What do dry eye tests mean?

Dry Eye is a complicated disease and testing can be complex and confusing. While I can’t interpret your specific tests, I can give a general idea of what tests mean. It is up to the dry eye specialist performing the tests to give the most accurate interpretation for each specific case.

That said, I will review some of the common tests you might find in a dry eye exam from a dry eye specialist. This list is not fully inclusive of all the tests a doctor might perform nor can I indicate every possible result.

History is perhaps the single most important diagnostic “test” we eye doctors (and really, virtually every doctor) have. Aside from determining the prior history, including any attempts to correct the dry eye problems, a validated questionnaire is very useful as it allows us to get a “number” relating to the degree of dry eye symptoms. While there are many such questionnaires, SPEED and OSDI are perhaps among the most common. Using “SPEED” (from https://eyewiki.aao.org/Dry_Eye_Syndrome_Questionnaires), Standard Patient Evaluation of Eye Dryness Questionnaire (SPEED)

“The SPEED questionnaire was designed by Korb and Blackie in order to quickly track the progression of dry eye symptoms over time.[9] This questionnaire gives a score from 0 to 28 that is the result of 8 items that assess frequency and severity of symptoms. The symptoms assessed include dryness, grittiness, scratchiness, irritation, burning, watering, soreness, and eye fatigue. The questionnaire further assesses whether these symptoms were not problematic, tolerable, uncomfortable, bothersome, or intolerable.[10] The questionnaire also monitored diurnal and symptoms changes over 3 months.[11] Validity of the questionnaire was determined by seeing how well it was able to segregate patients based on their symptoms, relative to the OSDI questionnaire (gold standard). The resulting sensitivity and specificity were 0.90 and 0.80 respectively.[11]”

A score of under 6 is considered minor but may still be associated with significant dry eye disease. The higher the number, the more symptomatic the individual. Because symptoms are so subjective, it is impossible to compare one patient’s symptoms to another. However, because the questionnaire is “validated.” It is likely that changes in a patients self-reported symptoms on this score will accurately reflect changes in their disease. We like to see progressive lowering of this score (indicating likely improvement).

Visual Acuity – probably one of the simplest and most underrated of dry eye tests. While 20/20 is considered “normal,” many eyes are capable of “better” - often as good as 20/15 (indicating what the average person can see at 15 feet, this eye can see at 20 feet). When eyes get dry, the surface gets irregular, and vision will suffer. When blinking affects vision (vision fluctuates with blinking), this is a common sign of dry eye disease. Checking for a glasses prescription is often an exercise in futility, as the variable surface gives variable results with almost every blink. A “Pinhole” is often employed to determine the best correctable vision, as this allows the patient to move the tiny hole over a more regular part of the eye, so vision can be optimal. If glasses are of a recent prescription and the pinhole still improves the vision further, this could be a sign of dry eye (or that the first prescription was incorrect). Other disease states (such as diabetes) can also result in fluctuating vision and an inaccurate prescription, so it is up to the doctor to determine the exact cause of blurry vision.

Another test common to most eye exams is most often included with dry eye exams – measuring IOP (IntraOcular Pressure). While a variety of technologies exist to do this, it is important to measure with the same technology each time as the results commonly vary between technologies but are validated within the same device. Average IOP is approximately 10-20 (or 22, depending on the group and the technology being used), measured in millimeters of mercury by convention. The reason this is important is that many times dry eye specialists rely on steroids to get inflammation under control – but steroids can lead to increased IOP and eventually, to glaucoma (the result of elevated IOP, resulting in damage to the nerve connecting our eyes with our brain). Losing that connection will result in permanent lose of vision (& ultimately to blindness).

I’ve blogged on the connection between dry eyes and glaucoma medications, so it should be obvious that patients on glaucoma medications are more prone to dry eye. What is also true, is that approximately 1 out of 10 average people placed on steroid eye drops will eventually (within weeks to months) have elevated IOP related to the steroids (the so-called “steroid responders”). Those with a tendency towards glaucoma (strong family history, and/or a tendency towards elevated IOPs and/or with “susceptible appearing nerves”), will have a likelihood of being a steroid responder as much as 1 out of 2 times. This means it is critical to monitor IOP when patients are being carried on topical steroids – to determine if they are a “steroid responder” and may progress to getting glaucoma. It is important to recognize that IOP is a relative number – and that some eyes may progress to severe glaucoma with IOP numbers that might be “normal” for others – where some patients may appear relatively immune to pressures that might normally cause glaucoma for others – so it is important to work closely with your eye doctors to determine what IOP is good for you.

More tests and interpretations coming next week!