8th December 2023

Dry eyes

Dry eye is a collective term for disease processes leading to deficient tear volume or excessive evaporation, creating a diseased ocular surface which is often inflamed. It is a multifactorial disease, and prevalence ranges from 5-35% depending on the age group. The tear film has three components: a mucin layer (mainly secreted by goblet cells), an aqueous layer (mainly secreted by the lacrimal glands) and a lipid layer (secreted by meibomian glands). Dry eye occurs from an interaction of mechanisms: tear instability, tear hyperosmolarity, inflammation and ocular surface damage. Inflammation is a key component which is present in the majority of patients with dry eyes. Dry eyes are classified according to the 2007 dry eyes workshop (DEWS).

The following illustrates the classification of dry eyes according to the dry eyes workshop:

Aqueous deficient dry eye

• Sjogren syndrome (primary and secondary)
• Non-Sjogren syndrome
• Lacrimal deficiency
• Lacrimal gland obstruction
• Circatrizing conjunctivitis
• Reflex hyposecretion
• Systemic drugs

Evaporative dry eye

• Intrinsic
• Meibomian gland disease
• Lid disorders
• Low blink rate
• Drug-induced
• Vitamin A deficiencies
• Extrinsic
• Contact lens use
• Ocular surface disease
• Topical drugs preservatives

Common symptoms include redness, pain and discomfort, sensation of dryness, foreign body sensation, photosensitivity, burning sensation, stringy discharge, intermittent or constant blurred vision and reflex watering. Symptoms worsen over the course of the day and are exacerbated by conditions which increase evaporation (outside on a windy day) or decrease blink rate (staring at a screen). Patients might complain of other symptoms of associated disease, such as a dry mouth in Sjogren’s syndrome. Examination may reveal lid margin disease or evidence of contributing disorders, conjunctival hypereamia, decreased tear break-up time, mucous debris, decreased tear film column and punctate epithelial erosions. According to the DEWS, dry eyes can be graded in terms of severity on a scale of 1 to 4 (see table below).

Source: Adapted from Lemp MA, Baudouin C, Baum J, et al. The definition and classification of dry eye disease: Report of the definition and classification subcommittee of the international Dry Eye WorkShop (2007). In: Ocular Surface. 2007, pp. 75–92.

Diagnosis of dry eyes is clinical. Investigations include measurement of the tear break-up time, Schirmer’s test to assess the extent of tear production and ocular surface staining. Laboratory tests can be carried out in cases such as Sjogren’s syndrome to test for specific autoantibodies. Management aims to control symptoms and prevent complications. Treatment options are shown in treatment box 3 and are based on the severity of dry eye according to the grading system. Management should also be tailored according to the aetiology of dry eyes and should include treatment of the underlying disease process.

Source: Adapted from Lin H, Yiu SC. Dry eye disease: A review of diagnostic approaches and treatments. Saudi J Ophthalmol 2014; 28: 173–181.

Grade 1 disease can be successfully managed in primary care settings, but Grade 2 and above will need specialist ophthalmic input. Children with dry eyes who have corneal changes should be referred urgently to ophthalmology. Patients suspected of having a systemic condition, persistent symptoms after 12 weeks or having abnormal eyelid structure of function should be referred to ophthalmology.  Complications of dry eyes include bacterial keratitis, corneal melt, corneal vascularisation, and corneal scarring.