Dry Eye Research in 2020: 33 Notable Human Studies

The 2020 picture

What the research shows

The 2020 research connected dry eye with population burden, environmental conditions, clinical pain, and diverse tear-film mechanisms. Controlled studies offered useful treatment comparisons, but many were small or followed patients only for weeks. Biomarker and imaging results offered promising tools for more precise diagnosis.

Treatment comparisons

The 2020 trials differed in treatment intensity, follow-up, and what they measured. For a clinical takeaway, between-group results matter more than improvement in both groups or change from baseline alone.

1. Intense pulsed light: four or five flashes versus placebo

   A double-masked randomized trial enrolled 87 people with meibomian gland dysfunction to compare pulsed-light regimens and placebo through day 105. Symptom and lipid-layer measures improved in active treatment groups, with some earlier changes in the five-flash group. The abstract emphasizes changes within groups more than a single placebo-adjusted main effect, so it should not be read as proof that every regimen is superior.

2. Perfluorohexyloctane and tear-film thickness

   A single-masked randomized study assigned 48 patients with mild to moderate dry eye to perfluorohexyloctane or preservative-free saline drops four times daily for four weeks. Tear-film thickness rose more with the water-free drop; other symptoms and signs improved in both groups without clear between-group differences. The measured film effect does not establish superior symptom relief.

3. Lifitegrast versus thermal pulsation for inflammatory gland disease

   A single-center, single-masked trial randomized 50 patients with inflammatory meibomian gland dysfunction to six weeks of lifitegrast or one thermal-pulsation procedure. Dryness, corneal staining, and lid redness improved more with lifitegrast by day 42. The small, short comparison applies to the study's inflammation-selected patients and does not settle longer-term treatment choices.

4. Comparing two pulsed-light schedules

   Sixty-two people with gland-related dry eye were randomized to two intense-pulsed-light protocols with different pulse patterns and visit schedules. Both groups improved from baseline; the optimal-pulse group had better meibum and some tear-breakup measures at follow-up. Because dose and schedule differed together and there was no sham arm, the trial cannot isolate which component mattered.

5. Sham-controlled gland probing in refractory disease

   A double-masked randomized trial assigned 42 patients with refractory obstructive gland dysfunction to probing with steroid-antibiotic ointment, probing with lubricant, or sham probing with lubricant. At four weeks, symptom gains were clearest in the probing plus medicated-ointment group; most objective signs did not significantly change. The design cannot fully separate probing from the ointment's contribution in that group.

6. Lubricant drops around cataract surgery

   A multicenter open-label trial randomized 45 cataract patients with healthy or mildly dry ocular surfaces to an antioxidant lubricant regimen or no tear substitute, starting before surgery. Tear breakup and symptom scores favored lubricant through two weeks after surgery; Schirmer and osmolarity did not clearly differ. The small unmasked study leaves longer-term value uncertain.

7. Preservatives in glaucoma drops over two years

   Thirty-six treatment-naive glaucoma patients were randomized to preservative-free, polyquad-preserved, or benzalkonium-chloride-preserved drops and followed for two years. Tear and conjunctival inflammatory signals rose more with benzalkonium chloride, beginning within months. This long follow-up connects medication formulation to surface inflammation, but the small groups were not a dry-eye treatment trial.

Population studies, daily burden, and exposures

Reported prevalence changes sharply with the population and diagnostic rule. These observational studies identify associations and practical burdens, not simple causes.

8. Symptoms and signs in the northern West Bank

   Investigators interviewed and examined 769 adults across 16 towns in the northern West Bank. Using an OSDI threshold plus at least one abnormal tear or staining test, 64% met the study's dry-eye definition, with higher rates in women and older adults. The striking figure depends on a relatively broad rule and this regional sample; it is not a universal prevalence estimate.

9. Age and dry-eye signs in a community sample

   A registry-based cross-sectional examination of 1,331 community residents linked older age with multiple dry-eye signs. Statistical cutoffs suggested gland findings could appear at younger ages than aqueous deficiency or staining. Because everyone was examined once, the study cannot actually establish the order in which an individual's disease develops.

10. Climate and dry-eye severity in DREAM participants

    Researchers matched repeated dry-eye measurements from 535 DREAM trial participants to government weather and pollution data across five climates. Lower humidity tracked more corneal staining, and several weather measures tracked tear breakup, but pollutant associations were mixed and symptoms did not correlate clearly with individual environmental measures. Geographic correlation does not prove personal exposure effects.

11. Patient-reported burden in a U.S. online survey

    An online cross-sectional study compared 1,003 U.S. adults reporting dry eye with 1,006 without it. The dry-eye group reported worse vision-related function and general health, and greater discomfort within that group tracked more work impairment. Self-reported diagnosis and comorbidity differences make this a burden estimate, not a causal measure.

12. Risk factors differ between aqueous and gland-related dry eye

    A New Zealand community study examined 372 residents using consensus-based definitions. Rheumatologic disease and antidepressant use were associated with aqueous tear deficiency; age, migraine, thyroid disease, and other factors were linked to meibomian gland dysfunction. The subtype-specific pattern is useful for clinical history taking, but the cross-sectional sample is too small for broad causal claims.

13. Dry-eye symptoms and depression in an app cohort

    A Japanese smartphone-app survey analyzed 4,454 users. Greater self-reported dry-eye symptom severity was associated with higher odds of depressive symptoms after adjustment for measured factors. Volunteers with an iPhone app were not a representative population, and the survey cannot show which condition preceded the other.

14. Sun exposure and dry eye across India

    A population-based cross-sectional study examined 9,735 Indians aged 40 or older in plain, hill, and coastal regions. Dry-eye prevalence under its symptom-and-sign definition was 26.2%, with large regional differences; longer sunlight exposure and indoor smoke were among adjusted associations. Geography and exposure were observed together, so residual environmental and socioeconomic differences remain possible.

15. Dry eye within a psychiatric-care cohort

    A Taiwanese claims analysis studied 75,650 patients with psychiatric diagnoses; 3,665 also had a coded dry-eye diagnosis and lubricant prescription. Dry eye was more common in several psychiatric subgroups and with some medication patterns. Claims definitions omit undiagnosed symptoms, and treatment or shared health factors may account for associations.

16. Dry-eye symptoms during breast-cancer treatment

    A cross-sectional questionnaire comparison included 200 women receiving adjuvant breast-cancer treatment and 200 age-matched controls. Symptomatic dry eye was reported by 59% of the treatment group versus 25.5% of controls, with more symptoms after additional treatment cycles. The design does not isolate a specific drug or prove treatment caused each symptom.

17. Outdoor pollutants and changes in dry-eye signs

    A prospective observational study repeatedly examined 43 South Korean dry-eye patients while estimating outdoor pollutant exposure near their homes. Ozone and fine particles tracked greater discomfort, while larger particles tracked shorter tear breakup. The small sample and address-based exposure estimates limit causal interpretation, but the distinct pollutant patterns warrant further study.

18. Activity, sitting, and screen time in a large Japanese cohort

    Researchers analyzed baseline survey data from more than 102,000 Japanese adults aged 40 to 74. Greater physical activity was associated with slightly lower odds of dry eye, while more sedentary time and visual display use tracked higher odds. Because exposure and dry-eye status were assessed together, the study cannot show that changing activity or screen time would prevent the condition.

19. Dry-eye signs and symptoms at age 45 in the Dunedin cohort

    The Dunedin birth cohort assessed 885 New Zealanders at age 45 with symptom questions and ocular-surface tests. About 9% met its dry-eye case definition, while some participants had abnormal signs without symptoms, showing how prevalence changes with the chosen definition. One age group in one cohort cannot provide a general population estimate across adulthood.

20. Dry-eye diagnoses among people using sleep-apnea masks

    A U.S. claims analysis followed more than 350,000 people using CPAP or other nasal-mask therapy for sleep apnea. New recorded dry-eye diagnoses accumulated over time, reaching about 10% by three years, particularly among older patients and women. Claims data miss undiagnosed symptoms, and the lack of an untreated comparison group means the increase cannot be attributed to masks alone.

Clinical course and lived symptoms

Surgery, screen work, contact lenses, and pain can change the patient's experience even when a familiar tear measure changes little.

21. Dry eye shortly after cataract surgery

    A prospective series followed 120 cataract patients who did not meet the study's dry-eye definition before surgery. Symptoms and tear measures worsened at one week and mostly recovered by one month, with differences between surgical techniques. The lack of an unoperated comparison makes the precise contribution of surgery and postoperative drops uncertain.

22. Expressible glands and symptom burden in clinic patients

    A clinical audit collected initial-visit data from 2,346 newly referred dry-eye patients. Among measured signs, fewer glands yielding liquid meibum and more lower-lid papillary change independently tracked higher symptom scores; Schirmer and tear breakup did not. Referral selection and the cross-sectional design prevent calling gland dysfunction the sole cause of symptoms.

23. Early dry-eye effects of LASIK versus SMILE

    An observational study followed 16 FS-LASIK and 13 SMILE patients for about a month after refractive surgery. Dry-eye symptoms and several tear and corneal-nerve changes were greater after LASIK. The nonrandomized, small groups and short follow-up mean the results describe early associations rather than definitive long-term superiority.

24. Severe ocular pain and reported treatment response

    A cross-sectional clinic survey of 144 dry-eye patients found greater pain associated with more systemic pain and mood conditions and less corneal staining. Patients with higher pain reported less relief from several previously tried surface treatments. Responses were recalled rather than assigned and measured prospectively, so this does not compare treatment efficacy.

25. Indoor particles and humidity at home

    Investigators examined 97 veterans in clinic, then measured home temperature, humidity, and particles within a week. Several indoor measures correlated with symptoms or surface findings, including an unexpectedly positive association of humidity with discomfort in this sample. The mostly male clinic population and one-time home readings limit generalization.

26. Corneal cells and nerves during contact-lens wear

    Twenty volunteers with mild dry eye who had never worn contact lenses began lens use and underwent repeated confocal imaging for 24 weeks. Corneal dendritic-cell measures rose early while some nerve densities fell; symptoms increased despite little change in Schirmer or tear breakup. With no nonwearing control group, the time course cannot exclude other influences.

27. Short reading tasks on four screen types

    Thirty-one healthy young adults completed 15-minute reading tasks on a laptop, tablet, e-reader, and smartphone. Tear and fatigue measures differed across devices, with the laptop causing the most disturbance under this protocol; pretask artificial tears did not clearly improve the measured outcomes. Brief controlled tasks in healthy students do not establish long-term device risk.

Biomarkers and diagnostic methods

These are exploratory or selected-population studies. Many candidate markers still need testing against clear reference standards in independent clinics.

28. Gut microbiota in Sjögren and other dry eye

    A stool-sequencing comparison included ten people with Sjögren syndrome, 14 with non-Sjögren dry eye, and 12 controls. The Sjögren group had distinct bacterial composition, and some taxa correlated with dry-eye signs. The groups were very small and observational; the findings neither prove a gut cause nor support microbiome treatment.

29. Deep learning applied to gland microscopy

    Researchers trained image classifiers using confocal images from 137 people with obstructive meibomian gland dysfunction and 84 controls. Selected models separated the study images with high reported discrimination. Those figures come from the development setting and require external testing before the method can be trusted in ordinary clinics.

30. Tear markers for Sjögren versus other dry eye

    A prospective case-control study of 62 people compared tear MUC5AC and inflammatory cytokines across Sjögren dry eye, non-Sjögren dry eye, and controls. Lower MUC5AC and higher IL-8 were associated with the Sjögren group alongside greater conjunctival staining. The candidate combination needs validation in patients whose diagnosis is still unknown.

31. Sequencing the ocular-surface microbiome

    A prospective observational study swabbed both eyes of 39 people across severe ocular-surface conditions and healthy controls. Only 60% of eye samples yielded usable bacterial sequences, and profiles sometimes differed between a person's eyes. Low sample biomass, small disease groups, and contact-lens or medication use make disease-specific interpretation difficult.

32. Tear cytokines in gland-related evaporative dry eye

    A case-control study compared tears from 30 patients with meibomian-gland-related evaporative dry eye and ten healthy volunteers. IL-8, IL-6, interferon-gamma, and ICAM-1 were higher in patients and some markers correlated with tear or gland measures. The small cross-sectional sample cannot show whether inflammation preceded gland dysfunction.

33. Osmolarity and MMP-9 in Sjögren dry eye

    Among 63 patients with Sjögren-associated dry eye, abnormal tear osmolarity separated several clinical signs more clearly than a positive MMP-9 test did. Combining the two tests produced groups with different tear-breakup and Schirmer findings. Because every participant already had Sjögren dry eye, the study cannot establish general diagnostic accuracy or screening value.