In this article, we want to introduce you to a simple but quite effective procedure.

This is a new test to determine the amount of tears produced. This examination is safe and discomfort is minimal.

Since problems associated with tear production deficiencies in animals are common, this test is very popular in veterinary medicine. It was named after its creator, the German ophthalmologist Otto Schirmer in 1903. In dogs the study was first described in 1962. Despite some criticism, it remains the standard for determining the amount of tear production in veterinaryof ophthalmology.

Technique of carrying out

The Schirmer test is performed at the beginning of the examination, before any manipulation of the patient's eye, since bright light or the use of medications can lead to false results.

There are Schirmer tests: 1 and 2. For the first procedure usually use special test strips 5 mm in width and 35 mm in length (Fig.1). They are packaged in 2 or 1 piece in a sterile bag and removed just before the procedure.

Contact with the working part of the test strip should be avoided to avoid bacterial contamination as well as ingestion of fat components from the skin of the hands. With the marked end of the test strip placed in the lateral (lateral) part of the conjunctival arch (under the lower eyelid), taking care to avoid excessive contact with the cornea.

The eyelids can be open or held closed, the latter prevents the test strip from falling out prematurely. The time is set for 1 minute, after which the patch is removed. The result should be read immediately (Figures 2 and 3). This test allows the study of total tear production, which consists of basal (basic) and reflex tear production.

To assess only the former, the Schirmer test 2. Before the examination, a local anesthetic is injected, which almost completely blocks the reflex tear secretion. The lower conjunctival layer is then dried.

Further actions are similar to those described above. The Schirmer 2 test is not widely used in veterinary practice, but is occasionally mentioned in clinical studies.

In some cases it may be difficult to place the test strip in the lower fornix of the conjunctiva due to the presence of volumetric neoplasms, corneal defects, etc. In this case it is acceptable to place the test strip under the upper eyelid.

But it should be taken into account that the normal result will be lower compared to the standard values.

Interpretation of results

Schirmer test values help to diagnose and control such a disease as dry eye syndrome (DOS). But it has other names: "dry" eye, keratoconjunctivitis (CCK).

Results may vary from one source to another. Average values are shown in Table No. 1.

In cats, a large difference in performance is due to the presence of stress. For this reason, the Schirmer test in these animals may be a questionable method and should be considered in the light of clinical manifestations.

Table No. 2: Interpretation of values

Young individuals have lower tear production rates than adults.

It has been determined that age, weight and gender affect tear production. Thus, it has been found that males have higher tear production than females. As for weight, the greater the weight, the higher the Schirmer test values. Age also plays an important role. The tear amount in a pup adds 0.15 mm/min each day until it reaches 9-10 weeks of age.

That is, by this time, puppy tear secretion levels reach normal adult values. The results of the study are shown in Figure 4 (taken from Veterinary Ophthalmology (2010) 13, 5, 321-325).

What are the causes of tear production disorders

So, we have already found out that the Schirmer test values can vary dramatically. Let us now understand the reasons that lead to this.

Signs of increased tear production:

• Irritating factors: conjunctivitis of various etiology; corneal problems (erosions, ulcers); mechanical traumatization (eyelid folding and as a consequence, contact with cornea), incorrectly growing eyelashes (dystychiasis, ectopic eyelashes), tumors; inflammatory processes inside eyes (uveitis, glaucoma); presence of foreign bodies;
• idiopathic epiphora.

Typically, elevated Schirmer test values have no diagnostic value. The most important assessment is for tear deficiency.

Causes of decreased tear production:

• Chronic blepharoconjunctivitis. May lead to lacrimal gland fibrosis (herpes virus type 1 in cats, leishmaniasis in dogs).
• Congenital: aplasia/hypoplasia of the lacrimal gland (Yorkshire terrier, pug and other miniature breeds).
• Drug-induced:
  • Topical/systemic (atropine, NSAIDs);
  • local/general anaesthesia (effect may last up to 24 h).
• Drug toxicity. Sulfonamide preparations (Sulfasalazine, Trimethoprim-sulfa).
• Immune-mediated:
  • local;
  • systemic (Sjögren's syndrome (dry mouth and eyes), systemic lupus erythematosus, leaf blistering, rheumatoid arthritis, hypothyroidism, diabetes, polymyositis and polyarthritis, atopy, glomerulonephritis and ulcerative colitis)
• Breed predisposition to the development of SSH:
  • Cavalier King Charles Spaniel
  • English Bulldog
  • Lhasa apso
  • Shih Tzu
  • West Highland-White Terrier
  • Pug
  • Bloodhound
  • American Cocker Spaniel
  • Pekingese
  • Boston Terrier
  • Miniature Schnauzer
  • Samoyed dog
• Radiation exposure (in the treatment of some tumors).
• Neurogenic. loss of parasympathetic innervation of the lacrimal gland (CN VII) and loss of sensory innervation and other neurological disorders, especially involving lesions of the trigeminal nerve (CN V) and dysautonomia.
• Iatrogenic cause:
  • removal of the lacrimal gland of the 3rd eyelid (often mistaken for an adenoma (tumor) of the lacrimal gland of the 3rd eyelid);
  • prosthetic eye.
• Systemic diseases:
  • plague of carnivores;
  • metabolic diseases: diabetes mellitus, hypothyroidism, hyperadrenocorticism (Cushing's syndrome in dogs).

• Orbital and supraorbital trauma.
• Age-related. senile (senile) atrophy of the lacrimal gland. Risk group: dogs over 10 years of age.

When to perform a Schirmer test

It's time to find out when it's necessary to do the study. The most basic indicator is the presence of a definite clinical picture.

If the pet has manifestations such as:

• Tear production (may be the first symptom of dry eye syndrome);
• mucopurulent discharge of yellow, yellow-green color;
• redness of the conjunctiva;
• itching in the eye area;
• corneal clouding;
• squinting your eyes;
• pigmentous keratitis.

If you find at least one of the above symptoms, you should visit an ophthalmologist who will measure the amount of tears produced.

Particular attention should be paid to owners of the breeds on the list above.

Pets with a history of endocrine diseases (diabetes mellitus, hypothyroidism, Cushing's syndrome) should have a preventive eye examination at least once a year. It should be mentioned that these pathologies can also be the cause of other serious ophthalmic ailments (e.g. cataracts).

Dry eye syndrome is common in animals with various autoimmune skin problems.

And also an indication for this test is the older age of the animal.

And, of course, constant monitoring is necessary for animals with removed 3rd eyelid or 3rd eyelid lacrimal gland, as well as for animals that have undergone surgery for a prosthetic eyeball.

Conclusion

As you can see from the above, Schirmer's test is simple but very useful. Although it is not difficult to perform, it is not advisable to perform the test yourself at home to avoid corneal trauma. And we should not forget that the diagnosis of dry eye syndrome is based on the combination of the clinical picture and the Schirmer's test.

The results may be within normal limits, but the doctor still diagnoses dry eye syndrome. This is due to the fact that this disease is divided into qualitative and quantitative SSI. With qualitative, the amount of tears will be normal, but the quality is unsatisfactory.

In this case all symptoms will be as in standard dry eye syndrome, so it is better to leave these subtleties to a professional. It is in your power to assess the signs of ocular discomfort in a pet and respond in time.

Unfortunately, in practice, specialists perform examinations in advanced stages, which, in turn, worsens the treatment prognosis.

The second way out is to conduct annual preventive eye examinations, especially for animals at risk (see above).

The article was prepared by an ophthalmologist of Belanta Veterinary Clinic

Svetlana Igorevna Formenova .