Bovis ISSN 2398-2993

Tonometry

Synonym(s): intraocular pressure

Contributor(s): Sarah Koll , Kristina Mueller

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Introduction

  • Assessment of intraocular pressure (IOP) is an essential diagnostic procedure for a thorough ophthalmic examination.
  • It is particularly useful to distinguish between cases of uveitis and glaucoma (low or high pressure):
    • Glaucoma is a rare disease in cattle, but congenital, hereditary and secondary glaucoma have been described.
    • Glaucoma can develop following an uncontrolled uveitis.
  • Types of tonometry:
    • Digital tonometry (index fingers).
    • Applanation tonometry (Tono-Pen AVIA, Tono-Pen Vet, Tono-Pen XL, Mackay-Marg tonometer, Perkins handheld tonometer.
    • Rebound tonometry (TonoVet).

Uses

Advantages

  • Digital Tonometry assists estimation of IOP and may help to differentiate between obviously soft or hard eyes.
  • Instrumental tonometers are atraumatic, portable and provide accurate and repeatable estimates of intraocular pressures by exerting minimal restraint of the patient if possible.
  • Treatment success can be evaluated in follow up examinations.
  • Rebound and applanation tonometers have demonstrated reliability in normal bovine eyes.
  • Applanation tonometers can be used in any orientation.
  • Rebound tonometers do not require topical anesthesia.

Disadvantages

  • All methods can be affected by blepharospasm, extraocular muscle rigidity, eyelid swelling, eyelid trauma Eyelid surgery: third eyelid flap, retrobulbar disease or enophthalmos.
  • Digital tonometry (using fingers) is subjective.
  • Electronic tonometers are expensive.
  • Applanation tonometers require training to be used correctly and topical anesthesia is necessary.
  • Rebound tonometers require the eye be directed forward to allow positioning of the tonometer parallel to the ground.
  • Animals not used to be handled around the face may shy away. Any tension on the neck or a tilted head position, as well as forcibly opening eyelids can falsely increase electronic IOP readings.
  • The effect of corneal surface disease on the accuracy of applanation and rebound tonometry has been determined in small animals and suggests to perform repeat measurements with the same type of tonometer.
  • The position of the eye in cattle precludes using the Schiotz tonometer.

Requirements

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Preparation

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Procedure

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Aftercare

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Spiessen von L, Karck J, Rohn K, Meyer-Lindenberg A (2015) Clinical comparison of the TonoVet(®) rebound tonometer and the Tono-Pen Vet(®) applanation tonometer in dogs and cats with ocular disease: glaucoma or corneal pathology. Vet Ophthalmol 18(1), 20-27 PubMed.
  • Tofflemire K L et al (2015) Schirmer tear test I and rebound tonometry findings in healthy calves. Vet Ophthalmol 18(2), 147-151PubMed.
  • Andrade S F et al (2013) Intraocular pressure measurements with the Tono-Pen XL® and Perkins® applanation tonometers in horses and cattle. Ciência Rural 43(5), 865-870.
  • Andrade S F et al (2011) Comparison of intraocular pressure measurements between the Tono-Pen XL® and Perkins® applanation tonometers in dogs and cats. Vet Ophthalmol 15, 14-20 PubMed.
  • Gum G G, Gelatt K N, Miller D N, MacKay E O (1998) Intraocular pressure in normal dairy cattle. Vet Ophthalmol 1(2-3), 159-161 PubMed.

Other sources of information

  • Peche N, Eule J C (2016) Intraocular Pressure Measurements in Cattle, Sheep and Goats with Two Different Tonometers. Abstracts: Annual Scientific Meeting of the European College of Veterinary Ophthalmologists, Budapest, Hungary May 19‐22, 2016. Vet Ophthalmol 19(19), E20.
  • Gelatt K N (2013) Veterinary Ophthalmology. Chapter 29 In: Food Animal Ophthalmology, Bovine. Vol. II. Wiley-Blackwell, p 2.


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