the same type of tonometer should be used for follow-up examinations, as measurement results of the TonoVet(®) and the Tono-Pen Vet(®) differ substantially with increasing IOP. Corneal pathology has considerable influence on both tonometers with the degree of over- or underestimation of IOP depending on the alteration of biomechanical properties of the cornea inflicted by various corneal pathologies.

Evaluierung des Tonovet®-Reboundtonometers in der klinischen Anwendung bei Hund und Katze

To evaluate the Tonovet® rebound tonometer in a larger number of dogs and cats free of ocular disease and to examine the impact of handling errors of the tonometer. In 100 ophthalmologically healthy dogs (n = 80) and cats (n = 20) of different breeds (beagle, dachshund, retriever, brachycephalic dogs, domestic shorthair cats), the intraocular pressure (IOP) was measured bilaterally using the Tonovet® according to the manufacturer's instructions. Subsequently, different aspects of handling/positioning were altered (localisation and angle of impact, distance of probe to corneal surface). Finally a comparative measurement was made using the Tonopen Vet® applanation tonometer. Mean IOP ± standard deviation (SD) in the dogs (160 eyes) was 13,7 ± 2.9 mmHg for the Tonovet® and 12.9 ± 3.1 mmHg for the Tonopen Vet®. In the cats (40 eyes) a IOP value of 16.7 mmHg ± 3.0 mmHg was obtained with the Tonovet® and 17.4 mmHg ± 3.0 mmHg with the Tonopen Vet®. Deviation from the manufacturer's recommendations on handling the Tonovet® during the measurement significantly affected the results obtained. Compared to the reference measurement, directing the Tonovet® onto the peripheral cornea (approximately 1.5 mm from the limbus) as well as reducing the measuring distance to <4 mm resulted in slightly elevated IOP readings. Substantial underestimation of IOP occurred with angular deviation of the measuring axis. The Tonovet® rebound tonometer proved to be a valuable alternative to conventional tonometers for clinical use in dogs and cats. It is well tolerated by both canine and feline patients. However, the use of the Tonovet® in a clinical setting requires the examiner to consider potential sources of error when handling the tonometer to avoid false IOP readings.

DETERMINATION OF REFERENCE VALUES FOR INTRAOCULAR PRESSURE AND SCHIRMER TEAR TEST IN CLINICALLY NORMAL OSTRICHES (STRUTHIO CAMELUS)

The purpose of this study was to establish normal physiologic reference values for intraocular pressure (IOP) and Schirmer tear test (STT) results in clinically normal ostriches (Struthio camelus). Twenty ostriches of both sexes, 10 juveniles (1.5-2 yr of age) and 10 adults, were included in this study. Complete ophthalmic examination was performed prior to this investigation. STT was performed by inserting a standard sterile STT strip over the ventral lid margin into the ventral conjunctival sac for 60 sec. Following the STT, IOP was measured using applanation tonometry with the Tono-Pen Vet tonometer after topical instillation of one drop of 0.5% proparacaine ophthalmic solution. The mean +/- SD and range of Tono-Pen readings of IOP for all birds was 18.8 +/- 3.5, with a range of 12-24. Mean IOP in juvenile ostriches was 19.7 +/- 3.6. Mean IOP in adult ostriches was 16.9 +/- 2.9. There was no statistically significant difference between young and adult birds (P = 0.07). The mean STT values in the present study were 16.3 +/- 2.5 mm/1 min when measurements from both eyes were averaged. Mean STT in juvenile and adult ostriches was 15.4 +/- 1.8 and 17.2 +/- 2.9 mm/1 min, respectively. There was no statistically significant difference between young and adult birds (P = 0.11). No statistically significant differences between genders were found for any of the results (P > or = 0.41). In conclusion, this study provides normal reference range values for STT and IOP in clinically healthy ostriches.

Evaluation of a rebound tonometer (Tonovet®) in clinically normal cat eyes

To determine the accuracy of and to establish reference values for a rebound tonometer (Tonovet) in normal feline eyes, to compare it with an applanation tonometer (Tonopen Vet) and to evaluate the effect of topical anesthesia on rebound tonometry. Six enucleated eyes were used to compare both tonometers with direct manometry. Intraocular pressure (IOP) was measured in 100 cats to establish reference values for rebound tonometry. Of these, 22 cats were used to compare rebound tonometry with and without topical anesthesia and 33 cats to compare the rebound and applanation tonometers. All evaluated eyes were free of ocular disease. Both tonometers correlated well with direct manometry. The best agreement with the rebound tonometer was achieved between 25-50 mmHg. The applanation tonometer was accurate at pressures between 0 and 30 mmHg. The mean IOP in clinically normal cats was 20.74 mmHg with the rebound tonometer and 18.4 mmHg with the applanation tonometer. Topical anesthesia did not significantly affect rebound tonometry. As the rebound tonometer correlated well with direct manometry in the clinically important pressure range and was well tolerated by cats, it appears suitable for glaucoma diagnosis. The mean IOP obtained with the rebound tonometer was 2-3 mmHg higher than that measured with the applanation tonometer. This difference is within clinically acceptable limits, but indicates that the same type of tonometer should be used in follow-up examinations in a given cat.

Effect of topical 0.5% betaxolol administration on intraocular pressure in clinically normal dogs

The aim of this study was to determine the effect of topically applied 0.5% betaxolol on intraocular pressure (IOP) in clinically normal dogs. Ten adult crossbred dogs without physical or ocular abnormalities were used in this study. Baseline IOPs were determined with the use of a Tono-Pen Vet. One drop of 0.5% betaxolol was administrated to a randomly chosen eye. All animals had their IOP measured at 15, 30, 60, 120, 360, and 720 min post-drug-administration. Results indicated that, 15 min after treatment, there was a significant decrease in IOP from baseline values in the treated (17.90 ± 2.12 mmHg) and untreated (21.20 ± 1.90 mmHg) eyes. The peak effect of topical 0.5% betaxolol in treated eyes was observed 2 h after treatment. We conclude that a single dose of topically applied 0.5% betaxolol significantly decreases IOP in the treated and contralateral eye in this small population of dogs.