Ophthalmology Tests
Posted: Tuesday, September 20th, 2022 | Updated: Tuesday, January 10th, 2023
Posted: Tuesday, September 20th, 2022 | Updated: Tuesday, January 10th, 2023
Schirmer Tear Test (STT):
Dogs will typically have a value of more than 15 mm of tear production produced in one minute. In cats, the test may be unreliable due to their tendency to have high sympathetic tone. The STT is typically done prior to any other testing, medications, or manipulation. The test strip is placed in the lower eyelid and most patients will tolerate having it be left in for the length of testing
Intraocular Pressure (IOP):
Dogs and cats normally have intraocular pressures ranging between 20-25 mmHg. With age, this number may lower. The Reichert Tono-Pen AVIA Vet is routinely used in veterinary medicine. To perform verification, hold the Tono-Pen with the transducer pointed directly toward the floor and press the button for five seconds. After the instrument beeps five times, the LCD screen will project the message dn. Hold the instrument steady for 15 seconds. Once the instrument beeps and the LCD screen displays the message UP, rotate it so that the transducer points straight up. If functioning properly, the Tono-Pen will display the message Pass and will beep. If the message displays Fail, repeat the verification process. Press the operating button to prepare the instrument to take a measurement. Always use a new cover for the transducer. These are called Ocu-Films. Once the device is ready to measure, you will see the following message displayed on the screen: ====. Briefly and gently contact the surface of the cornea with the tip of the transducer. The measurement should be displayed afterward
Fluorescein Staining:
A drop of fluorescein stain may be placed on the eye in order to determine if a corneal ulcer is present. If the test is positive, the stain will uptake where the ulcer is present. A light with a cobalt blue filter is best used when interpreting this test
Dazzle Reflex:
The dazzle reflex occurs when a bright light is aimed toward the eye and the patient blinks. This means that the light stimulus has successfully traveled via the retina to the optic nerve and has projected midbrain to initiate the blink reflex. This test is most helpful in patients with cataracts or elevated IOP where the menace response may be unreliable to determine if the patient has vision or not. Due to the dazzle reflex being a subcortical reflex, it's not truly indicative of vision
Pupillary Light Reflex (PLR):
The pupillary light reflex is used to evaluate the ability of the retina to perceive light along with the optic nerve and oculomotor nerve to adjust or respond appropriately. This assesses the functionality of CN II (optic nerve), and CN III (oculomotor nerve)
Palpebral Reflex:
The palpebral reflex is used to evaluate CN V (trigeminal nerve) and CN VII (facial nerve) by gently tapping the medial and lateral areas of the eyelids to elicit the patient to blink
Menace Response:
This test helps to determine whether or not a patient is visual. Some clinicians gently wave their hand toward the eye being evaluated to see whether the patient reacts appropriately by menacing
Dogs will typically have a value of more than 15 mm of tear production produced in one minute. In cats, the test may be unreliable due to their tendency to have high sympathetic tone. The STT is typically done prior to any other testing, medications, or manipulation. The test strip is placed in the lower eyelid and most patients will tolerate having it be left in for the length of testing
Intraocular Pressure (IOP):
Dogs and cats normally have intraocular pressures ranging between 20-25 mmHg. With age, this number may lower. The Reichert Tono-Pen AVIA Vet is routinely used in veterinary medicine. To perform verification, hold the Tono-Pen with the transducer pointed directly toward the floor and press the button for five seconds. After the instrument beeps five times, the LCD screen will project the message dn. Hold the instrument steady for 15 seconds. Once the instrument beeps and the LCD screen displays the message UP, rotate it so that the transducer points straight up. If functioning properly, the Tono-Pen will display the message Pass and will beep. If the message displays Fail, repeat the verification process. Press the operating button to prepare the instrument to take a measurement. Always use a new cover for the transducer. These are called Ocu-Films. Once the device is ready to measure, you will see the following message displayed on the screen: ====. Briefly and gently contact the surface of the cornea with the tip of the transducer. The measurement should be displayed afterward
Fluorescein Staining:
A drop of fluorescein stain may be placed on the eye in order to determine if a corneal ulcer is present. If the test is positive, the stain will uptake where the ulcer is present. A light with a cobalt blue filter is best used when interpreting this test
Dazzle Reflex:
The dazzle reflex occurs when a bright light is aimed toward the eye and the patient blinks. This means that the light stimulus has successfully traveled via the retina to the optic nerve and has projected midbrain to initiate the blink reflex. This test is most helpful in patients with cataracts or elevated IOP where the menace response may be unreliable to determine if the patient has vision or not. Due to the dazzle reflex being a subcortical reflex, it's not truly indicative of vision
Pupillary Light Reflex (PLR):
The pupillary light reflex is used to evaluate the ability of the retina to perceive light along with the optic nerve and oculomotor nerve to adjust or respond appropriately. This assesses the functionality of CN II (optic nerve), and CN III (oculomotor nerve)
Palpebral Reflex:
The palpebral reflex is used to evaluate CN V (trigeminal nerve) and CN VII (facial nerve) by gently tapping the medial and lateral areas of the eyelids to elicit the patient to blink
Menace Response:
This test helps to determine whether or not a patient is visual. Some clinicians gently wave their hand toward the eye being evaluated to see whether the patient reacts appropriately by menacing
Sources:
Reichert Tono-Pen AVIA Vet Quick Reference: Click Here For Document
Reinstein, Shelby. "Do You See What I See? Ophthalmology Exam Basics in Veterinary Medicine." Vetgirl Veterinary CE Blog, October 2021, https://vetgirlontherun.com/ophthalmic-exam-basics-with-dr-shelby-reinstein-dacvo-part-1-vetgirl-veterinary-continuing-education-blog/
Reichert Tono-Pen AVIA Vet Quick Reference: Click Here For Document
Reinstein, Shelby. "Do You See What I See? Ophthalmology Exam Basics in Veterinary Medicine." Vetgirl Veterinary CE Blog, October 2021, https://vetgirlontherun.com/ophthalmic-exam-basics-with-dr-shelby-reinstein-dacvo-part-1-vetgirl-veterinary-continuing-education-blog/