“Dry eye” refers to an ocular surface disease typically caused by an imbalance in the tear film. A common source of dry eye disease (DED) is an insufficient amount of tears or a chemical imbalance that affects the production of tears. In addition to the comprehensive eye exam, we have several objective and subjective tests we can utilize to determine whether a patient has DED.

FIRST, QUESTION THE PATIENT

The first step to diagnosing DED should begin with careful analysis using subjective patient surveys and questionnaires. This includes conducting a preliminary assessment of patients regarding their demographics, past medical history, medications and social history. Risk factors can then be analyzed using surveys based on DED symptoms.

Among these surveys are the Ocular Surface Disease Index (OSDI), Standard Patient Evaluation of Eye Dryness Questionnaire (SPEED) and the Symptom Assessment in Dry Eye (SANDE).

The OSDI is a subjective patient survey made up of 12 items that help evaluate the presence of ocular irritation often associated with DED and the functioning of vision.¹ The test is composed of three sections: ocular symptoms, vision-related function and environmental triggers. The patient’s response is recorded on a scale from 0 to 4 with 0 meaning “none of the time” and 4 being “all the time.” A total score ranging from 0 to 12 is considered normal, a score between 13 and 22 is assessed as mild DED, 23 to 32 as moderate DED, while a score greater than 33 as severe DED.²

The SPEED questionnaire consists of 20 items and records a score between 0 and 28. It gauges the prevalence of dry eyes by assessing the frequency and severity of symptoms, including dryness, grittiness, scratchiness, irritation, burning, watering, soreness and eye fatigue.³ The results of the questionnaire are correlated with the meibomian gland secretion score. Thus, it is a useful diagnostic tool for determination of meibomian gland dysfunction (MGD).⁴

SANDE is based on a visual analog scale that determines the severity and frequency of dry eye symptoms. It consists of two questions that implement a 100-mm horizontal linear visual analog scale. Responses from patients regarding symptom frequency may range from “rarely” to “all of the time,” and the symptom severity from “very mild” to “very severe.”⁵

These comprehensive questionnaires provide assessment of several DED symptoms, including eye discomfort and visual disturbances. Based on these evaluations, diagnostic tests can then be used to assess the classification of the DED, the disease etiology and the severity.⁶

OBJECTIVE TESTS

Following the subjective patient tests, several objective tests are available that can confirm the diagnosis of dry eye and help determine its underlying causes (for a full list, see Table).

One test is tear break-up time (TBUT). This test is performed by adding fluorescein dye to the cornea and examining the tear film by using a slit lamp to scan the eye with a cobalt blue light.⁷ The assessment of evaporative DED is accomplished by measuring the duration between a blink and the appearance of a dry spot in the tear film, a thin fluid layer covering the front part of the eye. In general, a value greater than 10 seconds is within normal limits. A TBUT between 5 and 10 seconds may be an indication of DED if the patient exhibits other clinical symptoms for dry eyes, such as itching, tearing and burning. A TBUT under 5 seconds indicates dry eyes syndrome.⁸

The Schirmer test measures the production of tears. It is performed by placing filter paper strips on the palpebral conjunctiva of the lower eyelids and the bulbar conjunctiva of the eye. Through capillary action, the water in tears travels along the paper strips with the travel rate being proportional to the rate of tear production.⁹ A score of more than 10 mm of moisture in 5 minutes is a general indication of normal tear production, whereas a score of less than 5 mm is an indicator of dry eyes.¹⁰

Matrix metalloproteinase-9 (MMP-9) tests (such as Quidel’s InflammaDry) check tears for MMP-9 protein, a marker for inflammation. The MMP-9 protein is commonly present in elevated levels in patients with DED. To perform this test, a sample of tears is collected into the tester and a blue or red line is displayed, indicating the presence of high levels of MMP-9. The appearance of both a red and blue line indicates a positive test with elevated levels of MMP-9, while the presence of only a blue line indicates a negative test. Through utilizing this test, patients who do not necessarily present with the clinical symptoms of the disease can be diagnosed accurately.

The Meibomian Gland Secretion Score (MGSS) measures the meibum secreted by the meibomian glands. Meibum helps protect the water from evaporating out of the tear film.¹¹ MGD occurs when there is an obstruction to the glands preventing it from secreting a sufficient amount of oil. Without proper treatment, MGD may cause dry eye symptoms. A MGSS score of less than 12 is an indication of MGD and potential source of dry eyes.

Confocal microscopy is an optical imaging technique mainly available at academic centers that uses light from a laser to increase resolution within a narrow plane of focus while blocking light emission from out-of-focus planes. Traditionally used to diagnose Acanthamoeba infections of the eye, it can be helpful in imaging corneal nerves, and especially helpful in imaging overactive corneal nerves. For patients who do not present with typical symptoms but do show signs such as fluctuating vision, this technique can be very helpful and is very useful in assessing neurotrophic keratitis as well.

CATEGORIES OF DED

Patients who present with DED symptoms make up one of the several categories of dry eye symptomatology. The first category is primarily patients who have already been diagnosed with DED or strongly suspect that they have it.

Another category is those presenting with the typical symptoms of the disease, including burning, tearing, itching, a sensation of pressure behind the eyes or presence of mucus.

The third category are those who do not report symptoms but experience vision fluctuations or other signs of DED. Since DED is essentially a disease of the ocular surface, vision fluctuations can be a major sign of light hitting this surface and bouncing off irregularly due to abnormalities of the tear film. For these patients, the subjective tests can be helpful in showing that they have a real disease and gaining treatment compliance.

A fourth category is patients coming in for refractive or cataract surgery. Even if asymptomatic, they may show underlying signs, such as a decreased TBUT or irregular test results from Schirmer’s or InflammaDry, that suggest the presence of DED. In these cases, it is crucial the patient is compliant with a dry eye regimen to optimize the ocular surface in order to obtain accurate measurements for surgery.

The final category is patients experiencing repeated styes. Imaging can help visualize their truncated and abnormal meibomian glands and emphasize the importance of consistent use of warm compresses and lid wipes, as well as treatment such as TearCare (Sight Sciences), LipiFlow (Johnson & Johnson Vision) or iLux (Alcon).

NOW YOU CAN TREAT

Once we determine the diagnose of the patient and determine which category of DED they fall under, we can then effectively treat that patient. But for any intervention to be successful, we must first make the correct diagnosis so that we can tailor the therapy to the patient. OM

REFERENCES

1. Schiffman RM, Christianson MD, Jacobsen G, et al. Reliability and Validity of the Ocular Surface Disease Index. Arch Ophthalmol. 2000;118:615–621. https://jamanetwork.com/journals/jamaophthalmology/fullarticle/413145 . Accessed Mar. 14, 2023.
2. Asiedu K. Rasch Analysis of the Standard Patient Evaluation of Eye Dryness Questionnaire. Eye & Contact Lens: Science & Clinical Practice. 2017;43:394-398.
3. Grubbs JR, Tolleson-Rinehart S, Huynh K, Davis RM. A review of quality of life measures in dry eye questionnaires. Cornea. 2014 Feb;33:215-218.
4. Okumura Y, Inomata T, Iwata N, et al. A review of dry eye questionnaires: Measuring patient-reported outcomes and health-related quality of life. Diagnostics. 2020;10:559. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7459853 . Accessed Mar. 14, 2023.
5. Amparo F, Schaumberg DA, Dana R. Comparison of two questionnaires for dry eye symptom assessment: The ocular surface disease index and the symptom assessment in dry eye. Ophthalmology. 2015;122:1498–1503. https://www.sciencedirect.com/science/article/abs/pii/S0161642015001815 . Accessed Mar. 13, 2023.
6. Craig JP, Nelson JD, Azar DT, et al. TFOS DEWS II report executive summary. Ocul Surf. 2017;15:802-812.
7. Dibajnia P, Mohammadinia M, Moghadasin M, Amiri MA. Tear film break-up time in bipolar disorder. Iran J Psychiatry. 2012 Fall;7:191-193.
8. Lee JH, Kee CW. The significance of tear film break-up time in the diagnosis of dry eye syndrome. Korean J Ophthalmol. 1988 Dec;2:69-71.
9. Brott NR, Ronquillo Y. Schirmer Test. [Updated 2022 May 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK559159 . Accessed Mar. 13, 2023.
10. Miyake H, Kawano Y, Tanaka H, et al. Tear volume estimation using a modified Schirmer test: a randomized, multicenter, double-blind trial comparing 3% diquafosol ophthalmic solution and artificial tears in dry eye patients. Clin Ophthalmol. 2016 May 13;10:879-886.
11. Fu J, Chou Y, Hao R, et al. Evaluation of ocular surface impairment in meibomian gland dysfunction of varying severity using a comprehensive grading scale. Medicine. 2019 Aug;98: e16547. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6709050 . Accessed Mar. 14, 2023.

Yuna Rapoport, MD, is a board-certified ophthalmologist with extra fellowship training in refractive, corneal and cataract surgery. Her academic interests are in dry eye management, specifically pre- and post-refractive and cataract surgery. Email her at yuna.rapoport@gmail.com. Dr. Rapoport reports no relevant financial disclosures.