If you have dry eye, it is important that you have this checked out. While, in most cases, it is not a serious condition (albeit uncomfortable), you should never gamble with your eyes. Additionally, by having tests completed, you will be able to identify the cause of your dry eye and find the appropriate treatment.
Different tests and procedures may be completed, including a comprehensive eye exam, a measurement of your tear volume, and a measurement of the quality of your tears. The table below highlights some of the things that a doctor would be looking at.
|What They Look At||Discomfort Level 1||Discomfort Level 2||Discomfort Level 3||Discomfort Level 4|
|Discomfort||Mild, every once in a while, if stressed||Moderate, can be chronic, appears without stress||Severe, constant, no stress||Disabling|
|Visual||Some fatigue||Limiting fatigue||Chronic fatigue||Disabling fatigue|
|Tear break-up time||Variable||Less than 10 seconds||Less than 5 seconds||Immediate|
Let’s take a look at some of the tests in greater detail.
Tear Breakup Time (TBUT)
The TBUT test is possibly the most important one. A strip is inserted into the eye to moisten it with tears. A device such as the Oculus Keratograph 5M will then measure the TBUT itself. If less than 10 seconds, it is classed as abnormal and indicative of dry eye or other more serious condition.
Different types of stains are used to better view devitalized, dead and healthy cells in the eyes. In a healthy eye, the cornea will stain more than the conjunctiva. In people with dry eye, the conjunctiva is generally more intensely stained. This is an indication of Meibomian gland dysfunction, or MGD, which means the patient will need treatment in order to have proper tear production. Different dyes are used for this staining, each with their own specific pros and cons.
The Schirmer Test
This test is designed to measure whether sufficient tears are produced in order to properly moisturize the eye. As with the TBUT, a strip of paper will be place in the eye, after some numbing drops have been used. There are different ways in which ophthalmologists perform this test, although it usually involves closing the eyes gently for a period of time. It is important to not rub the eyes or close them too tightly, as this may invalidate results. If, after five minutes, there is more than 10 mm of moisture on the paper, tear production is normal. Abnormal results are common, however, and may point to:
- Corneal ulcers and infections
- Climate changes
- Laser vision correction
- Infections, such as conjunctivitis
- Eyelid or facial surgery
- Rheumatoid arthritis
- Vitamin A deficiency
- Sjogren’s syndrome
The Schirmer test is one of the most commonly used tests to determine whether or not dry eye is present. Unfortunately, if results are abnormal, the test does not indicate what could be the cause of this abnormality. It is important, therefore, to not rely solely on this test. Interestingly, the test, which has been used for over a century, has recently been found to miss a lot of people who actually do have dry eye, particularly those who do produce a lot of tears, just not of the right quality.
Tear Component Tests
If it is suspected that someone does indeed have dry eye, for instance, because of the results of any of the tests above, further tests can be done to determine exactly what is causing the dry eye.
Firstly, there is the lipid component test. The eye has several Meibomian glands, which when squeezed, release an oily substance. This can be checked through a gas chromatography with mass spectroscopy test, or a high pressure liquid chromatography test.
Then, an ophthalmologist may want to check the aqueous or watery content of the tear. Different tests will measure how much protein is present in the tear. Some 20% to 40% of this protein should by lysozyme. If less (or more) is present, this could indicate a problem. At the same time, however, it could point towards bacterial conjunctivitis, herpes simplex keratitis and Meibomitis. This further demonstrates the fact that it is never possible to rely on just a single test. However, one study looked at 314 people aged between 18 and 82 years. They had all the tests above performed. It was found that tear osmolarity was the most adequate diagnostic available for dry eye syndrome. This is because it is a lot more sensitive.
Then, there is the mucin component test, which is used through a variety of techniques using complex ophthalmology equipment. What this measures is how many goblet cells are present, whether the epithelial cells increase, specifically their cytoplasm to nucleus ratio, and it looks at keratinization. This is a very sensitive technique and only very few ophthalmologists have been properly trained on it.
The matrix metalloproteinase 9 test, or MMP-9, may also be used. This is a particularly beneficial test for determining dry eye syndrome in contact lens wearers. Recently, the technology has advanced significantly and it is now incredibly popular because it requires minimal training, takes only around 20 minutes to complete, and can be performed in any setting. The machine used for it, the InflammaDry, by Rapid Pathogen Screening, Inc., was approved by the FDA in December 2013. The test only takes two minutes to complete and results are available within just 20 minutes. People who have dry eye have consistently been shown to have elevated scores on the MMP-9 test.
Another test is meibography, which can be done with a variety of different devices. Essentially, these tests are designed to enable ophthalmologists to determine how well the Meibomian glands are performing. This can be an excellent indication of dry eye.
There are a number of other tests available as well, including:
- TSAS (tear stability analysis system), to determine how stable the tear film is
- Evaporimetry, which measures how quickly tears evaporate
- TFI (tear function index), which measures the dynamics of the tears and looks at how well tears drain
- TFT (tear ferning test), which also looks at the quality of tears. This is particularly suitable for the diagnostics of hyperosmolarity and dry eye syndrome and is completed by observing and classifying the way tears crystallize.
- Meiboscopy or meibography, which determines whether or not the Meibomian gland is functioning properly
- Meniscometry, whereby the cross-sectional area, height and radius of the tear meniscus is measured. This is done with a specific type of imaging device.
- Measuring the thickness of the central cornea, which is often reduced in people who suffer from dry eye syndrome
- Fluorophotometry, whereby the tear turnover rate is measured to see whether the tears evaporate too quickly.
Resources and References:
Dry-Eye Diagnosis: 21st Century Tools – Diagnosis of dry eye. (Review of Ophthalmology)
The Pros and Cons of Dry-Eye Tests – Advantages and disadvantages of dry eye tests. (Review of Ophthalmology)
The Challenge of Dry Eye Diagnosis – Problems with dry eye diagnosis. (NIH.gov)
Comprehensive Adult Medical Eye Evaluation Preferred Practice Pattern Guidelines – Guidelines for eye evaluation of adult patients. (American Academy of Ophthalmology Preferred Practice Pattern Committee)