Introduction

Dry eye disease, also known as keratoconjunctivitis sicca, is a common eye disorder characterised by insufficient lubrication and moisture on the surface of the eye. This results in uncomfortable symptoms such as gritty feeling, stinging, eye watering and eye fatigue. It can cause visual disturbances and in severe cases can potentially damage the ocular surface.  

Tear Film Anatomy

• Mucin layer: Produced by goblet cells on the conjunctival epithelium. Its hydrophilic properties play a crucial role in stabilizing the tear film, facilitating the spread of aqueous fluid over the ocular surface.
• Aqueous layer: Produced by the lacrimal glands, the aqueous layer constitutes the majority of the tear film. It serves essential functions such as lubrication, flushing away contaminants, and nourishing the avascular cornea.
• Lipid Layer: Produced by the meibomian oil glands. This layer reduces tear film surface tension, facilitates film re-spreading and retards water evaporation (1).

Lacrimal Drainage System

Aetiology

Dry eye exists in two main types: aqueous deficit and evaporative. Some patients’ dry eyes may be caused by a mixture of both types (1).

1. Decreased aqueous tear production: Lacrimal glands not secreting enough of the aqueous layer of the tear film.
   1. Ageing
   1. Hormonal changes during menopause
   1. Medications such as antihistamines, anticholinergics, and antidepressants.
   1. Systemic medical conditions such as Sjögren’s syndrome, thyroid disorders, lupus, and rheumatoid arthritis
   1. Vitamin A deficiency
2. Increased tear evaporation: Tears consist of a complex mixture of water, oils, and mucus. Disruptions in this combination can lead to diminished tear quality and increased evaporation.
   1. Meibomian gland dysfunction (the most common cause)
   1. Eyelid abnormalities such as ectropion
   1. Contact lens wear: Prolonged wear of contact lenses can disrupt tear film stability
   1. Environmental factors: Exposure to dry or windy climates, air conditioning or heating systems
   1. Behavioural factors: Reduced blinking with prolonged screen use

Symptoms

• Dryness and Irritation: Persistent sensation of dryness, grittiness, itching or foreign body sensation in the eyes.
• Stinging: Sensations of burning or stinging, often worsened by environmental conditions or extended periods of visual focus.
• Eye watering: Paradoxically, some individuals may produce excessive tears as a reflex response to irritation to the ocular surface, however, these tears do not adequately relieve symptoms.
• Blurred Vision: Fluctuations in vision quality, especially during prolonged visual tasks or when blinking.

Examination

• Examination of the eyelids may reveal abnormalities contributing to dry eyes such as meibomian gland dysfunction of malposition of the eyelids.
• The examiner should note any signs which could be indicative of systemic disease such as malar flush in lupus or proptosis in thyroid eye disease.
• Utilizing the slit lamp facilitates more detailed examination of the eye, enabling direct observation of the tear film over the cornea. The tear breakup time (TBUT) test measures the time it takes for the tear film to evaporate. The examiner puts fluorescein dye into the eye and uses the slit lamp (with the blue filter) to observe the duration of tear film stability. The TBUT is the time between a blink and when the first dry area appears on the cornea; normal TBUT is above 10 seconds (2).
• The Schirmer’s test evaluates aqueous tear production levels. Administered with anaesthesia, it gauges baseline secretions, while without anaesthesia, it measures baseline plus reflex secretion. During the test, a strip is inserted between the eye and lower eyelid (inferior fornix) for 5 minutes with the eye closed. Afterward, the strip is removed, and the length of the moistened area is compared to the strip scale. A normal aqueous tear production is indicated by a measurement above 15 mm on the strip. Measurements of less than 10 mm indicate moderate dryness, while less than 5 mm indicates severe dryness (3).

Management

Conservative

• Lifestyle modification: Wearing glasses or sunglasses on windy days, avoiding air-conditioned environments, using a humidifier, frequent blinking and breaks during screentime, adequate sleep, and avoiding individual triggers such as alcohol and spicy foods.
• Meibomian gland therapy: Utilizing warm compresses and gentle massage to stimulate the expression of meibomian gland secretions, promoting optimal gland function and supporting healthy lid hygiene.

Pharmacological

• Artificial tears: Lubricating eye drops, gels or ointments can provide temporary relief by supplementing the natural tear film.
• Prescription medications: In severe instances, where dry eye has potentially caused surface inflammation or when autoimmune conditions trigger inflammation of the lacrimal glands, ophthalmologists may prescribe steroid and cyclosporine eye drops (4). Autologous serum eye drops may be used in cases that do not respond to the aforementioned drops (5).

Surgical

Punctal plug insertion is a simple procedure to treat dry eyes. By inserting small silicone plugs into the eyelid punctum, tear drainage is reduced, thus prolonging the duration that tears have to moisten the ocular surface (6). These plugs can be temporary or permanent and are often recommended when other treatments prove inadequate in providing relief. In severe cases, other complex surgical procedures may be recommended by an ophthalmologist.

Management of underlying conditions

Addressing underlying systemic conditions contributing to dry eye disease such as autoimmune disorders may improve symptoms. Additionally, dermatological conditions like seborrheic dermatitis and rosacea can lead to blepharitis, a common cause of dry eyes.

References

1. Salmon JF. Kanski’s Clinical Ophthalmology: A Systematic Approach. 9th ed. Edinburgh: Elsevier; 2019. p. 156-157.
2. American Academy of Ophthalmology. Dry Eye Syndrome. In: EyeWiki [Internet]. San Francisco: American Academy of Ophthalmology; 2024 [cited 2024 Aug 28]. Available from: https://eyewiki.org/Dry_Eye_Syndrome#cite_note-methodologies-5
3. Wu Y, Wang C, Wang X, et al. Advances in dry eye disease examination techniques. Front Med (Lausanne). 2022 Jan 25;8:826530.
4. Messmer EM. The pathophysiology, diagnosis, and treatment of dry eye disease. Dtsch Arztebl Int. 2015 Jan 30;112(5):71-81; quiz 82.
5. Royal College of Ophthalmologists. Serum Eye Drops Guideline [Internet]. London: Royal College of Ophthalmologists; 2020 [cited 2024 Aug 28]. Available from: https://www.rcophth.ac.uk/wp-content/uploads/2020/07/Serum-Eye-Drops-Guideline.pdf
6. Balaram M, Schaumberg DA, Dana MR. Efficacy and tolerability outcomes after punctal occlusion with silicone plugs in dry eye syndrome. American Journal of Ophthalmology. Elsevier; 2001;131(1): 30–36.

Written by Dr Abeku Koomson (FY2) and reviewed by Dr Taiwo Makanjuola (ST5 ophthalmologist)