Dry eye disease

The most prominent symptom of dry eye disease is tearing. Tearing is a paradoxical reflex from the brain on the irritation to help counteract the irritation.

Other symptoms include burning, stinging, itching, gritty (sandy) filling, foreign-body sensation, discharge, frequent blinking, and crusty eyelids.

Patients may also complain of blurry vision, light sensitivity, eye redness, and pain.

Healthcare professionals can utilise symptom questionnaires to establish a diagnosis of dry eye disease, validate the need for additional interventions, evaluate treatment outcomes, and determine the severity of the disease. Some of the frequently employed and validated questionnaires include the following.(9)

• OSDI (Ocular Surface Disease Index) is the most established study instrument.
• The Dry Eye Questionnaire (DEQ-5) is attractive due to its short length and discriminative ability The Dry Eye Questionnaire (DEQ-5) is particularly appealing due to its concise format and ability to distinguish between different levels of dry eye symptoms effectively.
• Consider SANDE (Symptom Assessment in Dry Eye) for repeated comfort assessment.

Ocular Surface Disease Index
The Ocular Surface Disease Index (OSDI) measures symptoms of ocular surface diseases (like dry eye syndrome), helping clinicians customise treatment based on their impact on a patient’s quality of life.(10)

• Normal ocular surface (0-12 points)
• Mild ocular surface disease (13-22 points)
• Moderate ocular surface disease (23-32 points)
• Severe ocular surface disease (33-100 points)

There are also questionnaires explicitly developed for contact lens wear, such as;

• Contact Lens Dry Eyes Questionaire (CLDEQ)
• 8-item Contact Lens Dry Eye Questionnaire (CLDEQ-8)
• Contact Lens Impact on Quality of Life (CLIQ)

Corneal sensation
Corneal sensation can be measured using a cotton tip applicator or, more precisely, with a Cochet-Bonnet esthesiometer.

* Remember that severe and chronic dry eye disease may cause a reduced corneal sensation.

The tear break-up test (TBUT) is determined by measuring the interval between the instillation of topical fluorescein 0.5% and the appearance of the first dry spots on the cornea. Measure it before the installation of any anaesthetic eye drops. Three consecutive measurements are taken, and the median value is recorded as TBUT. A TBUT of less than 10 seconds is considered abnormal and indicative of tear instability.

Tear film break-up time should ideally be measured non-invasively (NIBUT), e.g., using placeido ring instruments such as topographers with a dry eye module. But in lieu of this, use fluorescent tear-film break-up time (FBUT) as described above.

Epithelial staining
Fluorescein sodium is the most used stain in ophthalmology. Areas where the corneal or conjunctival surface epithelial cells are loose or desquamated will stain with fluorescein. Oxford Grading Scale (0-5) and National Eye Institute (NEI) scale (0-3) are the most used scales to grade fluorescein staining.

Lissamine green and Rose Bengal dyes can also be used. They are used for conjunctival staining, where lissamine green is better tolerated.

Schirmer test
The Schirmer test is performed by placing a paper test strip in the lateral third of the lower eyelid after drying the inferior fornix and then measuring the length of the moistened portion of the strip after 5 minutes. The patient’s eyes are then closed for 5 minutes, and the paper strip’s wetting is measured.

The Schirmer I test is performed without anaesthesia and, thus, measures basic and reflex tearing. Less than 5 mm of wetting is abnormal; 5 to 10 mm is equivocal.

The Schirmer II test also lacks anaesthesia but is done following nasal stimulation (nasal mucosal irritation induced with a cotton tip applicator). it measures reflex tearing only and is reduced more in Sjögren’s syndrome compared to non-Sjögren’s dry eye. Wetting of less than 15 mm after 5 minutes is consistent with abnormalities of reflex secretion.

* Remember that the test is variable and has low reproducibility. It may be insensitive for mild dry eye disease.

Delayed tear clearance and tear meniscus height measurement (meniscometry)

The persistence of fluorescein dye at various time points may indicate nasolacrimal duct issues. Then, the height of the tear meniscus less than 0.25 mm is suggestive of dry eye. Medical devices automatically measure the tear meniscus, which may be useful in diagnosing dry eye syndrome.

Tear osmolarity is used to measure the osmolarity of the tear film using a device. Patients with dry eyes have increased osmolarity of their tears (hyperosmolarity). Typical values are considered to be 296±9.8 mOsm/L.(11) Greater than 308 mOsm/L indicates at least mild dry eye and has been demonstrated to be an early indicator of ocular surface instability.(12)

Tear film interferometry is a noninvasive method of grading tear film quality and estimating the thickness of the lipid layer, which is abnormal in the evaporative dry eye that is secondary to meibomian gland dysfunction.

To differentiate between MGD as a cause of DED, the quality of meibum secretion and gland expressibility should be investigated. Advanced practices may also utilise meibography to image the meibomian glands to detect potential atrophy of the glands. 

The Management and Therapy Subcommittee of the Tear Film and Ocular Surface Society’s Dry Eye Workshop II (TFOS DEWS II) has proposed an updated (2017) algorithm to approach the treatment of dry eyes.(13)

Step 1

• Educate the patient regarding the condition, management, and prognosis
• Modify the patient’s local environment
• Educate the patient on dietary modifications (including oral essential fatty acid supplementation)
• Identify any potentially etiologic systemic/topical medications and consider modifying or eliminating offending agents.
• Apply ocular lubricants (lipid-containing supplements in patients with meibomian gland dysfunction.
• Institute proper lid hygiene and apply warm compresses.

Step 2 (used if the above options are inadequate)

• Use of nonpreserved ocular lubricants to minimize preservative-induced toxicity
• Tea tree oil therapy to treat demodicosis, if present
• Tear conservation therapy involves procedures such as punctal occlusion and the use of moisture chamber spectacles/goggles)
• Overnight treatments (e.g., ointment or moisture chamber devices)
• In-office, physical heating and expression of the meibomian glands (including device-assisted therapies [e.g., LipiFlow])
• In-office intense pulsed light therapy to treat MGD
• Prescription drug therapy (topical antibiotic with or without steroid applied to lid margins for anterior blepharitis, limited-duration topical corticosteroid, topical secretagogues, topical nonglucocorticoid immunomodulators (e.g., cyclosporine), topical LFA-1 antagonists (e.g., lifitegrast), oral macrolide or tetracycline antibiotics

Step 3 (used if the above options are inadequate)

• Oral secretagogue therapy
• Application of autologous/allogeneic serum eye drops
• Therapeutic contact lenses (soft bandage lenses, rigid scleral lenses)

Step 4 (used if the above options are inadequate)

• Longer-duration topical corticosteroid therapy
• Amniotic membrane grafting
• Surgical punctal occlusion
• Other surgical options (e.g., salivary gland transplantation, tarsorrhaphy)