Effects of Sildenafil and Tadalafil on Intraocular Pressure in Sheep: Implications for Aqueous Humor Dynamics

Gerometta, Rosana; Alvarez, Lawrence J.; Candia, Oscar A.

doi:10.1167/iovs.09-4862

Cited by 33 publications

(32 citation statements)

References 18 publications

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“…There are quite a few studies using applanation tonometry in animals (Priehs et al, 1990;Miller et al, 1990;Miller et al, 1991;Dziezyc et al, 1992;Passaglia et al, 2004;Candia et al, 2010;Gerometta et al, 2010;Ribeiro et al, 2010;Rusanen et al, 2010), but we found no reports on the assessment of the mean IOP in healthy sheep using the applanation tonometer Tonopen XL e . The purpose of this study was to determine the mean IOP in healthy adult sheep using applanation tonometry with Tonopen XL e .…”

Section: Introductionmentioning

confidence: 61%

“…The MacKay-Marg applanation tonometer, which is considered the golden standard in Veterinary Medicine, has no longer been manufactured. A portable Mackay-Marg-type tonometer (Tonopen) has been widely used among veterinary ophthalmologists and has been assessed in dogs, cats, horses, and in some extent in sheep (Miller et al, 1990;Priehs et al, 1990;Miller et al, 1991;Dziezyc et al, 1992;Passaglia et al, 2004;Candia et al, 2010;Gerometta et al, 2010;Rusanen et al, 2010); however, a controlled study measuring the baseline IOP in healthy sheep, using applanation tonometry with Tonopen XL e , has not yet been reported.…”

Section: Discussionmentioning

confidence: 99%

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Intraocular pressure measurement in sheep using an applanation tonometer

Pigatto¹,

Pereira

Albuquerque

et al. 2011

Rev. Ceres

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RESUMO Mensuração da pressão intraocular em ovinos, usando tonômetro de aplanaçãoO objetivo deste estudo foi avaliar e estabelecer os valores de pressão intraocular (PIO) média, em ovinos adultos saudáveis, usando a tonometria de aplanação. Foram utilizados no estudo 25 ovinos saudáveis (Ovis aries), da raça Texel, machos ou fêmeas de três anos de idade. Foram realizados exames oftálmicos, incluindo: avaliação dos reflexos pupilares, teste lacrimal de Schirmer, avaliação com lâmpada de fenda e coloração com fluoresceína, em ambos os olhos de todos os animais. Para a realização dos testes oftálmicos, os animais foram contidos pelo mesmo auxiliar, sem pressão na região jugular e as pálpebras foram delicadamente abertas. A PIO foi aferida, utilizando-se o tonômetro de aplanação Tonopen XL, tendo sido todos os exames realizados pelo mesmo examinador. Foram realizadas três avalia- The purpose of this study was to evaluate and establish the mean values of IOP in healthy adult sheep using an applanation tonometer. Information on age, sex, and breed was obtained for all animals included in this study. Twenty five healthy sheep (Ovis aries), of the same breed (Texel), male or female, with three years of age, received an ophthalmic examination in both eyes, including pupillary reflexes, Schirmer tear test, slit lamp biomicroscopy, and fluorescein staining. For all ophthalmic testing, animals were gently physically restrained, with no pressure in the jugular area and the eyelids were carefully open. IOP was measured by applanation tonometry (Tonopen XL). The same examiner performed the tonometry; measurements were taken three times for each eye, and their average was recorded as the IOP of the animal. Statistical analysis was performed using paired t-test and values of P < 0.05 were considered significant. The mean intraocular pressure in the whole group of 50 eyes was of 16.36 +/-2.19 mm Hg. The mean (SD) IOP in the right eye was of 15.96 +/-2.02 mm Hg, while the mean (SD) IOP in the left eye was of 16.76 +/-2.32 mm Hg. Significant differences in IOP were not found between right and left eyes. The applanation tonometer was adequate for measuring the intraocular pressure in sheep. Reference data will assist in diagnosing testing for ophthalmic disease in sheep, as 1 well as promote further studies in this area.

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Section: Introductionmentioning

confidence: 61%

Section: Discussionmentioning

confidence: 99%

Intraocular pressure measurement in sheep using an applanation tonometer

Pigatto¹,

Pereira

Albuquerque

et al. 2011

Rev. Ceres

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“…Later studies were made on felines (Gonçalves et al 2005), rabbits (Liu et al 2007) and sheep (Gerometta et al 2010).…”

Section: Discussionmentioning

confidence: 99%

Biometric, B-mode and color Doppler ultrasound assessment of eyes in healthy dogs

et al. 2018

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B-scan ultrasonography is an important diagnostic tool that allows characterization of internal organ anatomy and, when complemented by Doppler ultrasound, allows vascular hemodynamic assessment, increasing the diagnostic accuracy. Thus, the aim of the present study was the B-scan ultrasound characterization and measurement of the eyeball segments and assessment of the external ophthalmic artery by color and pulsed Doppler. Sixty eyeballs were assessed from 30 dogs of different breeds using an 8.5MHz microconvex transductor. First, biometry was performed by B-scan of the following segments: axial length (M1), anterior chamber depth (M2), lens thickness (M3), lens length (M4), vitreous chamber depth (M5), optical disc length (M6) and optic nerve diameter (M7). Colored Doppler identified the external ophthalmic article and pulsed Doppler assessed its flow, and the following were measured: systolic peak velocity (VPS), final diastolic velocity (VDF), resistivity index (IR) and pulse index (IP). No statistical difference was observed for the biometric values of the eye segments between the right and left eyes (p>0.05). The vitreous chamber depth (M5) was shown to be the biometric variable with greatest bilateral symmetry, varying from 0.79 to 0.87cm and 0.78 to 0.86cm for the right and left eye, respectively. The ophthalmic artery was visualized over the optic nerve towards the eyeball, with flow stained red. There was no significant statistical difference between the Doppler velocimetric values for the ophthalmic artery between the right and left eye of the animals assessed (p>0.05). The mean resistivity index (RI) showed average values equal to 0.63±0.03, bilaterally. The mean base velocity was 17.50cm/s and 18.18cm/s at the systolic peak and 6.21cm/s and 6.68cm/s at the end of the diastole, for the right and left eyes respectively. The anatomic, biometric and hemodynamic characterization using the ultrasound B-scan and the Doppler modalities permitted the ultrasonographic and Doppler velocimetric assessment of the eyeball components in dogs of different breeds, and it can be used in ophthalmic clinical routine to identify eye pathologies.

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“…However, the literature contained anecdotal reports observing an elevated IOP in senior patients (older than 70 years of age) who had taken sildenafil (Yajima et al, 2000). Because of the possibility that potent PDE5 inhibitors may increase IOP in a particular group of individuals, we recently tested the effects of sildenafil (and tadalafil, a longer lasting PDE5 inhibitor) on the IOP of a sheep animal model (Gerometta et al, 2010) Sheep were used because of the similarity to humans for their ocular response to topical glucocorticosteroid instillations and resulting ocular hypertension (Gerometta et al, 2009), which occurs due to a reduction in conventional outflow facility (Candia et al, 2010). Sheep also exhibited a robust increase in IOP one hour after oral ingestion of either sildenafil (50 and 100 mg) or tadalafil (20 mg).…”

Section: Introductionmentioning

confidence: 99%

“…Sheep also exhibited a robust increase in IOP one hour after oral ingestion of either sildenafil (50 and 100 mg) or tadalafil (20 mg). We earlier discussed in detail a potential model to explain the IOP rise secondary to sildenafil treatment (Gerometta et al, 2010). …”

Section: Introductionmentioning

confidence: 99%

Effect of sildenafil citrate on intraocular pressure and blood pressure in human volunteers

Gerometta

Alvarez

Candia

2011

Experimental Eye Research

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Anecdotal reports have suggested that the vasodilator, sildenafil citrate, which evokes its effect via a select inhibition of PDE5, has the potential to increase intraocular pressure (IOP) in some individuals. An ocular hypertensive effect by sildenafil was also recently described in a sheep animal model. In contrast, clinical studies have not found a direct association between sildenafil ingestion (commonly consumed as Viagra) and changes in IOP. However, some such studies also reported no effects of sildenafil on systemic blood pressure (BP) at the time of the IOP determination. Given this surprising result, our purpose was to repeat a study in human volunteers in the city of Corrientes, Argentina to corroborate the effects of sildenafil on human IOP and systemic BP. For the present study, 9 healthy volunteers (male and female, 18 to 74 years old) were selected as subjects after ophthalmic and cardiovascular evaluation indicated that they exhibited normal parameters for their age. In a masked, placebo-controlled study, the subjects ingested 100 mg sildenafil citrate (provided as Vorst from Laboratorios Bernabo, Argentina) in one session, and a placebo on a second separate occasion. IOP was measured with a Goldman applanation tonometer by an ophthalmologist, and BP by a second physician, neither of whom witnessed the tablet ingestion by the volunteers, nor provided with information on the nature of the test compounds. A third individual administered the tablets. The average baseline IOP of this group of 9 was 13.1 ± 0.6 mm Hg. Subsequent to sildenafil ingestion, IOP increased by 26% to 16.5 ± 0.8 mm Hg 60 min later (p< 0.005, as paired data), and returned to control values within 2 hrs. Both systolic and diastolic BP were significantly reduced by sildenafil ingestion. At the point of maximal systemic hypotension (90 min), the systolic and diastolic pressures declined by 15% and 13%, respectively. No significant changes in IOP or BP were recorded after ingestion of the placebo. Our results suggest that sildenafil can elicit a transient IOP increase that may be of importance to patients chronically treated with PDE5 inhibitors for various vascular diseases (e.g., pulmonary hypertension). We discuss possible mechanisms by which PDE5 inhibition might lead to a rise in IOP.

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Effects of Sildenafil and Tadalafil on Intraocular Pressure in Sheep: Implications for Aqueous Humor Dynamics

Cited by 33 publications

References 18 publications

Intraocular pressure measurement in sheep using an applanation tonometer

Intraocular pressure measurement in sheep using an applanation tonometer

Biometric, B-mode and color Doppler ultrasound assessment of eyes in healthy dogs

Effect of sildenafil citrate on intraocular pressure and blood pressure in human volunteers

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