The Schirmer test or Schirmer tear test (STT) is used to assess tear production, especially in patients with suspected keratoconjunctivitis sicca, dry eye, or tear overproduction. The test works by the principle of capillary action, which allows the water in tears to travel along the length of a paper test strip in an identical fashion as a horizontal capillary tube. The rate of travel along the test strip is proportional to the rate of tear production.[1]

To administer the test, Schirmer test strips are labeled as “L” and “R” for the left and right eyes, respectively. Next, each strip is bent at a 90-degree angle. The patient is instructed to look upward, and the patient’s eyelid is pulled down. The bent end of the test strip is placed in the eye such that it rests between the palpebral conjunctiva of the lower eyelid and the bulbar conjunctiva of the eye. This procedure is then repeated for the other eye. Once both strips have been placed, the patient is asked to keep the eyes gently closed (without squeezing) for five minutes. After five minutes, the patient is asked to open both eyes and look upward so the test strips may be removed. The Schirmer test score is determined by the length of the moistened area of the strips (using the scale packaged with the strips) and the duration of the measurement in minutes.[2] A score of greater than 10 mm in 5 minutes is accepted as normal. A score of less than 5 mm in 5 minutes indicates a tear deficiency.[3]

Some clinical studies have demonstrated that the STT does not reliably detect the efficacy of drugs in patients undergoing treatment for dry eye. This variation has led to the changing methodology of the test and investigations into the cause of the test’s variability. Some of the investigations have included a comparison of the test with eyes open vs. eyes closed,[4][5] eye position,[6] measurement time,[5][7] and the use of anesthesia.[3][8]

The Schirmer test is used in ophthalmic examination to measure tear production for the diagnosis of conditions such as keratoconjunctivitis sicca and dry eye, which can manifest in a number of symptoms such as foreign body or gritty sensations, burning/stinging, tearing, photophobia, and/or intermittent sharp pains in the eyes. Keratoconjunctivitis sicca refers to dry eye in general, as well as inflammation of the conjunctiva and cornea. Dry eye is divided into decreased tear production and increased tear evaporation subtypes, both of which result in an insufficient fluid layer (precorneal tear film) that normally covers the eye. It is the most prevalent ocular condition in elderly patients and one of the most common conditions seen in ophthalmology, with a worldwide prevalence between 5% to 34%. Risk factors for dry eye include refractive surgery, age greater than or equal to 50 years, and female sex. In 2007, the definition of dry eye was updated to designate it as a multifactorial disease involving the tears and ocular surface and causes discomfort or visual disturbance, with potential damage of the ocular surface. It is also accompanied by increased osmolarity of the tear film and an inflammation of the ocular surface.[9][10][11][12]

A positive Schirmer test alone does not definitively diagnose keratoconjunctivitis sicca or dry eye; rather, the diagnosis is made by a combination of subjective history and objective physical findings. There are several different underlying mechanisms that manifest in symptoms of dry eye—likewise, certain tests are better than others at elucidating the cause. Treatment should be tailored to the specific mechanism underlying the patient’s dry eye. All healthcare team members involved in the care of the patient undergoing the STT should share relevant information with each other and especially with the attending physician to ensure a disorder is correctly identified when present. Similarly, the healthcare team should continue to follow up with the patient to evaluate response to therapy, adjusting treatment when appropriate to improve patient outcomes.[13] [Level 1]