# Ocular Surface Disease: Dry Eye Diagnosis and Stepwise Management

## Definition and Classification (TFOS DEWS II)

Dry eye disease (DED) is a multifactorial condition of the ocular surface characterized by a loss of homeostasis of the tear film. It is associated with tear film instability and hyperosmolarity, ocular surface inflammation and damage, and neurosensory abnormalities. The TFOS DEWS II report classifies dry eye into two primary subtypes: aqueous deficient dry eye (ADDE), in which the lacrimal gland produces insufficient tears, and evaporative dry eye (EDE), in which excessive tear evaporation occurs, most commonly due to meibomian gland dysfunction (MGD). In practice, most patients have a mixed picture with elements of both mechanisms.

## Tear Film Structure

The traditional three-layer model of the tear film has given way to a more nuanced understanding of a mucin-aqueous gradient, though the layered framework remains clinically useful. The outermost lipid layer (~100 nm thick) is secreted by the meibomian glands and serves primarily to retard tear evaporation. The middle aqueous layer (~4 micrometers thick) is produced by the main lacrimal gland and accessory glands of Krause and Wolfring, and contains electrolytes, proteins, growth factors, and immunoglobulins. The innermost mucin component consists of membrane-bound mucins (MUC1, MUC4, MUC16) on the corneal and conjunctival epithelium along with secreted mucins (MUC5AC from goblet cells), which stabilize the tear film by reducing surface tension. The tear film turns over at approximately 16% per minute, with a total volume of about 7 microliters and a basal secretion rate of roughly 1.2 microliters per minute.

## Aqueous Deficient Dry Eye (ADDE)

### Sjogren Syndrome-Associated

Sjogren syndrome involves autoimmune destruction of the lacrimal and salivary glands. In primary Sjogren syndrome, keratoconjunctivitis sicca and xerostomia (dry mouth) occur in the absence of another autoimmune disease. Secondary Sjogren syndrome is associated with rheumatoid arthritis, systemic lupus erythematosus, or systemic sclerosis. The ACR/EULAR 2016 diagnostic criteria incorporate anti-SSA/Ro antibodies, labial salivary gland biopsy (focus score of 1 or greater), ocular staining score, Schirmer test results, and unstimulated salivary flow rate. Patients with Sjogren syndrome carry an increased risk of lymphoma, particularly MALT lymphoma of the orbit or lacrimal gland.

### Non-Sjogren ADDE

Non-Sjogren aqueous deficiency can result from age-related involution of the lacrimal gland, lacrimal gland infiltration by sarcoidosis, lymphoma, or amyloidosis, or lacrimal gland ablation or denervation. Numerous systemic medications reduce tear production, including antihistamines, anticholinergics, diuretics, beta-blockers, and SSRIs. Reflex secretion can also be blocked by contact lens wear, diabetic corneal neuropathy, or corneal nerve transection following LASIK.

## Evaporative Dry Eye

### Meibomian Gland Dysfunction (MGD)

MGD is the most common cause of dry eye, implicated in up to 86% of DED patients. The predominant form is obstructive MGD, in which terminal duct obstruction leads to thickened, turbid meibum that cannot spread effectively across the tear surface. Risk factors include advancing age, blepharitis, rosacea, Demodex infestation, contact lens use, androgen deficiency, and retinoid therapy. Meibomian gland dropout (atrophy) can be assessed with meibography using infrared imaging. On slit lamp examination, findings include capped gland orifices, thickened lid margins, telangiectasia, and collarettes at the lash bases (suggesting Demodex infestation).

### Other Evaporative Causes

Evaporative dry eye can also result from reduced blink rate associated with prolonged screen use or Parkinson disease. Lid abnormalities such as lagophthalmos, proptosis from thyroid eye disease, ectropion, and floppy eyelid syndrome all increase tear evaporation by impairing lid closure. Contact lens wear contributes to evaporation as well. Vitamin A deficiency causes xerophthalmia, Bitot spots, and in severe cases, keratomalacia. Chronic exposure to the preservative benzalkonium chloride (BAK) in topical drops is another important evaporative cause through direct toxic effects on the epithelium and goblet cells.

## Diagnostic Workup

### Symptoms Assessment

Standardized questionnaires are used to quantify symptom severity and track treatment response. The Ocular Surface Disease Index (OSDI) is a 12-question validated instrument scored from 0 to 100. The DEQ-5 (Dry Eye Questionnaire-5) provides a rapid 5-item screening. The SPEED (Standard Patient Evaluation of Eye Dryness) is another commonly used tool.

### Clinical Tests (in recommended order)

A systematic clinical evaluation should proceed from least to most invasive tests. **Tear meniscus height** is assessed at the slit lamp or with anterior segment OCT; a height less than 0.2 mm suggests aqueous deficiency. **Tear breakup time (TBUT)** is measured by instilling fluorescein and recording the time until the first dry spot appears under cobalt blue illumination; less than 10 seconds is abnormal and less than 5 seconds is diagnostic. **Non-invasive TBUT (NIBUT)**, measured with devices like the Keratograph or Tearscope, avoids the artifact introduced by fluorescein instillation; values greater than 10 seconds are normal.

**Ocular surface staining** provides direct evidence of epithelial damage. Fluorescein stains damaged corneal epithelium and is graded using the Oxford scheme (0-V) or NEI scale. Lissamine green stains dead and degenerate cells and is particularly useful for conjunctival staining and detecting lid wiper epitheliopathy. Rose bengal stains dead cells and mucin-devoid cells but is more irritating and less commonly used today.

The **Schirmer test** quantifies tear production. Schirmer I (without anesthesia) measures combined reflex and basal secretion; wetting less than 10 mm in 5 minutes is abnormal, and less than 5 mm is diagnostic of severe aqueous deficiency. Schirmer II (with nasal stimulation) assesses the reflex secretion pathway specifically. The basic secretion test (with topical anesthesia) isolates basal secretion alone.

**Tear osmolarity**, measured with the TearLab device, is considered one of the best single metrics for dry eye severity. Values exceeding 308 mOsm/L in either eye, or an inter-eye difference greater than 8 mOsm/L, are abnormal. **Inflammatory biomarkers** including MMP-9 (measured with the point-of-care InflammaDry test) and lactoferrin levels help identify inflammatory dry eye and guide anti-inflammatory therapy.

**Meibomian gland assessment** involves expressing the glands to evaluate meibum quality (clear, cloudy, granular, or toothpaste-like) and expressibility. Meibography uses infrared imaging to visualize gland morphology and dropout. LipiView interferometry measures lipid layer thickness; values below 60 nm suggest lipid deficiency.

## Dry Eye Diagnostic Tests Summary

| Test | What It Measures | Abnormal Value | Key Notes |
|------|-----------------|----------------|-----------|
| Tear meniscus height | Aqueous volume | < 0.2 mm | Quick, non-invasive |
| TBUT | Tear film stability | < 10 sec (< 5 diagnostic) | Fluorescein required |
| NIBUT | Tear film stability (non-invasive) | < 10 sec | Avoids fluorescein artifact |
| Schirmer I (no anesthesia) | Reflex + basal secretion | < 10 mm/5 min (< 5 severe) | Poorly reproducible alone |
| Tear osmolarity | Hyperosmolarity | > 308 mOsm/L or >8 inter-eye difference | Best single metric |
| MMP-9 (InflammaDry) | Ocular surface inflammation | Positive | Guides anti-inflammatory Rx |
| Meibography | Gland structure/dropout | Gland loss or shortening | Infrared imaging |
| LipiView | Lipid layer thickness | < 60 nm | Lipid deficiency |
| Fluorescein staining | Corneal epithelial damage | Oxford grade >I | Graded 0-V |
| Lissamine green | Conjunctival damage | Positive staining | Best for lid wiper epitheliopathy |

## Stepwise Management (TFOS DEWS II Treatment Algorithm)

### Step 1: Education, Environmental Modification, Tears

Management begins with patient education about the chronic nature of dry eye disease and the need for ongoing management. Environmental modifications include using humidifiers, reducing screen time, taking regular breaks (the 20-20-20 rule: every 20 minutes, look at something 20 feet away for 20 seconds), and avoiding direct airflow across the eyes. The role of omega-3 fatty acid supplementation remains debated; the DREAM study showed no benefit over olive oil placebo, though clinical discussion persists since both groups improved. Artificial tears are the mainstay of initial therapy, with preservative-free formulations preferred for patients using drops more than four times daily. Low-viscosity options include carboxymethylcellulose, hyaluronic acid, and polyethylene glycol; higher-viscosity gels are useful for nighttime application; and lipid-containing drops address the evaporative component. Lid hygiene includes sustained warm compresses (maintaining temperature above 40 degrees Celsius for 5-10 minutes), lid scrubs, and dilute tea tree oil or hypochlorous acid sprays for Demodex blepharitis. Following warming, eyelid massage helps express stagnant meibomian gland secretions.

### Step 2: Prescription Therapies

When Step 1 measures are insufficient, prescription anti-inflammatory therapy is initiated. Cyclosporine A 0.05% (Restasis) or 0.09% (Cequa) is dosed twice daily; it takes three to six months for full therapeutic effect, working by increasing goblet cell density and reducing T-cell-mediated inflammation. Lifitegrast 5% (Xiidra), an LFA-1 integrin antagonist that blocks T-cell activation and cytokine release, also dosed twice daily, has a faster onset than cyclosporine. A short course of topical corticosteroid (fluorometholone or loteprednol for two to four weeks) is commonly used as induction therapy to provide symptomatic relief while waiting for cyclosporine or lifitegrast to take effect.

For MGD associated with rosacea, oral antibiotics at anti-inflammatory doses are effective. Doxycycline 50-100 mg daily inhibits MMP-9 and modifies meibum lipid composition. Azithromycin 250 mg daily for three days per week over four weeks (pulse therapy) is an alternative.

Punctal plugs -- either collagen (temporary, lasting one to two weeks) or silicone (semi-permanent) -- reduce tear drainage and increase tear volume on the ocular surface. However, they should only be placed after ocular surface inflammation has been controlled, because plugging inflamed tears worsens surface disease. Potential complications include canaliculitis and spontaneous extrusion. Moisture chamber glasses or wraparound frames help reduce evaporation. In-office meibomian gland treatments such as LipiFlow (thermal pulsation), iLux, TearCare, and intense pulsed light (IPL) provide targeted gland debridement and heating.

### Step 3: Oral Secretagogues and Advanced Measures

For patients with Sjogren syndrome and severe aqueous deficiency, oral secretagogues such as pilocarpine 5 mg three times daily or cevimeline 30 mg three times daily (muscarinic agonists) can stimulate lacrimal secretion. Side effects include sweating, gastrointestinal upset, and bradycardia. Autologous serum tears at 20% concentration contain growth factors (EGF, TGF-beta, fibronectin), vitamin A, and anti-inflammatory cytokines. Prepared from the patient's own blood and stored frozen, they are effective for severe dry eye, neurotrophic keratopathy, and persistent epithelial defects. Therapeutic scleral contact lenses provide a fluid reservoir over the cornea, with the PROSE system (Prosthetic Replacement of the Ocular Surface Ecosystem) being a specialized version. Topical vitamin A (retinol palmitate) can be used to treat conjunctival squamous metaplasia.

### Step 4: Surgical and Advanced Options

The most severe cases may require surgical intervention. Tarsorrhaphy (partial or complete lid closure) is used for severe exposure or neurotrophic keratopathy. Conjunctivochalasis excision removes redundant conjunctiva that can disrupt the tear film and block the puncta. Amniotic membrane transplantation addresses persistent epithelial defects and severe ocular surface inflammation. Salivary gland transplantation (minor salivary gland autograft) provides a new source of secretory tissue for end-stage aqueous deficiency. For patients with severe dry eye complicated by corneal opacification who have failed conventional transplantation, a Boston keratoprosthesis (KPro) may be considered.

## Special Considerations

### Post-LASIK Dry Eye

LASIK creates a corneal flap that transects corneal nerves, disrupting the reflex arc between corneal sensation and lacrimal secretion. The resulting decreased corneal sensitivity leads to reduced blink rate and diminished tear production. This effect is usually self-limited, resolving over three to six months as nerves regenerate, but it may be prolonged in some patients. Pre-operative assessment of tear function is essential in all refractive surgery candidates.

### Ocular Surface Disease and Cataract Surgery

Dry eye commonly worsens after phacoemulsification due to corneal nerve damage, exposure to preservatives in perioperative drops, and light toxicity from the operating microscope. Pre-operative optimization of the ocular surface is critical because it directly improves biometry accuracy and surgical outcomes. Topographic mires are unreliable when the tear film is compromised, so the ocular surface should be treated and stabilized before measurements are taken for IOL calculations.

<image>Diagram of the tear film structure and dry eye subtypes. Left panel: cross-section of a healthy tear film showing the lipid layer (meibomian gland origin), aqueous layer (lacrimal gland), and mucin gradient (goblet cells and membrane-bound mucins on epithelial surface). Right panel: two pathways to dry eye — (1) Aqueous deficient: small, atrophic lacrimal gland with reduced aqueous volume and low tear meniscus; (2) Evaporative: obstructed meibomian glands with truncated/absent lipid layer and increased evaporation arrows from the tear surface. Show tear hyperosmolarity and epithelial damage as common endpoints of both pathways.</image>

<image>Clinical photograph montage of dry eye diagnostic tests. Six panels: (1) Fluorescein TBUT measurement showing a dry spot forming on the cornea with a stopwatch overlay showing less than 5 seconds; (2) Corneal punctate fluorescein staining under cobalt blue filter with diffuse fine dots across the inferior cornea; (3) Lissamine green conjunctival staining showing temporal conjunctival devitalized cells; (4) Schirmer strip in the lower fornix with ruler markings showing less than 5 mm wetting at 5 minutes; (5) Meibography showing infrared image of the lower tarsal plate with significant gland dropout (ghost glands); (6) LipiView interferometry showing a thin lipid layer with thickness less than 60 nm in color-coded display.</image>

<image>TFOS DEWS II stepwise treatment algorithm as a pyramid diagram. Four ascending tiers: Step 1 (base — green): education, environmental modification, artificial tears, warm compresses, lid hygiene, omega-3 consideration. Step 2 (yellow): cyclosporine/lifitegrast, short-course steroids, punctal plugs, oral doxycycline, in-office thermal treatments. Step 3 (orange): oral secretagogues, autologous serum tears, scleral lenses, topical vitamin A. Step 4 (red — apex): tarsorrhaphy, amniotic membrane, salivary gland transplantation, keratoprosthesis. Arrows between tiers indicate escalation based on severity and treatment response.</image>

## Key Clinical Pearls

MGD is the most common cause of dry eye, so the meibomian glands and lipid layer should always be evaluated during the workup. Tear osmolarity greater than 308 mOsm/L and a positive MMP-9 test correlate with inflammatory ocular surface disease and support the use of anti-inflammatory therapy. Punctal plugs must not be placed until ocular surface inflammation is controlled, because trapping inflammatory mediators on the eye is counterproductive. A short course of topical steroids (loteprednol or fluorometholone for two to four weeks) provides rapid symptomatic relief while waiting for cyclosporine or lifitegrast to reach full efficacy. The DREAM study found no significant benefit of omega-3 supplementation over olive oil placebo, though the debate continues since both treatment groups improved. The ocular surface should always be optimized before cataract surgery or IOL calculations, as a compromised tear film produces unreliable biometry and poorer visual outcomes. Sjogren syndrome patients require systemic monitoring for lymphoma risk alongside management of their ocular and oral sicca symptoms. Finally, the Schirmer test alone is poorly reproducible and should always be interpreted in conjunction with other clinical tests for a reliable diagnosis.

## References

- Craig JP, et al. TFOS DEWS II Report Executive Summary. Ocul Surf. 2017;15(4):802-812.
- Jones L, et al. TFOS DEWS II Management and Therapy Report. Ocul Surf. 2017;15(3):575-628.
- DREAM Study Research Group. n-3 Fatty Acid Supplementation for the Treatment of Dry Eye Disease. NEJM. 2018;378(18):1681-1690.
- Nichols KK, et al. The international workshop on meibomian gland dysfunction. Invest Ophthalmol Vis Sci. 2011;52(4):1917-1921.
- AAO BCSC Section 8: External Disease and Cornea. 2023-2024.