The eye is a mirror of health and should never be considered separately as an organ, but rather as an organ that projects the general state of the body. Lesions in the eye are often the result of life-threatening pathological conditions, whether the eye is the primary cause of the disease or eye is the organ in which the systemic disease is manifested.
Also, even if the eye disease is not a life-threatening condition, the dog with vison issues or ocular pain, is not a happy dog. Such a pet will spend more time asleep, will be moody and inactive, and its daily activities will become hateful or possibly dangerous.
It is common for owners to be unaware of how much of a problem their pet has, until they visit an ophthalmologist. Only after the problem has been cured, then do you notice changes in your pet, you notice that it is more playful and that it has “rejuvenated”. For that reason, a detailed and professional general clinical examination of a dog or cat and a detailed and professional ophthalmological examination is necessary for a precise diagnosis and decision on therapy.
A detailed eye examination should include all or some of the following steps:
- Carefully taken medical history
- Ophthalmological examination
- Special diagnostic tests
Each medical examination starts with detailed medical history. All information, including the breed, age, sex of the patient, previous medical history, information on current therapy or recent therapy, information on travel or change of residence as well as everything noticed by the owner regarding the general condition of the patient and/or changes in eye or eyes, or changes in the quality of the vision must be carefully documented.
The ophthalmological examination includes:
- Examination of the eye by palpation and retropulsion
- Evaluation the light reflex of the pupil
- Evaluation of the palpebral reflex, which involves blinking after a tactile stimulus
- Menace response – (examination of blinking reflex to the rapidly approaching of object)
- Dazle reflex- (blink caused by strong focal light directed at the eye)
- Schirmer test- test which determines the tear film quantity
- Fluorescein test to determine the presence of corneal ulcers
- Cannulation of the lacrimal system to evaluate its patency
- Tonometry-test which evaluates the pressure within in the eye (intraocular pressure)
- Conjunctival and corneal cytology and microbiology
- Ophthalmoscope eye examination
- Examination of the eye with a slit lamp
- Electroretinography (ERG)
- Ultrasound examination of the eye
If the additional evaluation of the vision is needed, the veterinary ophthalmologist will perform a “Maze test with obstacles” or a test with a cotton ball, as well as an electroretinogram and ultrasound examination of the eye, especially if the front segment of the eye is not transparent. An electroretinogram is necessary for us to diagnose diseases that can lead or have led to vision loss.
Special diagnostic tests
Many eye diseases are a repercussion of systemic diseases, so when an ophthalmologist suspects such conditions, he or she should check the patient’s complete blood count and biochemistry, determine the endocrine status, perform allergy tests or tests for the presence of infectious diseases. Sometimes, in order to make a diagnosis, it is necessary to perform cytological and microbiological examinations, sample tissues for histopathology evaluation, examine certain regions of the body with ultrasound, X-ray, computed tomography (CT scanner), magnetic resonance imaging and perform other necessary diagnostic tests.
Schirmer tear production test
Schirmer tear test determines the tear film quantity and includes the following tools and steps:
- Schirmer tear film quantity test strips (normal value for dogs is> 15 mm / min; normal value for cats is between 8 and 15 mm / min)
- Break the strip while it is still packed to avoid contamination of the strip with grease from the skin which can artificially change the test values
- Insert the tape into the fornix of the lower eyelid
- Close the eyelids for one minute, after which the production of tears can be read from the calibrated scale
The photographs show patient fixation methods to ensure a safe clinical examination in aggressive patients
Tear production is evaluated with Schirmer test
Pupil reflex testing with chromatic light
Jones test is used to detect obstruction of the nasolacrimal ducts. Fluorescein is placed in both eyes and a trace of fluorescein should appear from both nostrils within 5-10 minutes.
In the dog in the picture, we see that fluorescein appears from the right nostril, while the left one remained uncolored and dry, so we can conclude that for some reason the nasolacrimal system of the left eye is not patent
Examination of the dog by ultrasound biomicroscopy
This technique allows a detailed examination of the anterior chamber of the eye and drainage structures for the aqueous humor, which can determine the predisposition for primary hereditary glaucoma, or detect the presence of tumors of the anterior part of the eye at a very early stage
The dog is under general anesthesia because it is prepared for the surgery, and the ultrasound examination is performed prior to surgery. Under other circumstances, neither general anesthesia nor sedation is necessary for this type of examination.