淚膜結構：最外層是油脂層（瞼板腺分泌），下方是水分與黏液素混合成的「黏液水層」，黏液素濃度越靠近角膜越高；傳統「油脂、水液、黏液三層」的畫法是簡化（TFOS DEWS II 淚膜報告）。油脂層有助於穩定淚膜、減少水分蒸發。瞼板腺機能障礙（MGD）時油脂層不足 → 水分蒸發太快 → 蒸發型乾眼。TFOS DEWS III 指出，至少三分之二的乾眼屬蒸發型。
迷思 1 · 「人工淚液越點越乾、會依賴」
迷思：點久了眼睛會習慣，自己分泌的淚水會越來越少，變成不點不行。
真相：對的成分不會。會讓眼睛越來越乾的，是人工淚液裡的「BAK 防腐劑」，不是淚液本身。
BAK 是氯化苯二甲烴銨（benzalkonium chloride）的縮寫，是多劑型瓶裝眼藥水常用的防腐劑。TFOS DEWS II 把局部防腐劑列為乾眼的醫源性原因之一；2025 年 TFOS DEWS III 報告指出：BAK 等防腐劑對眼表有毒性並會引發發炎，可能讓乾眼的徵象與症狀惡化。文獻回顧也提到，BAK 可能降低淚膜穩定度、減少角膜神經（Walsh 2019）。
真正的「依賴感」其實來自兩件事：（1）患者本身的瞼板腺機能障礙（MGD）持續惡化，讓淚膜越來越不穩定，自然越點越要點；（2）反覆使用含 BAK 滴劑造成的醫源性傷害。
解法很簡單：美國眼科醫學會 2023 年版乾眼症臨床指引（AAO Preferred Practice Pattern，PPP）建議，若一天點超過 4 次或長期頻繁使用，一般改用無防腐劑（preservative-free）人工淚液，例如單支裝，或 ABAK、COMOD 等設計成防止汙染的無防腐劑多劑型瓶。這類產品不含防腐劑，可依需要使用，不會有防腐劑累積的毒性。
Craig JP, et al. TFOS DEWS II Definition and Classification Report. Ocul Surf. 2017;15(3):276-283. doi:10.1016/j.jtos.2017.05.008
Wolffsohn JS, et al. TFOS DEWS II Diagnostic Methodology Report. Ocul Surf. 2017;15(3):539-574.
Jones L, et al. TFOS DEWS II Management and Therapy Report. Ocul Surf. 2017;15(3):575-628.
Amescua G, et al. Dry Eye Syndrome Preferred Practice Pattern. American Academy of Ophthalmology. Ophthalmology. 2024;131(4):P1-P49.
Dry Eye Assessment and Management Study Research Group; Asbell PA, et al. n-3 Fatty Acid Supplementation for the Treatment of Dry Eye Disease. N Engl J Med. 2018;378(18):1681-1690.
Walsh K, Jones L. The use of preservatives in dry eye drops. Clin Ophthalmol. 2019;13:1409-1425.
Geerling G, et al. The international workshop on meibomian gland dysfunction: report of the subcommittee on management and treatment of meibomian gland dysfunction. Invest Ophthalmol Vis Sci. 2011;52(4):2050-2064.
Wolffsohn JS, et al. TFOS DEWS III: Diagnostic Methodology. Am J Ophthalmol. 2025;279:387-450.
Jones L, et al. TFOS DEWS III: Management and Therapy. Am J Ophthalmol. 2025;279:289-386.
Stapleton F, et al. TFOS DEWS III: Digest. Am J Ophthalmol. 2025;279:451-553.
Lemp MA, et al. Distribution of aqueous-deficient and evaporative dry eye in a clinic-based patient cohort: a retrospective study. Cornea. 2012;31(5):472-478.
Age-Related Eye Disease Study 2 Research Group. Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration: the Age-Related Eye Disease Study 2 (AREDS2) randomized clinical trial. JAMA. 2013;309(19):2005-2015.
Nichols JJ, et al. The TFOS International Workshop on Contact Lens Discomfort: executive summary. Invest Ophthalmol Vis Sci. 2013;54(11):TFOS7-TFOS13.
Wolffsohn JS, et al. TFOS Lifestyle: Impact of the digital environment on the ocular surface. Ocul Surf. 2023;28:213-252.
Blackie CA, et al. Inner eyelid surface temperature as a function of warm compress methodology. Optom Vis Sci. 2008;85(8):675-683.
Vaidyanathan U, et al. Persistent Corneal Epithelial Defects: A Review Article. Med Hypothesis Discov Innov Ophthalmol. 2019;8(3):163-176.
Willcox MDP, et al. TFOS DEWS II Tear Film Report. Ocul Surf. 2017;15(3):366-403.
Tsubota K, Nakamori K. Dry eyes and video display terminals. N Engl J Med. 1993;328(8):584. PMID: 8426634.
Myth 1 · "Artificial tears make your eyes drier; you'll become dependent on them"
Myth: The longer you use them, the less your eyes produce on their own; eventually you can't stop.
Truth: Not the tears themselves — it's the BAK preservative inside that damages eyes long-term.
BAK (benzalkonium chloride) is a common preservative in multi-dose eye-drop bottles. The TFOS DEWS II lists topical preservatives among iatrogenic causes of dry eye; the 2025 TFOS DEWS III report notes that preservatives such as BAK have toxic and pro-inflammatory effects on the ocular surface and can worsen dry eye signs and symptoms. A literature review also reports that BAK may reduce tear film stability and corneal nerves (Walsh 2019).
The "dependency" feeling actually comes from two sources: (1) the patient's underlying meibomian gland dysfunction (MGD) progressively worsens, making the tear film increasingly unstable; (2) iatrogenic injury from chronic BAK use.
The fix is simple: the AAO 2023 Dry Eye Syndrome Preferred Practice Pattern (PPP) generally recommends preservative-free tears when drops are used frequently and chronically (e.g., more than 4 times a day) — single-dose vials, or multi-dose preservative-free bottles designed to prevent contamination (such as ABAK or COMOD). Without preservative, they can be used as often as needed without preservative toxicity accumulating.
Myth 2 · "Watery eyes can't be dry eye"
Myth: My eyes water all day — when I look at screens, when wind blows — so I can't possibly have dry eye.
Truth: Tearing is itself a common dry eye symptom (the AAO Dry Eye PPP lists it among dry eye symptoms) — often reflex tearing from an irritated ocular surface.
Evaporative dry eye is the most common form: TFOS DEWS III notes that at least two-thirds of dry eye is evaporative, and in one clinic-based study about 86% of dry eye patients showed signs of meibomian gland dysfunction (MGD), with only about 14% purely aqueous-deficient (Lemp 2012). MGD leads to insufficient lipid in the tear film and faster evaporation. Persistent ocular-surface irritation activates a trigeminal reflex that makes the lacrimal gland release watery reflex tears.
But this reflex tear is mostly water and cannot replace the deficient lipid layer, so it only briefly covers the surface before evaporating. So the patient experiences a paradox: watering and dryness/burning/blurriness at the same time.
Diagnosis cannot rest on "do you tear?" alone. Under TFOS DEWS III (2025), diagnosis requires a positive symptom screen (OSDI-6) plus at least one sign: non-invasive tear break-up time <10 s, tear hyperosmolarity, or ocular surface staining. Tests such as tear meniscus height, Schirmer (tear secretion), and meibography (gland atrophy) then help identify the cause — aqueous-deficient vs evaporative — and treatment differs.
Myth 3 · "Dry eye is a senior disease; the young don't get it"
Myth: I'm only 28 — dry eye is for the elderly or postmenopausal women, right?
Truth: Young people get dry eye too. Epidemiology summarized in TFOS DEWS III shows that dry eye is common in both young and older people; defined by symptoms and signs, rates are fairly consistent across adult age groups, with some evidence that prevalence is increasing over time.
TFOS DEWS III links reduced blinking during screen use and contact lens wear to dry eye. Three common drivers in young people:
Screen use — blinking becomes much less frequent (in a study of 104 healthy office workers, the mean blink rate was about 22/min when relaxed, 10/min while reading a book and 7/min while viewing a video display terminal; Tsubota 1993) and often incomplete, causing tear film instability and increased evaporation (TFOS Lifestyle digital environment report, TFOS DEWS III); incomplete blinking is also associated with meibomian gland dropout and poorer meibum quality (AAO PPP).
Soft contact lenses — up to half of contact lens wearers experience contact lens discomfort, with dryness a common symptom (TFOS International Workshop on Contact Lens Discomfort, 2013).
Autoimmune disease — Sjögren's syndrome, SLE, and RA may present with dry eye, dry mouth, or joint pain. The AAO PPP notes that dry eye is most common in postmenopausal women, so dry eye in younger patients or men should prompt a search for associated systemic or local conditions.
If you're under 30, work long screen hours, wear contacts, and complain of burning/grittiness — it isn't your imagination. See an ophthalmologist.
Myth 4 · "Lutein cures dry eye"
Myth: The pharmacy clerk recommended lutein for "eye health" — that should help my dry eye, right?
Truth: Lutein's role is in AMD supplement formulas; evidence for lutein alone in dry eye is scant. Omega-3 is one of the more studied supplements, but results are inconsistent.
Lutein and zeaxanthin are the principal carotenoids of the macular pigment. The key evidence comes from the AREDS2 study: in 4,203 people at risk of progression to advanced age-related macular degeneration (AMD), adding lutein + zeaxanthin to the AREDS formulation did not further reduce progression in the primary analysis, but because beta carotene may raise lung cancer risk in former smokers, lutein + zeaxanthin was considered an appropriate substitute for it. That is AMD research — it has nothing to do with dry eye.
The supplement with theoretical basis for dry eye is omega-3 polyunsaturated fatty acids (EPA / DHA) — modulating the inflammatory cascade and improving meibum fluidity. But the 2018 NEJM DREAM trial (n=535) found no significant difference between 3000 mg/day omega-3 and olive oil placebo over 12 months in symptoms (OSDI) or signs (tear break-up time, Schirmer, staining).
Accordingly, the AAO 2023 Dry Eye Syndrome PPP rates oral omega-3 as discretionary — try if you wish, but it's not primary therapy — and TFOS DEWS III considers its role in dry eye uncertain. As for lutein, DEWS III only notes that a combination supplement (lutein, zeaxanthin, curcumin, vitamin D) improved tear volume and stability in 2 randomized trials; evidence is still limited, so lutein cannot be said to treat dry eye.
Myth 5 · "A short course of medication will cure it"
Myth: I'll take the prescribed drops for a month and be cured.
Truth: Dry eye is a chronic disease — like hypertension or diabetes. Long-term management is required; recurrence on stopping is normal.
TFOS DEWS III (2025) defines dry eye as "a multifactorial, symptomatic disease characterized by a loss of homeostasis of the tear film and/or ocular surface, in which tear film instability and hyperosmolarity, ocular surface inflammation and damage, and neurosensory abnormalities are etiological factors." The AAO Dry Eye PPP stresses educating patients about its chronic nature — not an acute infection cured in one course; it requires long-term management like blood pressure or blood sugar.
The staged approach from TFOS DEWS II, reproduced in the AAO 2023 PPP (summary):
資料表可左右捲動查看；用鍵盤時，選取表格後按左右方向鍵。
Step
Treatment
When
Step 1
Education, environmental modification, dietary advice (including oral essential fatty acids), review of offending medications, ocular lubricants (lipid-containing if MGD), eyelid hygiene and warm compresses
Initial
Step 2
Preservative-free lubricants; Demodex treatment (e.g., tea tree oil); punctal plugs, moisture-chamber spectacles; overnight ointment; in-office meibomian gland heating and expression (incl. thermal pulsation); prescription drugs such as short-term corticosteroids, secretagogues (e.g., diquafosol), cyclosporine, lifitegrast, oral tetracyclines or macrolides
If Step 1 inadequate
Step 3
Oral secretagogues, autologous/allogeneic serum, platelet-rich plasma drops, therapeutic contact lenses (soft bandage lenses with caution, or rigid scleral lenses)
If above inadequate
Step 4
Longer-term topical corticosteroids, amniotic membrane grafts, surgical punctal occlusion (cautery), other surgery (e.g., tarsorrhaphy, minor salivary gland transplantation)
If above inadequate
The PPP notes that therapies may be chosen from any category regardless of severity, depending on physician experience and patient preference; TFOS DEWS III (2025) goes further, matching evidence-based treatments to the etiology (tear film deficiency, eyelid anomalies, ocular surface abnormalities). "Stopping the drops makes it come back" is common and isn't treatment failure — it's the same as blood pressure rising once the antihypertensive is stopped.
Myth 6 · "All artificial tears are basically the same — pick the cheapest"
Myth: There are dozens of brands but they're all basically water — just buy the cheapest.
Truth: Composition, preservative, osmolarity, and viscosity all differ. The wrong choice may work poorly, and frequent long-term use of preserved drops can harm the ocular surface.
TFOS DEWS III groups tear supplement ingredients roughly as follows:
資料表可左右捲動查看；用鍵盤時，選取表格後按左右方向鍵。
Type
Active ingredient
Best for
Viscosity-enhancing
CMC, HPMC, PVA, HP-guar, PEG
Aqueous-based; for aqueous deficiency
Hyaluronate
Sodium hyaluronate
Increasingly common; hydrating, lubricating
Lipid-based
Phospholipids, mineral oil, castor oil, etc. (emulsions or liposomal sprays)
MGD-related dry eye (prescription in the US; a medical device elsewhere)
But the bigger lever is the preservative. Multi-dose bottles may contain BAK; others use gentler preservatives (e.g., Purite, sodium perborate, Polyquad) or contamination-resistant preservative-free multi-dose bottles (TFOS DEWS III). High-frequency long-term use of BAK-containing drops can accumulate ocular surface toxicity.
Selection rules
Mild dry eye, healthy ocular surface, ≤4 uses/day → preserved multi-dose is usually fine
>4 uses/day, or frequent long-term use → preservative-free generally recommended (single-dose, or preservative-free multi-dose such as ABAK, COMOD) (AAO PPP)
History of eye-drop allergy (itch, redness, sting) → preservative-free directly
Myth 7 · "Warm compresses don't work; it's just placebo"
Myth: Warm compresses just feel nice; no real evidence — better to skip them and use drops.
Truth: They are a standard at-home treatment for MGD — but temperature and time matter (TFOS DEWS III: about 40–41.5°C, once daily for 10 min or twice daily for 5 min), followed by gentle lid massage to express the thickened meibum.
Secretions from obstructed meibomian glands are thicker, with higher melting points: normal meibum begins to melt at about 32°C, obstructive MGD meibum at about 35°C (International Workshop on MGD, 2011). Warm compresses aim to heat the lids to around 40°C so the thickened meibum softens and drains; cold or room-temperature compresses can't raise lid temperature and do little for MGD.
Three conditions for an effective warm compress:
Temperature about 40–41.5°C — as recommended by TFOS DEWS III; too hot risks burning the lid skin, too low fails to soften meibum.
Once daily for 10 min, or twice daily for 5 min — heat must be sustained; one study found at least about 4 minutes was needed for the inner lid to reach ≥40°C (Blackie 2008).
Gentle massage — immediately after the compress, roll-press from lid base toward the lash margin to express the softened meibum.
Many commercial warming products exist, but not all have evidence for safety and efficacy, and different heating methods may not be equally effective (TFOS DEWS III). Warm towels work too: towels reheated to 45°C every 2 minutes delivered heat comparably to commercial devices, but it is labor-intensive. In-clinic IPL (intense pulsed light) or LipiFlow thermal pulsation are further options.
Myth: It's not glaucoma or cataract — it doesn't hurt vision, just live with it.
Truth: Mild — yes, harmless. Severe dry eye can cause corneal epithelial defects, filamentary keratitis, ulcers, even perforation and blindness.
Mild dry eye is annoying but harmless. Severe dry eye — especially in Sjögren's, SLE, or GVHD after hematopoietic stem cell transplant — can cause:
Filamentary keratitis — mucin filaments adherent to cornea; each blink tugs them, severe pain and foreign-body sensation.
Persistent epithelial defect (PED) — an epithelial defect that fails to heal within 10–14 days, prone to infection, ulceration, even perforation (Vaidyanathan 2019).
Corneal ulcer — may be microbial or sterile (AAO PPP); infectious ulcers need aggressive antibiotic treatment.
Corneal melt — can occur in severe dry eye with systemic inflammatory (e.g., autoimmune) disease; can perforate and cause blindness — an emergency.
So recurrent redness, pain, or vision loss should never be ignored. Get Schirmer + TBUT + corneal staining (fluorescein / lissamine green / rose bengal) without delay; tertiary referral if needed.
5 things you can do at home
Dry eye self-care checklist
If symptoms persist despite all five — eyes stuck shut on waking, fluctuating vision — see an ophthalmologist for a full workup, including Sjögren's screening.
Key references
Craig JP, et al. TFOS DEWS II Definition and Classification Report. Ocul Surf. 2017;15(3):276-283.
Wolffsohn JS, et al. TFOS DEWS II Diagnostic Methodology Report. Ocul Surf. 2017;15(3):539-574.
Jones L, et al. TFOS DEWS II Management and Therapy Report. Ocul Surf. 2017;15(3):575-628.
Amescua G, et al. Dry Eye Syndrome Preferred Practice Pattern. American Academy of Ophthalmology. Ophthalmology. 2024;131(4):P1-P49.
Dry Eye Assessment and Management Study Research Group; Asbell PA, et al. n-3 Fatty Acid Supplementation for the Treatment of Dry Eye Disease. N Engl J Med. 2018;378(18):1681-1690.
Walsh K, Jones L. The use of preservatives in dry eye drops. Clin Ophthalmol. 2019;13:1409-1425.
Geerling G, et al. The international workshop on meibomian gland dysfunction: report of the subcommittee on management and treatment of meibomian gland dysfunction. Invest Ophthalmol Vis Sci. 2011;52(4):2050-2064.
Wolffsohn JS, et al. TFOS DEWS III: Diagnostic Methodology. Am J Ophthalmol. 2025;279:387-450.
Jones L, et al. TFOS DEWS III: Management and Therapy. Am J Ophthalmol. 2025;279:289-386.
Stapleton F, et al. TFOS DEWS III: Digest. Am J Ophthalmol. 2025;279:451-553.
Lemp MA, et al. Distribution of aqueous-deficient and evaporative dry eye in a clinic-based patient cohort: a retrospective study. Cornea. 2012;31(5):472-478.
Age-Related Eye Disease Study 2 Research Group. Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration: the Age-Related Eye Disease Study 2 (AREDS2) randomized clinical trial. JAMA. 2013;309(19):2005-2015.
Nichols JJ, et al. The TFOS International Workshop on Contact Lens Discomfort: executive summary. Invest Ophthalmol Vis Sci. 2013;54(11):TFOS7-TFOS13.
Wolffsohn JS, et al. TFOS Lifestyle: Impact of the digital environment on the ocular surface. Ocul Surf. 2023;28:213-252.
Blackie CA, et al. Inner eyelid surface temperature as a function of warm compress methodology. Optom Vis Sci. 2008;85(8):675-683.
Vaidyanathan U, et al. Persistent Corneal Epithelial Defects: A Review Article. Med Hypothesis Discov Innov Ophthalmol. 2019;8(3):163-176.
Willcox MDP, et al. TFOS DEWS II Tear Film Report. Ocul Surf. 2017;15(3):366-403.
Tsubota K, Nakamori K. Dry eyes and video display terminals. N Engl J Med. 1993;328(8):584. PMID: 8426634.
